Versatility of Cyclic Triimidazole to Assemble 1D, 2D, and 3D Cu(I) Halide Coordination Networks

Cyclic triimidazole (C9H6N6, L), with C-3h molecular symmetry and three nitrogen atoms available for coordination, is here successfully employed for the first time in the synthesis of coordination compounds. In particular, by varying the reaction conditions (e.g., solvent, temperature, template), seven Cu(I)-halide coordination polymers of different dimensionality are obtained: two 1D polymers, [CuIL](n) (1) and {[CuIL]center dot(I-2)(0.5)}(n) (2), three 2D nets, [CuXL](n) (X = I, Br) (3-5), and two 3D networks, [CuCIL](n) (6) and {[Cu3L4]I-3}(n) (7). Single crystal X-ray diffraction analysis reveals that the structural versatility of both the ligand and the CuX moiety allows isolating 1D double-stranded stairs in which L is monodentate, 2D layers containing either Cu-2(mu-X)(2) or Cu-2(mu-X) moieties and bidentate L ligands, 3D frameworks built up by tridentate L linkers and either monodentate or noncoordinating halogen atoms. The 3D frameworks show nets of srs and bor topologies. The SHG efficiency of powders of 7 (the only noncentrosymmetric derivative of the series) is 10 times higher than that of sucrose. Phosphorescent emission of XLCT character is observed for 1 and 6.