cis- and trans-9,10-di(1H-imidazol-1-yl)-anthracene based coordination polymers of ZnII and CdII: synthesis, crystal structures and luminescence properties

New functional coordination polymers based on the semi-flexible 9,10-di(1H-imidazol-1-yl)-anthracene ligand (L) with ZnII and CdII, namely {[Zn(μ2-L)2](ClO4)2·m(MeOH)·n(DCM)}n (1), {[Zn(μ2-L)2](BF4)2·m(MeOH)·n(DCM)}n (2), {[Zn(μ2-L)2(p-Tos)2]·m(DCM)·n(MeOH)}n (3), {[Cd(μ2-L)2(p-Tos)2]·m(DCM)}n (4) {[Cd(μ2-L)2(p-Tos)2]·m(MeOH)·n(Dioxane)}n (5) and {[Zn(μ2-L)2(CF3CO2)2]·2(Dioxane)}n (6), were obtained. Dissolving L in polar solvent mixtures MeOH–DCM (4 : 1) or MeOH–dioxane (1 : 1) with ZnII and CdII salts resulted in the formation of complexes 1, 2, and 5 adopting a cis-conformation of the imidazole groups with respect to anthracene. In less polar mixtures of solvents such as MeOH–DCM (1 : 4) trans-L is observed, leading to the coordination polymers 3–4 with ZnII and CdII. In an intermediate solvent mixture such as MeOH–dioxane (1 : 4), the cis- and trans-conformation coexist as exemplified in complex 6 with ZnII. In the solid state, complexes 1–5 assemble as supramolecular 2-D coordination polymers with a (4,4) topology, while 6 forms a tridimensional porous network with a cds topology. All compounds reveal strong blue emission in the solid state at room temperature.