Articoli di riviste: "Ligand field theory"

1

Ballhausen, C. J. "Crystal and ligand field theory". International Journal of Quantum Chemistry 5, S5 (18 giugno 2009): 373–77. http://dx.doi.org/10.1002/qua.560050844.

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Daul, Claude A. "Ligand Field Theory: An ever-modern theory". Journal of Physics: Conference Series 428 (5 aprile 2013): 012023. http://dx.doi.org/10.1088/1742-6596/428/1/012023.

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Tatarchuk, T. R., H. O. Sirenko e U. L. Kush. "The Solution of Applied Problems of Complex Compounds with the d-Elements Central Atoms Surrounded by Octahedral Ligand Based on the Theory of Crystal Field". Фізика і хімія твердого тіла 16, n. 1 (15 marzo 2015): 145–54. http://dx.doi.org/10.15330/pcss.16.1.145-154.

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The crystal field theory as applied to complex compounds of d-elements surrounded by octahedral ligans was described. Ligand field causes the splitting of d-orbitals, which is characterized by the energy splitting Δo. The spectrochemical series of ligands and examples of high-spin and low-spin complex compounds depending on the degree of force field were presented. Deformation of octahedral complexes by the Jahn-Teller effect was described. It shows the calculation of gains power as a result of complex formation, called the crystal field stabilization energy (CFSE) depending on the electronic structure of the central ion and the ligand position in spectrochemical series. It shows the distribution of electrons in orbitals of eg and t2g complex ions with different electronic configurations (from d1 to d10), examples values of energy orbitals and energy of crystal field stabilization for high-spin and low-spin octahedral complexes.

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Sastri, V. S., J. R. Perumareddi, M. Lashgari e M. Elboujdaini. "Application of Ligand Field Theory in Corrosion Inhibition". CORROSION 64, n. 4 (aprile 2008): 283–88. http://dx.doi.org/10.5006/1.3278472.

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Kutzelnigg, Werner. "Hans Bethe (1906-2005) and Ligand Field Theory". Angewandte Chemie International Edition 44, n. 25 (20 giugno 2005): 3800–3801. http://dx.doi.org/10.1002/anie.200501634.

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Johnson, Brian J., e Kate J. Graham. "A Guided Inquiry Activity for Teaching Ligand Field Theory". Journal of Chemical Education 92, n. 8 (17 giugno 2015): 1369–72. http://dx.doi.org/10.1021/acs.jchemed.5b00019.

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Sambe, Hideo, e Ronald H. Felton. "Connection between the Xα method and ligand field theory". International Journal of Quantum Chemistry 10, S10 (18 giugno 2009): 155–58. http://dx.doi.org/10.1002/qua.560100816.

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Schäffer, Claus E., e Jesper Bendix. "Kohn–Sham DFT and ligand-field theory — Is there a synergy?" Canadian Journal of Chemistry 87, n. 10 (ottobre 2009): 1302–12. http://dx.doi.org/10.1139/v09-061.

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In forming electronic states of the partially filled shell of transition-metal atomic and molecular systems, real, symmetry-based, fixed, Kohn–Sham eigenorbitals can be used to bridge KS-states with strong-field, ligand-field states. Thereby, DFT computations, restrained by the use of these frozen orbitals of the so-called average-of-configuration type, allow a central-field modeling of the partially filled shell whose Hamiltonian matrix consists of mutually orthogonal diagonal and non-diagonal parts, of which only the former can be computed. Mutually orthogonal operators of ligand-field theory are particularly suited to parameterize the energy “data” obtained from the bridges between molecular Kohn–Sham DFT states and ligand-field states. With the d2 configuration as the simplest example encompassing both ligand-field and interelectronic repulsion, each one-electron parameter, though defined by energy differences of perturbed d orbitals, is associated with a 45 × 45, diagonal, theoretical, strong-field-type coefficient matrix of the ligand field repulsion model (LFR), which is mapped in a one-to-one fashion onto a likewise diagonal KS-DFT computational energy matrix. For sets of mutually orthogonal operators, the mapping determines the value of any such ligand-field parameter as a scalar product between the DFT matrix and the coefficient matrix of the associated ligand-field operator. Each and every two-electron parameter of LFR is in the same strong-field function basis associated with a 45 × 45 coefficient matrix that includes a non-diagonal part. This matrix, nevertheless, by the formation of a scalar product with the appropriate diagonal, computational DFT matrix, provides the value of the two-electron parameter. In spite of the lacking non-diagonal DFT information, its non-diagonal elements of the two-electron interelectronic repulsion matrices are indirectly accessible through the parameterization based upon the computed diagonal DFT matrices combined with the mapping of the DFT energy results onto the parametric LFR. In this way, LFR delivers back to DFT a quantification of the deviation of the systems’ eigenbasis from the DFT-computed states, which are defined by having unit occupation numbers. This work focuses firstly on using the LFR model for forming a full DFT energy matrix and dissecting it into mutually orthogonal one- and two-electron parts and secondly on the use of the two-electron parts to obtain a complete ligand-field image of a nephelauxetic, molecular atom, intrinsic of the chemical system.

