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Journal articles on the topic 'Weakly Bound Molecules/Complexes'

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Author: Grafiati

Published: 7 September 2023

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1

Dimowa, Louiza, Nadia Petrova, Yana Tzvetanova, Ognyan Petrov, and Iskra Piroeva. "Structural Features and Thermal Behavior of Ion-Exchanged Clinoptilolite from Beli Plast Deposit (Bulgaria)." Minerals 12, no. 12 (December 8, 2022): 1576. http://dx.doi.org/10.3390/min12121576.

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The structural features and the thermal behavior of natural, Na-, Ca-, K-, Mg-, and Cd-exchanged clinoptilolite from the Beli Plast deposit (Bulgaria) were studied. Purified clinoptilolite sample was preliminary prepared and ion-exchanged at 100 °C for six days. DSC-TG analyses were performed for all studied forms. The effects in the DSC curves show differences with temperature due to release of weakly bound H2O molecules and strongly bound ones. The endotherm minima temperatures were between 78 and 115 °C decreasing in the sequence K- < Na- < Natural- < Ca- ≤ Mg- < Cd-clinoptilolite. The hydrate complexes around the exchanged cations also influenced the DSC curves. The cation-coordinating H2O molecules and the non-coordinating ones were determined by XRD structural refinement for all exchanged samples. The H2O molecules of the cation–hydrate complexes are released at higher temperatures than weakly bound ones and affected the DSC curves differently. The structural adjustments made by the Rietveld method, as well as the applied EDS analyzes for the chemical composition of the samples, allowed us to correlate these data to the thermal characteristics of the studied clinoptilolite samples.

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2

Shaw, Robert A., and J. Grant Hill. "Midbond basis functions for weakly bound complexes." Molecular Physics 116, no. 11 (February 26, 2018): 1460–70. http://dx.doi.org/10.1080/00268976.2018.1440018.

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3

Kraevsky, Sergey V., Nikolay A. Barinov, Olga V. Morozova, Vladimir V. Palyulin, Alena V. Kremleva, and Dmitry V. Klinov. "Features of DNA–Montmorillonite Binding Visualized by Atomic Force Microscopy." International Journal of Molecular Sciences 24, no. 12 (June 6, 2023): 9827. http://dx.doi.org/10.3390/ijms24129827.

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In the present work, complexes of DNA with nano-clay montmorillonite (Mt) were investigated by means of atomic force microscopy (AFM) under various conditions. In contrast to the integral methods of analysis of the sorption of DNA on clay, AFM allowed us to study this process at the molecular level in detail. DNA molecules in the deionized water were shown to form a 2D fiber network weakly bound to both Mt and mica. The binding sites are mostly along Mt edges. The addition of Mg2+ cations led to the separation of DNA fibers into separate molecules, which bound mainly to the edge joints of the Mt particles according to our reactivity estimations. After the incubation of DNA with Mg2+, the DNA fibers were capable of wrapping around the Mt particles and were weakly bound to the Mt edge surfaces. The reversible sorption of nucleic acids onto the Mt surface allows it to be used for both RNA and DNA isolation for further reverse transcription and polymerase chain reaction (PCR). Our results show that the strongest binding sites for DNA are the edge joints of Mt particles.

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4

Nesbitt, David J. "High-resolution infrared spectroscopy of weakly bound molecular complexes." Chemical Reviews 88, no. 6 (September 1988): 843–70. http://dx.doi.org/10.1021/cr00088a003.

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5

Emery, Luke C., and W. Daniel Edwards. "Intermolecular dynamics for weakly bound donor-acceptor complexes." International Journal of Quantum Chemistry 40, S25 (1991): 347–58. http://dx.doi.org/10.1002/qua.560400834.

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6

Varadwaj, Pradeep R. "Does Oxygen Feature Chalcogen Bonding?" Molecules 24, no. 17 (August 30, 2019): 3166. http://dx.doi.org/10.3390/molecules24173166.

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Using the second-order Møller–Plesset perturbation theory (MP2), together with Dunning’s all-electron correlation consistent basis set aug-cc-pVTZ, we show that the covalently bound oxygen atom present in a series of 21 prototypical monomer molecules examined does conceive a positive (or a negative) σ-hole. A σ-hole, in general, is an electron density-deficient region on a bound atom M along the outer extension of the R–M covalent bond, where R is the reminder part of the molecule, and M is the main group atom covalently bonded to R. We have also examined some exemplar 1:1 binary complexes that are formed between five randomly chosen monomers of the above series and the nitrogen- and oxygen-containing Lewis bases in N2, PN, NH3, and OH2. We show that the O-centered positive σ-hole in the selected monomers has the ability to form the chalcogen bonding interaction, and this is when the σ-hole on O is placed in the close proximity of the negative site in the partner molecule. Although the interaction energy and the various other 12 characteristics revealed from this study indicate the presence of any weakly bound interaction between the monomers in the six complexes, our result is strongly inconsistent with the general view that oxygen does not form a chalcogen-bonded interaction.

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7

Ritschel, Thomas, Lutz Zülicke, and Philip J. Kuntz. "Cationic Van-der-Waals Complexes: Theoretical Study of Ar2H+ Structure and Stability." Zeitschrift für Physikalische Chemie 218, no. 4 (April 1, 2004): 377–90. http://dx.doi.org/10.1524/zpch.218.4.377.29196.

