Photochemistry of 2-(methylamino)pyridine in a low-temperature argon matrix: Amino–imino tautomerism and rotational isomerism

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Vol. 187; no. 1; pp. 113 - 118
• Main Authors: Akai, Nobuyuki, Ohno, Keiichi, Aida, Misako
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.03.2007
• Subjects: 2-(Methylamino)pyridine; Amino–imino tautomerism; DFT calculation; Matrix-isolation infrared spectroscopy; Rotational isomerism; Rotational isomerism; DFT calculation; Matrix-isolation infrared spectroscopy; Amino–imino tautomerism; 2-(Methylamino)pyridine
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2006.10.002

Photoreaction of 2-(methylamino)pyridine in a low-temperature argon matrix was investigated by infrared spectroscopy and density functional theory calculation. The two amino tautomers with nearly isoenergetic conformation (TA and CA) around the C–N(HCH 3) bond for 2-(methylamino)pyridine change into N-2(1 H)-pyridinylidenemethanamine as the methyl-imino tautomers (TMI and CMI) by intramolecular hydrogen-atom (or proton) transfer upon UV irradiation (320 > λ ≥ 300 nm). The reverse tautomerism occurs by longer-wavelength light irradiation (370 > λ ≥ 340 nm), where only the amino tautomer TA is reproduced from the methyl-imino tautomer TMI.