# Organophosphides: A New Class of Luminophore Ligands for Copper(I) Carbene Based TADF Emitters and Photocatalysts

## TL;DR

A new class of copper(I) carbene complexes using dimesityl phosphide ligands shows orange emission and photocatalytic potential for hydrophosphination.

## Contribution

Dimesityl phosphide ligands are introduced as a new class of luminophores for copper(I) carbene complexes with enhanced photonic and catalytic properties.

## Key findings

- Dimesityl phosphide ligands cause a bathochromic shift in emission to orange-red and near-infrared wavelengths.
- The complexes exhibit thermally activated delayed fluorescence with high quantum yields and dissymmetry factors.
- They act as efficient blue light photocatalysts for hydrophosphination of alkynes in solution.

## Abstract

Luminescent carbene copper(I) charge transfer complexes are promising candidates as molecular materials for photonic applications. Apart from steric and electronic modification of the acceptor carbene, most of the research has been dedicated to amide donor ligands to control the luminescence properties, while the remaining pnictogen group as anionic electron donating ligands is photophysically underrepresented. Herein, we demonstrate that dimesityl phosphide (Mes2P–) as a heavier homologue in [Cu(cAAC)(PMes2)] (cAAC = cyclic amino(alkyl) carbene) gives rise to orange emission with quantum yields of up to ϕ
max  = 0.52 in the solid state that is bathochromically shifted by ∼3000 cm−1 in comparison to related amide complexes due to the lower electronegativity of phosphorus. Time‐resolved variable temperature studies reveals that the µs‐lifetimes and radiative rate constants of ca. k
r
  =  5 ⋅ 104 s−1 are due to thermally activated delayed fluorescence (TADF) as the dominating emission mechanism at room temperature. In polystyrene matrices, the complexes exhibit environment dependent chiroptical properties (up to g
lum  =  10−2, B
CPL  =  1.31 M−1 cm−1, k
CPL  =  41.5 s−1) and are efficient blue light photocatalysts for hydrophosphination of alkynes in solution, highlighting the potential of heavier pnictogen ligands for photonic materials.

Dimesitylphosphide as a heavier congener of established amide ligands for charge‐transfer copper(I) complexes leads to bathochromic shift of the emission by up to 3645 cm−1 into the orange‐red (solid, polymer films) and even NIR (solution). The thermally activated delayed fluorescence exhibits high dissymmetry factors of glum = 10−2 in polystyrene. An inner‐sphere visible‐light photocatalytic mechanism could be exploited for hydrophosphination.