Journal articles: 'Host-Guest moleculars'

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Malinska, Maura. "Insights into molecular recognition from the crystal structures of p-tert-butylcalix[6]arene complexed with different solvents." IUCrJ 9, no. 1 (November 16, 2021): 55–64. http://dx.doi.org/10.1107/s2052252521010678.

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Calixarenes are host molecules that can form complexes with one or more guest molecules, and molecular recognition in calixarenes can be affected by many factors. With a view to establishing molecular recognition rules, the host p-tert-butylcalix[6]arene (TBC6) was crystallized with different guest molecules (cyclohexane, anisole, heptane, toluene, benzene, methyl acetate, ethyl acetate, dichloromethane, tetrahydrofuran and pyridine) and the obtained structures were characterized by X-ray diffraction. With most solvents, 1:1 and/or 1:3 host–guest complexes were formed, although other stoichiometries were also observed with small guest molecules, and crystallization from ethyl acetate produced the unsolvated form. The calculated fill percentage of the TBC6 cavity was ∼55% for apolar guests and significantly lower for polar solvents, indicating that polar molecules can bind to apolar cavities with significantly lower packing coefficients. The most stable crystals were formed by 1:1 host–guest inclusion complexes. The ratio between the apolar surface area and the volume was used to predict the formation of inclusion versus exclusion complexes, with inclusion complexes observed at ratios <40. These findings allow the binding of potential guest molecules to be predicted and a suitable crystal packing for the designed properties to be obtained.

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Chen, Kaifei, Seyed Hesam Mousavi, Ranjeet Singh, Randall Q. Snurr, Gang Li, and Paul A. Webley. "Gating effect for gas adsorption in microporous materials—mechanisms and applications." Chemical Society Reviews 51, no. 3 (2022): 1139–66. http://dx.doi.org/10.1039/d1cs00822f.

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External stimuli or host–guest interactions induce structural changes, producing a gating effect in which an adsorbent suddenly becomes accessible to guest molecules. This effect greatly facilitates gas separation, storage, and molecular detection.

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Lebedinskiy, Konstantin, Ivan Barvík, Zdeněk Tošner, Ivana Císařová, Jindřich Jindřich, and Radim Hrdina. "Spatial arrangements of cyclodextrin host–guest complexes in solution studied by ¹³C NMR and molecular modelling." Beilstein Journal of Organic Chemistry 20 (February 20, 2024): 331–35. http://dx.doi.org/10.3762/bjoc.20.33.

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13C NMR spectroscopic analyses of Cs symmetric guest molecules in the cyclodextrin host cavity, combined with molecular modelling and solid-state X-ray analysis, provides a detailed description of the spatial arrangement of cyclodextrin host–guest complexes in solution. The chiral cavity of the cyclodextrin molecule creates an anisotropic environment for the guest molecule resulting in a splitting of its prochiral carbon signals in 13C NMR spectra. This signal split can be correlated to the distance of the guest atoms from the wall of the host cavity and to the spatial separation of binding sites preferred by pairs of prochiral carbon atoms. These measurements complement traditional solid-state analyses, which rely on the crystallization of host–guest complexes and their crystallographic analysis.

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Elemans, Johannes A. A. W., Roeland J. M. Nolte, and Alan E. Rowan. "Hierarchical self-assembly of a host-guest porphyrin array." Journal of Porphyrins and Phthalocyanines 07, no. 04 (April 2003): 249–54. http://dx.doi.org/10.1142/s1088424603000331.

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The construction of a porphyrin array by a stepwise, hierarchical self-assembly process is described. Four molecular clip host molecules are complexed, in a solid state self-assembly process, to one porphyrin guest molecule. When dissolved in chloroform, the 4:1 host-guest complexes spontaneously self-assemble into an array in which the porphyrins are organized in a cofacial stack. The ensemble is stabilized by a combination of π-π interactions between the porphyrins and between the aromatic surfaces of the host molecules.

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Liang, Guodong, Jacky W. Y. Lam, Wei Qin, Jie Li, Ni Xie, and Ben Zhong Tang. "Molecular luminogens based on restriction of intramolecular motions through host–guest inclusion for cell imaging." Chem. Commun. 50, no. 14 (2014): 1725–27. http://dx.doi.org/10.1039/c3cc48625g.

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Suzuki, Akira, Yuya Miyake, Ryoga Shibata, and Kazuyuki Takai. "Spin and charge interactions between nanographene host and ferrocene." Beilstein Journal of Organic Chemistry 20 (May 2, 2024): 1011–19. http://dx.doi.org/10.3762/bjoc.20.89.

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Ferrocene (FeCp2) was introduced as a non-magnetic guest molecule to activated carbon fibers (ACFs) as a nanographene-based host having localized spins originating from zigzag edges of graphene. The introduction of the guest molecule was confirmed by FTIR for ACFs-FeCp2 introduced at 55 (150) °C (FeCp2-ACFs-55(150)). The appearance of satellite Fe2p peaks and the increase in shake-up peak intensity of the C1s in the XPS spectrum proved the emergence of charge-transfer host–guest interaction in FeCp2-ACFs-150, supported by the red-shift of the G-band in the Raman spectrum. The six-times enhancement in the spin concentration in FeCp2-ACFs-150 compared with ACFs indicates the spin magnetism of the non-magnetic guest FeCp2+ molecule induced by a charge-transfer host–guest interaction in the nanographene host. The larger ESR linewidth than that expected from the dipolar interaction estimated by the localized spin concentration suggests the exchange interaction between the nanographene and FeCp2 spins. The narrowing of the ESR linewidth of FeCp2-ACFs-55 upon higher excitation microwave power suggests the inhomogeneity of the environment for FeCp2+ molecules in the nanographene host. The observed induction of spin magnetism by the interfacial interactions between the nanographene host and the guest molecules will be a promising strategy for developing a new class of molecular magnets.

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Sun, Zhaoxi, Qiaole He, Zhihao Gong, Payam Kalhor, Zhe Huai, and Zhirong Liu. "A General Picture of Cucurbit[8]uril Host–Guest Binding: Recalibrating Bonded Interactions." Molecules 28, no. 7 (March 31, 2023): 3124. http://dx.doi.org/10.3390/molecules28073124.

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Atomic-level understanding of the dynamic feature of host–guest interactions remains a central challenge in supramolecular chemistry. The remarkable guest binding behavior of the Cucurbiturils family of supramolecular containers makes them promising drug carriers. Among Cucurbit[n]urils, Cucurbit[8]uril (CB8) has an intermediate portal size and cavity volume. It can exploit almost all host–guest recognition motifs formed by this host family. In our previous work, an extensive computational investigation of the binding of seven commonly abused and structurally diverse drugs to the CB8 host was performed, and a general dynamic binding picture of CB8-guest interactions was obtained. Further, two widely used fixed-charge models for drug-like molecules were investigated and compared in great detail, aiming at providing guidelines in choosing an appropriate charge scheme in host-guest modelling. Iterative refitting of atomic charges leads to improved binding thermodynamics and the best root-mean-squared deviation from the experimental reference is 2.6 kcal/mol. In this work, we focus on a thorough evaluation of the remaining parts of classical force fields, i.e., the bonded interactions. The widely used general Amber force fields are assessed and refitted with generalized force-matching to improve the intra-molecular conformational preference, and thus the description of inter-molecular host–guest interactions. The interaction pattern and binding thermodynamics show a significant dependence on the modelling parameters. The refitted system-specific parameter set improves the consistency of the modelling results and the experimental reference significantly. Finally, combining the previous charge-scheme comparison and the current force-field refitting, we provide general guidelines for the theoretical modelling of host–guest binding.

