Infrared spectra of the PH3, AsH3, and SbH3--HX hydrogen bonded complexes in solid argon

Infrared spectra have been observed for several group V base–HX (X=F, Cl) hydrogen bonded complexes formed by codeposition of Ar/base and Ar/HX samples. The decrease in displacement of the H–X stretching fundamentals for the heavier bases parallels a similar decrease in base proton affinities, indicating decreasing hydrogen bond strengths. A single, sharp degenerate librational mode was observed, which indicates C3v structures for the complexes. The decrease in librational fundamentals observed in the order PH3>AsH3>SbH3 and decreasing 2νl/νl ratios indicate increasing anharmonicity and less rigid structures for the heavier complexes. Polarization of the phosphine lone pair and concentration of the P-H bonding electrons is suggested by blue-shifted νc3 and νc1 complex modes. OFF