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Lang, Lucas, Mihail Atanasov e Frank Neese. "Improvement of Ab Initio Ligand Field Theory by Means of Multistate Perturbation Theory". Journal of Physical Chemistry A 124, n. 5 (24 gennaio 2020): 1025–37. http://dx.doi.org/10.1021/acs.jpca.9b11227.

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Wissing, K., e J. Degen. "Dynamic ligand-field theory for square planar transition metal complexes". Journal of Molecular Structure: THEOCHEM 431, n. 1-2 (aprile 1998): 97–107. http://dx.doi.org/10.1016/s0166-1280(97)00433-8.

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Dong-Ping, Ma, e Chen Ju-Rong. "Improved Ligand-Field Theory with Effect of Electron-Phonon Interaction". Communications in Theoretical Physics 43, n. 3 (marzo 2005): 529–38. http://dx.doi.org/10.1088/0253-6102/43/3/032.

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Gatteschi, D., L. Sorace, R. Sessoli e A. L. Barra. "High-frequency EPR: An occasion for revisiting ligand field theory". Applied Magnetic Resonance 21, n. 3-4 (dicembre 2001): 299–310. http://dx.doi.org/10.1007/bf03162409.

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13

Toader, Ana Maria, Maria Cristina Buta, Fanica Cimpoesu e Adela Mihai. "The Holohedrization Effect in Ligand Field Models". Symmetry 16, n. 1 (23 dicembre 2023): 22. http://dx.doi.org/10.3390/sym16010022.

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The ligand field theory is an early and yet perennial class of quantum models accounting for the optical and magnetic properties of metal ions as a function of their environment in compounds. In the context of modern quantum chemistry, in order to predict properties from first principles, the ligand field paradigm can serve to illuminate the black box of heavy calculations, extracting heuristic meaning and causal roots. The genuine ligand field models are tacitly affected by an artificial feature, so-called holohedrization. It induces an inversion symmetry, even in cases where the local geometry does not show this element. This aspect received little attention over decades of using the ligand field Hamiltonians. In this work, we systematically investigate, assisted by state-of-the-art ab initio computer experiments, whether holohedrization is a hidden drawback of early models or if it also appears in realistic modeling. We found that the holohedrization trend also appears when using data from modern ab initio calculations.

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Ramanantoanina, Harry, Werner Urland, Amador García-Fuente, Fanica Cimpoesu e Claude Daul. "Ligand field density functional theory for the prediction of future domestic lighting". Phys. Chem. Chem. Phys. 16, n. 28 (2014): 14625–34. http://dx.doi.org/10.1039/c3cp55521f.

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Moore, D. J., e G. E. Stedman. "Effects of time-odd electron-phonon coupling in ligand field theory". Journal of Physics: Condensed Matter 2, n. 11 (19 marzo 1990): 2559–77. http://dx.doi.org/10.1088/0953-8984/2/11/005.

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Hassan, M. A., M. Farouk, A. H. Abdullah, I. Kashef e M. M. ElOkr. "ESR and ligand field theory studies of Nd2O3 doped borochoromate glasses". Journal of Alloys and Compounds 539 (ottobre 2012): 233–36. http://dx.doi.org/10.1016/j.jallcom.2012.06.060.

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Turner, John F. C. "Ligand Field Theory and Its Applications (Figgis, Brian N.; Hitchman, Michael A.)". Journal of Chemical Education 79, n. 9 (settembre 2002): 1072. http://dx.doi.org/10.1021/ed079p1072.2.

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del Rosal, Iker, Maxime Mercy, Iann C. Gerber e Romuald Poteau. "Ligand-Field Theory-Based Analysis of the Adsorption Properties of Ruthenium Nanoparticles". ACS Nano 7, n. 11 (9 ottobre 2013): 9823–35. http://dx.doi.org/10.1021/nn403364p.

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Deeth, Robert J. "Impact on ligand-field theory of the real ground state for CuCl2". Journal of the Chemical Society, Dalton Transactions, n. 7 (1993): 1061. http://dx.doi.org/10.1039/dt9930001061.

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20

Gatteschi, D., L. Sorace, R. Sessoli e A. L. Barra. "ChemInform Abstract: High-Frequency ESR: An Occasion for Revisiting Ligand Field Theory". ChemInform 33, n. 37 (20 maggio 2010): no. http://dx.doi.org/10.1002/chin.200237299.

