Journal of Molecular Structure, ( ISI ), Volume (1034), No (2), Year (2013-2) , Pages (354-362)

Title : ( Combination of X-ray crystallography and theoretical study to evaluate the effect of N-H...O=P versus N-H...O=C hydrogen bonds on the N-H stretching frequencies )

Authors: Mehrdad Pourayoubi , Mohammad Izadyar , behrouz elahi , Masood Parvez ,

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Two new CCl3C(O)NHP(O)X compounds [X = NH(CH2)3NH (1) and NHCH2C(CH3)2CH2NH (2)] were synthesized and characterized by spectroscopic methods and X-ray crystallography. In each of 1 and 2, the phosphoryl and carbonyl groups are gauche relative to one another and the P atom is in a tetrahedral environment. The 1,3-diazaphosphorinane moiety adopts conformation between chair and envelope with the P=O in an equatorial position. In the structure 1, the asymmetric unit contains one molecule; whereas, the asymmetric unit of 2 is composed of two independent molecules. In the crystal packing of 1 and 2, the N-H...O hydrogen bonds lead to two-dimensional arrangements along (-101) plane for 1 and (010) plane for 2. In order to precise assignments of different N-H units stretching frequencies in compounds 1 and 2, quantum chemical calculations were performed, with B3LYP method using 6-311++G(d,p) basis set. Theoretical procedure was performed for the individual molecule (monomer) and also for the hydrogen-bonded clusters of the molecules. In the H-bonded molecules, the effect of hydrogen bonds formation and their strengths in different N-H...O=P and N-H...O=C units were considered to close the theoretical frequencies of absorption bands to the real values. It is found that the stronger N-H...O=P hydrogen bond creates more changes in the N-H stretching frequency than the weaker N-H...O=C hydrogen bond makes. The natural bond orbital analysis showed a positive character for H atom and a negative character for N and O atoms. The hydrogen bond formation was studied by the AIM method through the Laplacian analysis.

Keywords

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@article{paperid:1031764,
author = {Pourayoubi, Mehrdad and Izadyar, Mohammad and Elahi, Behrouz and Masood Parvez},
title = {Combination of X-ray crystallography and theoretical study to evaluate the effect of N-H...O=P versus N-H...O=C hydrogen bonds on the N-H stretching frequencies},
journal = {Journal of Molecular Structure},
year = {2013},
volume = {1034},
number = {2},
month = {February},
issn = {0022-2860},
pages = {354--362},
numpages = {8},
keywords = {X-ray DFT Phosphoramidate Hydrogen-bond AIM NBO},
}

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%0 Journal Article
%T Combination of X-ray crystallography and theoretical study to evaluate the effect of N-H...O=P versus N-H...O=C hydrogen bonds on the N-H stretching frequencies
%A Pourayoubi, Mehrdad
%A Izadyar, Mohammad
%A Elahi, Behrouz
%A Masood Parvez
%J Journal of Molecular Structure
%@ 0022-2860
%D 2013

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