The vibrational characteristics of deuterated acetonitrile dissolved in isopropanol, dimethyl formamide (DMF), and dimethyl sulfoxide (DMSO) have been studied. Observed vibrational bands show substantial frequency shifts, the amounts of which vary almost linearly with concentration. The absorption feature in the region of 2220–2280cm−1 was deconvoluted to the consisting absorption bands. The band at 2258cm−1 of pure CD3CN, which is on the low frequency side of the monomer CN stretch (ν2), is attributed to the CN stretch of the dimer (ν′2). The shoulder found on the further low frequency side of the ν2 band, particularly in dilute solution, is believed to be due to ν5, and its frequency and intensity vary largely as a function of concentration along with those of other vibrational bands involved with the CD3 group. The ν5 band of pure CD3CN is believed to be active and located at about 2251cm−1. Ab initio calculations have also been performed for the solute–solvent complexes, CD3CN–DMF and CD3CN–DMSO, at the MP2/6-31+G(2d,p) level assuming anti-parallel configurations. The calculated results show a good agreement with the observed results.