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YANG, KUO, YONG SONG e JIAN TANG. "THEORETICAL STUDY ON THE ENERGY SPECTRUM AND PRESSURE SHIFTS OF R1 LINE FOR LiNbO3:Cr3+". Modern Physics Letters B 25, n. 17 (10 luglio 2011): 1503–10. http://dx.doi.org/10.1142/s0217984911026899.

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Based on the improved ligand-field theory, the energy levels of spectrum, wavefunctions and crystal-field parameters of LiNbO 3: Cr 3+ at 10 K and normal pressure, have been calculated by diagonalizing the complete d3+ energy matrix (120 × 120) under the strong-field scheme of the ligand-field theory. Furthermore, the values of R1 line of LiNbO 3: Cr 3+ under different pressure have been calculated, which agrees well with the experimental data. At last, the contributions from various crystal-field parameters to the energy levels at normal pressure and the variaton rates of the R1 line shifting with the pressure have been calculated, and the physical origin of the red shift of R1 line under the increasing pressure has been clearly shown.

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22

Feng, Wen-Lin. "Theoretical Investigation of the g Factors for Copper (II) Ion in an Orthorhombic Crystal and its Application to (CuCl4)2– Cluster". Zeitschrift für Naturforschung A 65, n. 3 (1 marzo 2010): 251–62. http://dx.doi.org/10.1515/zna-2010-0315.

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On the basis of the crystal- and ligand-field theory, the high-order perturbation formulas of the g factors (gx, gy, gz) are established for Cu2+ ions in an orthorhombic tetrahedral field with D2 symmetry, including the central cationic and ligand anionic spin-orbital coupling interactions. By using these formulas, the anisotropic g factors of Cu2+ ion in (CuCl4)2− cluster are calculated. The results are consistent with the experimental values. The calculations show that the contribution from covalency of the central ion and the 3p orbital ligand can not be neglected

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Sakiyama, Hiroshi, Rin Kimura, Haruto Oomiya, Ryoji Mitsuhashi, Sho Fujii, Katsuhiko Kanaizuka, Mohd Muddassir, Yuga Tamaki, Eiji Asato e Makoto Handa. "Relationship between Structure and Zero-Field Splitting of Octahedral Nickel(II) Complexes with a Low-Symmetric Tetradentate Ligand". Magnetochemistry 10, n. 5 (24 aprile 2024): 32. http://dx.doi.org/10.3390/magnetochemistry10050032.

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Octahedral nickel(II) complexes are among the simplest systems that exhibit zero-field splitting by having two unpaired electrons. For the purpose of clarifying the relationship between structure and zero-field splitting in a low-symmetric system, distorted octahedral nickel(II) complexes were prepared with a tetradentate ligand, 2-[bis(2-methoxyethyl)aminomethyl]-4-nitrophenolate(1−) [(onp)−]. The complex [Ni(onp)(dmso)(H2O)][BPh4]·2dmso (1) (dmso = dimethyl sulfoxide) was characterized as a bulk sample by IR, elemental analysis, mass spectrometry, electronic spectra, and magnetic properties. The powder electronic spectral data were analyzed based on the angular overlap model to conclude that the spectra were typical of D4-symmetric octahedral coordination geometry with a weak axial ligand field. Simultaneous analysis of the temperature-dependent susceptibility and field-dependent magnetization data yielded the positive axial zero-field splitting parameter D (H = guβSuHu + D[Sz2 − S(S + 1)/3]), which was consistent with the weak axial ligand field. Single-crystal X-ray analysis revealed the crystal structures of [Ni(onp)(dmso)(H2O)][BPh4]·dmso (2) and [Ni(onp)(dmf)2][BPh4] (3) (dmf = N,N-dimethylformamide). The density functional theory (DFT) computations based on the crystal structures indicated the D4-symmetric octahedral coordination geometries with weak axial ligand fields. This study also showed the importance of considering g-anisotropy in magnetic analysis, even if g-anisotropy is small.

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Stoilov, Anton, Borislav Yurukov e Peter Milanov. "Analysis of docking algorithms by HPC methods generated in bioinformatics studies". ITM Web of Conferences 16 (2018): 02009. http://dx.doi.org/10.1051/itmconf/20181602009.

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High-performance computing (HPC) is an important domain of the computer science field. For more than 30 years, it has allowed finding solutions to problems and enhanced progress in many scientific areas such as bioinformatics and drug design. The binding of small molecule ligands to large protein targets is central to numerous biological processes. The accurate prediction of the binding modes between the ligand and protein (the docking problem) is of fundamental importance in modern structure-based drug design. The interactions between the receptor and ligand are quantum mechanical in nature, but due to the complexity of biological systems, quantum theory cannot be applied directly. Consequently, most methods used in docking and computational drug discovery are more empirical in nature and usually lack generality.

