Effect of meta substitution of methyl group on 2-hydroxypyridine: Spectroscopic investigation
Keywords: methyl torsion, REMPI, ab initio, hyperconjugation, HOMO, LUMO
AbstractWe have reported here the detailed investigation of the effect of methyl group substitution on the meta-position of the 2-hydroxypyridine molecule. Resonance enhanced multiphoton ionization (REMPI), FT-IR and Raman spectroscopic techniques have been used for the experimental study of the molecules. Ab initio calculations were used for theoretical investigations of the molecules. The origin band of the molecules 3-methyl-2-hydroxypyridine (3M2HP) and 5-methyl-2-hydroxypyridine (5M2HP) was observed at 33830 and 34105 cm–1 in their REMPI spectroscopy, and the bands assigned as a ππ* transition state. The vibronic coupling of nπ* and ππ* transition states took place in 3M2HP, thus some low intense bands near the origin band of the molecule were observed in the REMPI spectrum. However, there was no such kind of bands in 5M2HP. The π*–σ* hyperconjugation is responsible for the conformational change of the methyl group in 3M2HP upon excitation (S0 → S1).
Atoms and Molecules