Ramaiyer Venkatraman

Molecular structure and IR spectra of bromomethanes by DFT and post-Hartree-Fock MP2 and CCSD(T) calculations

The molecular parameters (geometries, rotational constants, dipole moments) and vibrational IR spectra (harmonic wavenumbers, absolute intensities) of bromomethanes (CH3Br, CH2Br2, CHBr3, CBr4) are predicted by a density functional theory with the hybrid Becke3-LYP functional (DFT) and post-Hartree-Fock methods (MP2, CCSD(T)) using a 6-311G(2d,2p)-type basis set. The MP2 calculations are carried out with different numbers of frozen core orbitals to find how the number of bromine orbitals used for electron correlation influences the predicted molecular parameters and IR spectra of the species in question. Three options were used: (a) all electrons (full), with both the core and valence orbitals considered; (b) partial frozen core option (pfc), when the orbitals up to 3p of bromine were frozen; and (c) full frozen core option (ffc), when all core orbitals up to 3d were frozen. The CCSD(T) calculations for geometric parameters were carried out with both the pfc and ffc options, while for the prediction of the IR spectra only the ffc option was used. In addition, the calculations at the DFT and MP2(pfc) levels with inclusion of f functions on carbon and bromine atoms in bromomethanes (and also the CCSD(T)(pfc) calculations for CH3Br) were carried out to predict the changes in the geometric parameters and/or vibrational IR spectra of the molecules upon inclusion of f functions The geometries of bromomethanes (particularly the CBr bond lengths) are predicted better by the DFT and CCSD(T) calculations when the f functions (in particular on bromine atom) are included, while the MP2 calculations without f functions are good enough for correct predictions of the molecular geometries. The molecular parameters and vibrational IR spectra of bromomethanes in question and their deuterated species predicted by the DFT, MP2(ffc) and CCSD(T)(ffc) with the 6-311G(2d,2p) basis set agree well with the available experimental data.

Cocrystallization of melaminium levulinate monohydrate.

Crystals of 2,4,6-triamino-1,3,5-triazin-1-ium levulinate (4-oxopentanoate) monohydrate, C(3)H(7)N(6)(+).C(5)H(7)O(3)(-).H(2)O, are formed via self-assembled hydrogen bonding by cocrystallization of melamine and levulinic acid. Two N-H.N hydrogen bonds and four N-H.O hydrogen bonds connect two melaminium entities such that each of two pairs of N-H.O bonds bridges two H atoms belonging to the amine groups of two different melaminium cations via the carbonyl O atom of one levulinate molecule.

syn,E-1-cyclopentano-4-ethyl-3-thiosemicarbazone and syn,E-1-cyclopentano-4-phenyl-3-thiosemicarbazone

The structures of two thiosemicarbazones are described: syn,E-1-cyclopentano-4-ethyl-3-thiosemicarbazone (1) and syn,E-1-cyclopentano-4-phenyl-3-thiosemicarbazone (2). Crystal data: for 1: tetragonal, P43 (#78), a = b = 8.922(7) Å, c = 12.899(13) Å, and Z = 4; for 2: monoclinic a = 15.163(18) Å, b = 7.482(5) Å, c = 12.467(15) Å, β = 119.04(7)°, and Z = 4. In 1, molecules are linked by hydrogen-bonding into infinite chains with non-planar 9-ring subunits in which thioamides interact with the H—N—C—N—N groups of neighbors. Thioamide groups in 2 form dimers linked by N—B···HS hydrogen-bonds with a planar 8-ring as in solid state structures of carboxylic acids. The semicarbazide syn conformation fosters formation of N—H···N intramolecular hydrogen-bonding in each structure. The solid state structures are consistent with their infrared and proton nuclear magnetic resonance spectra.

Theoretical study on the kinetics and mechanism of the hydrogen atom abstraction reactions of CF3O+H2O and CF3OH+OH

Quantum mechanical ab initio calculations have been performed at various levels of theory to study kinetics of the reactions leading to formation/decay of CF3OH in the gas phase. It is shown that two considered reactions i.e., CF3O+H2O (reaction (1)) and CF3OH+OH (−1) proceed via formation of intermediate complexes. Mechanism of the reactions appears to be more complex, and may consist of three consecutive processes. Calculated rate constants are in excellent agreement with available experimental data. Derived expressions: k1=2.5×10−13×(T/300)1.4×exp(−3130/T)cm3molec−1s−1 and k−1=1.9×10−12×(T/300)1.0×exp(−3650/T)cm3molec−1s−1 allow a description of the kinetics of the reactions under investigation in the temperature range 300–1000 K.

1,3-Bis[2-(2-oxo-1,3-oxazolidin-3-yl)eth-yl]-1H-benzimidazol-2(3H)-one.

The molecular structure of the title compound, C17H20N4O5, contains a central fused-ring system, comprised of six- and five-membered rings. This unit is linked by C2 chains to two 2-oxo-1,3-oxazolidine five-membered rings. The central fused-ring system is essentially planar, with a maximum deviation of 0.008 (1) Å from the mean plane. Both oxazolidine five-membered rings are also nearly planar, with maximum deviations of 0.090 (1) and 0.141 (1) Å.