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Lazzarini, Ennio. "An attempt to apply ligand field theory to positronium reactions with 3d complexes". RENDICONTI LINCEI 14, n. 1 (marzo 2003): 5–75. http://dx.doi.org/10.1007/bf02915466.

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Hidayat, Yuniawan, Ria Armunanto e Harno Dwi Pranowo. "QMCF-MD Simulation and NBO Analysis of K(I) Ion in Liquid Ammonia". Indonesian Journal of Chemistry 18, n. 2 (30 maggio 2018): 203. http://dx.doi.org/10.22146/ijc.26788.

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Ab initio of Quantum Mechanics Charge Field Molecular Dynamic (QMCF-MD) of K(I) ion in liquid ammonia has been studied. A Hartree-Fock level of theory was coupled with LANL2DZ ECP basis set for K(I) ion and DZP (Dunning) for ammonia. Two regions as first and second solvation shell were observed. In the first solvation shell at distance 3.7 (Å), K(I) ion was coordinated by four to eight ammonia molecules dominated by K(NH3)6+ species. Second shell of solvation was ranging between 3.7 Å to 7.3 Å. Within simulation time of 20 ps, the frequent exchange processes of ligands indicating for a very labile solvation structure. Four mechanism types of ligand exchange between first and second solvation shell were observed. Mean residence time of ligand is less than 2 ps confirming weak in ion-ligand interaction. Evaluation of K(NH3)6+ using natural bond orbital analysis shows that the Wiberg bond Index is less than 0.05 indicating weak electrostatic interaction of K-N.

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Wachters, A. J. H., e W. C. Nieuwpoort. "Crystal field splitting and born repulsion in KNiF3. Contribution to the panel discussion on ligand field theory". International Journal of Quantum Chemistry 5, S5 (18 giugno 2009): 391–96. http://dx.doi.org/10.1002/qua.560050846.

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Anthon, Christian, Jesper Bendix e Claus E. Schäffer. "An Average-of-Configuration Method for Using Kohn−Sham Density Functional Theory in Modeling Ligand-Field Theory†". Inorganic Chemistry 42, n. 13 (giugno 2003): 4088–97. http://dx.doi.org/10.1021/ic0262233.

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Ramanantoanina, Harry, Michał Studniarek, Niéli Daffé e Jan Dreiser. "Non-empirical calculation of X-ray magnetic circular dichroism in lanthanide compounds". Chemical Communications 55, n. 20 (2019): 2988–91. http://dx.doi.org/10.1039/c8cc09321k.

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Mangione, G., M. Sambi, M. V. Nardi e M. Casarin. "A theoretical study of the L3 pre-edge XAS in Cu(ii) complexes". Phys. Chem. Chem. Phys. 16, n. 37 (2014): 19852–55. http://dx.doi.org/10.1039/c4cp02441a.

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L_2,3 spectra of Cu(ii) complexes have been simulated by means of time dependent DFT. Besides the agreement between theory and experiment, the adopted approach provided further insights into the use of the Cu(ii) L₃-edge intensity and position to investigate the Cu–ligand symmetry-restricted covalency and the ligand-field strength.

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Schäffer, Claus E., Christian Anthon e Jesper Bendix. "Bridging Kohn - Sham DFT and the Angular Overlap Model. Ligand-Field Parameters and Bond Covalencies in Tetrahedral Complexes". Australian Journal of Chemistry 62, n. 10 (2009): 1271. http://dx.doi.org/10.1071/ch09335.

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Kohn–Sham density functional theory (DFT), constrained by the average-of-configuration computations, allows the valence shell of regular tetrahedral chlorido complexes of a complete series of 3d transition metal ions to be orbitally compared. The concept of classificational parentage provides a handle on the discussion of the energetic ordering of all the valence orbitals and illuminates an almost identical ordering for all the systems. Only the participation of the metal 4s orbital in bonding causes a few minor fluctuations. The partially filled ‘3d’ molecular orbitals sit in an energy window framed by completely filled ‘ligand orbitals’ on the low-energy side and an empty metal ‘4s’ orbital on the high-energy side. Regular tetrahedral symmetry requires the halides to be linearly ligating and this property is stable within the ‘experimental’ uncertainty for small distortions. By lowering the symmetry towards the planar configuration, keeping the equivalence of the ligands stable, the information content of the computations was doubled and the angular overlap energy parameters referring to the individual ligands obtained. The orbital energies of the partially filled shell depend linearly on the Angular Overlap Model (AOM) parameters eλ, the slope being the sum of the squares of the single-ligand λ angular overlaps (λ = σ and π). Mulliken population analysis shows the contents of the appropriate ligand orbitals in the ‘d’ orbitals to vary in parallel with the molecular orbital AOM energies and to increase pronouncedly with the oxidation number z. Results for tetraoxidoferrate(vi) show a remarkable resemblance with the chloride complexes of even the divalent metal ions. However, although the bonding orbitals are more π-bonding, the totally symmetrical bonding orbitals use M_4s less in the oxido complex. The sensitivity of covalency and spectroscopic energy parameters towards radial distortions are examined and show Werner-type complexes and the high-valent FeO42– to behave somewhat differently.

