title: Electronic states of o-nitrobenzaldehyde: a combined experimental and theoretical study.
abstract: The experimental UV/vis absorption spectrum of ortho-nitrobenzaldehyde (o-NBA) has been assigned by means of MS-CASPT2/CASSCF, TD-DFT, and RI-CC2 theoretical computations. Additional information on the nature of the absorbing bands was obtained by comparing the o-NBA spectrum with that of related compounds, as, e.g., nitrobenzene and benzaldehyde. For wavelengths larger than approximately 280 nm, the absorption spectrum of o-NBA is dominated by a series of weak n pi* absorptions from the NO2 and CHO groups. These weak transitions are followed in energy by a more intense band, peaking at 250 nm and arising from charge transfer pi pi* excitations involving mainly benzene and nitro orbitals. Finally, the most intense band centered at 220 nm has its origin in the overlap of two different absorptions: the first one localized in the NO2 substituent and the second one arising from a charge transfer excitation involving the NO2 and the CHO fragments, respectively.
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany.
authors.forename: Verónica
authors.initials: V
authors.lastname: Leyva
authors.forename: Inés
authors.initials: I
authors.lastname: Corral
authors.forename: Thomas
authors.initials: T
authors.lastname: Schmierer
authors.forename: Björn
authors.initials: B
authors.lastname: Heinz
authors.forename: Ferran
authors.initials: F
authors.lastname: Feixas
authors.forename: Annapaola
authors.initials: A
authors.lastname: Migani
authors.forename: Lluís
authors.initials: L
authors.lastname: Blancafort
authors.forename: Peter
authors.initials: P
authors.lastname: Gilch
authors.forename: Leticia
authors.initials: L
authors.lastname: González