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Journal ArticleDOI

From weak to strong interactions: A comprehensive analysis of the topological and energetic properties of the electron density distribution involving X–H⋯F–Y systems

04 Sep 2002-Journal of Chemical Physics (American Institute of Physics)-Vol. 117, Iss: 12, pp 5529-5542

Abstract: The topological and energetic properties of the electron density distribution ρ(r) of the isolated pairwise H⋯F interaction have been theoretically calculated at several geometries (0.8
Topics: Molecular orbital (51%), Electron density (51%)
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Journal ArticleDOI
Xuan Meng1, Liying Song1, Haiyun Han, Jinfeng Zhao1  +1 moreInstitutions (1)
Abstract: In this work, we explore the excited-state intramolecular proton transfer (ESIPT) mechanisms and relative solvent effects for three novel 3-hydroxylflavone derivatives (i.e., HOF, SHOF, and NSHOF) in acetonitrile, dichloromethane, and toluene solvents. Through calculations, we optimize the structures of HOF, SHOF, and NSHOF. Through the analysis of a series of structural parameters related to hydrogen bonding interactions, it could be found that the hydrogen bonds of the three derivatives are all enhanced in the S1 state, and more importantly, the excited-state hydrogen bonds of HOF are stronger than those of SHOF and NSHOF. In order to explore the effects of solvent polarity, we analyze the core-valence bifurcation (CVB) index, infrared (IR) vibration spectrum, and the potential energy curves. We find that for HOF, SHOF, and NSHOF, the strength of the excited-state hydrogen bonds increases as the solvent polarity decreases. The solvent polarity dependent ESIPT mechanisms pave the way for further designing novel flavonoid-based solvatofluorochromic probes in future.

2 citations

Journal ArticleDOI
Soheila Mir1, Bahram Yadollahi1, Reza Omidyan1Institutions (1)
Abstract: In the present study, molecular geometry, electronic structure, first row transition metal-polyoxometalate interactions, transition metal-H2O bonding, and simulated infrared (IR) spectrum of H2O ligated/unligated transition metal substituted Keggin type polyoxometalates ([PW11O39(MII/MIIOH2)]5-, MII ​= ​Cr, Mn, Fe, Co, Ni, Cu and Zn) have been studied through Density Functional Theory (DFT) calculations. From the results, it has been predicted that the interaction of H2O ligand with MII leads to a stable [PW11O39(MII-H2O)]5- complex, without spin crossing during water attachment. The calculations have also revealed that interaction of H2O ligand with [PW11O39(MII)]5- could be discussed in two different classes: when MII is Cr, Mn and Fe, the H2O molecule interacts directly to MII from O side, while for MII ​= ​Co, Ni, Cu and Zn, the H-bond interaction between H2O and O atoms around the M, leads to the stabilization of POM-H2O system. Moreover, it has been predicted that the binding properties of H2O strikingly depends on axial 3dz2 orbital of MII. In this regard, it has been exhibited that the affinity of H2O for MII in [PW11O39(MII)]5- with a filled 3dz2 orbital, is strongly reduced as measured by increasing in calculated MII-ligand distance. Also, strong contributions of MII 3d as well as the 2p orbitals of five oxygen donor atoms in polyoxometalate cluster results in the bonding interaction between MII and lacunary Keggin polyoxometalate. The DFT-derived IR spectra showed displacement and splitting in four previously known vibrational bands of Keggin-type polyoxometalate, α-[PW12O40]3-, owing to transition metal substitution and H2O ligation.

Journal ArticleDOI
Abstract: A DFT tetramer model constructed of multi-H-bonds at B3LYP/6-311G(d,p) level has been proposed for L-(+)-2-Chlorophenylglycine. Motivation in part for the tetramer model comes from the observed IR spectra near 3400−2500 cm−1 showing a very broad sub-band structure spread over ∼ 900 cm−1 without distinct sharp bands; secondly, XRD structures of similar molecular solids show multiple H-bonds among monomers. Therefore, the proposed tetramer consists of fourteen H-bonds arising from a network of inter-/intra-molecularly X−H···Y bonds: N−H···O, C−H···O and Cα−H···Cl bonds, all from four monomer species. The strengths and degree of these H-bonds being covalent, ionic or partial have been determined using topological parameters from AIM calculations. Other weaker van der Waals interactions and steric clashes in relation to the N−H···O, C−H···O and Cα−H···Cl bonds have also been evaluated by the method of ‘non-covalent interactions (NCI)’. Further, the charge transfer from the Y lone pair orbital (donor) to the X−H anti-bonding orbital (acceptor) have been explained on the basis of overlapping of orbitals using NBO analysis. Computed stabilization energies for the X−H···Y bonds have shown the inter-molecular N−H···O bonds to be the strongest of the H-bonds. Concentration-dependent UV spectral analysis aided by TD-DFT-based calculations at B3LYP/6-311G(d,p) with SMD model in water has shown that a strong band at 221 nm, among other bands, blue-shifts to 194 nm with a concomitant arrival of a shoulder band at 219 nm. The bands are assigned to the π→π* transition. This observation has been interpreted to be the result of dissociation of the tetrameric species into monomeric species and is supported by the stabilization of computed ground and excited electronic levels. By the same interpretation, three vibronic bands seen at 260−280 nm also have been explained. Computed vibrational modes of the tetramer fit very well with the experimental IR and Raman band features including low frequency Raman modes below 350 cm−1. It has been shown the consistency among the H-bonding descriptors - H···Y bond distance, change in X−H bond length, X−H frequency shifts, electron density, H-bond energy and stabilization energy by graphical correlations.