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Chang, Tsu Hsin, e Jeffrey I. Zink. "The .sigma. and .pi. interactions of the carbonyl ligand determined from single-crystal polarized electronic spectroscopy and ligand field theory". Journal of the American Chemical Society 109, n. 3 (febbraio 1987): 692–98. http://dx.doi.org/10.1021/ja00237a009.

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Sacher, E. "Ligand-field theory of inductive effects in the photoelectron spectra of transition-metal compounds". Physical Review B 34, n. 8 (15 ottobre 1986): 5130–35. http://dx.doi.org/10.1103/physrevb.34.5130.

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Chan, Yue, Jonathan J. Wylie, Liang Xia, Yong Ren e Yung-Tsang Chen. "Modelling of particle-laden flow inside nanomaterials". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, n. 2192 (agosto 2016): 20160289. http://dx.doi.org/10.1098/rspa.2016.0289.

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In this paper, we demonstrate the usage of the Nernst–Planck equation in conjunction with mean-field theory to investigate particle-laden flow inside nanomaterials. Most theoretical studies in molecular encapsulation at the nanoscale do not take into account any macroscopic flow fields that are crucial in squeezing molecules into nanostructures. Here, a multi-scale idea is used to address this issue. The macroscopic transport of gas is described by the Nernst–Planck equation, whereas molecular interactions between gases and between the gas and the host material are described using a combination of molecular dynamics simulation and mean-field theory. In particular, we investigate flow-driven hydrogen storage inside doubly layered graphene sheets and graphene-oxide frameworks (GOFs). At room temperature and with slow velocity fields, we find that a single molecular layer is formed almost instantaneously on the inner surface of the graphene sheets, while molecular ligands between GOFs induce multi-layers. For higher velocities, multi-layers are also formed between graphene. For even larger velocities, the cavity of graphene is filled entirely with hydrogen, whereas for GOFs there exist two voids inside each periodic unit. The flow-driven hydrogen storage inside GOFs with various ligand densities is also investigated.

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Kang-Cheng e Changhua-Zou. "Modeling SARS-CoV-2 and preventing COVID-19 pandemic". Magna Scientia Advanced Research and Reviews 6, n. 2 (30 dicembre 2022): 024–33. http://dx.doi.org/10.30574/msarr.2022.6.2.0077.

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Backgrounds: Since December 2019, COVID-19 pandemic has globally killed more than 6.602 millions, infected more than 635.2 millions of people and lasted almost three years, as of 11/22/2022. The pandemic is still killing more than 7,261 and infecting more than 2.259 millions of people per week in the whole world today. We think the rates of the fatality, infection and the long term of the pandemic are related to proliferation characteristics and biological structures of SARS-CoV-2. Methods and Objectives: We apply theories of biology, ligand field, biophysics, biochemistry, virology, classic electrodynamics, and published biological data, to model proliferation characteristics and biological structures of SARS-CoV-2. Modeling Results and Outcomes: We coin a concept: quasi identical biological objects carry the quasi identical biological information (spatial, temporal, electromagnetic and mass properties), and they cannot occupy the same biological envelope if their repulsive forces between them are stronger than the resistances. We propose two models of exclusions. Exclusion of RNA (DNA) strands: No normally and naturally replicated quasi identical RNA (DNA) strands can occupy the same virus. Exclusion of viruses: No normally and naturally proliferated quasi identical viruses can occupy the same biological host cell. For a SARS-CoV-2, we model the charged ssRNA and N proteins as a negatively charged central body, the charged proteins in the biological membrane as dynamic ligands, the electric field between the center and ligands as a dynamic ligand field. Conclusions: The biological models of exclusions of RNA strands in a virus and viruses in a host cell qualitatively respectively answer the questions why or how there is only one mature ssRNA strand inside a SARS-CoV-2 membrane envelope and the virus proliferate; it is suitable to extend or analogize the ligand field theory to illustrate the stability of SARS-CoV-2 in biophysical structures (topologic constructions). Our models could be applicable to other biological objects.

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Toader, Ana Maria, Bogdan Frecus, Corneliu Ioan Oprea e Maria Cristina Buta. "Assessing Quantum Calculation Methods for the Account of Ligand Field in Lanthanide Compounds". Physchem 3, n. 2 (16 giugno 2023): 270–89. http://dx.doi.org/10.3390/physchem3020019.

