Excited-state forms of 2-methylamino-6-methyl-4-nitropyridine N-oxide and 2-butylamino-6-methyl-4-nitropyridine N-oxide.
Excited-state quantum chemical calculations of two 2-alkyloamino-6-methyl-4-nitropyridine N-oxides are presented. Several different calculation methods and different basis sets were used, which all lead to similar results, although the precise values of excited-state energies and excited-state dipole moments differ. All methods used predict that in the S(1) excited state four types of isomers occur. In three cases, these excited-state local energy minima correspond to ground-state isomers, and these all have a pi pi* character. The fourth excited-state minimum, which we denote L*, does not have a corresponding ground-state isomer and has an n pi* character. This isomer is stable and plays an important role in understanding the photophysics of these molecules. In addition, we also calculated barriers between these excited-state minima, using predescribed reaction pathways. The theoretical results derived in this Article are confronted with experimental data from earlier papers.
Makarewicz
Artur
A
Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland.
Szemik-Hojniak
Anna
A
van der Zwan
Gert
G
Deperasińska
Irena
I