1 citations

Journal ArticleDOI
Jiajun Wang1, Xue Chen1, Baosheng Zhang1, Chuanbi Li1  +1 moreInstitutions (2)
Abstract: In this article, we synthesized the coordination complex: thiabendazole (TBZH) iron 5-aminoisophthalate (AIP), ([(Fe(TBZH)(AIP)(3H2O)]·2.5 H2O), and characterized by the X-ray single crystal diffraction analysis, the result reveals the iron center is six coordinated and formed a slightly distorted octahedron coordinated geometry. In the structure, the Nitrogen of AIP adopts κN coordination mode connecting the metal center and the two carboxylate groups are deprotonized. The TGA manifests there are three weight loss steps and the residue suggest it to be the ferroferric oxide. The Hirshfeld analysis reveals in dnorm-surfac, the O(N)–H···O hydrogen-bonds corresponds to the dark red spots near the hydrogen-bonds acceptor and donor atoms. The presence of patterns of red- and blue triangles on the same region of the shape-index surfaces is a characteristic of π···π stacking. The theoretical calculated the molecular orbitals, it shows that the LUMO orbital, the electron cloud is located at coordinated water molecules (O1, O3) and the free water (O1w). The electron cloud of the HOMO orbitals is mainly sited at the carboxylate groups and the benzene rings of AIP. The bond orders reveal the value of Fe-N1 and Fe-N2 are larger than that of the Fe-N4, Fe-O3, Fe-O2 and Fe-O1. The second-order perturbation energy analysis shown the most of the E(2) stabilization energies of LP(N) → LP*(Fe) is larger than those of the LP(O) → LP*(Fe), indicating the N atom in complex is the main contributor to the coordination. The AIM analysis found the bond critical point (BCP) of the complex, the electron density value ρBCP (from 0.007 to 0.034 a.u.) for the O(C)–H···O hydrogen bonds are all in the suggested interval of 0.002–0.035 a.u. the ρBCP order of Fe-N and Fe-O sequences are ρBCP(Fe-N1) > ρBCP(Fe-N2) > ρBCP(Fe-N4) and ρBCP(Fe-O1) > ρBCP(Fe-O3) > ρBCP(Fe-O2) shown the firm degree of the bond, these are consistent with the bond order. The Laplacian of electron density (∇2ρBCP) are positive and the |v(r)|/g(r)

Journal ArticleDOI
Abstract: Interatomic interactions and charge state of atoms in hexanuclear complex [Cu6(hfa)4(dpm)4(OH)4] have been studied by the methods of quantum chemistry and X-ray photoelectron spectroscopy (XPS). The shape and energy position of the Cu2p3/2-lines indicate that all copper atoms state could be interpreted as Cu2+. It was also analyzed the quantum chemical and XPS data on atomic charge distribution for monoligandic bis-β-diketonate Cu(hfa)2 and Cu(dpm)2 complexes. The comparison of calculated and experimental data for monoligandic and hexanuclear complexes revealed the electronic density redistribution on the oxygen and copper atoms in 1 due to the charge transfer interaction between Cu(hfa)2- and Cu(dpm)-fragments with participation of the bridging OH-groups, which was confirmed by NBO analysis.