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We obtained thorough insight into the capabilities of various computational methods to account for the ligand field (LF) regime in lanthanide compounds, namely, a weakly perturbed ionic body and quasidegenerate orbital multiplets. The LF version of the angular overlap model (AOM) was considered. We intentionally took very simple idealized systems, the hypothetical [TbF]2+, [TbF2]+ and [Tb(O2NO)]2+, in order to explore the details overlooked in applications on complex realistic systems. We examined the 4f and 5d orbital functions in connection to f–f and f–d transitions in the frame of the two large classes of quantum chemical methods: wave function theory (WFT) and density functional theory (DFT). WFT methods are better suited to the LF paradigm. In lanthanide compounds, DFT faces intrinsic limitations because of the frequent occurrence of quasidegenerate ground states. Such difficulties can be partly encompassed by the nonstandard control of orbital occupation schemes. Surprisingly, we found that the simplest crystal field electrostatic approximation, reconsidered with modern basis sets, works well for LF parameters in ionic lanthanide systems. We debated the largely overlooked holohedrization effect that inserts artificial inversion symmetry into standard LF Hamiltonians.

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Padilla, Juan, e William E. Hatfield. "σ and π-interactions of the pyrrolic ligand of sandwich-like lanthanide phthalocyanines determined from magnetic susceptibility and ligand-field theory". Inorganica Chimica Acta 172, n. 2 (giugno 1990): 241–45. http://dx.doi.org/10.1016/s0020-1693(00)80862-2.

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Saureu, Sergi, e Coen de Graaf. "TD-DFT study of the light-induced spin crossover of Fe(iii) complexes". Physical Chemistry Chemical Physics 18, n. 2 (2016): 1233–44. http://dx.doi.org/10.1039/c5cp06620d.

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Two light-induced spin-crossover Fe(iii) compounds have been studied with time-dependent density functional theory (TD-DFT) to investigate the deactivation mechanism and the role of the ligand-field states as intermediates in this process.

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Kharwar, Ajit Kumar, Arpan Mondal e Sanjit Konar. "Field Induced Slow Magnetic Relaxation in a Non Kramers Tb(III) Based Single Chain Magnet". Magnetochemistry 4, n. 4 (19 dicembre 2018): 59. http://dx.doi.org/10.3390/magnetochemistry4040059.

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Herein, we report a novel Tb(III) single chain magnet with the chemical formulae [Tb(μ-OH2)(phen)(μ-OH)(nb)2]n by using 4-nitrobenzoic acid (Hnb) and 1,10-phenanthroline (phen) as ligand system. The single-crystal X-ray diffraction reveals that 4-nitrobenzoic acid acts as a monodentate ligand, water and hydroxyl ions are the bridging ligand and the phen serves as a bidentate chelating ligand. The static magnetic susceptibility measurement (from 2 K to 300 K) shows ferromagnetic interaction at very low temperature (below 6 K). The alternating current (AC) susceptibility data of the complex show temperature and frequency dependence under an applied 2000 Oe DC (direct current) field. The phen moiety behaves as an antenna and enables the complex to show the green light fluorescence emission by absorption-energy transfer-emission mechanism. To calculate the exchange interaction, broken symmetry density functional theory (BS-DFT) calculations have been performed on a model compound which also reveals weak ferromagnetic interaction. Ab initio calculations reveals the anisotropic nature (gz = 15.8, gy, gy = 0) of the metal centre and the quasi doublet nature of ground state with small energy gap and that is well separated from the next excited energy state.

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García-García, Amalia, Andoni Zabala-Lekuona, Ainhoa Goñi-Cárdenas, Javier Cepeda, José M. Seco, Alfonso Salinas-Castillo, Duane Choquesillo-Lazarte e Antonio Rodríguez-Diéguez. "Magnetic and Luminescent Properties of Isostructural 2D Coordination Polymers Based on 2-Pyrimidinecarboxylate and Lanthanide Ions". Crystals 10, n. 7 (2 luglio 2020): 571. http://dx.doi.org/10.3390/cryst10070571.

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A couple of isostructural coordination polymers with the general formula [Ln4(pymca)4(AcO)8]n have been obtained from reactions between pyrimidine-2-carboxylate (pymca) ligand and rare-earth ions (Ln = Dy (1), Nd (2)). These two-dimensional compounds have been characterized and the crystal structures have been solved by single-crystal X-ray diffraction technique, resulting in layers along the bc plane based on pymca and acetate anions that act as bridging ligands between metal atoms. Given that pymca and acetate anions possess carboxylate and hetero-nitrogen groups, it is possible to build a coordination polymer whose metal centers have a nine coordination. Furthermore, static and dynamic magnetic measurements of compound 1 reveal the lack of single molecule-magnet (SMM) behavior in this system due to the following two effects: (i) the ligand field does not stabilize magnetic ground states well separated from excited states, and (ii) anisotropy axes are not collinear, according to results with Magellan software. On another level, luminescent properties of compounds 1 and 2 are attributed to singlet π-π* transitions centered on pymca ligand as corroborated by time-dependent density functional theory (TD-DFT) calculations.

