title: Solvent influence on the excited states of the oxo form of barbituric acid and the mechanisms of the out-of-plane non-radiative elongation of the N-H bond: a comparative theoretical and experimental study.
abstract: The solvent influence on the excited states, emission and absorption energies of the oxo for of barbituric acid was studied with experimental (UV and fluorescence spectra) and theoretical methods. The excited-state reaction paths of the out-pf-plane elongation of the N-H bond of the oxo form of barbituric acid were also investigated (TD DFT level) to the conical intersections mediating internal conversions to the ground state. The (1)nσ* excited state was found to be the driven electronic state. We found that the increase of the polarity of the solvent reduces the (1)nσ* excited state decay rate through a non-planar conical intersection and increases its energy. Thus, solvents with higher polarity disfavor the non-radiative decay through conical intersections.
authors.affiliation: Dept. Inorganic and Physical Chemistry, University of Food Technologies, Maritza 26 Str., 4002 Plovdiv, Bulgaria.
authors.forename: Ivan G
authors.initials: IG
authors.lastname: Shterev
authors.affiliation: Dept. Physical Chemistry, University of Plovdiv, Tzar Assen 24 Str., 4000 Plovdiv, Bulgaria. Electronic address: vdelchev@uni-plovdiv.net.
authors.forename: Vassil B
authors.initials: VB
authors.lastname: Delchev
mesh_terms: D001463:Barbiturates / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004560:Electricity; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D012997:Solvents / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D001463:Barbiturates; D012997:Solvents; C032232:barbituric acid
keywords: Barbituric acid; Conical intersections; DFT calculations; Emission energies; Excited-state reaction paths; Vertical excitation energies