Ab Initio Study of the Electronic Spectrum of Formamide with Explicit Solvent

• DOI: 10.1021/ja990064d
• Publication Date: 2002-07-26T05:36:28Z
• Authors: Nicholas A. Besley; Jonathan D. Hirst
• Keywords: Solvatochromism; Molecular electronic transition; Oscillator strength; Blueshift

Of the many roles that solvent plays, its influence on molecular electronic structure is perhaps one of more challenging phenomena to study. In this study, effect solvation spectrum formamide investigated. Ab initio complete-active-space self-consistent field (CASSCF) and multiconfigurational second-order perturbation theory (CASPT2) methods are used compute ground- excited-state energies complexed with one, two, three water molecules. addition, a semicontinuum approach employed, in which formamide−(H2O)n (n = 1, 3) complexes studied within continuum model. The presence explicit molecules destabilizes Rydberg states by approximately 0.5 eV. case πnbπ* transition, red shift from 7.41 eV (gas phase) 7.16 observed, oscillator strength increases ∼10%. nπ* transition undergoes blue dependent O- - -H formamide−water hydrogen bond distance. physical origin these solvatochromic shifts former effects have been well reproduced previous ab study contrast, at least molecule needed observe transition. provides description solvated captures important local bulk effects.