A simple coordination complex exhibiting colour change on slight structural modification: Synthesis and crystal structures of violet and yellow forms of [Ni < sup > II < /sup > (opda) < inf > 2 < /inf > (NCS) < inf > 2 < /inf > ] (opda = orthophenylenediamine)

Abstract

The violet-coloured compound [NiII(opda)2(NCS) 2] (1) undergoes colour change to strawyellow colour retaining its molecular composition on standing over long period of time at room temperature in the solid state. Compound 1 (violet form) and its yellow-form [Ni II(opda)2(NCS)2] (2) (opda = orthophenylenediammine) have been characterized by routine spectroscopic methods and single crystal X-ray diffraction analysis. Compound 1 crystallizes in monoclinic space group P21/c and its yellow form (compound 2) retains same space group. Their crystal structures show an intricate supramolecular network based on N-H···S hydrogen bonds, that involve amine and thiocyanate groups coordinated to nickel(II). © Indian Academy of Sciences.