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41

Krüger, Peter. "First-Principles Calculation of Ligand Field Parameters for L-Edge Spectra of Transition Metal Sites of Arbitrary Symmetry". Symmetry 15, n. 2 (10 febbraio 2023): 472. http://dx.doi.org/10.3390/sym15020472.

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Recently we have proposed a simple method for obtaining the parameters of a ligand field multiplet model for L-edge spectra calculations from density functional theory. Here we generalize the method to systems where the metal site has arbitrary point symmetry. The ligand field-induced splitting of the metal d-level becomes a hermitian matrix with cross-terms between the different d-orbitals. The anisotropy of the covalency is fully taken into account and it rescales the electron–electron interaction and the oscillator strength in an orbital-dependent way. We apply the method to polarization-dependent V L-edge spectra of vanadium pentoxide and obtain very good agreement with the experiment.

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42

Cortes-Llamas, Sara Angelica, José Miguel Velázquez-López, Irma Idalia Rangel-Salas, Morelia Eunice López-Reyes, Alfredo Rosas-Sánchez, Leticia Lozada-Rodríguez, Gabriela De Jesús Soltero-Reynoso e Saul Gallegos-Castillo. "High- or low-spin complex? A guide to facilitate the selection in Ligand Field Theory". Educación Química 33, n. 1 (14 gennaio 2022): 41. http://dx.doi.org/10.22201/fq.18708404e.2022.1.78867.

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43

Schäffer, Claus E. "Extension of ligand-field theory to encompass bridged structures. Emphasis on the angular overlap model". Inorganica Chimica Acta 300-302 (aprile 2000): 1035–76. http://dx.doi.org/10.1016/s0020-1693(99)00599-x.

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44

Lueken, Heiko. "Buchbesprechung: Ligand Field Theory and Its Applications. Von Brain N. Figgis und Michael A. Hitchman." Angewandte Chemie 113, n. 3 (2 febbraio 2001): 649–50. http://dx.doi.org/10.1002/1521-3757(20010202)113:3<649::aid-ange649>3.0.co;2-#.

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45

Chiu, Ying-Nan. "Crystal-field theory for the Rydberg states of polyatomic molecules". Canadian Journal of Physics 64, n. 7 (1 luglio 1986): 782–95. http://dx.doi.org/10.1139/p86-140.

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The potential on a Rydberg electron due to the cluster of atoms near the center of a polyatomic molecule is expanded in powers of spherical harmonics. Nonvanishing potentials in totally symmetric irreducible representations are obtained using the crystal field of the cluster of atoms in D3h, C3v, D4v, C4v, Td, and D2d symmetries. Odd as well as the usual even powers of spherical harmonics are included up to [Formula: see text]. Spectroscopically observable differences in potentials between a planar versus a nonplanar XY3 molecule and among a square planar, pyramidal, tetrahedral, and dihedral XY4 molecule are exhibited. First-order energies are given for a Rydberg [Formula: see text] state showing λ dependence. Second-order energies due to mixing of Rydberg states by odd and even power potentials and splitting of ±λ degeneracies are shown analytically for an nd as well as an nf Rydberg electron. The formalism is applicable to nonpenetrating Rydberg orbitals. Approximate radial integrals are obtained. Exact angular integrals for the first- and second-order energies are given. Symmetry-adapted combinations of the separated Y3 and Y4 ligand atomic orbitals are derived up to d orbitals. The correlations between these linear combinations of atomic orbitals as molecular configurations change are shown, e.g., as an XY4 molecule distorts from (D4h, C4v) to (D2d, Td) and vice versa.

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46

Bahrami, Homayoon, Narges Ostadhosseini, Hamid Reza Shamlouei e Mansour Zahedi. "Study of six coordinated cobalt(III) oxophlorin with different axial ligands: Optimization of geometry and determining of energy and electronic configuration at various spin states by employing of B3LYP, BV86P and M06-2X methods". Journal of Porphyrins and Phthalocyanines 28, n. 03 (marzo 2024): 173–91. http://dx.doi.org/10.1142/s1088424624500147.

