Control of Structures and Emission Properties of (CuI) _n 2-Methyldithiane Coordination Polymers

A structurally unique and strongly luminescent nonporous 3D coordination polymer (CP) [Cu₈I₈(methyldithiane)₄] _n, CP3, has been prepared in a quasi-anticipated manner from 2-methyl-1,3-dithiane, L1, and CuI. This CP incorporates an unprecedented Cu₈I₈ cluster built upon two side-fused open cubanes. The crystal structure of CP3 has been determined at 100, 150, 200, 250, 300, 350, and 400 K to study the temperature dependence of the Cu···Cu distances. Two other topological 1D and 2D CPs isomers of formula [{Cu₂I₂}(L1)₂] _n featuring dinuclear {Cu₂(μ₂-I)₂} rhomboids were also obtained independently by control of the reaction conditions. These two CPs convert into CP3 in hot PrCN, thus indicating that this latter material is the thermodynamic product. While CP1 and CP2 are not emissive, CP3 exhibits an intense luminescence due to the incorporation of the octanuclear Cu₈I₈ clusters as secondary building units within the network. The photophysical properties of CP3 have been investigated and rationalized by means of DFT and TDDFT computing. Furthermore, the thermal stability of these materials has been studied by ATG and DSC analyses. The Raman spectra of CP1-3 have been recorded in the solid state in the 50-500 cm^-1 region.