DFT and MP2 study of isomery scheme in Formazan and intermolecular and intramolecular proton transfer between its tautomers

Abstract

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.

The Substituent Effect on the Energy Profiles of Inter and Intramolecular Proton Transfers between Phosphine Oxide‐Phosphinous Acid Tautomers

“…Moreover, the energy profile of tautomeric process is closely related to understanding their biological behavior and physicochemical properties. In this line, solvents have direct contribution to the tautomeric processes by playing their important role in biological and chemical reactions [18,19]. It has been proven that the energy profiles of different phenomena in the solvent are close to the results obtained from the real biological system and in many computational studies, solvents have been employed to obtain the more reliable results.…”

Frontiers of Formazans Chemistry: A Review

“…[162] The properties of the formazans have been mostly investigated by UV-visible spectroscopy and theoretical and experimental results have been reported. [163][164][165] Formazan peaks λ max values are generally observed at 410-500nm and may be shifted to 550-600nm based upon the structure. These peaks are due to π-π* electronic transitions in formazan skeleton.…”

Bazi 5-Sübsti̇tüe Feni̇l-3-(4-Metoksi̇feni̇l)-1-(2-(Feni̇lti̇yo)feni̇l Formazan Türevi̇ Bi̇leşi̇kleri̇ni̇n Yapi Kararliliklarinin Teori̇k Olarak İncelenmesi̇

“…Formazanların tautomerik dengesini ve proton transfer mekanizmasını anlamak için bazı deneysel ve teorik çalışmalar yapılmıştır (Arslan vd. 2014;Sun vd, 2012;Tavakol 2012;Toy vd., 2015).…”

“…Teorik veri, deneysel çalışmayı yönlendirici ve aydınlatıcı olabilmekte veya deneysel çalışma ile kıyaslamalı olarak kullanılabilmektedir. Son yıllarda, yoğunluk fonksiyonlu teori (DFT) yöntemi bu amaçla kullanılmaktadır (Ebead 2011;Tavakol 2012;Sıdır vd. 2015).…”