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The six coordinated CoIIIoxophlorin have been studied with imidazole, pyridine and t-butylcyanide as axial ligands using B3LYP, BV86P and MO6-2X methods. Conversion between two isomers [(L)2CoIII(PO)][Formula: see text] and [(L)2CoIII(PO)][Formula: see text] can be occurred at various spin multiplicities, namely singlet, triplet and quintet states. L is employed to show axial ligand namely, imidazole or pyridine. London forces have a basic role in the stability of the mentioned complexes due to non-specific solvent effects. The latter fact has been obtained using the PCM model. Also, it is specified that minimum geometries have not been obtained for some parallel or perpendicular six-coordinated complexes with special axial ligands at a finite spin state. The B3LYP method indicates that one and three [Formula: see text]-electron can be found on the Co atom in every optimized complex at triplet and quintet spin states, respectively. Also, another [Formula: see text]-electron is placed on the ring of oxophlorin. This fact is obtained for different isomers of [(IM2(CoIII(PO)] and [(Py)2CoIII(PO)] at triplet and quintet spin states, while these complexes are optimized using B3LYP. Besides, results obtained from B3LYP show that the most stable state for six coordinated CoIIIoxophlorin with any axial ligand is the singlet state. Based on crystal field theory and molecular orbital theory, electron configuration and hybridization of cobalt in [(IM)2CoIII(PO)] at singlet state can be written as t2g6 eg0 and sp3d2, respectively. Former electronic configuration indicates a strong field with low spin for d orbitals of cobalt, and latter hybridization is expected for a metal with a coordination number of 6 in a complex with Oh symmetry. The results obtained are completely satisfied by NBO analysis.

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47

Suta, Markus, Fanica Cimpoesu e Werner Urland. "The angular overlap model of ligand field theory for f elements: An intuitive approach building bridges between theory and experiment". Coordination Chemistry Reviews 441 (agosto 2021): 213981. http://dx.doi.org/10.1016/j.ccr.2021.213981.

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48

Cheng, Haojin, Brandon Djukic, Hilary A. Jenkins, Serge I. Gorelsky e Martin T. Lemaire. "Iron(II) complexes containing thiophene-substituted “bispicen” ligands — Spin-crossover, ligand rearrangements, and ferromagnetic interactions". Canadian Journal of Chemistry 88, n. 9 (settembre 2010): 954–63. http://dx.doi.org/10.1139/v10-086.

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The synthesis and characterization of three new tetradentate “bispicen-type” ligands containing a substituted thiophene heterocycle are described [2,5-thienyl substituents = H (7), Ph (8), or 2-thienyl (9)]. Iron(II) bis(thiocyanate) coordination complexes containing 7–9 were prepared, and the electronic and variable-temperature magnetic properties of complexes containing 7 (10) and 9 (12) are described. Complex 10 features a gradual and incomplete spin crossover in the solid state, and 12 remains high-spin over the entire temperature range. Complex 11 is extremely unstable and rearranges to another iron(II) complex (13), which was structurally characterized. The temperature-dependent magnetic properties of 13 are described as a one-dimensional ferromagnetic chain, with interchain antiferromagnetic interactions and (or) zero-field splitting dominant at low temperatures. The magnetic analysis is corroborated by the molecular packing and density functional theory calculations, which suggest intermolecular interactions between coordinated thiocyanate ligands bearing a significant spin density.

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49

Deeth, Robert J. "d-orbital energy levels in planar [MIIF4]2−, [MII(NH3)4]2+ and [MII(CN)4]2− complexes: the nature of M–L π bonding and the implications for ligand field theory". Dalton Transactions 49, n. 28 (2020): 9641–50. http://dx.doi.org/10.1039/d0dt02022b.

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50

Goswami, Debpriyo, Shanti Gopal Patra e Debashis Ray. "Magneto-Structural Analysis of Hydroxido-Bridged CuII2 Complexes: Density Functional Theory and Other Treatments". Magnetochemistry 9, n. 6 (10 giugno 2023): 154. http://dx.doi.org/10.3390/magnetochemistry9060154.

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A selection of dimeric Cu(II) complexes with bidentate N,N′ ligands with the general formula [Cu(L)(X)(μ-OH)]2·nH2O and [Cu(L)(μ-OH)]2X2·nH2O were magneto-structurally analyzed using the Density Functional Theory (DFT). A Broken Symmetry-Density Functional Theory (BS-DFT) study was undertaken for these complexes with relevant decomposition schemes that gave insight into the effect of the nature of the ligand and coordination environment on the DFT-predicted coupling constants (J). The impact of the spin population, which correlates well with the Cu-O-Cu bridging angles and the calculated coupling constant (J) values, was studied. The models were further refined using a complete active space self-consistent field (CASSCF) while expanding the active space from 2 orbitals 2 electrons (2,2) to 10 orbitals 18 electrons (18,10). These models were approximated using multireference methods (n-electron valence state perturbation theory and difference dedicated configuration interaction), and a better approximation of J values was found as expected. Orbitals involved in the superexchange pathway were also visualized.

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