Spectrochemical Study of Microscopic Crystals. II. Dichroism of Cobalt (III)-Praseo Salts

Abstract

Abstract The dichroisms of 1,6-[Co(en)2Cl2]Cl·HCl·2H2O and of 1,6-[Co(en)2Cl2]NO3 have been measured by the microscopic method. From consideration of the results, it has been presumed that, in the crystal of the hydrochloride, the line connecting Co with two Cl atoms is almost parallel to the b -axis, that the plane containing one Co and four N atoms of two ethylene-diamine molecules around Co is almost parallel to the plane formed by the a- and the c-axis. The nature of absorption bands of metallic complexes has been discussed on the basis of dichroism for the single praseo-ion, which has been determined from the above assumption. Arrangement of the complex ions in the nitrate has been inferred from observations as to the nature of dichroism in several faces. From comparison of the crystal structures of the two compounds and consideration of other properties, it has been suggested that the HCl molecule of crystallization in the crystal of the hydrochloride plays an important part in holding the complex ions together so that all the complex ions take the same orientation.