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AbstractThe electronic and geometric structure, stability and molecular properties of the cationic van-der-Waals complex Ar2H+ in its ground electronic state are studied by means of two ab-initio quantum-chemical approaches: conventional configuration interaction (multi-reference and coupled-cluster methods) and a diatomics-in-molecules model with ab-initio input data. To ensure consistency between the two approaches, one and the same one-electron atomic basis set (aug-cc-pVTZ by Dunning) is employed in both. The topography of the ground-state potential-energy surface is examined with respect to the nature of the binding and the stability of structures corresponding to stationary points. In accordance with most earlier theoretical work, there are two local minima at linear arrangements: a strongly bound centro-symmetric moiety, (Ar–H–Ar)+, and a weakly bound van-der-Waals complex, Ar···ArH+. These are separated by a low barrier. Only the centro-symmetric molecule is significantly stable (De = 0.68eV) against fragmentation into Ar + ArH+ and should have structural and dynamical relevance. A fairly simple diatomics-in-molecules model taking into account only the few lowest electronic fragment states yields a qualitatively correct description of the ground state but shows quantitative deviations from the more accurate configuration-interaction data in detail. Nevertheless, it should provide a good starting point for the treatment of larger complexes ArnH+ with n > 2.

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8

Desfrancois, C., H. Abdoul-Carime, C. P. Schulz, and J. P. Schermann. "Laser Separation of Geometrical Isomers of Weakly Bound Molecular Complexes." Science 269, no. 5231 (September 22, 1995): 1707–9. http://dx.doi.org/10.1126/science.269.5231.1707.

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9

Gianturco, F. A., G. Delgado-Barrio, O. Roncero, and P. Villarreal. "Dynamical coupling and energy transfer in weakly bound molecular complexes." International Reviews in Physical Chemistry 7, no. 1 (January 1988): 1–17. http://dx.doi.org/10.1080/01442358809353203.

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10

Krupa, Justyna, Maria Wierzejewska, and Jan Lundell. "Matrix Isolation FTIR and Theoretical Study of Weakly Bound Complexes of Isocyanic Acid with Nitrogen." Molecules 27, no. 2 (January 13, 2022): 495. http://dx.doi.org/10.3390/molecules27020495.

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Weak complexes of isocyanic acid (HNCO) with nitrogen were studied computationally employing MP2, B2PLYPD3 and B3LYPD3 methods and experimentally by FTIR matrix isolation technique. The results show that HNCO interacts specifically with N2. For the 1:1 stoichiometry, three stable minima were located on the potential energy surface. The most stable of them involves a weak, almost linear hydrogen bond from the NH group of the acid molecule to nitrogen molecule lone pair. Two other structures are bound by van der Waals interactions of N⋯N and C⋯N types. The 1:2 and 2:1 HNCO complexes with nitrogen were computationally tracked as well. Similar types of interactions as in the 1:1 complexes were found in the case of the higher stoichiometry complexes. Analysis of the HNCO/N2/Ar spectra after deposition indicates that the 1:1 hydrogen-bonded complex is prevalent in argon matrices with a small amount of the van der Waals structures also present. Upon annealing, complexes of the 1:2 and 2:1 stoichiometry were detected as well.

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11

Jimenez-Fabian, Issac, Abraham Jalbout, and Abderahim Boutalib. "Conformational study on the structures and energies of the weakly bound complexes of AlCl3 with diatomic molecules." Open Chemistry 5, no. 4 (December 1, 2007): 1007–18. http://dx.doi.org/10.2478/s11532-007-0046-4.

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AbstractIn this work we present the results of high level ab initio calculations on weakly bound complexes of aluminium trichloride and hydrogen halides, HX, halogens, X2 and diatomic interhalogens, XY (where X, Y = F, Cl, Br). Based upon these calculations we have predicted that all structures in the staggered conformation (except for Cl3AlFH and Cl3AlClH) are stable minima while those in the eclipsed configurations are transition state structures. In the XH complexes the strength of interaction with the Cl3Al group is FH > ClH > BrH. In the case of X2 species it is Br2 > F2 > Cl2, and finally in the XY (YX) group it is: FBr > ClBr > FCl > BrCl > BrF > ClF.

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12

Stevenson, K. P., J. D. Close, P. L. Muiño, and R. O. Watts. "Potential Energy Surfaces for Unsaturated Hydrocarbons from Crossed Molecular Beams." Australian Journal of Physics 50, no. 3 (1997): 683. http://dx.doi.org/10.1071/p96079.

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The total differential scattering cross sections for several important unsaturated hydrocarbon molecules with common atmospheric gases were measured in a crossed molecular beam apparatus. The experiments show quantum interferences which relate to potential energy surface parameters, such as the well depth and radial minimum. The damping of the quantum features, over contributions from experimental resolutions, provides information on the angular and radial anisotropies present in the potential energy surfaces. We have investigated two areas: (1) the role of the probe partner in determining the interaction strength for a given hydrocarbon target, and (2) the effect of increasing the overall length of the hydrocarbon molecule for a fixed probe. By comparing results for a class of scattering systems, we can identify chemical and physical trends that determine the van der Waals potential energy surfaces of larger molecules. We expect these results to aid in the prediction and interpretation of complementary experimental measurements on the high resolution infrared spectroscopy of weakly bound complexes.

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13

Briggs, Edward A., and Nicholas A. Besley. "Modelling excited states of weakly bound complexes with density functional theory." Phys. Chem. Chem. Phys. 16, no. 28 (2014): 14455–62. http://dx.doi.org/10.1039/c3cp55361b.

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14

Aminev, Timur, Irina Krauklis, Oleg Pestsov, and Alexey Tsyganenko. "Ozone Activation on TiO2 Studied by IR Spectroscopy and Quantum Chemistry." Applied Sciences 11, no. 16 (August 20, 2021): 7683. http://dx.doi.org/10.3390/app11167683.

