Reactant ratio-modulated six new copper(i)–iodide coordination complexes based on diverse [CumIm] aggregates and biimidazole linkers: syntheses, structures and temperature-dependent luminescence properties

Abstract

A total of six copper(I)–iodide coordination complexes with diverse [CumIm] aggregates and bidentate biimidazole bridging ligands, [Cu2I2(dmimb)]n (1), [Cu4I4(dmimb)]n (2), [Cu6I6(dmimb)3]n (3), [Cu4I4(dimb)]n (4), [Cu2I2(dimb)2]n (5), and [Cu4I4(dimb)3]n (6), (dmimb = 1,4-di(2-methyl-imidazol-1-yl)butane, dimb = 1,3-di(imidazol-1-yl)benzene), have been synthesized and structurally characterized by single-crystal X-ray diffraction analyses and further characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Single-crystal X-ray diffraction analysis reveals that 1 is a double-chain based 1D ribbon incorporating a discrete [Cu4I4] stepped cubane aggregate. Complex 2 is a 2D layer based on the 1D infinite [Cu6I6]n column aggregate. Complex 3 is a triple-chain based 1D ribbon incorporating a discrete ladder-like [Cu6I6] aggregate. Interestingly, 1 and 3 are a pair of genuine supramolecular isomers controlled by the reaction ratio with an identical chemical composition. In the 2D layered structure of complex 4, the rare “S-shaped-double-bowl” Cu10I10 aggregate is observed and share the Cu2I2 rhomboids to form the 1D infinite [Cu10I10]n column. Complex 5 is a binuclear 18-membered metal–organic macrocycle with [CuI] monomeric units. Complex 6 is also a 2D layer constructed from a 1D infinite [Cu8I8]n aggregate which consists of a 1D infinite [Cu6I6]n column and a [Cu2I2]n ladder. In the overall view, the biimidazole linkers play an important role in the formation of diverse [CumIm] aggregates as well as the resulting structures and topologies. The structural changes of 1/2/3 and 4/5/6 are highly influenced due to the change of the reaction stoichiometry. For 1, 2, 5 and 6, they are non-emissive at both 298 K and 77 K, whereas 3 and 4 exhibit interesting temperature-dependent luminescence properties. The correlation between the luminescence thermochromism and the temperature-dependent variation of the Cu⋯Cu distance is also elucidated.