Structural Chemistry

1,3-bis(benzimidazol-2-yl)-2-thiapropane (L) ligand and its zinc halide ZnX2 (X = Cl, Br, I) complexes have been synthesized. The compounds were characterized using the elemental analysis, molar conductivity, FT-Raman, FT-IR (mid i.r., far i.r.), 1H and 13C NMR spectra, and quantum chemical calculations performed with Gaussian 03 package program set. The optimized geometries and vibrational frequencies of the ligand and [Zn(L)Cl2] complex were calculated using the DFT/B3LYP method with a 6–31g(d) basis set. The geometry optimization of [Zn(L)Cl2] yields a slightly distorted tetrahedral environment around Zn ion, while the molecule clearly reveals the Cs symmetry. The molar conductivity data reveals that the complexes are neutral. The ligand is bidentate, via two of the imine nitrogen atoms in the bis-imidazole ring units, and together with the monodentate coordination of the two halides to the metal centre.

... Subhra Basak Æ Soma Sen Æ Samiran Mitra Æ C. Marschner Æ WS Sheldrick ... Lorenzotti A (1999) Polyhedron 18:3041 3. Talukder P, Datta A, Mitra S, Rosair G (2004) Z Naturforsch 59b:655 and references therein 4. Mondal N, Mitra S, Gramlich V, Ghodsi SO, Malik KMA (2001 ...

A semiempirical theory of ring π currents is developed, which accurately takes into account the electron correlation using the full configuration interaction (FCI) method. An elementary model is proposed, in which the calculation of the π-electron correlation is reduced to the model of generalized alternative Hückel systems. The FCI and SCF (self-consistent field) methods are used to calculate the diamagnetic susceptibilities and ring currents for some typical π systems. It is shown that, as a rule, the SCF method allows the qualitatively true description of the magnetic properties of condensed systems, although for antiaromatic molecules it often yields underestimated values of paramagnetic currents. The results of the FCI calculations suggest that electronic excitations can induce transitions from π paramagnetism to π diamagnetism (e.g., in fulvenes) and back (in quinones).

Page 1. REVIEW ARTICLE Interplay of thermochemistry and Structural Chemistry, the journal (volume 21, 2010) and the discipline Maja Ponikvar-Svet • Joel F. Liebman Received: 24 January 2011 / Accepted: 16 February 2011 © Springer Science+Business Media, LLC 2011 ...

A new liquid crystalline, optical material-based Schiff base core with a near to room-temperature mesophase, (4-methoxybenzylideneamino)phenyl oleate (I), was prepared from a natural fatty acid derivative, and its physical and chemical properties investigated by experimental and theoretical approaches. The molecular structure was confirmed by elemental analysis, FT-IR (Fourier-Transform-Infrared Spectroscopy) and NMR (nuclear magnetic resonance) spectroscopy. Optical and mesomorphic activities were characterized by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The results show that compound (I) exhibits an enantiotropic monomorphic phase comprising a smectic A phase within the near to room-temperature range. Ordinary and extraordinary refractive indices as well as birefringence with changeable temperatures were analyzed. Microscopic and macroscopic order parameters were also calculated. Theoretical density functional theory (DFT) calculations were carried out to estimate the geometrical molecular structures of the prepared compounds, and the DFT results were used to illustrate the mesomorphic results and optical characteristics in terms of their predicted data. Three geometrical isomers of the prepared compound were investigated to predict the most stable isomer. Many parameters were affected by the geometrical isomerism such as aspect ratio, planarity, and dipole moment. Thermal parameters of the theoretical calculations revealed that the highest co-planar aromatic core is the most stable conformer.

Quinine, an active antimalarial compound, is one of the most abundant constituents extracted from the bark ofCinchona trees. The activity differences among structurally related molecules appear to depend on the absolute stereochemistry of some functional groups, a result that has stimulated a detailed conformational analysis of these molecules of biological interest. In the present study the potential energy surface (PES)

The naturally occurring compounds of thorium ThSiO4, ThSiO4· nH2O, and (Th, Fe)SiO4 and uranium USiO4· nH2O have been studied by X-ray photoelectron spectroscopy in the range of electron binding energies from 0 to 1200 eV. The oxidation state of Th in the natural compounds is close to that in Th(OH)4; for uranium, it is similar to that in UO2. Based

Gas phase reaction between germane GeH4 and water H2O was investigated at CCSD(T)/[aug-cc-pVTZ-pp for Ge + Lanl2dz for H and O]//MP2/6-31G(d,p) level. Only the hydrogen elimination channels are monitored. Within the energy range of 100 kcal/mol, we located nine equilibrium and six transition states on the potential energy surface (PES) of the Ge–O–H systems. GeH4 reacts with H2O exothermically (by 2.37 kcal/mol) without a barrier to form a non-planar complex GeH4·H2O which isomerizes to GeH3OH·H2 and H2GeOH2·H2 with a barrier of 44.34 kcal/mol and 53.75 kcal/mol respectively. The first step of hydrogen elimination gives two non-planar species, GeH3OH and H2GeOH2 but germinol GeH3OH is found to be more stable. Further thermal decomposition reactions of GeH3OH involving hydrogen elimination have been studied extensively using the same method. The final hydrogen elimination step gives HGeOH which can exist in cis and trans forms. As the trans form is more stable, only the trans form is considered on the potential energy surface (PES) of the reaction. The important thermochemical parameters (∆rEtot + ZPE), ∆rH and ∆rG for the H2 elimination pathways are predicted accurately.

... Part IV. Synthesis and characterization of pyridoxilidene Girard-T hydrazone complexes. Crystal structure of the copper(II) complex Ljiljana S. Vojinovic-Ješic Æ Goran A. Bogdanovic Æ Vukadin M. Leovac Æ Valerija I. Cˇ ešljevic Æ Ljiljana S. Jovanovic ...