Solvent-free synthesis of luminescent copper(i) coordination polymers with thiourea derivatives

This communication reports the solvent-free synthesis of a series of copper(I) cyanide (CuCN) -based coordination polymers showing interesting luminescence properties and specific three-dimensional structures. The new compounds have been achieved by directly grinding CuCN together with thiourea (tu), N-methylthiourea (mtu), N-phenylthiourea (ptu), N,N′-diphenylthiourea (dptu), and 2,4-difluorophenylthiourea (fptu). The resulting compounds are [(CuCN)2(tu)]n, [(CuCN)5(mtu)3]n, [(CuCN)3(mtu)2]n, [CuCN(ptu)]n, [CuCN(dptu)]n, and [(CuCN)3(fptu)2]n. “Seeding” crystallization was successful for [(CuCN)2(tu)]n, [CuCN(ptu)]n, [CuCN(dptu)]n, and [(CuCN)3(fptu)2]n, and their structures have been resolved using X-ray single crystal diffraction. Owing to the microcrystalline powdered nature of compounds [(CuCN)5(mtu)3]n and [(CuCN)3(mtu)2]n, their characterization was mainly based on solid-state NMR, via 13C cross polarization magic angle spinning for ligand coordination and 1H magic angle spinning for the weak interactions involving hydrogen atoms. Other solid-state techniques (infrared spectroscopy, X-ray powder diffraction, differential scanning calorimetry, and thermogravimetric analysis) completed the characterization. Finally, the luminescence properties were explored by recording emission and excitation spectra and by evaluating the luminescence quantum yields and lifetimes. Such in-depth study gives promising results for the potential application as luminescent sensors of such compounds.