Computational investigation of the solvent and temperature effects on the tautomerization of 7-amino-1,3-dioxo-2,5-diphenyl-2,3-dihydro-1H, 5H-pyrazolo[1,2-a][1,2,4]triazole-6-carbonitrile

Abstract

This research examines the effects of solvent polarity and temperature on the tautomerization of 7-amino-1,3-dioxo-2, 5-diphenyl-2,3-dihydro-1H,5H-pyrazolo[1,2-a][1,2,4]triazole-6-carbonitrile at CAM-B3LYP/6-311G (d,p) level of theory. The selected solvents are n-hexane, diethyl ether, pyridine, ethanol, methanol, and water. The solvent effects have been examined by the self-consistent reaction field theory (SCRF) based on conductor-like polarizable continuum model (CPCM). The solvent effects have been explored on the energy barrier, frontier orbitals energies, and HOMO-LUMO gap. Dependencies of thermodynamic parameters (G andH) on the dielectric constants of solvents have also been tested. Specifically, the temperature dependencies of the thermodynamics parameters have been studied within 100-1000 K range. The rate constant of the tautomerism reaction is computed from 300 to 1200 K, in the gas phase.