Quantum Chemical Calculations Of Molecular Structure Research Articles

On the Spectroscopy of Phosphaalkynes: Millimeter- and Submillimeter-Wave Study of C2H5CP.

Ethyl phosphaethyne, C2H5CP, has been characterized spectroscopically in the gas phase for the first time, employing millimeter- and submillimeter-wave spectroscopy in the frequency regime from 75 to 760 GHz. Spectroscopic detection and analysis was guided by high-level quantum-chemical calculations of molecular structures and force fields performed at the coupled-cluster singles and doubles level extended by a perturbative correction for the contribution from triple excitations, CCSD(T), in combination with large basis sets. Besides the parent isotopologue, the three singly substituted 13C species were observed in natural abundance up to frequencies as high as 500 GHz. Despite the comparably low astronomical abundance of phosphorus, phosphaalkynes, R-CP, such as C2H5CP are promising candidates for future radio astronomical detection.

DFT Quantum-Chemical Calculations of Molecular Structures for Heteroligand M(III) Complexes of 3d Elements with Porphyrazine and Fluoride Ion

The molecular structures of heteroligand (6666)macrotetracyclic chelates of M(III) (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, or Cu) with porphyrazine (an (NNNN)-donating ligand) and F– ion are calculated by the DFT OPBE/TZVP method. The key bond lengths, bond angles, and nonbonded angles in these complexes are reported. The standard enthalpies, entropies, and Gibbs free energies of formation are calculated for the complexes. All complexes have a slightly distorted tetragonal-pyramidal geometry, where the complex former M(III) is to some degree raised above the pyramid base made up of the donor nitrogen atoms. Characteristically, all 6-membered metal chelate rings in these metal chelates are identical to one another both in terms of the sum of bond angles and in their varieties.

DFT quantum-chemical calculations of molecular structures for template heteroligand (5757)macrocyclic M(II) chelates of 3d elements with a 16-membered macrocyclic ligand and Br– ions

The geometric parameters of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) (5757)macrocyclic complexes with the NSSN-coordination of the donor sites of the chelant, which can be generated in template processes in M(II)–N-methylthiocarbohydrazide–hexanedione-2,5 systems and in the subsequent reaction of the newly formed metal chelate with 1,2-di(bromomethyl)benzene, have been calculated by the OPBE/TZVP functional density theory (DFT) hybrid method using the Gaussian09 program package. The 5-membered chelate ring is strictly planar in none of the complexes,. In all complexes (except for the Co(II) complex), 5-membered chelate rings are identical to each other. Both 7-membered chelate rings generated by the template links have a pronounced non-coplanarity. The bond angles between M–Br bonds are not 180° in any one of the complexes studied, although approaching this value.

Quantum-chemical calculations of molecular structure of trans-isomeric chelate of Ni(II) with hydrazinomethanethioamide using different versions of DFT method

The results of quantum-chemical calculations of the molecular structure parameters (bond lengths, bond and torsion angles) of the trans-chelate of Ni(II) with hydrazinomethanethioamide obtained by different versions of the density functional theory (DFT) method and GAUSSIAN09 program are summarized. The calculated data were compared with the corresponding experimental data. Although the structural data obtained using different methods of DFT are in good agreement with experiment they give different results in the evaluation of the spin multiplicity of the ground state and the relative energies between ground and excited states. The best agreement with experiment was observed in the calculation by OPBE/TZVP method.