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Yoshida, Hiroaki, Ken Kikuta, and Toshiyuki Kida. "Fabrication of supramolecular cyclodextrin–fullerene nonwovens by electrospinning." Beilstein Journal of Organic Chemistry 15 (January 9, 2019): 89–95. http://dx.doi.org/10.3762/bjoc.15.10.

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Direct electrospinning of small molecules has great potential to fabricate a new class of fiber materials because this approach realizes the creation of various functional materials through the numerous molecular combinations. In this paper, we demonstrate a proof-of-concept to fabricate supramolecular fiber materials composed of cyclodextrin (CD)–fullerene inclusion complexes by electrospinning. Similar to the molecular state of fullerenes in solution, the resulting fibers include molecularly-dispersed fullerenes. We believe such a concept could be expanded to diverse host–guest complexes, opening up supramolecular solid materials science and engineering.

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Archana Sumohan Pillai, Sivaraj Ramasamy, Varnitha Manikandan, Aleyamma Alexander, and Israel V.M.V. Enoch. "Anticancer Activity of the Host-Guest Complex of Camptothecin with β-Cyclodextrin-Folate Conjugate. Encapsulation and Efficacy." International Journal of Research in Pharmaceutical Sciences 11, SPL4 (December 21, 2020): 1286–91. http://dx.doi.org/10.26452/ijrps.v11ispl4.4294.

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Cyclodextrins are cyclic oligosachcharides that act as molecular hosts and accommodate drug molecules forming host: guest complexes. They aid in the sustained release of the encapsulated drugs through diffusion in solution and protect their unstable forms. In this paper, we report the synthesis of a β-cyclodextrin-folate by a simple coupling reaction. The compound is characterized using IR, NMR, and mass spectroscopic techniques. The amide carbonyl band is observed at 1680 cm-1. The mass spectrum shows the molecular ion peak of the β-cycloxetrin-folate conjugate at an m/z value of 1615.35. An inclusion complex of the anticancer drug, camptothecin, with the β-cycloxetrin-folate is formed on the stepwise addition of the β-cycloxetrin-folate to the guest molecule. The complex formation is studied using UV-visible and fluorescence spectroscopy. The formation of host: guest complexes is known to enable the sustained release of the encapsulated drug molecule. Herein, we examined the in vitro anticancer activity of the host: guest complex against cervical cancer (HeLa) cells. The host: guest complex formation results in enhanced efficacy of the drug. Dose-dependent cytotoxicity is observed for the β-cyclodextrin-folate: camptothecin complex. The cytotoxicity is more for the complex than for the free drug in solution.

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Wen, Huimin, Wengang Li, Jiewei Chen, Gen He, Longhua Li, Mark A. Olson, Andrew C. H. Sue, J. Fraser Stoddart, and Xuefeng Guo. "Complex formation dynamics in a single-molecule electronic device." Science Advances 2, no. 11 (November 2016): e1601113. http://dx.doi.org/10.1126/sciadv.1601113.

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Single-molecule electronic devices offer unique opportunities to investigate the properties of individual molecules that are not accessible in conventional ensemble experiments. However, these investigations remain challenging because they require (i) highly precise device fabrication to incorporate single molecules and (ii) sufficient time resolution to be able to make fast molecular dynamic measurements. We demonstrate a graphene-molecule single-molecule junction that is capable of probing the thermodynamic and kinetic parameters of a host-guest complex. By covalently integrating a conjugated molecular wire with a pendent crown ether into graphene point contacts, we can transduce the physical [2]pseudorotaxane (de)formation processes between the electron-rich crown ether and a dicationic guest into real-time electrical signals. The conductance of the single-molecule junction reveals two-level fluctuations that are highly dependent on temperature and solvent environments, affording a nondestructive means of quantitatively determining the binding and rate constants, as well as the activation energies, for host-guest complexes. The thermodynamic processes reveal the host-guest binding to be enthalpy-driven and are consistent with conventional 1H nuclear magnetic resonance titration experiments. This electronic device opens up a new route to developing single-molecule dynamics investigations with microsecond resolution for a broad range of chemical and biochemical applications.

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Marjo, CE, R. Bishop, DC Craig, and ML Scudder. "A Tetrachloro Guest in a Molecular Box." Australian Journal of Chemistry 49, no. 3 (1996): 337. http://dx.doi.org/10.1071/ch9960337.

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The new lattice inclusion host exo-7,exo-15-dibromo-6,7,14,15-tetrahydro-6,14-methanocycloocta[1,2-b:5,6-b'] diquinoxaline (6) has been synthesized in three steps from bicyclo [3.3.1]nonane-2,6-dione and benzofurazan oxide. It preferentially forms crystalline inclusion compounds with small polyhaloalkane guest molecules, and the crystal structure of the 1,1,2,2-tetrachloroethane compound [(C21H14N4Br2)2.C2H2Cl4, Pbcn , a 11.663(2), b 13.195(3), c 27.444(5) Ǻ, Z 4, R 0.041] is described. The key characteristic of this compound is a series of molecular boxes in which the guest molecules reside. Construction of the six surrounding walls is achieved with the aromatic rings of just four host molecules, and the guest molecule occupies a fixed position within the box. The intermolecular forces resulting in formation of this novel inclusion structure are analysed in detail.

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Serillon, Dylan, Carles Bo, and Xavier Barril. "Testing automatic methods to predict free binding energy of host–guest complexes in SAMPL7 challenge." Journal of Computer-Aided Molecular Design 35, no. 2 (January 19, 2021): 209–22. http://dx.doi.org/10.1007/s10822-020-00370-6.

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AbstractThe design of new host–guest complexes represents a fundamental challenge in supramolecular chemistry. At the same time, it opens new opportunities in material sciences or biotechnological applications. A computational tool capable of automatically predicting the binding free energy of any host–guest complex would be a great aid in the design of new host systems, or to identify new guest molecules for a given host. We aim to build such a platform and have used the SAMPL7 challenge to test several methods and design a specific computational pipeline. Predictions will be based on machine learning (when previous knowledge is available) or a physics-based method (otherwise). The formerly delivered predictions with an RMSE of 1.67 kcal/mol but will require further work to identify when a specific system is outside of the scope of the model. The latter is combines the semiempirical GFN2B functional, with docking, molecular mechanics, and molecular dynamics. Correct predictions (RMSE of 1.45 kcal/mol) are contingent on the identification of the correct binding mode, which can be very challenging for host–guest systems with a large number of degrees of freedom. Participation in the blind SAMPL7 challenge provided fundamental direction to the project. More advanced versions of the pipeline will be tested against future SAMPL challenges.

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Ward, M. D., and A. M. Pivovar. "Organic host–guest molecular assemblies." Current Opinion in Solid State and Materials Science 4, no. 6 (December 1999): 581–86. http://dx.doi.org/10.1016/s1359-0286(00)00013-9.

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Ono, Toshikazu, and Yoshio Hisaeda. "Vapochromism of Organic Crystals Based on Macrocyclic Compounds and Inclusion Complexes." Symmetry 12, no. 11 (November 19, 2020): 1903. http://dx.doi.org/10.3390/sym12111903.

