Single-crystal Raman and infrared study of aluminium trichloride hexa-hydrate

Abstract

Single-crystal Raman spectra obtained at 115 K are reported for [Al(OH₂)₆]Cl₃ and its deuteriate. Single-crystal i.r.-reflectance spectra have been recorded at ambient temperature for both materials. All the Raman bands predicted by factor-group analysis (f.g.a.) are observed, as are most of the i.r. bands. On the basis of the f.g.a. an assignment is made of the ‘external’ modes(wag, twist, and rock) of co-ordinated water with the order wag > twist > rock, and ν₁(of AlO₆) is placed at 524 cm^–1. An alternative assignment places ν₁ at 701 cm^–1 but yields less satisfactory force constants. The chief ambiguity remaining is in the location of ν₃(of AlO₆) which is probably at ca. 670 cm^–1.