TEMPERATURE-DEPENDENCE OF THE NU(S)(OH) BAND SHAPE OF ORTHO-MANNICH BASES IN GAS-PHASE AND LIQUID XENON SOLUTION

Infrared spectra of the two ortho-Mannich bases 2-(N,N-dimethylaminome thyl)-4-chlorophenol (I) and 2-(N,N-dimethylaminomethyl)-4,6-dichlorop henol (II) with a medium-strong intramolecular hydrogen bond, were mea sured in a wide frequency (4000-50 cm(-1)) and temperature (-105 degre es C to + 120 degrees C) range in liquid Xe, CCl4 solutions and gas ph ase. The temperature studies of the first and second spectral moments of the upsilon(s)(OH) band in liquid Xe within the temperature range f rom -105 to +30 degrees C allow for the analysis of the upsilon(s)(OH) mode coupled with the low-frequency vibrations (upsilon(l)) of the no n-linear hydrogen bond. Transitions located at ca. 150, 250 and 340 cm (-1) were selected as such upsilon(l) modes. The effective coupling pa rameter between high-frequency upsilon(s)(OH) and low-frequency upsilo n(l) vibrations of the hydrogen bridge was evaluated: b = alpha(ssl)/o mega(l) similar or equal to 0.7. Model calculations accounting for the hot and combination transitions give satisfactory reproduction of the gas phase upsilon(s)(OH) and upsilon(s)(OD) bands shapes. Both temper ature experiments and model calculations predict that even at 0 K the halfwidth of the upsilon(s)(OH) band can be quite large, viz. ca. 200- 400 cm(-1).