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Vapochromic materials, which change color and luminescence when exposed to specific vapors and gases, have attracted considerable attention in recent years owing to their potential applications in a wide range of fields such as chemical sensors and environmental monitors. Although the mechanism of vapochromism is still unclear, several studies have elucidated it from the viewpoint of crystal engineering. In this mini-review, we investigate recent advances in the vapochromism of organic crystals. Among them, macrocyclic molecules and inclusion complexes, which have apparent host–guest interactions with analyte molecules (specific vapors and gases), are described. When the host compound is properly designed, its cavity size and symmetry change in response to guest molecules, influencing the optical properties by changing the molecular inclusion and recognition abilities. This information highlights the importance of structure–property relationships resulting from the molecular recognition at the solid–vapor interface.

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Chan, Alan Kwun-Wa, Wai Han Lam, Yuya Tanaka, Keith Man-Chung Wong, and Vivian Wing-Wah Yam. "Multiaddressable molecular rectangles with reversible host–guest interactions: Modulation of pH-controlled guest release and capture." Proceedings of the National Academy of Sciences 112, no. 3 (January 7, 2015): 690–95. http://dx.doi.org/10.1073/pnas.1423709112.

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A series of multiaddressable platinum(II) molecular rectangles with different rigidities and cavity sizes has been synthesized by endcapping the U-shaped diplatinum(II) terpyridine moiety with various bis-alkynyl ligands. The studies of the host–guest association with various square planar platinum(II), palladium(II), and gold(III) complexes and the related low-dimensional gold(I) complexes, most of which are potential anticancer therapeutics, have been performed. Excellent guest confinement and selectivity of the rectangular architecture have been shown. Introduction of pH-responsive functionalities to the ligand backbone generates multifunctional molecular rectangles that exhibit reversible guest release and capture on the addition of acids and bases, indicating their potential in controlled therapeutics delivery on pH modulation. The reversible host–guest interactions are found to be strongly perturbed by metal–metal and π–π interactions and to a certain extent, electrostatic interactions, giving rise to various spectroscopic changes depending on the nature of the guest molecules. Their binding mode and thermodynamic parameters have been determined by 2D NMR and van’t Hoff analysis and supported by computational study.

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Itoh, H., B. Chazallon, H. Schober, K. Kawamura, and W. F. Kuhs. "Inelastic neutron scattering and molecular dynamics studies on low-frequency modes of clathrate hydrates." Canadian Journal of Physics 81, no. 1-2 (January 1, 2003): 493–501. http://dx.doi.org/10.1139/p03-034.

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Low-frequency modes of gas hydrates with Xe, Ar, O2, and N2 atoms/molecules have been studied by inelastic neutron-scattering and molecular dynamics simulations. Type I and type II clathrate hydrates show some small but significant differences of the low-frequency host contribution to the density of states. Both differ markedly from that of ice Ih and depend only weakly on the guest. The vibrational modes associated with Xe atoms were observed at 2.2, 2.9, and 4.0 meV (T = 100 K). They are in good agreement with predictions from molecular dynamics simulations. In the case of N2 hydrate we found a well-defined peak at about 2 meV, which shows a remarkable shift to higher frequency with increasing temperature. This peak and a broad peak that is overlapped with the host lattice modes (6.5 and 10.5 meV) are assigned to the vibration of N2 molecules in the large and small cages, respectively. The calculated vibrational spectra of N2 molecules in doubly occupied large cages show a significant distinct spectral distribution. The anharmonic shift of the guest atoms in large cages is significantly less pronounced in Xe hydrates suggesting that guest-host interactions can vary considerably from one system to another. PACS Nos.: 82.75-z, 78.70N, 71.15Pd, 63

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Zhou, Mingming, Caichao Ye, and Dong Xiang. "Theoretical Studies on the Role of Guest in α-CL-20/Guest Crystals." Molecules 27, no. 10 (May 19, 2022): 3266. http://dx.doi.org/10.3390/molecules27103266.

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The contradiction between energy and safety of explosives is better balanced by the host–guest inclusion strategy. To deeply analyze the role of small guest molecules in the host–guest system, we first investigated the intermolecular contacts of host and guest molecules through Hirshfeld surfaces, 2-D fingerprint plots and electrostatic interaction energy. We then examined the strength and nature of the intermolecular interactions between CL-20 and various small molecules in detail, using state-of-the-art quantum chemistry calculations and elaborate wavefunction analyses. Finally, we studied the effect of the small molecules on the properties of CL-20, using density functional theory (DFT). The results showed that the spatial arrangement of host and guest molecules and the interaction between host and guest molecules, such as repulsion or attraction, may depend on the properties of the guest molecules, such as polarity, oxidation, hydrogen content, etc. The insertion of H2O2, H2O, N2O, and CO2 had significant influence on the electrostatic potential (ESP), van der Waals (vdW) potential and chemical bonding of CL-20. The intermolecular interactions, electric density and crystal orbital Hamilton population (COHP) clarified and quantified the stabilization effect of different small molecules on CL-20. The insertion of the guest molecules improved the stability of CL-20 to different extents, of which H2O2 worked best.

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Sinawang, Garry, Motofumi Osaki, Yoshinori Takashima, Hiroyasu Yamaguchi, and Akira Harada. "Supramolecular self-healing materials from non-covalent cross-linking host–guest interactions." Chemical Communications 56, no. 32 (2020): 4381–95. http://dx.doi.org/10.1039/d0cc00672f.

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Martín Carmona, María Antonia. "Natural and synthetic cavitands: challenges in chemistry and pharmaceutical technology." Anales de la Real Academia Nacional de Farmacia 87, no. 87(04) (2021): 381–94. http://dx.doi.org/10.53519/analesranf.2021.87.04.02.

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Supramolecular chemistry involves non-covalent interactions and specific molecular recognition of molecules/analytes by host molecules or supramolecules. These events are present in synthesis, catalysis, chiral separations, design of sensors, cell signaling processes and drug transport by carriers. The typical behavior of supramolecules is derived from their ability to build well-structured self-assembled and self-organized entities. Cavitands are a particular group of supramolecules possessing a cavity able to include a variety of compounds thanks to host-guest non-covalent interactions developed among cavitands and analytes. Some typical cavitands are crown ethers, calixarenes, cucurbiturils, porphyrins and cyclodextrins. The two latter families are natural product cavitands that are generally considered models for molecular recognition of cations and organic and inorganic guest molecules, being attractive host molecules from the sustainability point of view. The natural cyclodextrins (𝛼-, 𝛽- and 𝛾-CD) are obtained with reasonable cost by enzymatic treatment of starch under adequate temperature conditions. They are profusely used in pharmaceutical, food and cosmetic industries due to their very low toxicity and side effects. This review is focused on the relevance and applications of cyclodextrins in pharmaceutical technology for their ability to increase solubility and stabilize drug molecules, thereby enhancing their bioavailability. The association of cyclodextrins with diverse nanostructured materials, i.e. carbon nanotubes, magnetic nanoparticles, silica and molecularly imprinted polymers, allows to synergize the properties of cyclodextrins and these nanostructured materials to reach highly specific molecular recognition of analytes. The exploitation of these benefits for analytical sample pre-treatment and chiral chromatographic separations are described. The use of cyclodextrins as mobile phases additives in HPLC provides interesting results for green and sustainable chromatographic separations. Polymers incorporating cyclodextrins show exceptional adsorption properties for retaining toxic compounds and persistent organic pollutants from soils and water samples, allowing satisfactory recoveries of these environmental samples according to the Stockholm convection principles.

