Origin of Three Fold Torsional Potential in Methylated 2-Hydroxypyridine

In this paper, the detailed study of the methylated 2-hydroxypyridine molecule has been carried out using resonance-enhanced multiphoton ionization (REMPI) spectroscopic technique. However, the theoretical investigations have been performed using ab initio calculations. The origin band of the molecules 4-methyl-2-hydroxypyridine (4M2HP) and 6-methyl-2-hydroxypyridine (6M2HP) was observed at 34987 cm-1 and 35405 cm-1 in their REMPI spectrum and the bands assigned as ππ* transition state. The vibronic coupling of the nπ* and ππ* transition states took place in 4M2HP, thus some low intense bands near the original band of the molecule were observed in the spectrum. However, no such kind of bands observed in 6M2HP. The π*–σ* hyperconjugation is responsible for the conformational change of the methyl group in 4M2HP upon excitation (S0→S1).