Neutral Coordination Polymers Based on a Metal-Mono(dithiolene) complex: Synthesis, Crystal Structure and Supramolecular Chemistry of [Zn(dmit)(4,4′-bpy)]_n, [Zn(dmit)(4,4′-bpe)]_n and [Zn(dmit)(bix)]_n (4,4′-bpy = 4,4′-bipyridine, 4,4'-bpe = trans-1,2-Bis(4-pyridyl)ethene, bix= 1,4-bis(imidazole-1-ylmethyl)-benzene

Abstract

This article describes a unique synthetic route that enables a neutral mono(dithiolene)metal unit, {Zn(dmit)}, to link with three different organic molecules, resulting in the isolation of a new class of neutral coordination polymers. The species {Zn(dmit)} coordinates with 4,4′-bipyridine (4,4′-bpy), trans-1,2-bis(4-pyridyl)ethene (4,4′'-bpe) and 1,4-bis(imidazole-1-ylmethyl)-benzene (bix) as linkers giving rise to the formation of coordination polymers [Zn(dmit)(4,4′-bpy)]_n (1), [Zn(dmit)(4,4′-bpe)]_n (2) and [Zn(dmit)(bix)]_n (3) respectively. Compounds 1-3 were characterized by elemental analyses, IR, diffuse reflectance and single crystal X-ray diffraction studies. Compounds 1 and 3 crystallize in the monoclinic space group P21/n, whereby compound 2 crystallizes in triclinic space group P. In the present study, we chose three linkers 4,4′-bpy, 4,4′-bpe and bix (see Schemes 1-3, respectively, for their structural drawings), that differ in terms of their molecular dimensions. The crystal structures of compounds 1-3 are described here in terms of their supramolecular diversities that include p-p interactions, not only among aromatic stacking (compounds 1 and 3), but also between an aromatic ring and an ethylenic double bond (compound 2). The electronic absorption spectroscopy of compounds 1-3 support these intermolecular π -π interactions.