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Zhang, Meng, Nicolas Levaray, Josée R. Daniel, Karen C. Waldron, and X. X. Zhu. "Cholic acid dimers as invertible amphiphilic pockets: synthesis, molecular modeling, and inclusion studies." Canadian Journal of Chemistry 95, no. 7 (July 2017): 792–98. http://dx.doi.org/10.1139/cjc-2016-0621.

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Two dimers of cholic acid were synthesized through simple covalent linkers. The dimers form invertible molecular pockets in media of different polarity; hydrophobic pockets are formed in water and hydrophilic pockets are formed in organic media. Fluorescence studies show that pockets formed by these dimers can serve as invertible hosts for the hydrophobic guest pyrene and the hydrophilic guest coumarin 343. The molecular pocket also enhances dissolution of the weakly soluble cresol red sodium salt in organic media. Molecular modeling was performed to better understand the host–guest complexation process of the invertible amphiphilic pockets. The calculated free energy changes indicate that the two dimers form the most stable complexes with coumarin 343 at a host to guest ratio of 2:2, whereas the host to guest ratio differs in the formation of complexes with pyrene for the two dimers. The dimer with the shorter, less flexible linker seems to form host–guest complexes that are more stable in both water and organic solvents.

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Goubitz, Kees, Pavla Čapková, Klára Melánová, Wim Molleman, and Henk Schenk. "Structure determination of two intercalated compounds VOPO4·(CH2)4O and VOPO4·OH—(CH2)2—O—(CH2)2—OH; synchrotron powder diffraction and molecular modelling." Acta Crystallographica Section B Structural Science 57, no. 2 (April 1, 2001): 178–83. http://dx.doi.org/10.1107/s0108768100015603.

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The crystal structures of two intercalated compounds have been determined using a combination of synchrotron powder diffraction and molecular mechanics simulations: (1) vanadyl phosphate intercalated with tetrahydrofuran, VOPO4·(CH2)4O, and (2) vanadyl phosphate intercalated with diethylene glycol, VOPO4·HO(CH2)2O(CH2)2OH. Both intercalates preserve the tetragonal space group P4/n, as found in the host structure VOPO4·2H2O. (1): a = 6.208, c = 8.930 Å, Z = 2, Dx = 2.51 g cm−3; (2): a = 6.223, c = 11.417 Å, Z = 2, Dx = 2.66 g cm−3. Both intercalates exhibit the same type of orientational disorder in the arrangement of guest molecules, as observed in the same host compound intercalated with water. These two intercalates also exhibit, rather surprisingly, perfect ordering in layer stacking without the displacement disorder, characteristic of many intercalated layered structures. Thanks to this regularity in the arrangement of guests and layers, synchrotron powder diffraction could be used in the present structure determination. The present results also enabled the analysis of the effect of geometrical parameters characterizing the mutual host–guest complementarity and the effect of host–guest and guest–guest interaction on the crystal packing of intercalates.

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Nagatomo, Nao, Hisashi Oishi, Yutaka Kuwahara, Makoto Takafuji, Reiko Oda, Taisuke Hamada, and Hirotaka Ihara. "Enantioselective Self-Assembled Nanofibrillar Network with Glutamide-Based Organogelator." Nanomaterials 11, no. 6 (May 23, 2021): 1376. http://dx.doi.org/10.3390/nano11061376.

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A chiral molecular gelation system, as a chiral host, was used to effectively realize enantioselectivity using the simple carboxylic acid functional group. For this purpose, an L-glutamic-acid-based lipidic amphiphile (G-CA) with a carboxylic head group was selected and its responsiveness to cationic guest molecules was investigated. The dispersion morphology of G-CA in its solution state was examined by confocal and transmission electron microscopies, while interactions between the G-CA, as the host system, and guest molecules were evaluated by UV-visible, circular dichroism, and fluorescence spectroscopies. As a result, enantioselectivity was effectively induced when G-CA formed highly ordered aggregates that provide negatively charged surfaces in which carboxyl groups are assembled in highly ordered states, and when the two cationic groups of the guest molecule are attached to this surface through multiple interactions.

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Bruns. "Exploring and Exploiting the Symmetry-Breaking Effect of Cyclodextrins in Mechanomolecules." Symmetry 11, no. 10 (October 5, 2019): 1249. http://dx.doi.org/10.3390/sym11101249.

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Cyclodextrins (CDs) are cone-shaped molecular rings that have been widely employed in supramolecular/host–guest chemistry because of their low cost, high biocompatibility, stability, wide availability in multiple sizes, and their promiscuity for binding a range of molecular guests in water. Consequently, CD-based host–guest complexes are often employed as templates for the synthesis of mechanically bonded molecules (mechanomolecules) such as catenanes, rotaxanes, and polyrotaxanes in particular. The conical shape and cyclodirectionality of the CD “bead” gives rise to a symmetry-breaking effect when it is threaded onto a molecular “string”; even symmetrical guests are rendered asymmetric by the presence of an encircling CD host. This review focuses on the stereochemical implications of this symmetry-breaking effect in mechanomolecules, including orientational isomerism, mechanically planar chirality, and topological chirality, as well as how they support applications in regioselective and stereoselective chemical synthesis, the design of molecular machine prototypes, and the development of advanced materials.

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Eikeland, Espen, Solveig Madsen, Jacob Overgaard, Mark Spackman, and Bo Iversen. "Exploring Host-Guest Interactions: a Single Crystal High-Pressure study." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C756. http://dx.doi.org/10.1107/s2053273314092432.

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Single crystal X-ray diffraction data from several Hydroquinone clathrate systems, with various small guest molecules (e.g. HCOOH, MeOH), have been obtained up to a pressure of 10 GPa, using a diamond anvil cell (DAC). Hydroquinone clathrates are key examples of supramolecular aggregates, having a diverse structural chemistry controlled, to a large extent, by the detailed intermolecular interactions between the host and the guest molecules. Although supramolecular chemistry is the foundation for the design and development of advanced materials (e.g. for catalysis, targeted drug delivery, chemical separation and nonlinear optics) the basic understanding leading to such complex systems are often lacking. High pressure (HP) crystallography is an excellent method of systematically increasing host-guest interactions by forcing the molecules closer together, often leading to interesting and unexpected results. At ambient pressure smaller guest molecules are often disordered inside the clathrate cavities. As the external pressure increases the cavities shrink, and it seems likely that guest molecules will order inside the cavity breaking the host symmetry. Guest ordering transitions are also found upon cooling. In this work, results from HP studies of the hydroquinone – formic acid system reveal that the structure is stable up to 10 GPa, at which pressure the guest cavity volume is reduced by more than 50 % without ordering of the guest atoms. Earlier studies have shown that the empty Hydroquinone clathrate undergoes a phase transition into a nonporous structure already at 0.4 GPa. [1] This indicates that formic acid stabilizes the host framework through strong intermolecular host-guest interactions, but without lowering the host symmetry.

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Rissanen, Kari. "Crystallography of encapsulated molecules." Chemical Society Reviews 46, no. 9 (2017): 2638–48. http://dx.doi.org/10.1039/c7cs00090a.

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Ahn, Yun-Ho, Byeonggwan Lee, and Kyuchul Shin. "Structural Identification of Binary Tetrahydrofuran + O2 and 3-Hydroxytetrahydrofuran + O2 Clathrate Hydrates by Rietveld Analysis with Direct Space Method." Crystals 8, no. 8 (August 18, 2018): 328. http://dx.doi.org/10.3390/cryst8080328.

