The Crystal Absorption Spectra of Some Hexachloroiridate(IV) Salts

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Abstract
The absorption spectra of the single-crystals of several hexachloroiridate(IV) salts and the doped crystals of the hexachlorostannate(IV) salts and the hexachloroplatinate(IV) salt with the IrCl62− anion were measured. Distinct dichroisms appeared in the polarized absorption spectra of all the anisotropic crystals studied. The splittings of the bands and the dichroisms of the spectra were interpreted in terms of the lowering of the symmetry of the IrCl62− anions in the crystal. The absorption bands at 19760 and 20000 cm−1 in the spectra of (CH3NH3)2-Sn(Ir)Cl6 could be assigned to the E′g→E″u and E′g→E′u transitions respectively from their polarizations in the double group, D3d*. Similarly, the bands at 23100, 23500, and 24500 cm−1 were assigned to the E′g→E′u, E′g→E″u, and E′g→E′u transitions respectively. The polarized absorption spectra of Na2IrCl6·6H2O and Na2Pt-(Ir)Cl6·6H2O were also interpreted, assuming that the IrCl62 anions in these crystals were of the D4d symmetry.