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The adsorption of different isotopic ozone mixtures on TiO2 at 77K was studied using FTIR spectroscopy and DFT calculations of cluster models. In addition to weakly bound ozone with band positions close to those of free or dissolved molecules, the spectrum of chemisorbed species was observed. The splitting of the ν1+3 combination band to eight maxima due to different isotopomers testified to the loss of molecule symmetry. The frequencies of all the isotopic modifications of the ozone molecules which form monodentate or bidentate complexes with four- or five-coordinated titanium atoms were calculated and compared with those of experimentally observed spectra. The four considered complexes adequately reproduced the splitting of the ν1+3 vibration band and the lowered anharmonism of chemisorbed O3. The energetically most favorable monodentate complex with four-coordinated titanium atoms showed good agreement with the observed spectra, although a large difference between the frequencies of ν1 and ν3 modes was found. For better coherence with the experiment, the interaction of the molecule with adjacent cations must be considered.

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15

Zhou, Tian, Santanu Malakar, Steven L. Webb, Karsten Krogh-Jespersen, and Alan S. Goldman. "Polar molecules catalyze CO insertion into metal-alkyl bonds through the displacement of an agostic C-H bond." Proceedings of the National Academy of Sciences 116, no. 9 (February 12, 2019): 3419–24. http://dx.doi.org/10.1073/pnas.1816339116.

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The insertion of CO into metal-alkyl bonds is the key C-C bond-forming step in many of the most important organic reactions catalyzed by transition metal complexes. Polar organic molecules (e.g., tetrahydrofuran) have long been known to promote CO insertion reactions, but the mechanism of their action has been the subject of unresolved speculation for over five decades. Comprehensive computational studies [density functional theory (DFT)] on the prototypical system Mn(CO)5(arylmethyl) reveal that the polar molecules do not promote the actual alkyl migration step. Instead, CO insertion (i.e. alkyl migration) occurs rapidly and reversibly to give an acyl complex with a sigma-bound (agostic) C-H bond that is not easily displaced by typical ligands (e.g. phosphines or CO). The agostic C-H bond is displaced much more readily, however, by the polar promoter molecules, even though such species bind only weakly to the metal center and are themselves then easily displaced; the facile kinetics of this process are attributable to a hydrogen bonding-like interaction between the agostic C-H bond and the polar promoter. The role of the promoter is to thereby catalyze isomerization of the agostic product of CO insertion to give an η2-C,O-bound acyl product that is more easily trapped than the agostic species. This ability of such promoters to displace a strongly sigma-bound C-H bond and to subsequently undergo facile displacement themselves is without reported precedent, and could have implications for catalytic reactions beyond carbonylation.

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16

Surin, L. A. "Millimeter-Wave Spectroscopy of Weakly Bound Molecular Complexes and Small Clusters." EPJ Web of Conferences 195 (2018): 06019. http://dx.doi.org/10.1051/epjconf/201819506019.

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17

Kwang-Hua, Chu Rainer. "Formation of weakly bound molecular complexes: ( $$^3$$ 3 He) $$_2$$ 2." Journal of Mathematical Chemistry 54, no. 1 (August 25, 2015): 100–108. http://dx.doi.org/10.1007/s10910-015-0551-1.

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18

Akulin, V. M., V. Aquilanti, B. Brunetti, and F. Vecchiocattivi. "Subthreshold Ionization of Weakly Bound Complexes: Stochastic Analysis of the Role of the Rydberg Quasicontinuum." Laser Chemistry 11, no. 3-4 (January 1, 1991): 191–98. http://dx.doi.org/10.1155/lc.11.191.

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Recent evidence for subthreshold ionization (i.e. electron loss at energies less than anticipated from vertical transitions assuming adiabatic separation of nuclear motion) points at the role of nonadiabatic coupling of high Rydberg terms of molecules. Sinai's billiard model for the chaotic motion of the Rydberg electron, that leads to a diffusion over the energy ladder as a result of electronic–vibrational exchange, is suggested as the classical mechanism of autoionization. A quantum expression for the branching ratio between autoionization and spontaneous fluorescence is obtained and discussed with reference to experimental results on associative ionization in atomic collisions and on laser ionization of van der Waals diatomics.

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19

Robl, Christian. "Komplexe mit aromatischen Carbonsäuren, IV. Ca2[C6H2(COO)4]·6H2O - Eine neue Schichtstruktur/ Complexes with Aromatic Carboxylic Acids, IV. Ca2[C6H2(COO)4]·6H2O - A Novel Layer Structure." Zeitschrift für Naturforschung B 43, no. 8 (August 1, 1988): 993–97. http://dx.doi.org/10.1515/znb-1988-0813.

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AbstractSingle crystals of Ca2[C6H2(COO)4]·6H2O were grown in aqueous silica gel. Ca2+ has CN 6+2. The coordination polyhedron is formed by three water molecules and five oxygen atoms of carboxylate groups. Six oxygen atoms are closely bound (235,9-243,9 pm), the two remaining coordination partners are considerably more remote from Ca2+ (268,2 and 273,8 pm). COO- groups chelate Ca2+ in an asymmetric manner, but the C -O bond lengths do not differ markedly (125,2-126,3 pm). The connection of Ca2+ with [C6H2(COO)4]4- leads to rigid layers. Adjacent layers are interlinked by hydrogen bonds. Those oxygen atoms which are weakly bound to Ca2+ are favoured as proton acceptors in hydrogen bonds. The COO groups are tilted differently against the C6-ring plane. One is approximately coplanar, but the other is oriented almost perpendicularly.

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20

Bruce, Michael I. "Some Organometallic Chemistry of Tetracyanoethene: CN-displacement and Cycloaddition Reactions with Alkynyl - Transition Metal Complexes and Related Chemistry." Australian Journal of Chemistry 64, no. 1 (2011): 77. http://dx.doi.org/10.1071/ch10307.