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The structural determination of clathrate hydrates, nonstoichiometric crystalline host-guest materials, is challenging because of the dynamical disorder and partial cage occupancies of the guest molecules. The application of direct space methods with Rietveld analysis can determine the powder X-ray diffraction (PXRD) patterns of clathrates. Here, we conducted Rietveld analysis with the direct space method for the structural determination of binary tetrahydrofuran (THF) + O2 and 3-hydroxytetrahydrofuran (3-OH THF) + O2 clathrate hydrates in order to identify the hydroxyl substituent effect on interactions between the host framework and the cyclic ether guest molecules. The refined PXRD results reveal that the hydroxyl groups are hydrogen-bonded to host hexagonal rings of water molecules in the 51264 cage, while any evidences of hydrogen bonding between THF guests and the host framework were not observed from PXRD at 100 K. This guest-host hydrogen bonding is thought to induce slightly larger 512 cages in the 3-OH THF hydrate than those in the THF hydrate. Consequently, the disorder dynamics of the secondary guest molecules also can be affected by the hydrogen bonding of larger guest molecules. The structural information of binary clathrate hydrates reported here can improve the understanding of the host-guest interactions occurring in clathrate hydrates and the specialized methodologies for crystal structure determination of clathrate hydrates.

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27

Cheng, Peiming, Lixuan Cai, Danni Yan, Lipeng Zhou, and Qingfu Sun. "Molecular Cage Promoted Aerobic Oxidation or Photo-Induced Rearrangement of Spiroepoxy Naphthalenone." Catalysts 11, no. 4 (April 9, 2021): 484. http://dx.doi.org/10.3390/catal11040484.

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Herein, we report a Pd4L2-type molecular cage (1) and catalyzed reactions of spiroepoxy naphthalenone (2) in water, where selective formation of 2-(hydroxymethyl)naphthalene-1,4-dione (3) via aerobic oxidation, or 1-hydroxy-2-naphthaldehyde (4) via photo-induced rearrangement under N2 have been accomplished. Encapsulation of four molecules of guest 2 within cage 1, i.e., (2)4⊂1, has been confirmed by NMR, and a final host-guest complex of 3⊂1 has also been determined by single crystal X-Ray diffraction study. While the photo-induced ring-opening isomerization from 2 to 4 are known, appearance of charge-transfer absorption on the host-guest complex of (2)4⊂1 allows low-power blue LEDs irradiation to promote this process.

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28

Tanaka, Koichi, Takaichi Hiratsuka, Yuko Kojima, and Yasuko T. Osano. "Synthesis, Structure and Chiral Inclusion Crystallisation of Tetrakis(4-Ethynylphenyl)Ethylene Derivatives." Journal of Chemical Research 2002, no. 5 (May 2002): 209–12. http://dx.doi.org/10.3184/030823402103171889.

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Achiral host molecules, tetrakis(4-ethynylphenyl)ethylene 3 and tetrakis(4-bromoethynylphenyl)ethylene 4, formed chiral host–guest inclusion crystals with achiral guest molecules via weak intermolecular interactions.

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29

Shao, Li, Bin Hua, Jie Yang, and Guocan Yu. "Construction of a photo-responsive supra-amphiphile based on a tetracationic cyclobis(paraquat-p-phenylene) and an azobenzene-containing guest in water." Chemical Communications 52, no. 39 (2016): 6573–76. http://dx.doi.org/10.1039/c6cc02434c.

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A photo-responsive supra-amphiphile was constructed based on the host–guest molecular recognition between a tetracation cyclophane cyclobis(paraquat-p-phenylene) host and an azobenzene-containing guest.

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30

Hayashida, Osamu, Yudai Tanaka, and Takaaki Miyazaki. "Synthesis and Guest-Binding Properties of pH/Reduction Dual-Responsive Cyclophane Dimer." Molecules 26, no. 11 (May 22, 2021): 3097. http://dx.doi.org/10.3390/molecules26113097.

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A water-soluble cyclophane dimer having two disulfide groups as a reduction-responsive cleavable bond as well as several acidic and basic functional groups as a pH-responsive ionizable group 1 was successfully synthesized. It was found that 1 showed pH-dependent guest-binding behavior. That is, 1 strongly bound an anionic guest, 6-p-toluidinonaphthalene-2-sulfonate (TNS) with binding constant (K/M−1) for 1:1 host-guest complexes of 9.6 × 104 M−1 at pH 3.8, which was larger than those at pH 7.4 and 10.7 (6.0 × 104 and 2.4 × 104 M−1, respectively), indicating a favorable electrostatic interaction between anionic guest and net cationic 1. What is more, release of the entrapped guest molecules by 1 was easily controlled by pH stimulus. Large favorable enthalpies (ΔH) for formation of host-guest complexes were obtained under the pH conditions employed, suggesting that electrostatic interaction between anionic TNS and 1 was the most important driving force for host-guest complexation. Such contributions of ΔH for formation of host-guest complexes decreased along with increased pH values from acidic to basic solutions. Upon addition of dithiothreitol (DTT) as a reducing reagent to an aqueous PBS buffer (pH 7.4) containing 1 and TNS, the fluorescence intensity originating from the bound guest molecules decreased gradually. A treatment of 1 with DTT gave 2, having less guest-binding affinity by the cleavage of disulfide bonds of 1. Consequently, almost all entrapped guest molecules by 1 were released from the host. Moreover, such reduction-responsive cleavage of 1 and release of bound guest molecules was performed more rapidly in aqueous buffer at pH 10.7.

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31

Thomas, Sajesh, Rebecca Fuller, Alexandre Sobolev, Philip Schauer, Simon Grabowsky, George Koutsantonis, and Mark Spackman. "Supramolecular Stark Effect in Host-Guest Complexes via Charge Density Analysis." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C674. http://dx.doi.org/10.1107/s2053273314093255.

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The effect of an electric field on the vibrational spectra, the Vibrational Stark Effect (VSE), has been utilized extensively to probe the local electric field in the active sites of enzymes [1, 2]. For this reason, the electric field and consequent polarization effects induced by a supramolecular host system upon its guest molecules attain special interest due to the implications for various biological processes. Although the host-guest chemistry of crown ether complexes and clathrates is of fundamental importance in supramolecular chemistry, many of these multicomponent systems have yet to be explored in detail using modern techniques [3]. In this direction, the electrostatic features associated with the host-guest interactions in the inclusion complexes of halogenated acetonitriles and formamide with 18-crown-6 host molecules have been analyzed in terms of their experimental charge density distribution. The charge density models provide estimates of the molecular dipole moment enhancements which correlate with the simulated values of dipole moments under electric field. The accurate electron density mapping using the multipole formalism also enable the estimation of the electric field experienced by the guest molecules. The electric field vectors thus obtained were utilized to estimate the vibrational stark effect in the nitrile (-C≡N) and carbonyl (C=O) stretching frequencies of the guest molecules via quantum chemical calculations in gas phase. The results of these calculations indicate remarkable elongation of C≡N and C=O bonds due to the electric fields. The electronic polarization in these covalent bonds induced by the field manifests as notable red shifts in their characteristic vibrational frequencies. These results derived from the charge densities are further supported by FT-IR experiments and thus establish the significance of a phenomenon that could be termed as the "supramolecular Stark effect" in crystal environment.

