FIRST EXAMPLE OF THE ABC NU(OH) ABSORPTION STRUCTURE FOR BOTH GASEOUSAND CRYSTALLINE PHASE - INFRARED STUDIES OF DIMETHYLPHOSPHINIC ACID

Infrared spectra for both gaseous (4000-1000 cm(-1)) and polycrystalli ne (4000-400 cm(-1)) samples of dimethylphosphinic acid (CH3)(2)POOH ( DMPA) at various temperatures are reported and discussed. The main att ention is focused on the hydrogen bond vibrations. For the first time, the characteristic ABC structure of the v(OH) band, occurring in the spectra of solid samples of strongly hydrogen bonded complexes was obs erved in the gas phase spectra of DMPA dimers. In spite of different t ypes of aggregates present in the solid state a similar shape of the v (OH) absorption was found in the crystalline sample spectra. However, an inverse intensity distribution of the ABC subbands was observed. Th e presented results fully confirm the explanation of the ABC structure as being due to the Fermi resonances between v(OH) and overtones of t he deformation modes 2 delta(OH) and 2 gamma(OH). (C) 1997 Elsevier Sc ience B.V.