Structures and UV‐Visible Absorption Properties of Unsymmetrical Bisdithiolene Nickel Complexes

A new unsymmetrical bisdithiolene nickel complex Ni(Et 2 dazdt)(mnt) was synthesized and structurally characterized, where Et 2 dazdt and mnt denote 1,4‐diethyl‐perhydrodiazepine‐2,3‐dithione and maleonitrildithiolate, respectively. Its crystal structure and absorption spectrum were determined and compared to those of Ni(Et 2 pipdt)(mnt), where Et 2 pipdt is 1,4‐diethyl‐piperazine‐2,3‐dithione. X‐ray diffraction analysis reveals that the Ni(S 2 C 2 ) 2 moiety of Ni(Et 2 dazdt)(mnt) is not planar due to the twist conformation of a seven‐member ring of Et 2 dazdt ligand. The twisting of Et 2 pipdt is less severe and NiS 4 center of Ni(Et 2 pipdt)(mnt) possesses a closer to planar conformation than that of Ni(Et 2 dazdt)(mnt). Unlike Ni(Et 2 pipdt)(mnt), Ni(dazdt)(mnt) shows two major separated absorption bands in the visible and near‐IR region, although both absorption bands show negative solvatochromism similar to that of Ni(Et 2 pipdt)(mnt).