Structural characterization, photoluminescence and sensing properties of two copper(I)-iodide compounds

Two copper(I) iodide compounds with formula of {[Cu2I2 (2-mna)].DMA} (1) and {[CuI(6-mna)]center dot DMSO} (2) (2-mna = 2-mercaptonanicotinic acid; 6-mna = 6-mercaptonanicotinic acid; DMA = dimethylacetamide; DMSO = dimethyl sulfoxide) have been prepared by reaction and evaporation between CuI and 2-mna/6-mna at room temperature. Four Cu atoms in 1 are linked by I- ions and 2-mna ligands into [Cu4I4(2-mna)(2)] units which are further linked into a 1D inorganic-organic chain by sharing Cu-I bonds. In 2, thiolate sulfur of 6-mna adopts mu(2)-coordination modes to bridge two Cu atoms, forming [Cu-2(6-mna)(2)] building units, which are further connected by I- ions into 1D chain structure. It is worth mentioning that the Cu center dot center dot center dot Cu distances in 1 and 2 are shorter than the sum of the van der Waals radii of copper(I) (2.80 angstrom), implying the metal-metal bonding interactions. Interestingly, compounds 1 and 2 display blue and red fluorescence emission bands in the solid state, respectively. In particular, compound 2 exhibits the capability to selectively detect Fe3+ ion as a fluorescence turn-off sensor.