Infrared laser induced conformational and structural changes of glycine and glycine·water complex in low-temperature matrices

Highlights: Excitations of the νOH fundamentals induce conversions between glycine conformers. The νOH excitation induced processes are less complex than the 2νOH induced ones. The νOH induced conversions have quantum yields smaller by c.a. 2 orders of magnitude. Some conversions take place below the barrier by H-atom tunneling. νOH excitations can also induce structural conversions of glycine·water complexes. Conformational and structural changes of matrix-isolated glycine and glycine·water complexes induced by the selective MIR excitation of the fundamental OH and NH stretching vibrational modes were studied. The observed spectral changes are consistent with the former assignments based on matrix-isolation IR spectroscopy combined with NIR laser irradiation. Since fewer conformational barriers can be reached by MIR than by NIR excitations, fewer processes are promoted effectively by MIR radiation. The comparison of spectral changes induced by selective MIR and NIR excitations can facilitate the conformational analysis of complex molecular systems and it can also yield information on the barrier heights.