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Structuring and destructuring effects along a pathway toward formation of zwitterionic glycine···(H 2 O) 2 complex: many body analysis of clusters and molecular electrostatic potential investigations
Author(s) -
Kulkarni Anant D.,
Rai Dhurba,
Gejji Shridhar P.,
Bartolotti Libero J.,
Pathak Rajeev K.
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.24287
Subject(s) - chemistry , intramolecular force , density functional theory , proton , cooperativity , molecule , hydrogen bond , chemical physics , tautomer , computational chemistry , ionic bonding , cluster (spacecraft) , stereochemistry , ion , physics , quantum mechanics , organic chemistry , biochemistry , computer science , programming language
We investigate molecular cooperativity in the process of conversion of neutral “canonical” form of glycine···(H 2 O) 2 to its zwitterionic form by an intramolecular proton transfer induced by displacement of the oxygen of the water molecule proximal to the amino group, toward the hydrogen bonded H of the latter. In one of the possible pathways considered here, the carboxyl proton is seen to migrate to the amino group resulting into a stable, energetically locally minimal albeit slightly higher, zwitterionic state. Second‐order Møller‐Plesset perturbation theory (MP2) is used for this study; also, the Density Functional Theory (DFT) that includes popular density functionals, viz. B3LYP, B3PW91, as well as a new‐generation functional M06‐L; in conjunction with the basis set 6‐311++G(2d,2p). The proton transfer concomitantly brings in tangible changes in the molecular electrostatic potential profiles as well as repercussions in the salient infra‐red spectra. It is gratifying that DFT provides a consistently competent description of the transfer process. The proton transfer is examined through a “many‐body interaction‐energy analysis of clusters” scheme whence it is perceived that glycine primarily is neither a structure maker nor a breaker with respect to water···water interactions in the cluster. © 2012 Wiley Periodicals, Inc.