Emissive and birefringent Hg(CN)2-based coordination polymer materials with very distorted coordination geometries

New compounds and coordination polymers with highly polarizable metals (M = Hg, Pb) and 2,2’;6’2’-terpyridine (terpy) and 2,6-bis(benzimidazol-2-yl)pyridine (bbp) ligands have been synthesized and characterized for their photo-physical and optical properties. Hg(L)(CN) 2 (L = terpy, bbp) exhibit π-stacking interactions, which form a supramolecular alignment of the planar terpy and bbp units. Pb(terpy)X 2 [Hg(CN) 2 ] 0.5 (X = Cl, Br) generate 1D coordination polymers through bridging Hg(CN) 2 linkers and hydrogen-bonding interactions. All of the metal centres have very distorted coordination geometries. Hg(L)(CN) 2 (L = terpy, bbp) and Pb(terpy)Br 2 [Hg(CN) 2 ] 0.5 show terpy or bbp based emission. The materials are very birefringent, with ∆n ranging from 0.37(2) to 0.45(2). The magnitude of the observed birefringence depends on the orientation of the highly polarizable terpy and bbp units in relation to the viewing axis ...