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32

Bhaskar Reddy, Manda, Myadaraboina Shailaja, Alla Manjula, Joseph Richard Premkumar, Garikapati Narahari Sastry, Katukuri Sirisha, and Akella Venkata Subrahmanya Sarma. "Design and synthesis of Tröger's base ditopic receptors: host–guest interactions, a combined theoretical and experimental study." Organic & Biomolecular Chemistry 13, no. 4 (2015): 1141–49. http://dx.doi.org/10.1039/c4ob02266a.

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The host–guest interaction between flexible ditopic receptors and bisammonium ion has been investigated experimentally and computationally. The conformation folding of guest bisammonium ion molecules leads to the oscillation of the host–guest interaction.

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33

LEE, WONBAE, JUN CHUN, YOON KYUNG CHANG, YOUNG KWAN LIM, CHEON-GYU CHO, and HAIWON LEE. "IMMOBILIZATION AND CHARACTERIZATION OF AN ARTIFICIALLY ASSEMBLED TRI-STRAND β-SHEET STRUCTURE ON A RIGID Au(111) SURFACE." International Journal of Nanoscience 05, no. 06 (December 2006): 803–8. http://dx.doi.org/10.1142/s0219581x06005182.

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We designed and synthesized diurea type host molecules for the recognition of the tri-peptide guest molecule through the artificial formation of three-strand β-sheet structures on a rigid surface. The immobilizations of those host molecules on Au (111) surface, and the insertion of the guest molecules into the corresponding sites of immobilized host molecules were successfully carried out. Their binding characteristics were monitored by analyzing STM images before and after the insertion of guest peptides, and the characterization of the insertion in bulk phase was accomplished by NMR study.

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34

Bock, Hans, Norbert Nagel, and Christian Näther. "Wechselwirkungen in Molekülkristallen, 147 [1, 2]. Isostrukturelle Wirt/Gast-Einschluß-Verbindungen von N,N'-Ditosyl- p-phenylendiamin mit Aceton, Cyclopentanon, Cyclopent-2-en-l-on, 1,3-Dioxolan, Tetrahydrofuran und 2,5-Dihydrofuran / Interactions in Molecular Crystals, 147 [1, 2], Isostructural Host/Guest-Inclusion Compounds of N,N'-Ditosyl-p-phenylenediamine with Acetone, Cyclopentanone, Cyclopent-2-ene-l-one, 1,3-Dioxolane, Tetrahydrofurane, and 2,5-D ihydrofurane." Zeitschrift für Naturforschung B 53, no. 12 (December 1, 1998): 1401–12. http://dx.doi.org/10.1515/znb-1998-1202.

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Abstract Six isostructural inclusion compounds of various ketone and ether guest molecules into the hydrogen-bonded host-matrix of N,N’-ditosyl-p-phenylenediamine are presented. Crystal growth, structure determinations as well as the arrangement within the clathrates formed is reported and discussed in detail. Packing coefficients and especially the volume ratios between the guest-containig channels and the unit cells allow to estimate the size-limit of guest molecules, which can cocrystallize. Additional crystal growth experiments yield information concerning other types of guest molecules, inclusion from solvent mixtures and guest removal as well as guest exchange processes observed for the N,N′-ditosyl-p-phenylenediamine host matrix.

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35

Danylyuk, Oksana, Karolina Kedra-Krolik, Marta Worzakowska, Joanna Osypiuk-Tomasik, and Vladimir Fedin. "Phase transformations in cucurbituril host-guest complexes." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C646. http://dx.doi.org/10.1107/s205327331409353x.

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The retention of crystallinity upon desolvation of molecular crystals is not common, as the molecules are rigidly and densely packed in the crystals and the original framework usually collapses once solvent is removed from the structure. However, in rare cases the host framework remains substantially unaffected by solvent (guest) removal yielding structure with open channels or discrete lattice voids that can show permanent porosity. [1] Furthermore, sometimes happens, the desolvation process proceeds as single-crystal to single-crystal transformation resulting in distortion and sliding of the structure, changes in conformation, coordination modes and/or space group. Here we would like to present crystallographic study and thermal analysis on the dehydration process of the crystalline supramolecular complex between macrocyclic host cucurbit[6]uril and dopamine. In the solid state the 1:1 host-guest complex assembles into hexameric tubes with water-filled interior channels. Another set of water channels is created between three neighboring tubes in the crystal lattice. The crystals of such supramolecular assembly are not stable when out from mother solution and immediately start to loose water upon exposure to air. However, despite severe cracking the crystals dried in air maintained their integrity and still gave satisfactory diffraction pattern. The X-ray analysis showed significant decrease in the unit cell volume of the partially dehydrated crystals that corresponds to the liberation of some of the water molecules from the channels. Moreover, the reorganization of dopamine guest molecules has occurred in the crystal lattice as a response to the escape of water molecules from the structure. The partial dehydration and reorganization of the supramolecular framework proceeds via a single-crystal to single-crystal mechanism.

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36

Zyryanov, Grigory V., Dmitry S. Kopchuk, Igor S. Kovalev, Sougata Santra, Adinath Majee, and Brindaban C. Ranu. "Pillararenes as Promising Carriers for Drug Delivery." International Journal of Molecular Sciences 24, no. 6 (March 8, 2023): 5167. http://dx.doi.org/10.3390/ijms24065167.

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Since their discovery in 2008 by N. Ogoshi and co-authors, pillararenes (PAs) have become popular hosts for molecular recognition and supramolecular chemistry, as well as other practical applications. The most useful property of these fascinating macrocycles is their ability to accommodate reversibly guest molecules of various kinds, including drugs or drug-like molecules, in their highly ordered rigid cavity. The last two features of pillararenes are widely used in various pillararene-based molecular devices and machines, stimuli-responsive supramolecular/host–guest systems, porous/nonporous materials, organic–inorganic hybrid systems, catalysis, and, finally, drug delivery systems. In this review, the most representative and important results on using pillararenes for drug delivery systems for the last decade are presented.

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37

Kärger, Jörg, Dieter Freude, and Jürgen Haase. "Diffusion in Nanoporous Materials: Novel Insights by Combining MAS and PFG NMR." Processes 6, no. 9 (September 1, 2018): 147. http://dx.doi.org/10.3390/pr6090147.

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Pulsed field gradient (PFG) nuclear magnetic resonance (NMR) allows recording of molecular diffusion paths (notably, the probability distribution of molecular displacements over typically micrometers, covered during an observation time of typically milliseconds) and has thus proven to serve as a most versatile means for the in-depth study of mass transfer in complex materials. This is particularly true with nanoporous host materials, where PFG NMR enabled the first direct measurement of intracrystalline diffusivities of guest molecules. Spatial resolution, i.e., the minimum diffusion path length experimentally observable, is limited by the time interval over which the pulsed field gradients may be applied. In “conventional” PFG NMR measurements, this time interval is determined by a characteristic quantity of the host-guest system under study, the so-called transverse nuclear magnetic relaxation time. This leads, notably when considering systems with low molecular mobilities, to severe restrictions in the applicability of PFG NMR. These restrictions may partially be released by performing PFG NMR measurements in combination with “magic-angle spinning” (MAS) of the NMR sample tube. The present review introduces the fundamentals of this technique and illustrates, via a number of recent cases, the gain in information thus attainable. Examples include diffusion measurements with nanoporous host-guest systems of low intrinsic mobility and selective diffusion measurement in multicomponent systems.

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38

Snelgrove, Matthew P., and Michaele J. Hardie. "Coordination polymers with embedded recognition sites: lessons from cyclotriveratrylene-type ligands." CrystEngComm 23, no. 23 (2021): 4087–102. http://dx.doi.org/10.1039/d1ce00471a.

