The existence of two conformers with “compact” and “stretched” geometry of Cu4I4 demonstrating green and red emissions was established for the octahedral L2Cu4I4 complex with the conformationally restricted P,N-ligand. Stretching of the Cu4I4 core provides the drastic change of the emission and might be a reason for the dual emission of the Cu4I4 octahedral complexes.
A conformationally restricted P,N-ligand capable of the design of polynuclear copper(I) complexes was synthesized via the reaction of primary pyridylphosphine, paraformaldehyde, and benzhydrylamine. The reaction of the ligand with copper(I) iodide leads to the tetranuclear copper(I) complex with the octahedral type of copper-iodide core. Different orientation of coordination bonds of the ligands relative to the P,N2-heterocyclic fragments and to the Cu4I4 cores leads to the existence of two types of conformers of the complex with “compact” or “stretched” geometry of the Cu4I4 cluster. This lability of the complex allowed for obtaining two crystalline phases displaying green or red luminescence. The TDDFT computations along with XRD structural analysis gave a strong interpretation of the green emission belonging to the “compact” form of the complex and belonging of the red emission to the “stretched” form. Moreover, both crystalline phases demonstrate the strong vapochromic responses of luminescence on the vapors of wide range of solvents.Zum Volltext