Quantitative Solvent-Free Thermal Synthesis of Luminescent Cu(I) Coordination Polymers

The luminescent Cu(I) coordination polymers [Cu2I2(m,m′-bpy)]n (CuI-m; m,m′-bpy = m,m′-bipyridine; m = 3, 4) were successfully synthesized by the solvent-free thermal reaction of the metal salt CuI with the organic linkers m,m′-bpy. Powder X-ray diffraction analysis revealed that CuI-3 was immediately formed when a mixture of CuI and 3,3′-bpy was ground in a mortar at room temperature (20 °C). In contrast, a temperature >120 °C was required to synthesize the CuI-4 isomer, probably because of the higher melting point of the 4,4′-bpy linker. Although excess bpy linker was necessary to afford the CuI-m in high yield, the quantitative synthesis, without any purification processes, was successfully achieved by simple heating at 140 °C, whereby the excess bpy linker was thermally removed by evaporation. Single crystal X-ray structural analysis indicated that in CuI-3 the dinuclear {Cu2I2} rhombic cores were bridged by 3,3′-bpy linkers. A similar structure was observed for CuI-4; however, the intermolecular π–π ...