Vibrational spectra and phase transition in Cd(CN) 2 ·G clathrates [G = HCCl 3 , HCBr 3 , CH 3 CCl 3 , (CH 3 ) 3 CCl or CHCl 2 CHCl 2 ]

Vibrational spectra of Cd(CN) 2 ·G clathrates were observed and changes in the spectral features with temperature analyzed, deducing phase transitions. A two‐step transition was found in the clathrates with G = HCCl 3 ( T c = 188, 122 K), HCBr 3 (249, 134 K) and CH 3 CCl 3 (228, 154 K). The upper transition is ascribed to the ordering of the three‐site structure, pointing out similarity in the manner of interaction between the clathrates with C 3v and T d guests. The lower transition is of a new type, which is considered to be an ordering process of dipoles. In Cd(CN) 2 ·CHCl 2 CHCl 2 a phase transition was found at 160 K. Its low transition temperature is ascribed to the difference in disordered structures between the C 3v and CHCl 2 CHCl 2 systems. 2 H NMR spectral features of Cd(CN) 2 ·DCCl 3 are reported. Copyright © 2002 John Wiley & Sons, Ltd.