Vibrational spectroscopic studies of trivalent hexa-aqua-cations: single-crystal Raman spectra between 275 and 1 200 cm–1 of the caesium alums of titanium, vanadium, chromium, iron, gallium, and indium

Abstract

Oriented single-crystal Raman spectra have been recorded at 80 or 90 K for CsM(SO₄)₂·12H₂O (M = Ti, V, Cr, Fe, Ga, or In), CsM(SeO₄)₂·12H₂O (M = Cr or Fe), and CsFe(SO₄)₂·12D₂O. A complete assignment of the spectra between 275 and 1 200 cm^–1 has been made. The total symmetric metal–water stretching modes of the trivalent hexa-aqua-cations occur at 517 (Ti), 525 (V), 540 (Cr), 523 (Fe), 537 (Ga), and 505 cm^–1(In), significantly higher than values previously reported. The wavenumbers of these modes vary with the reciprocal of the metal(III)–water bond lengths.