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Hydrogen bonds between pyrazine and RCOOH (R = H, CH 3 , and C 6 H 5 ): A theoretical study
Author(s) -
Nascimento Renata X. D.,
Belarmino Márcia K. D. L.,
Lima Nathália B. D.
Publication year - 2012
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.24091
Subject(s) - pyrazine , chemistry , hydrogen bond , molecule , hydrogen , proton , computational chemistry , basis set , molecular vibration , crystallography , photochemistry , stereochemistry , organic chemistry , quantum mechanics , physics
Theoretical calculations using Møller–Plesset perturbation theory (MP2) levels of calculation with a 6‐31++G(d,p) basis set have been performed to determine stable structures and molecular properties for the 1:1 and 1:2 hydrogen complexes involving pyrazine as proton acceptor and RCOOH (R = H, CH 3 , and C 6 H 5 ). Six complexes have been characterized as minima as no imaginary frequency was found. As expected, the HO chemical bonds lengths are increased after complexation. For the strongly bound complex, the doubly complexed pyrazine acts as a bridge between the two end molecules while transferring electrons. The vibrational changes that take place in the RCOOH after complexation with pyrazine follow the usual behavior, and the HO stretching frequency is shifted downward whereas its irradiated intensity is much enhanced. As unexpected result, the vibrational modes of the CH stretching of pyrazine has its frequencies shifted to the blue. © 2012 Wiley Periodicals, Inc.