2 citations

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Journal ArticleDOI
TL;DR: This work represents the first calculation of integrated atomic properties derived from the fitting of Gaussian density functions to experimental X-ray diffraction data, and shows qualitatively similar properties to those obtained from conventional ab initio gas-phase calculations, though the quantitative differences are often substantial.
Abstract: A constrained wavefunction model has been used to extract a Hartree–Fock wavefunction for C2H2O4·4H2O from both low-angle (\sin \theta / \lambda < 0.71 A−1, 571 reflections) and full (\sin \theta / \lambda < 1.00 A−1, 968 reflections) experimental X-ray diffraction data for crystalline α-oxalic acid dihydrate (α-C2H2O4·2H2O) using polarized double-ζ and triple-ζ Gaussian basis sets. Properties obtained from the zero-flux partitioning of the total charge-density distribution derived from these wavefunctions, as well as from multipole refinement of the experimental data, are calculated and compared. This work represents the first calculation of integrated atomic properties derived from the fitting of Gaussian density functions to experimental X-ray diffraction data. In particular, atomic kinetic energies derived from experimental data are presented for the first time. The results obtained from the constrained (experimental) charge density show qualitatively similar properties to those obtained from conventional ab initio gas-phase calculations, though the quantitative differences are often substantial. The accuracy of integrated properties calculated using this procedure was established from the analysis of a wavefunction derived from simulated random-error diffraction data; that is, data obtained by adding normally distributed errors to the experimental structure factors. Analysis of this random-error wavefunction indicated that most topological properties are accurate to within approximately 5%, although the error is much larger for those properties that have a steep gradient in the region being evaluated [e.g. the value of ∇2ρ(rb) at bond critical points] or are very small (e.g. the atomic dipole moment). Calculations of the constrained wavefunction using both the larger basis set and the complete set of experimental data yield results that agree quantitatively with the smaller calculations.

47 citations

Journal ArticleDOI
Abstract: The variation with the intermolecular distance of features in hydrogen bond (HB) dimers dependent on the electron density ρ(r) are studied in four complexes representative of weak/medium HB interactions. Topological properties, energy densities and integrated atomic properties are obtained with ρ(r) of dimers at B3LYP/6-311++G(d,p) optimized structures obtained upon fully relaxing the geometry of monomers. The dependence of A–H⋯B bond properties on intermolecular R(H⋯B) distances allows to characterize the nature of the interaction as monomers move nearer from infinite separation. At long distances the interaction is only electrostatic while for separations about 1 A larger than the equilibrium distance Req, quantum effects arising from ρ(r) begin to dominate. In the immediate neighborhood of Req the interaction is mainly led by the stabilization of the H-donor due in turn to energy lowerings in A and B atoms associated to polarization effects. The mutual penetration of electron densities of donor and acc...

112 citations

Journal ArticleDOI
Abstract: In an attempt to discover and analyze trends in distance relationships and properties at the bond critical point (BCP) in linear or near-linear N−H···N hydrogen bonds, the geometry of such bonds in a large number of suitable simple chemical species was optimized at the RHF/6-31G** level. The results for 67 of these are reported here; the geometry of 19 of them was optimized also at the MP2/6-31G** level. Correlations between the internuclear N−H, H···N, and N···N separations as well as between the N···BCP and H···BCP distances for these data sets and for different model functions are described in detail. The special case of symmetric N−H−N bonds is discussed; comparison with available experimental evidence shows that the correlation functions derived from the ab initio data have useful predictive value for crystallographic determinations involving short N−H−N bonds. Analysis of the correlation between the d(N−H) distance and the electron density ρc at the BCP has shown that although acceptable d,ρc repres...

95 citations

Journal ArticleDOI
Enrique Espinosa1, Ibon Alkorta2, Isabel Rozas2, José Elguero2  +1 moreInstitutions (2)
Abstract: The local kinetic G( r ) , potential V( r ) and total E( r ) energy densities, calculated at the critical points of 37 H⋯F closed-shell interactions by quantum mechanical methods, have been compared to their estimated values obtained by using an approximate evaluation of G( r ) and the local form of the virial theorem. The results presented here show very small differences between the corresponding quantities, and therefore support the validity of the estimations. Thus, the equations used in this procedure provide useful information for topological studies of experimental electron densities, permitting the evaluation of those energetic properties from the modelling of the topological properties of the electron density distribution.

338 citations

Journal ArticleDOI
Abstract: The dependence of the total electron energy density at the (3,−1) critical point (CP) of the H…O interaction against the interatomic distance (ECP) has been obtained by the addition of the local electron kinetic (GCP) and potential (VCP) energy densities dependences (ECP=GCP+VCP) for a set of 83 X-H…O hydrogen bonds (X=C, N, O) The ECP function has been related to the interaction potential by means of a proportionality relationship U=−υ⋅ECP, υ being a positive constant in volume units Based on the GCP and VCP functionalities, the proposed H…O interaction potential has been successfully checked against several physical and chemical properties The behavior of the U function has been compared to Morse and Buckingham-type potentials, leading to an almost perfect matching between all of them when they were constrained to have the same three parameters: the potential well depth U0, its position r0, and the curvature of the potential function at r0 The resulting U(r) function is simply described by the addit

236 citations

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