Emission and Luminescent Vapochromism Control of Octahedral Cu4I4 Complexes by Conformationally Restricted P,N Ligands

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.