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The highly electron-deficient cyanocarbons tetracyanoethene (tcne) and, to a lesser extent, tetracyanoquinodimethane (tcnq), display a fascinating chemistry with transition metal substrates. In particular, the [2 + 2]-cycloadditions of the cyanocarbons with alkynyl- or poly-ynyl–metal complexes have been extensively studied by the author’s group. These reactions proceed via polar adducts to give σ-cyclobutenyl complexes, which then undergo facile ring-opening (retro-electrocyclic) reactions to form the corresponding butadienyl derivatives. In some cases, further reactions can occur by displacement of weakly bound ligands from the metal centre. The subsequent chemistry of these derivatives has been only cursorily investigated, while related studies of organic analogues have produced molecules with interesting electronic and optical properties.

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21

Felker, Peter M., Patrick M. Maxton, and Mark W. Schaeffer. "Nonlinear Raman Studies of Weakly Bound Complexes and Clusters in Molecular Beams." Chemical Reviews 94, no. 7 (November 1994): 1787–805. http://dx.doi.org/10.1021/cr00031a003.

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22

Potapov, A. V., L. A. Surin, V. A. Panfilov, and B. S. Dumesh. "Millimeter-wave spectroscopy of weakly bound molecular complexes: Isotopologues of He-CO." Optics and Spectroscopy 106, no. 2 (February 2009): 183–89. http://dx.doi.org/10.1134/s0030400x09020064.

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23

Jimenez-Fabian, Isaac, Abraham Jalbout, and Abderahim Boutalib. "Conformational study on the structures and energies of the weakly bound complexes of AlCl3 with diatomic molecules." Open Chemistry 6, no. 1 (March 1, 2008): 133. http://dx.doi.org/10.2478/s11532-007-0057-1.

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24

Cwiok, Tatiana, Bogumil Jeziorski, Wlodzimierz Kolos, Robert Moszynski, and Krzysztof Szalewicz. "Symmetry-adapted perturbation theory of potential-energy surfaces for weakly bound molecular complexes." Journal of Molecular Structure: THEOCHEM 307 (April 1994): 135–51. http://dx.doi.org/10.1016/0166-1280(94)80124-x.

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25

Gotch, Albert J., R. Nathan Pribble, Frederick A. Ensminger, and Timothy S. Zwier. "The Spectroscopy and Photophysics of π Hydrogen-Bonded Complexes: Benzene–CHCl3." Laser Chemistry 13, no. 3-4 (January 1, 1994): 187–205. http://dx.doi.org/10.1155/1994/41604.

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A vibronic level study of the spectroscopy and photophysics of the C6H6–CHCl3 complex has been carried out using a combination of laser-induced fluorescence and resonant two-photon ionization (R2PI). In C6H6-CHCl3, the S1–S0 origin remains forbidden while the 1610 transition is weakly induced. Neither 610 nor 1610 are split by the presence of the CHCl3 molecule. On this basis, a C3vstructure is deduced for the complex, placing CHCl3 on the six-fold axis of benzene. The large blue-shift of the complex’s absorption relative to benzene (+178 cm–1) and the efficient fragmentation of the complex following one-color R2PI reflect a hydrogen-bonded orientation for CHCl3 relative to benzene’ π cloud. Dispersed fluorescence scans place a firm upper bound on the ground state binding energy of the complex of 2,024 cm–1. Both the 61and 61 11 levels do not dissociate on the time-scale of the S1 fluorescence and show evidence of extensive state mixing with van der Waals’ levels primarily built on the 00 level of benzene. The C6H6–(CHCl3)2 cluster shows extensive intermolecular structure beginning at +84 cm–1, a strong origin transition, and splitting of 61. A structure which places both CHCl3 molecules on the same side of the benzene ring is suggested on this basis. The vibronic level scheme used to deduce the structure of C6H6–CHCl3 is tested against previous data on other C6H6–X complexes. The scheme is found to be capable, in favorable cases, of deducing the structures of C6H6–X complexes based purely on vibronic level data. Finally, the results on C6H6–CHCl3 are compared with those on C6H6–HCl and C6H6-H2O to evaluate the characteristics of the n hydrogen bond.

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26

Jenne, Carsten, and Valentin van Lessen. "Na+[Me3NB12Cl11]−·SO2: a rare example of a sodium–SO2 complex." Acta Crystallographica Section E Crystallographic Communications 75, no. 5 (April 9, 2019): 607–10. http://dx.doi.org/10.1107/s2056989019004663.

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In the title compound, Na+[Me3NB12Cl11]−·SO2 [systematic name: sodium 1-(trimethylammonio)undecachloro-closo-dodecaborate sulfur dioxide], the SO2 molecule is η 1-O-coordinated to the Na+ cation. Surprisingly, the SO2 molecule is more weakly bound to sodium than is found in other sodium–SO2 complexes and the SO2 molecule is essentially undistorted compared to the structure of free SO2. The Na+ cation has a coordination number of eight in a distorted twofold-capped trigonal prism and makes contacts to three individual boron cluster anions, resulting in an overall three-dimensional network. Although the number of known η 1-O-coordinated SO2 complexes is growing, sodium-SO2 complexes are still rare.

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27

Wallis, Alisdair O. G., and Roman V. Krems. "Rotational predissociation of extremely weakly bound atom-molecule complexes produced by Feshbach resonance association." Journal of Chemical Physics 135, no. 12 (September 28, 2011): 124313. http://dx.doi.org/10.1063/1.3641643.

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28

Walters, Richard S., and Michael A. Duncan. "Infrared Spectroscopy of Solvation and Isomers in Fe+(H2O)1,2Arm Complexes." Australian Journal of Chemistry 57, no. 12 (2004): 1145. http://dx.doi.org/10.1071/ch04118.

