Towards Optimized Photoluminescent Copper(I) Phenanthroline-Functionalized Complexes: Control of the Photophysics by Symmetry-Breaking and Spin–Orbit Coupling

Abstract

The electronic and structural alterations induced by the functionalization of the 1,10-phenanthroline (phen) ligand in [Cu(I) (phen-R2)2]+ complexes (R=H, CH3, tertio-butyl, alkyl-linkers) and their consequences on the luminescence properties and thermally activated delay fluorescence (TADF) activity are investigated using the density functional theory (DFT) and its time-dependent (TD) extension. It is shown that highly symmetric molecules with several potentially emissive nearly-degenerate conformers are not promising because of low S1/S0 oscillator strengths together with limited or no S1/T1 spin–orbit coupling (SOC). Furthermore, steric hindrance, which prevents the flattening of the complex upon irradiation, is a factor of instability. Alternatively, linking the phenanthroline ligands offers the possibility to block the flattening while maintaining remarkable photophysical properties. We propose here two promising complexes, with appropriate symmetry and enough rigidity to warrant stability in standard solvents. This original study paves the way for the supramolecular design of new emissive devices.

Structural change dynamics of heteroleptic Cu(i) complexes observed by ultrafast emission spectroscopy

“…13,15,21,24,47 Recently, heteroleptic copper(I) complexes, which have both phosphine and diimine ligands, have attracted attention because this class of Cu complexes exhibit attractive and advanced photochemical and photophysical properties. [48][49][50][51][52][53][54][55][56][57][58] Especially, [Cu(I)(dmp)(P) 2 ] + (dmp = 2,9-dimethyl-1,10-phenanthroline derivatives; P = phosphine ligand) (Fig. 1) has big potential to work as a photosensitizer in photocatalytic systems.…”