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Optimized geometry, vibration (IR and Raman) spectra and nonlinear optical activity of p-nitroanilinium perchlorate molecule: A theoretical study

Tamer O., Atalay A. S., Avci D., Atalay Y., Tarcan E., Marchewka M. K.

Materials Science Poland

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2016

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Vol. 34, No. 1

192--203

EN

The molecular modeling of p-nitroanilinium perchlorate molecule was carried out by using B3LYP and HSEH1PBE levels of density functional theory (DFT). The IR and Raman spectra were simulated and the assignments of vibrational modes were performed on the basis of relative contribution of various internal co-ordinates. NBO analysis was performed to demonstrate charge transfer, conjugative interactions and the formation of intramolecular hydrogen bonding interactions within PNAPC. Obtained large dipole moment values showed that PNAPC is a highly polarizable complex, and the charge transfer occurs within PNAPC. Hydrogen bonding and charge transfer interactions were also displayed by small HOMO-LUMO gap and molecular electrostatic potential (MEP) surface. The strong evidences that the material can be used as an efficient nonlinear optical (NLO) material of PNAPC were demonstrated by considerable polarizability and hyperpolarizability values obtained at DFT levels.

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The Bonds Analysis of Hexamethylenetetramine

Trzęsowska A., Kruszyński R.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 7

1155-1168

EN

Natural Bond Orbital (NBO) method was used for the investigation of the hexamethylenetetramine (hmt). The nature of bonds and electronic properties of the titled compound were analysed by means of quantum mechanical calculations on the structural molecular geometries from neutron diffraction measurements carried out in seven, different temperatures. Calculations were performed using density functional theory method (B3LYP) with 6-31++G(d,p) basis set. The values of total and stabilization energy, orbital populations, vibrational frequencies, dipole moments are discussed. As expected, the total hmt energy value decreases as the temperature decreases. The most profitable energy value was obtained for the lowest hmt measurement temperature, which implies that the significant and favourable reduction of thermal motion took place. The geometric parameters of hmt molecule are similar in all structures, the only normality is the shortening and hence enhancing of C-N bond with the temperature increasing. The NBO analysis of donor-acceptor interactions resulted in decreasing of localized nN, sigma CH orbital occupancy, increasing of CN * occupancy and stabilization energy associated with following delocalizations: nN sigma CN * and sigma CH sigma CN * . The results indicated that there exist very slight interactions between this nitrogen pair and the C-H antibonding orbitals of nearest neighbouring hmt molecule when the sets of hmt molecules are considered.

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Quantum chemical calculations on S-centered 1,3-dipoles : 1. Molecular and electronic structures of thiocarbonyl S-imides

Fabian J., Mlostoń G.

Polish Journal of Chemistry

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1999

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vol. 73 nr 4

669-681

EN

Results of high level quantum chemical calculations on thiocarbonyl S-imides of type 4 are reported. Structure and properties of thioformaldehyde S-imide (4b) (CH2SNH) and its derivatives were calculated by DFT(B3LYP) in conjunction with 6-31+G(d,p) and 6-31+G(3df,3dp) basis sets. For the sake of comparison conventional ab initio quantum chemical calculations were also performed at MP2 and QCISD(T) levels. The calculated geometry and molecular properties of 4b are compared with those of closely related ylidic structures such as thioformaldehyde S-methylide (1, R1-R4 =H), thioformaldehyde S-oxide (2,R1-R2 =H), and thioformaldehyde S-sulfide (3, R1-R2 = H). Differently substituted thiocarbonyl S-imides 4d-i were calculated to show the effect of substitution on their molecular and electronic structure as well as on some physical properties. The parent compound 4b in the molecular ground state is predicted to be most stable in the planar and bent anti-conformation with geometric parameters and electronic characteristics of a predominantly ylidic structure. The IR and UV absorption maxima of 4b were calculated and discussed with respect to the expected structure of this reactive intermediate.