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Vibrational spectroscopy in the OH-stretching region is reported for the mass-selected ion–molecule complexes Fe+(H2O)Ar2 and Fe+(H2O)2Ar. These species are produced by laser vaporization in a pulsed nozzle cluster source, mass-selected with a reflectron time-of-flight mass spectrometer, and studied with infrared laser photodissociation spectroscopy. To achieve efficient photodissociation, the pure metal–water complexes are ‘tagged’ with weakly bound argon atoms. Such tagging is expected to exert a minor perturbation on the spectroscopy. However, we find that this may not be true depending on the binding site. The symmetric stretch and asymmetric stretch of water in these complexes shifts 30–50 cm−1 to the red as a result of binding to the metal cation, and an additional redshift is found for isomers with argon bound to the OH of water. The relationships between isomers and infrared spectra are discussed.

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29

Pirani, F., P. Candori, M. S. Pedrosa Mundim, L. Belpassi, F. Tarantelli, and D. Cappelletti. "On the role of charge transfer in the stabilization of weakly bound complexes involving water and hydrogen sulphide molecules." Chemical Physics 398 (April 2012): 176–85. http://dx.doi.org/10.1016/j.chemphys.2011.03.030.

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30

Kutsevol, N., Yu Kuziv, V. Zorin, I. Kravchenko, T. Zorina, A. Marynin, and L. Bulavin. "Evaluation of a Dextran-Poly(N-Isopropylacrylamide) Copolymer as a Potential Temperature-Dependent Nanocarrier for Photosensitizers with Different Properties." Ukrainian Journal of Physics 65, no. 7 (July 15, 2020): 638. http://dx.doi.org/10.15407/ujpe65.7.638.

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Thermosensitive polymer poly-N-isopropylacrylamide (PNIPAM) having a conformational transition in the interval of physiological temperatures was discussed last years as a novel drug delivery system. Chlorin e6 (Ce6) is a photosensitizer used in the photodynamic anticancer therapy. The comparative study of the encapsulation of Ce6 and its derivative, dimethylether of chlorine e6 (DME Ce6), into a water-soluble star-like PNIPAM-based copolymer to prevent the aggregation of a photosensitizer in the water medium is carried out. The photophysical properties of the copolymer/photosensitizer complexes as functions of the temperature in the region of the conformational transition of the polymer matrix have been studied and discussed. It is shown that Ce6 at low temperatures interacts weakly with the polymer phase. As a result, the absorption and fluorescence properties of Ce6 in aqueous and polymer solutions are practically identical. Fluorescence characteristics of Ce6 in a copolymer solution remain unchanged, when it is heated, which indicates the lack of a possibility for this sensitizer to bind in the bulk of the polymer phase. Following fluorescence data, all DME Ce6 molecules are bound with the polymer matrix, when a temperature is higher than the Lower Critical Solution Temperature (LCST) of the polymer. The formed complexes are quite stable. In the presence of serum proteins, the molecules of the photosensitizer remain associated for a long time with the polymer. At temperatures below LCST, DME Ce6 is not bound by the polymer. Moreover, the cooling of a solution of DME Ce6/polymer complexes leads to the rapid dissociation of photosensitizer molecules with subsequent aggregation or binding to biological structures in an aqueous medium. The obtained results show that the possibility of using the polymer PNIPAM as a temperature-dependent nanocarrier strongly depends on the properties of the loaded drug.

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31

Aoyagi, Youko, Elisabeth E. Adderson, Craig E. Rubens, John F. Bohnsack, Jin G. Min, Misao Matsushita, Teizo Fujita, Yoshiyuki Okuwaki, and Shinji Takahashi. "L-Ficolin/Mannose-Binding Lectin-Associated Serine Protease Complexes Bind to Group B Streptococci Primarily through N-Acetylneuraminic Acid of Capsular Polysaccharide and Activate the Complement Pathway." Infection and Immunity 76, no. 1 (October 15, 2007): 179–88. http://dx.doi.org/10.1128/iai.00837-07.

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ABSTRACT Group B streptococci (GBS) are the most common cause of neonatal sepsis and meningitis. Most infants who are colonized with GBS at birth do not develop invasive disease, although many of these uninfected infants lack protective levels of capsular polysaccharide (CPS)-specific antibody. The lectin pathway of complement is a potential mechanism for initiating opsonization of GBS with CPS-specific antibody-deficient serum. In this study, we determined whether mannose-binding lectin (MBL)/MBL-associated serine protease (MASP) complexes and L-ficolin/MASP complexes bind to different strains of GBS to activate the lectin pathway, and we identified the molecules recognized by lectins on the GBS surface. We found that MBL did not bind to any GBS examined, whereas L-ficolin bound to GBS cells of many serotypes. L-ficolin binding to GBS cells correlated with the CPS content in serotypes Ib, III (restriction digestion pattern types III-2 and III-3), and V but not with the group B-specific polysaccharide (GBPS) content or with the lipoteichoic acid (LTA) content. L-ficolin bound to purified CPS and GBPS in a concentration-dependent manner but not to purified LTA. All strains to which L-ficolin/MASP complexes bound consumed C4. When N-acetylneuraminic acid (NeuNAc) was selectively removed from GBS cells by treatment with neuraminidase, the reduction in L-ficolin binding was correlated with the amount of NeuNAc removed. Additionally, L-ficolin was able to bind to wild-type strains but was able to bind only weakly to unencapsulated mutants and a mutant strain in which the CPS lacks NeuNAc. We concluded that L-ficolin/MASP complexes bind to GBS primarily through an interaction with NeuNAc of CPS.

