Calculated infrared spectra of hydrogen-bonded methanol-water, water-methanol, and methanol-methanol complexes

Ab initio calculations at the B3LYP/aug-cc-pVDZ, B3PW91/aug-cc-pVDZ, MP2/aug-cc-pVDZ, B3LYP/6-311++G(2d,2p), B3PW91/6-311++G(2d,2p), and MP2/6-311++G(2d,2p) levels are performed for the IR spectra of isolated water and methanol molecules and hydrogen-bonded water-methanol, methanol-water, and methanol-methanol complexes. Frequency shifts and changes in intensities are obtained for the proton donor molecule and the results are compared with available experimental and theoretical results. Characteristic changes are discussed in all cases. For methanol we obtained considerable shifts in the OH group. The C-OH wag is calculated to blue shift and the OH stretch is calculated to red shift and increase in intensity is compared to the isolated methanol molecule. The magnitude of these shifts are obtained and discussed. For the methanol dimer the C-CH wag increases the frequency by similar to 400 cm(-1) and the CH stretch decreases the frequency by similar to 170 cm(-1), with an increase in intensity of nearly 15 times. (c) 2005 Wiley Periodicals, Inc.