A comparative analysis of the UV/Vis absorption spectra of nitrobenzaldehydes.

Leyva, Veronika; Corral, Ines; Schmierer, Thomas; Gilch, Peter and Gonzales, Leticia (2011): A comparative analysis of the UV/Vis absorption spectra of nitrobenzaldehydes. In: Physical Chemistry Chemical Physics, Vol. 13, No. 10: pp. 4269-4278

Abstract

In a joint experimental and theoretical study, the UV/Vis absorption spectra of the three isomers (ortho, meta, para) of nitrobenzaldehyde (NBA) were analyzed. Absorption spectra are reported for NBA vapors, cyclohexane and acetonitrile solutions. All spectra are poor in vibronic structure and hardly affected in shape by the surroundings (vapor or solution). Moderate solvatochromic shifts of [similar]−0.2 eV are measured. For all isomers vertical transition energies, oscillator strengths, and excited state dipole moments were computed using the MS-CASPT2/CASSCF and CC2 methods. Based on these calculations the experimental transitions were assigned. The spectra of all isomers are characterized by weak (εmax ≈ 100 M−1 cm−1) transitions around 350 nm (3.6 eV), arising from nπ* absorptions starting from the lone pairs of the nitro and aldehyde moieties. The next band of intermediate intensity peaking around 300 nm (4.2 eV, εmax ≈ 1000 M−1 cm−1) is dominated by ππ* excitations within the arene function. Finally, strong absorptions (εmax ≈ 10 000 M−1 cm−1) were observed around 250 nm (5.0 eV) which we ascribe to ππ* excitations involving the nitro and benzene groups.

• Item Type: Journal article
• Form of publication: Publisher's Version
• Faculties: Chemistry and Pharmacy
• Subjects: 500 Science > 530 Physics; 500 Science > 540 Chemistry
• Alliance/National Licence: This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.
• Language: English