VIBRATIONAL STUDY OF OXALIC ACID-PYRAZINE HYDROGEN-BONDED ADDUCTS

Infrared and Raman spectra of anhydrous and hemi-hydrated pyrazine-oxa lic acid crystallized complexes and their deuterated analogues have be en investigated between 4000 and 30 cm(-1) in the 400-90 K temperature range. Pyrazine retains its high molecular symmetry and the two nitro gens are involved in the complexation. From the spectroscopic data it is found that the general pattern consists of infinite chains of alter nated pyrazine and oxalic acid molecules built by OH ... N hydrogen bo nds with R(OH .. N) = 2.65 Angstrom. For deuterated and hemi-hydrated derivatives, this hydrogen bond is weaker.