DEPENDENCE OF THE CHARGE-TRANSFER SPECTRA OF (C2H5NH3)(2)CDCL4-CU2-PRESSURE - STRUCTURAL-CHANGES AROUND CU2+( WITH HYDROSTATIC)

This paper investigates the variation of the charge transfer (CT) spec tra of the Cu2+ doped (EtNH3)(2)CdCl4 (Et = C2H5) layer perovskite und er hydrostatic pressure. The aim is to explain the strong redshift (-4 000 cm(-1)) undergone by the first CT band of the formed CuCl64- compl ex on passing from (EtNH3)(2)CdCl4: Cu2+ to the isomorphous (EtNH3)(2) MnCl4: Cu2+ crystal, which is accompanied by a change of color from li ght yellow to deep red. The pressure experiments show that the first C l- --> Cu2+ CT band experience an abrupt shift of -1200 cm(-1) between 23 and 26 kbar. The comparison of these results with those previously obtained in the pure (EtNH3)(2)CuCl4 suggests that this shift is asso ciated with a local change around the Cu2+ from an elongated octahedro n geometry (P = 1 atm) to a more compressed situation similar to that found for the Mn crystal. (C) 1997 Elsevier Science Ltd. All rights re served.