Electronic states of o-nitrobenzaldehyde: a combined experimental and theoretical study |
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Authors: | Leyva Verónica Corral Inés Schmierer Thomas Heinz Björn Feixas Ferran Migani Annapaola Blancafort Lluís Gilch Peter González Leticia |
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Affiliation: | Institut für Chemie und Biochemie, Freie Universit?t Berlin, Takustr. 3, 14195 Berlin, Germany. |
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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. |
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