INFRARED PHOTOISOMERIZATION OF THE METHANOL CYCLIC TRIMER TRAPPED IN A NITROGEN MATRIX

Condensation of nitrogen/methanol mixtures at 15 K revealed broad 3450 and 3284 cm(-1) absorptions assignable to (CH3OH)(n) aggregates, n gr eater than or equal to 3. The 3450 cm(-1) band is infrared photosensit ive and progressively disappears upon irradiation in the beam of the s pectrometer, with appearance of three main V-OH bands at 3661.9, 3433. 3 and 3389.2 cm(-1) growing at the same rate. Mixed CH3OH/CH3OD sample s revealed several mixed isotopic satellites of these three bands in b oth v(OH) and Y-OD regions, which allows us to conclude that the stabl e cyclic trimer responsible for the 3450 cm(-1) absorption is converte d upon OH (OD) vibrational excitation into an open chain trimer consis ting of three non-equivalent subunits. This conclusion agrees with com plementary observations in the v(co) region.