Vibrational–Structural Combined Study into Luminescent Mixed Copper(I)/Copper(II) Cyanide Coordination Polymers

Herein, we report the characterization of a series of CuCN-based coordination polymers that display different crystal packing and electronic properties, namely, [Na2Cu(CN)3·3H2O]n(1), [Cu4(CN)5(NH3)2(H2O)]n(2), [Cu3(CN)4(NH3)3]n(3), [Cu3(CN)3(O)0.25(NH3)]n(4), [Cu5(CN)6(NH3)4]n(5), and [Cu5(CN)6(NH3)2]n(6). Spectroscopic evidence of the presence of ammonia molecules coordinated to the metal centers is provided, in particular for 4, which is a new structure. The characterization has been performed by single-crystal XRD (SCXRD), micro- IR spectroscopy, micro-Raman spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The photophysical properties have been studied through solid-state luminescence spectroscopy by acquiring the emission and excitation spectra and evaluating the emission quantum yields, which is an approach that has recently grown in importance in the solid-state field. The goals of this work are (1) to elucidate the correlation between the luminescence properties and the presence of either CuIor mixed CuI/CuIIoxidation states, (2) to evaluate the presence of NH3, H2O, or both in the polymers through a combined crystallographic–spectroscopic study, and (3) to rationalize the supramolecular architecture and its influence on the resulting luminescence.