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 (DG andDH) 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.