Measurement of Circular Birefringence and Circular Dichroism of the Single Crystals of Γ-(+)₅₈₉- and Δ-(-) ₅₈₉-Tris(ethylenediamine)cobalt(III) Triiodide Monohydrate by the Extended HAUP Method

We have achieved measuring four optical parameters simultaneously, namely, linear birefringence (LB), circular birefringence (CB), linear dichroism (LD), and circular dichroism (CD), of single crystals of Γ-(+)₅₈₉- and Δ-(-)₅₈₉-tris(ethylenediamine) cobalt(III) triiodide monohydrate (1) along the 〈001〉 plane at the fixed wavelength (514.5 nm). Such measurements are possible only when the High Accuracy Universal Polarimeter (HAUP) is employed; it is called the extended HAUP method. Our experimental results showed that both LB and LD of the Γ-(+) ₅₈₉-(1) crystal have the same magnitude as those of the Δ-(-)₅₈₉-(1) crystal. It was also revealed for the first time that the CB data of crystals of Γ-(+)₅₈₉-(1) and Δ-(-)₅₈₉-(1) are almost of the same magnitude, but are of opposite sign, reflecting their opposite absolute configurations. On the other hand, although the CD data obtained for Γ-(+)₅₈₉-(1) is almost three times larger than that for Δ-(-)₅₈₉-(1), these CD data are also opposite in sign, as expected from the opposite chirality of crystals.