Infrared-induced conformer interconversion processes for allylamine in argon matrices: Wavelength dependence on the kinetics

Abstract

Infrared photoisomerization of allylamine trapped in solid argon is studied by irradiation either at specific wavelengths emitted by a CO 2 laser in coincidence with bands of the three conformers (S + G + , ST and CT) or in several mid- or near-IR domains using broad band filters. Upon irradiation with broad band filters the CT → ST process is mainly observed whatever the frequency domain, with only a slight intensity increase of the S + G + bands. Upon irradiation with CO 2 lines in coincidence with CT bands the conversion CT → ST is observed; the reverse process is evidenced by irradiation at ST frequencies. Irradiation at S + G + frequency shows no effect on the conformational equilibrium. Kinetic rate constants are measured and normalized to constant light power absorbed by the sample. They are compared with those calculated by the RRKM theory of first-order processes, assuming the same torsional barrier around the CC bond as in the gas phase. The good agreement between experimental and calculated values suggests the absence of vibrational selectivity in this photoisomerization process.