New copper(I) iodides with bisimidazole molecules: Synthesis, structural characterization and photoluminescence property

The hydro(solvo)thermal reactions of CuI with diverse bisimidazole molecules were investigated, affording five new copper(I) iodides [Cu₄I₄(L1)₂] (L1=1,3-bis(2-methylimidazol-1-ylmethyl)benzene) 1, [CuI(L2)] (L2=4,4′-bis(imidazolyl)biphenyl) 2, [Cu₄I₄(L3)] (L3=1,3-bis(2-methylimidazol-1-yl)propane) 3, [Cu₄I₄(L4)₂] (L4=1,4-bis(2-ethylimidazol-1-yl)butane) 4, and [Cu₄I₄(L5)] (L5=1,4-bis(1-imidazoly)benzene) 5. X-ray single-crystal diffraction analysis reveals that (i) in 1, a tetranuclear Cu-I cluster (stepped cubane) is observed, and the L1 molecule only acts as an ancillary ligand; (ii) in 2, the L2 molecules extend the castellated Cu-I chains into a 2-D layer network with a certain thickness; (iii) in 2-D single-layer network of 3, a 1-D Cu-I column is found, which can be viewed as a longitudinal packing of stepped Cu₄I₄ cubanes; (vi) in 4, the L4 molecules propagate the cubic Cu₄I₄ cubanes into a 3-D 4-fold interpenetrated network with a cds topology; and (v) in 5, the L5 molecules link the 1-D Cu-I ribbons into a 2-D single-layer network. The photoluminescence analysis indicates that 1, 2 and 4 emit light (red light for 1; yellow light for 2 and 4), while 3 and 5 are not emissive. Their photoluminescence behaviors are confirmed to be related to the Cu···Cu interactions in the molecules.