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Palazzetti, Federico, Cecilia Coletti, Alessandro Marrone, and Fernando Pirani. "Potential Energy Surfaces for Noble Gas (Ar, Kr, Xe, Rn)–Propylene Oxide Systems: Analytical Formulation and Binding." Symmetry 14, no. 2 (January 27, 2022): 249. http://dx.doi.org/10.3390/sym14020249.

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Multidimensional potential energy surfaces for heavy noble gas–propylene oxide systems are obtained by applying the phenomenological method successfully used to describe homologous systems involving He and Ne atoms. Such potential energy surfaces, where the interaction exclusively arises from the anisotropic van der Waals interaction components, are given in an analytical form. Therefore, they can be easily used as force fields to carry out molecular simulations to evaluate spectroscopic features and the dynamical selectivity of weakly bound complexes formed by propylene oxide (a prototype chiral species) with a noble gas atom (a prototype isotropic partner) by two-body collisions under a variety of conditions. Several potential energy minima are identified on the surfaces, which are confirmed and characterized by high level ab initio calculations. The next step to further generalize this methodology is its extension to systems involving propylene oxide-diatomic molecules (as H2, O2 and N2), as well as to propylene oxide dimers.

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33

Chetioui, Souheyla, Hassiba Bougueria, Ouarda Brihi, Mehdi Boutebdja, Nadia Bouroumane, Hocine Merazig, and Rachid Touzani. "Crystal structure, characterization and Hirshfeld analysis of bis{(E)-1-[(2,4,6-tribromophenyl)diazenyl]naphthalen-2-olato}copper(II) dimethyl sulfoxide monosolvate." Acta Crystallographica Section E Crystallographic Communications 76, no. 3 (February 18, 2020): 382–86. http://dx.doi.org/10.1107/s2056989020001863.

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In the title compound, [Cu(C16H8Br3N2O)2]·C2H6OS, the CuII atom is tetracoordinated in a square-planar coordination, being surrounded by two N atoms and two O atoms from two N,O-bidentate (E)-1-[(2,4,6-tribromophenyl)diazenyl]naphthalen-2-olate ligands. The two N atoms and two O atoms around the metal center are trans to each other, with an O—Cu—O bond angle of 177.90 (16)° and a N—Cu—N bond angle of 177.8 (2)°. The average distances between the CuII atom and the coordinated O and N atoms are 1.892 (4) and 1.976 (4) Å, respectively. In the crystal, complexes are linked by C—H...O hydrogen bonds and by π–π interactions involving adjacent naphthalene ring systems [centroid–centroid distance = 3.679 (4) Å]. The disordered DMSO molecules interact weakly with the complex molecules, being positioned in the voids left by the packing arrangement of the square-planar complexes. The DMSO solvent molecule is disordered over two positions with occupancies of 0.70 and 0.30.

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34

Kang, Cheolhwa, and David W. Pratt *. "Structures, charge distributions, and dynamical properties of weakly bound complexes of aromatic molecules in their ground and electronically excited states." International Reviews in Physical Chemistry 24, no. 1 (January 2005): 1–36. http://dx.doi.org/10.1080/01442350500161453.

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35

Fraser, G. T., F. J. Lovas, and R. D. Suenram. "On the Apparent Methyl Internal-Rotation Barrier Decrease in Weakly Bound Methanol Complexes." Journal of Molecular Spectroscopy 167, no. 1 (September 1994): 231–35. http://dx.doi.org/10.1006/jmsp.1994.1229.

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36

Seo, Hyun-Il, Ju-Yong Sun, Chang-Ho Shin, and Seung-Joon Kim. "Structure and dissociation energy of weakly bound H2n+1+ (n = 5−8) complexes." International Journal of Quantum Chemistry 107, no. 4 (2006): 988–97. http://dx.doi.org/10.1002/qua.21212.

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37

Potapov, Alexey. "Weakly bound molecular complexes in the laboratory and in the interstellar medium: A lost interest?" Molecular Astrophysics 6 (March 2017): 16–21. http://dx.doi.org/10.1016/j.molap.2017.01.001.

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38

Aquilanti, V., M. Bartolomei, D. Cappelletti, E. Carmona-Novillo, and F. Pirani. "Photodynamics of clusters of the major components of the atmosphere." International Journal of Photoenergy 6, no. 2 (2004): 53–59. http://dx.doi.org/10.1155/s1110662x0400008x.

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Weakly interacting molecules leading to collisional complexes, and to either stable or metastable dimers, potentially play an important role in molecular and surface physics, in astrophysics, in atmospheric photochemistry and physics, and climate. Accurate intermolecular potential energy surfaces for the major components of the atmosphere, leading to the characterization of theO2-O2,N2-N2andN2-O2dimers, have been obtained from the analysis of scattering experiments from our laboratory, also exploiting where available second virial coefficient data. A spherical harmonic expansion functional form describes the geometries of the dimers and accounts for the relative contributions to the intermolecular interaction from components of different nature. ForO2-O2, singlet, triplet and quintet surfaces are obtained accounting for the role of spin-spin coupling. The new surfaces allow the full characterization of structure and internal dynamics of the clusters, whose bound states and eigenfunctions are obtained by exact quantum mechanics. Besides the information on the nature of the bond, these results can be of use in modelling the role of dimers in air and the calculated rotovibrational levels provide a guidance for the analysis of spectra, thus establishing the ground for atmospheric monitorings. Reference is also briefly made to recent insight on the role of water.

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39

Schaletzky, Julia, and Tom A. Rapoport. "Ribosome Binding to and Dissociation from Translocation Sites of the Endoplasmic Reticulum Membrane." Molecular Biology of the Cell 17, no. 9 (September 2006): 3860–69. http://dx.doi.org/10.1091/mbc.e06-05-0439.

