INFRARED PHOTOISOMERIZATION OF THE METHANOL DIMER TRAPPED IN ARGON MATRIX - MONOCHROMATIC IRRADIATION EXPERIMENTS AND DFT CALCULATIONS

In a first part we propose an accurate assignment of the vibrational s pectra of (CH3OH)(2) and ((CH3OH)-O-18)(2) trapped in argon at 7 K, wh ich differentiates the proton donor (PD) and proton acceptor (PA) mole cules of four open chain conformers stable at this temperature. Then w e describe the effects of monochromatic irradiations in the OH and CO stretching regions which give rise not only to interconversions betwee n these conformers but also to the appearance of one highly unstable s pecies with a lifetime of about 4 minutes at 7 K. Its structure is dis cussed in the framework of DFT calculations after having checked the r eliability of the method on the stable dimeric form. (C) 1997 Elsevier Science B.V.