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.
Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland.
Artur
A
Makarewicz
Anna
A
Szemik-Hojniak
Gert
G
van der Zwan
Irena
I
Deperasińska