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DFT and MP2 study of isomery scheme in Formazan and intermolecular and intramolecular proton transfer between its tautomers
Author(s) -
Tavakol Hossein
Publication year - 2011
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.23092
Subject(s) - tautomer , chemistry , intermolecular force , intramolecular force , formazan , molecule , transition state , proton , phase (matter) , chloroform , computational chemistry , stereochemistry , organic chemistry , catalysis , biochemistry , physics , quantum mechanics
DFT and Moller Plesset (MP2) calculations were applied to study of isomery scheme in formazan. Formazan that can be presented by three tautomers and eight isomers has various applications in dyes, complexes, and biochemistry. The structures of its isomers and related transition states were optimized, and important molecular parameters, IR frequencies, and energetic results were extracted. The relative stabilities of formazan isomers in the gas phase were found to be as 1EZ >1ZZ >1EE >1ZE >2EE > 3 >2EZ >2ZZ >TS1 >TS3 >TS2. Thermodynamic data confirms that tautomer 1 is major tautomer, and all possible tautomerism interconversions have small rates at room temperature. Then, relative stabilities were calculated in different solvents (chloroform, tetrahydrofuran, acetone, and water). The relative stabilities and thermodynamic data in solvents are nearly similar to those in the gas phase, but the rate constants are slightly more than that in the gas phase. Moreover, relative stabilities of formazan isomers and intermolecular proton transfer in presence of one to three molecules of water have been studied. The results showed that activation barriers in water‐assisted tautomerisms are in general lower than those in the gas phase, but the relative energies of isomers do not change importantly by water clusters. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012