"Electronic States of o-Nitrobenzaldehyde: A Combined Experimental and Theoretical Study"Verónica Leyva, Inés Corral, Thomas Schmierer, Björn Heinz, Ferran Feixas,|
Annapaola Migani, Lluis Blancafort, Peter Gilch, Leticia Gonzalez
J. Phys. Chem. A 112 (2008) 5046-5053
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 ∼280 nm, the absorption spectrum of o-NBA is dominated by a series of weak nπ* 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 ππ* 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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