Aqua(1,10-phenanthroline)(L-prolinato)-copper(II) nitrate monohydrate

The reaction of copper(II) nitrate hydrate with L-proline in the presence of one equivalent of 1,10-phenanthroline produces the title ternary complex, [Cu(C 5 H 8 NO 2 )(C 12 H 8 N 2 )(H 2 O)]NO 3 .H 2 O. The enantiomorphous molecules contain two square-pyramidal complex cations as a loosely associated dimer. The bidentate proline ligands differ in conformation in the cations. In one cation, L-proline α-CH and NH groups lie on the same side as coordinated water and the Cu-OH 2 distance [2.382 (3) A] is longer than in the other cation [2.234 (4) A], in which the α-CH and NH groups lie below the pyramid base away from coordinated water. Additionally, copper is coordinated weakly by carboxyl oxygen from a neighboring inequivalent complex trans to water, with the longer C=O...Cu distance [3.390 (4) A] opposite the shorter Cu-OH 2 distance, and the shorter C=O...Cu distance [3.102 (4) A] opposite the longer Cu-OH 2 distance. Uncoordinated nitrates are hydrogen bonded to both coordinated and uncoordinated waters.

Chloridodiphen­yl{[1-(1,3-thia­zol-2-yl-κN)ethyl­idene]-4-phenyl­thio­semicarbazidato-κ2 N 1,S}tin(IV) methanol monosolvate

The title compound, [Sn(C6H5)2(C12H11N4S2)Cl]·CH4O, is formed during the reaction between 2-acetylthiazole 4-phenylthiosemicarbazone (Hacthptsc) and diphenyltin(IV) dichloride in methanol. In the crystal structure, the Sn atom exhibits an octahedral geometry with the [N2S] anionic tridentate thiosemicarbazone ligand having chloride trans to the central N and the two phenyl groups trans to each other. The Sn—Cl distance is 2.5929 (6), Sn—S is 2.4896 (6) and Sn—N to the central N is 2.3220 (16) Å. The MeOH molecules link the Sn complexes into one-dimensional chains via N—H⋯O and O—H⋯Cl hydrogen bonds.

A DFT and MP2 Study on the Molecular Structure and Vibrational Spectra of Halogenosubstituted Phosphoryl and Thiophosphoryl Compounds

The molecular geometrical parameters, rotational constants, dipole moments and vibrational infrared properties of a series of phosphoryl compounds (OPXiYjZk, X, Y, Z = F, Cl, Br; i+ j + k = 3) and their thio analogs are predicted by density functional and MP2 calculations using the 6-311G(2d,2p) basis set. Both methods yielded similar results. The predicted molecular parameters and the vibrational Raman and infrared spectra agree well with the available experimental data. The Raman Scattering Activities (RSA) and depolarization ratios (Dep) of the molecules are obtained by DFT calculations. Considering the different substitution modes of various halogen atoms, the resultant changes in the geometrical and vibrational properties are discussed. Such studies permit detailed information to be obtained concerning unknown molecules and can define the guidelines for synthesizing molecules of particular characteristics.

{4-Phenyl-1-[1-(1,3-thia­zol-2-yl)ethyl­idene]­thio­semicarbazidato}{4-phenyl-1-[1-(1,3-thia­zol-2-yl)ethylidene]­thio­semi­carbazide}nickel(II) chloride mono­hydrate

In the title compound, [Ni(C12H11N4S2)(C12H12N4S2)]Cl·H2O, the NiII ion is chelated by two 2-acetylthiazole-3-phenylthiosemicarbazone ligands, forming a distorted octahedral complex. The metal ion is coordinated via the thiazole nitrogen, imine nitrogen and thione sulfur atoms from each thiosemicarbazone ligand, and two coordinating units lie almost perpendicular to each other give dihedral angle = 81.89 (1)°]. One thiosemicarbazone unit is found to bind a chloride anion through two hydrogen bonds, while the other is linked with the disordered crystal water molecule. Two molecules are connected to each other through an intermolecular N—H⋯S interaction, forming a centrosymmetric dimer. Dimers are linked into sheets by π–π stacking of two phenyl rings [shortest C⋯C distance = 4.041 (3) Å].

Iodidotris(triphenyl-phosphine)copper(I) acetonitrile solvate.

The title compound, [CuI(C18H15P)3]·C2H3N, was obtained from the reaction of triphenylphosphine and copper(I) iodide in acetonitrile. The monomeric form of the complex has slightly distorted coordination of Cu by the I atom and three P atoms. The crystal structure is stabilized by C—H⋯π interactions between phenyl H atoms and phenyl rings. In addition, the complex molecules exhibit C—H⋯N hydrogen bonds between phenyl H atoms and acetonitrile N atoms. The crystal used was an inversion twin, with nearly equal component populations of 0.522 (8) and 0.478 (8).