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We have addressed how ribosome-nascent chain complexes (RNCs), associated with the signal recognition particle (SRP), can be targeted to Sec61 translocation channels of the endoplasmic reticulum (ER) membrane when all binding sites are occupied by nontranslating ribosomes. These competing ribosomes are known to be bound with high affinity to tetramers of the Sec61 complex. We found that the membrane binding of RNC–SRP complexes does not require or cause the dissociation of prebound nontranslating ribosomes, a process that is extremely slow. SRP and its receptor target RNCs to a free population of Sec61 complex, which associates with nontranslating ribosomes only weakly and is conformationally different from the population of ribosome-bound Sec61 complex. Taking into account recent structural data, we propose a model in which SRP and its receptor target RNCs to a Sec61 subpopulation of monomeric or dimeric state. This could explain how RNC–SRP complexes can overcome the competition by nontranslating ribosomes.

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40

Ming, Qianqian, David Gonzalez-Perez, and Vincent C. Luca. "Molecular engineering strategies for visualizing low-affinity protein complexes." Experimental Biology and Medicine 244, no. 17 (June 11, 2019): 1559–67. http://dx.doi.org/10.1177/1535370219855401.

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The growing availability of complex structures in the Protein Data Bank has provided key insight into the molecular architecture of protein–protein interfaces. The remarkable diversity observed in protein binding modes is paralleled by a tremendous variation in binding affinities, with interaction half-lives ranging from days to milliseconds. Within the protein interactome, low-affinity binding events have been particularly difficult to visualize by traditional structural methods, which has spurred the development of innovative strategies for reconstituting these short-lived yet biologically essential assemblies. An important takeaway from structural studies of low-affinity systems is that there is no universal solution for stabilizing protein complexes, and approaches such as single-chain fusions, biochemical linkages, and affinity-maturation have each been successful in certain contexts. In this article, we review how advances in molecular engineering have been used to capture weakly associated complexes for structure determination, and we provide perspectives on how the continued application of these methods can shed new light on the “hidden world” of low-affinity interactions. Impact statement Low-affinity protein interactions, while biologically essential, have been difficult to visualize by traditional methods in structural biology. In this review, we describe a series of innovative molecular engineering strategies that have been used to stabilize weakly bound protein complexes for structure determination. By highlighting several examples from the literature along with potential advantages and disadvantages of the individual approaches, we hope to provide an introductory resource for structural biologists studying low-affinity systems.

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41

Hall, T. J., and M. B. Rittenberg. "The interaction of monomeric and complexed mouse monoclonal IgG with rat basophilic leukemia cells: a subset of IgG molecules can bind to RBL cell Fc receptors for IgG." Journal of Immunology 137, no. 7 (October 1, 1986): 2331–38. http://dx.doi.org/10.4049/jimmunol.137.7.2331.

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Abstract Rat basophilic leukemia (RBL) cells were shown to bind mouse monoclonal (MC) IgE and certain mouse monomeric IgG1 and IgG2b monoclonal antibodies (MAb) by using a haptenated sheep red blood cell (SRBC) rosetting assay. Rosette formation was antibody concentration dependent with all three immunoglobulin isotypes, but at least 100 times more IgG than IgE was required to form a similar number of rosettes. It was shown by FACS analysis and rosette formation that a subset (8/23) of the IgG MC was able to bind to RBL cells as monomers. However, the majority 15/23 did not bind or bound weakly (less than 25% rosettes) unless in the form of antigen-antibody complexes. As complexes, all IgG subclasses except IgG3 could produce rosettes with RBL cells. None of the IgM or IgA MC tested formed rosettes, even in complexed form. By inhibition studies it is demonstrated that mouse IgG1, IgG2a, and IgG2b MC bind to the same Fc receptor. Mouse IgE was only partially able to inhibit IgG-dependent rosettes at high concentrations, and none of the IgG MC were able to inhibit IgE-dependent rosettes. These results suggest that the interaction of mouse IgG is quite specific for the RBL cell FcG receptor. Because deaggregated polyclonal mouse IgG was a weak inhibitor of MC IgG sensitization of RBL cells, the results are discussed in terms of the heterogeneity and possible abnormality of some MAb.

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Schmidt, T. W., T. Pino, J. van Wijngaarden, K. Tikhomirov, F. Güthe, and J. P. Maier. "Electronic photodissociation spectra of the Arn–C4H2+ (n=1–4) weakly bound cationic complexes." Journal of Molecular Spectroscopy 222, no. 1 (November 2003): 86–92. http://dx.doi.org/10.1016/s0022-2852(03)00014-6.

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43

Walters, E. A., and J. R. Grover. "Prospects for photoionization studies of weakly bound molecular complexes using free-electron-laser vacuum-ultraviolet radiation." Journal of the Optical Society of America B 6, no. 5 (May 1, 1989): 1072. http://dx.doi.org/10.1364/josab.6.001072.

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44

Roncaratti, L. F., L. Belpassi, D. Cappelletti, F. Pirani, and F. Tarantelli. "Molecular-Beam Scattering Experiments and Theoretical Calculations Probing Charge Transfer in Weakly Bound Complexes of Water†." Journal of Physical Chemistry A 113, no. 52 (December 31, 2009): 15223–32. http://dx.doi.org/10.1021/jp905584p.

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45

Altun, Bleda, and Trindle. "Production of Carbamic Acid Dimer from Ammonia-Carbon Dioxide Ices: Matching Observed and Computed IR Spectra." Life 9, no. 2 (April 23, 2019): 34. http://dx.doi.org/10.3390/life9020034.