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Coordination polymers with molecular recognition sites are assembled using cyclotriveratrylene ligands. Many show differential guest-spaces with host and lattice sites available, however common host–guest and self-inclusion motifs can block sites.

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39

Kalchenko, Olga, Sergiy Cherenok, Sergiy Suikov, and Vitaly Kalchenko Vitaly Kalchenko. "Study of Calixarene Complexation with Biologically Active." French-Ukrainian Journal of Chemistry 5, no. 2 (2017): 49–55. http://dx.doi.org/10.17721/fujcv5i2p49-55.

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Host-Guest complexation of octakis(diphenoxyphosphoryloxy)tetramethylcalix[4]resorcinarene CRA and 5,17-bis-(N-tolyliminomethyl)-25,27-dipropoxycalix[4]arene CA with bio relevant aromatic, pyridine and diterpenoid carboxylic acids in water-organic solution had been studied by the RP HPLC and molecular modelling methods. The stability constants KA (387-1914 М-1) of the supramolecular complexes had been determined. It was shown the Host-Guest interactions are depended on structure of the Host molecules and log P values of the Guests. The complexation is determined by the hydrogen bonds of the COOH group of the carboxylic acids with P=O oxygen atom of diphenoxyphosphoryl group of the calixresorcinarene CRA, and oxygen or nitrogen atoms located on the lower or the upper rim of the calixarene CA.

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40

Khan, Sadaf Bashir, and Shern-Long Lee. "Supramolecular Chemistry: Host–Guest Molecular Complexes." Molecules 26, no. 13 (June 30, 2021): 3995. http://dx.doi.org/10.3390/molecules26133995.

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In recent times, researchers have emphasized practical approaches for capturing coordinated and selective guest entrap. The physisorbed nanoporous supramolecular complexes have been widely used to restrain various guest species on compact supporting surfaces. The host–guest (HG) interactions in two-dimensional (2D) permeable porous linkages are growing expeditiously due to their future applications in biocatalysis, separation technology, or nanoscale patterning. The different crystal-like nanoporous network has been acquired to enclose and trap guest molecules of various dimensions and contours. The host centers have been lumped together via noncovalent interactions (such as hydrogen bonds, van der Waals (vdW) interactions, or coordinate bonds). In this review article, we enlighten and elucidate recent progress in HG chemistry, explored via scanning tunneling microscopy (STM). We summarize the synthesis, design, and characterization of typical HG structural design examined on various substrates, under ambient surroundings at the liquid-solid (LS) interface, or during ultrahigh vacuum (UHV). We emphasize isoreticular complexes, vibrant HG coordination, or hosts functional cavities responsive to the applied stimulus. Finally, we critically discuss the significant challenges in advancing this developing electrochemical field.

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41

Yoshida, Jun, Shuhei Tamura, Hidetaka Yuge, and Go Watanabe. "Left- and right-circularly polarized light-sensing based on colored and mechano-responsive chiral nematic liquid crystals." Soft Matter 14, no. 1 (2018): 27–30. http://dx.doi.org/10.1039/c7sm01975k.

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A liquid crystal host–guest system composed of achiral organic molecules (host) and colored chiral metal complexes (guest) was fabricated to sense both right- and left-handed circularly polarized light (r- and l-CPL), depending on the guest (dopant) concentration.

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42

Sheng, Xinru, Errui Li, and Feihe Huang. "Construction of pillar[4]arene[1]quinone–1,10-dibromodecane pseudorotaxanes in solution and in the solid state." Beilstein Journal of Organic Chemistry 16 (December 2, 2020): 2954–59. http://dx.doi.org/10.3762/bjoc.16.245.

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We report novel pseudorotaxanes based on the complexation between pillar[4]arene[1]quinone and 1,10-dibromodecane. The complexation is found to have a 1:1 host–guest complexation stoichiometry in chloroform but a 2:1 host–guest complexation stoichiometry in the solid state. From single crystal X-ray diffraction, the linear guest molecules thread into cyclic pillar[4]arene[1]quinone host molecules in the solid state, stabilized by CH∙∙∙π interactions and hydrogen bonds. The bromine atoms at the periphery of the guest molecule provide convenience for the further capping of the pseudorotaxanes to construct rotaxanes.

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43

Chong, Samantha, Tom Hasell, Jamie Culshaw, Marc Little, Marc Schmidtmann, Daniel Holden, Linjiang Chen, Kim Jelfs, and Andrew Cooper. "Exploiting weak supramolecular interactions to assemble organic cage materials." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C632. http://dx.doi.org/10.1107/s205327331409367x.

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Intensive research into microporous materials has been driven by potential applications in areas such as catalysis, gas separation, storage, and sensing. Recently, a new class of purely organic molecular cage materials has emerged, which can exhibit significant porosity arising from the internal molecular cavity as well as extrinsic porosity from packing in the crystal structure [1]. Unlike extended frameworks, porous molecular materials lack strongly directional interactions to drive their assembly, complicating the crystal engineering possible for isoreticular metal-organic frameworks [2], for example. Our work has focused on covalent imine-linked cages, which exhibit diverse crystal chemistry. The connectivity of the pore network is derived from the cage packing: Therefore, the crystal structure directly affects the observed porosity. The imine cages synthesised so far lack strongly hydrogen bonding groups. Thus, the solid state supramolecular assembly of cage molecules is governed by the aggregate of weak interactions, such as van der Waals forces. By identifying robust `tectons', that is, regularly occurring supramolecular motifs, progress toward designing the crystal structure and therefore controlling the physical properties of organic cage materials becomes possible. Here, we report exploiting robust supramolecular motifs, comprising either cage modules or host and guest molecules to gain control over the porosity of the bulk material. We demonstrate how formation of a desired void network topology can be driven by hosting a specific guest in preferred sites which maximise weak host-guest interactions [3]. Subsequent guest removal can produce stable polymorphs, one of which exhibited double the Brunauer-Emmett-Teller surface area with respect to the originally observed polymorph. We also examine how the interaction between gas phase guests and cage host is important in the application of porous organic cages in rare gas separation.

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44

Kircheva, Nikoleta, Vladislava Petkova, Stefan Dobrev, Valya Nikolova, Silvia Angelova, and Todor Dudev. "N-Methyl- and N-Phenylpiperazine Functionalized Styryl Dyes Inside Cucurbiturils: Theoretical Assessment of the Factors Governing the Host–Guest Recognition." Molecules 28, no. 24 (December 16, 2023): 8130. http://dx.doi.org/10.3390/molecules28248130.

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The family of cucurbiturils (CBs), the unique pumpkin-shaped macrocycles, has received great attention over the past four decades owing to their remarkable recognition properties. They have found diverse applications including biosensing and drug delivery technologies. The cucurbituril complexation of guest molecules can modulate their pKas, improve their solubility in aqueous solution, and reduce the adverse effects of the drugs, as well as enhance the stability and/or enable targeted delivery of the drug molecule. Employing twelve cationic styryl dyes with N-methyl- and N-phenylpiperazine functionality as probes, we attempted to understand the factors that govern the host–guest complexation of such molecules within CB[7] and CB[8] host systems. Various key factors determining the process were recognized, such as the pH and dielectric constant of the medium, the cavity size of the host, the chemical characteristics of the substituents in the guest entity, and the presence/absence of metal cations. The presented results add to our understanding (at the molecular level) of the mechanism of encapsulation of styryl dyes by cucurbiturils, thus shedding new light on various aspects of the intriguing complexation chemistry and the underlying recognition processes.

