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 Xray 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 13 C cross polarization magic angle spinning for ligand coordination and 1 H 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.
■ INTRODUCTIONLuminescent coordination polymers have been widely studied in recent decades, and several new materials have been produced and tested. 1 In particular, the chemisorption of small molecules onto these materials has been shown to alter their luminescence properties, 2 prospecting potential applications as molecular sensing systems. In this context, copper(I) coordination polymers have not been as widely explored, if compared to other transition metal or lanthanide analogues. 3−7 In particular, CuCN can provide interesting luminescence properties when reacted with proper ligands. A recent computational study described its particular structure highlighting that, conversely to many inorganic salts forming twoor three-dimensional (2D or 3D) arrays, CuCN is characterized by one-dimensional polymer chains consisting of twocoordinated metal centers and bridging cyano ligands. 8 CuCN itself is characterized by a weak luminescence. 9 However, its photoluminescence emission interestingly shifts from the near UV (392 nm) into the visible region upon the coordination of nucleophiles, while the intensity increases by several orders of magnitude. In some cases, small differences in the ligands, such as the presence of methyl or ethyl groups like in piperazine, methylpiperazine, and ethylpiperazine, can result in remarkable differences in the emission color of the obtained coordination polymers, providing several luminescence tuning possibilities. 10 Despite these promising properties,...