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The production of complex molecules in ammonia–carbon dioxide ices is presumed to pass through species of formula H3N:CO2 with further addition of ammonia and carbon dioxide. One possible landmark, carbamic acid, H2NCOOH, has been implicated among the products of warming and irradiation of such ices. Experimental study of the IR spectra of residues has suggested the presence of related species, including weakly bound 1:1 and 2:1 complexes of ammonia with carbon dioxide, zwitterionic carbamic acid, ammonium carbamate, and the dimer of carbamic acid. We computed the energetics and vibrational spectra of these species as well as the complex between ammonia and carbamic acid for gas and condensed phases. By means of a new spectrum-matching scoring between computed and observed vibrational spectra, we infer species that are most probably present. The leading candidates are ammonium carbamate, the carbamic acid–ammonia complex, and the carbamic acid dimer.

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46

Mandal, Sanat K., Laurence K. Thompson, Kamalaksha Nag, Jean-Pierre Charland, and Eric J. Gabe. "Copper (II) complexes of a macrocyclic binucleating ligand which exhibit two-electron oxidation and two-electron reduction. Structure of [Cu2(C24H34N4O2)(CH3OH)2](ClO4)2, a macrocyclic dicopper(II) complex involving coordinated methanol." Canadian Journal of Chemistry 65, no. 12 (December 1, 1987): 2815–23. http://dx.doi.org/10.1139/v87-468.

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The saturated ligand H2L1, derived by template condensation of 4-methyl-2,6-diformylphenol and 1,3-diaminopropane, followed by borohydride reduction, generates binuclear, antiferromagnetically coupled, copper(II) complexes which exhibit cyclic voltammetry involving two one-electron oxidation steps (E1/2 = 1.1 to 1.2 V, 1.3 to 1.4 V; Pt/CH3CN/SCE) and two one-electron reduction steps (E1/2 = −0.75 to −0.76 V, −0.89 to −0.90 V (GC/DMSO/SCE) with the formation of Cu(III)–Cu(III) and Cu(I)–Cu(I) and mixed oxidation state species. A trinuclear derivative, [Cu2(L1)(CuCl4)], appears to contain a spin-coupled binuclear species bound to a magnetically isolated tetrachlorocuprate(II) entity. The complex [Cu2(L1)(CH3OH)2](ClO4)2 forms brown crystals with a = 8.6516(7), b = 11.6832(9), c = 16.7205(6) Å, β = 92.596(5)°, P21/n, Z = 2, Rf = 0.037 and has a copper–copper separation of 3.088(1) Å and two weakly bound trans-axial methanol molecules (Cu—O, 2.413(4) Å). Variable temperature magnetic studies on [Cu2(L1)(ClO4)2] and [Cu2(L1)](ClO4)2 indicate strong antiferromagnetic exchange (−2J = 824 ± 5cm−1, 827 ± 7cm−1, respectively) in both cases.

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47

Li, Qianshu, Penggang Yin, Yongdong Liu, Au Chin Tang, Hongxing Zhang, and Yanbo Sun. "Ab initio and DFT studies of the weakly bound nitrogen molecule complexes (N2)n (n=3–6)." Chemical Physics Letters 375, no. 5-6 (July 2003): 470–76. http://dx.doi.org/10.1016/s0009-2614(03)00891-1.

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48

Shaheen, Muhammad Ashraf, Muhammad Nawaz Tahir, Sarwat Sabir, Aneela Anwar, Anvarhusein A. Isab, Abdul Rahman Al-Arfaj, Saeed Ahmad, and Shahzad Sharif. "Synthesis and crystal structures of bis(imidazolidine-2-thione-κS)bis(thiocyanato-κS)mercury(II) and bis(cyanido)bis(μ2-imidazolidine-2-thione-κS)mercury(II).Hg(CN)2." Zeitschrift für Naturforschung B 72, no. 9 (September 26, 2017): 671–76. http://dx.doi.org/10.1515/znb-2017-0080.

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AbstractTwo mercury(II) complexes containing imidazolidine-2-thione (Imt) and thiocyanate or cyanide ligands, [Hg(Imt)2(SCN)2] (1) and [Hg(Imt)2(CN)2].Hg(CN)2(2), have been prepared and characterized by IR and NMR spectroscopy and X-ray crystallography. In compound1, the mercury atom is located on a two-fold rotation axis and is coordinated to two thione sulfur atoms of imidazolidine-2-thione (Imt) and to two sulfur atoms of thiocyanate in a distorted tetrahedral mode with the S-Hg-S bond angles in the range of 98.96(3)–148.65(6)°. In2, the mercury atom is hexa-coordinated having a distorted octahedral geometry composed of two cyanide C atoms [Hg-C=2.055(5) Å] and four weakly bound thione S atoms of imidazolidine-2-thione (Imt) [Hg-S=3.1301(13) and 3.1280(13) Å]. One free Hg(CN)2molecule is also present in the crystal. In both complexes, the molecular structure is stabilized by N-H…N and N-H…S hydrogen bonding interactions.

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Brookes, Matthew D., Changhong Xia, Jian Tang, James A. Anstey, Bryan G. Fulsom, Ke-Xian Au Yong, Jenna M. King, and A. R. W. McKellar. "Tunable diode laser spectrometer for pulsed supersonic jets: application to weakly-bound complexes and clusters." Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 60, no. 14 (December 2004): 3235–42. http://dx.doi.org/10.1016/j.saa.2003.11.041.

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50

Woon, David E., Kirk A. Peterson, and Thom H. Dunning. "Benchmark calculations with correlated molecular wave functions. IX. The weakly bound complexes Ar–H2 and Ar–HCl." Journal of Chemical Physics 109, no. 6 (August 8, 1998): 2233–41. http://dx.doi.org/10.1063/1.476510.

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