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Souza, Barbara E., and Jin-Chong Tan. "Mechanochemical approaches towards the in situ confinement of 5-FU anti-cancer drug within MIL-100 (Fe) metal–organic framework." CrystEngComm 22, no. 27 (2020): 4526–30. http://dx.doi.org/10.1039/d0ce00638f.

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46

Ling, Xing Yi, David N. Reinhoudt, and Jurriaan Huskens. "From supramolecular chemistry to nanotechnology: Assembly of 3D nanostructures." Pure and Applied Chemistry 81, no. 12 (November 3, 2009): 2225–33. http://dx.doi.org/10.1351/pac-con-09-07-04.

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Fabricating well-defined and stable nanoparticle crystals in a controlled fashion receives growing attention in nanotechnology. The order and packing symmetry within a nanoparticle crystal is of utmost importance for the development of materials with unique optical and electronic properties. To generate stable and ordered 3D nanoparticle structures, nanotechnology is combined with supramolecular chemistry to control the self-assembly of 2D and 3D receptor-functionalized nanoparticles. This review focuses on the use of molecular recognition chemistry to establish stable, ordered, and functional nanoparticle structures. The host–guest complexation of β-cyclodextrin (CD) and its guest molecules (e.g., adamantane and ferrocene) are applied to assist the nanoparticle assembly. Direct adsorption of supramolecular guest- and host-functionalized nanoparticles onto (patterned) CD self-assembled monolayers (SAMs) occurs via multivalent host–guest interactions and layer-by-layer (LbL) assembly. The reversibility and fine-tuning of the nanoparticle-surface binding strength in this supramolecular assembly scheme are the control parameters in the process. Furthermore, the supramolecular nanoparticle assembly has been integrated with top-down nanofabrication schemes to generate stable and ordered 3D nanoparticle structures, with controlled geometries and sizes, on surfaces, other interfaces, and as free-standing structures.

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Facey, Glenn A., and Ilia Korobkov. "Investigation of the disorder of dibromo- and dichloromethane in their tri-ortho-thymotide clathrates using X-ray diffraction and solid-state 2H NMR spectroscopy." Canadian Journal of Chemistry 89, no. 7 (July 2011): 854–62. http://dx.doi.org/10.1139/v10-178.

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The tri-ortho-thymotide (TOT) clathrates of dibromo- and dichloromethane were characterized by single crystal X-ray diffraction at 200 K and solid-state 2H NMR spectroscopy as a function of temperature. The host structure was found to be typical of other cage-type TOT clathrates. The X-ray results showed a substantial amount of disorder among the guest molecules. In both clathrates, multiple guest molecule positions could be modeled. The heavy atoms of all the guest molecule positions lie approximately in the same plane, with some out-of-plane distortion. The guest molecules were of two different types in positions symmetric about the crystallographic twofold rotation axis: type A guests, with carbon atoms well removed from the crystallographic twofold axis, and type B guests, with carbon atoms very close to the twofold axis. The 2H NMR spectra for the guests confirmed that the disorder was dynamic. The experimental results could be accounted for by the presence of three simultaneous types of molecular motion, all fast with respect to the 2H quadrupolar interaction: (i) twofold molecular flips about the molecular C2 symmetry axis, (ii) exchange between the type A and type B sites in a single plane, and (iii) a two-site libration of the plane containing the heavy atoms of the A and B guest sites with a temperature-dependent amplitude.

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Wu, Jinyang, Xuan Sun, Xianghui Li, Xiaowei Li, Wen Feng, and Lihua Yuan. "Multi-Responsive Molecular Encapsulation and Release Based on Hydrogen-Bonded Azo-Macrocycle." Molecules 28, no. 11 (May 30, 2023): 4437. http://dx.doi.org/10.3390/molecules28114437.

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Research on stimuli-responsive host–guest systems is at the cutting edge of supramolecular chemistry, owing to their numerous potential applications such as catalysis, molecular machines, and drug delivery. Herein, we present a multi-responsive host–guest system comprising azo-macrocycle 1 and 4,4′-bipyridinium salt G1 for pH-, photo-, and cation- responsiveness. Previously, we reported a novel hydrogen-bonded azo-macrocycle 1. The size of this host can be controlled through light-induced E↔Z photo-isomerization of the constituent azo-benzenes. The host is found in this work to be capable of forming stable complexes with bipyridinium/pyridinium salts, and implementing guest capture and release with G1 under light in a controlled manner. The binding and release of the guest in the complexes can also be easily controlled reversibly by using acid and base. Moreover, the cation competition-induced dissociation of the complex 1a2⊃G1 is achieved. These findings are expected to be useful in regulating encapsulation for sophisticated supramolecular systems.

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Mustafa, Siti Fatimah Zaharah, Hasmerya Maarof, Mohammed Abu Naser, Hassan H. Abdallah, Ahmad Irfan, and Rashid Ahmed. "Behavioral pattern exploration of single guest, hexadecane-1,16-diol and hexadecane in urea inclusion compounds via molecular dynamics simulation." Journal of Theoretical and Computational Chemistry 15, no. 06 (September 2016): 1650047. http://dx.doi.org/10.1142/s0219633616500474.

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The urea inclusion compounds, a unique polar organic crystalline complex, are considered as a potential candidate for a molecular separator of long chain alkane molecule. A well-defined structure of the crystalline channel systems constructed from hydrogen bonding arrangement of the urea molecules, can be used to understand the fundamental aspects of the processes involving ions or molecules transportation. To do so, in our work, molecular dynamics approach is implemented to understand the behavioral pattern of the hexadecane-1,16-diol and hexadecane guests’ related to translational and rotational orientation along the urea tunnel. Our obtained results reveal that high interaction of hexadecane-1,16-diol with urea host molecules offers a restricted environment inside urea tunnel, resulting in slowing down the guest movement. Hexadecane guest system, on the contrary, exhibits lower interaction whereby the translational and rotational movement is faster. Moreover, as the distance increases (along [Formula: see text]-axis) in the urea tunnel, both guest systems favor a clockwise rotational orientation. Preference of the respected orientation indicates the influence of chiral urea tunnel on achiral guests that is clathrate inside the tunnel structure.

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50

Mujahid, Adnan, Adeel Afzal, and Franz L. Dickert. "Transitioning from Supramolecular Chemistry to Molecularly Imprinted Polymers in Chemical Sensing." Sensors 23, no. 17 (August 27, 2023): 7457. http://dx.doi.org/10.3390/s23177457.

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Abstract:

This perspective article focuses on the overwhelming significance of molecular recognition in biological processes and its emulation in synthetic molecules and polymers for chemical sensing. The historical journey, from early investigations into enzyme catalysis and antibody–antigen interactions to Nobel Prize-winning breakthroughs in supramolecular chemistry, emphasizes the development of tailored molecular recognition materials. The discovery of supramolecular chemistry and molecular imprinting, as a versatile method for mimicking biological recognition, is discussed. The ability of supramolecular structures to develop selective host–guest interactions and the flexible design of molecularly imprinted polymers (MIPs) are highlighted, discussing their applications in chemical sensing. MIPs, mimicking the selectivity of natural receptors, offer advantages like rapid synthesis and cost-effectiveness. Finally, addressing major challenges in the field, this article summarizes the advancement of molecular recognition-based systems for chemical sensing and their transformative potential.

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Journal articles on the topic 'Host-Guest moleculars'

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