Synthesis of novel pyridyl containing phospholanes and their polynuclear luminescent copper(i) complexes

Abstract

A novel type of cyclic P,N-ligands, pyridyl containing phospholanes, has been synthesized in a moderate yield by the reaction of primary phosphines with 1,4-dichlorobutane in a superbasic medium. A series of homo tetranuclear octahedral Cu₄I₄L₂, dinuclear tetrahedral Cu₂I₂L₃, and dinuclear “head-to-tail” Cu₂I₂L₂ luminescent complexes with these ligands were obtained. All the compounds were characterized using a range of spectroscopic and computational techniques, and in the case of some Cu₄I₄L₂ and Cu₂I₂L₃ complexes, by single crystal X-ray diffraction. The structural diversity of the obtained complexes was reflected in their photophysical properties: phosphorescence spectra of the compounds display emission in broad spectral range of 471–615 nm. TD-DFT computations allow the assignment of a single emission band around 550 nm for Cu₂I₂L₃ complexes and 471 nm for Cu₂I₂L₂ complex to a vertical triplet–singlet transition from a metal-to-ligand and halide-to-ligand charge-transfer ³(M + X)LCT excited state, whereas a second band at around 600 nm in the spectra of octahedral Cu₄I₄L₂ complexes was assigned predominantly to Cu₄I₄ cluster-centered (³CC) excited state.