Issue 41, 2020

Understanding the luminescence properties of Cu(i) complexes: a quantum chemical perusal

Abstract

Electronic structures and excited-state properties of Cu(I) complexes with varying coordination numbers have been investigated by means of advanced quantum chemical methods. The computational protocol employs density functional-based methods for geometry optimizations and vibrational analyses including solvent effects through continuum models. Excitation energies, spin–orbit couplings and luminescence properties are evaluated using multireference configuration interaction methods. Rate constants of spin-allowed and spin-forbidden transitions have been determined according to the Fermi golden rule. The computational results for the 4-coordinate (DPEPhos)Cu(PyrTet), the 3-coordinate [IPr–Cu–Py2]+, and the linear CAACMe2–Cu–Cl complexes agree well with experimental absorption and emission wavelengths, intersystem crossing (ISC) time constants, and radiative lifetimes in liquid solution. Spectral shifts on the ligand-to-ligand charge transfer (LLCT) and metal-to-ligand charge transfer (MLCT) transitions caused by the polarity of the environment are well represented by the continuum models whereas the shifts caused by pseudo-Jahn–Teller distortions in the MLCT states are too pronounced in comparison to solid-state data. Systematic variation of the ligands in linear Cu(I) carbene complexes shows that only those complexes with S1 and T1 states of LLCT character possess sufficiently small singlet–triplet energy gaps ΔEST to enable thermally activated delayed fluorescence (TADF). Complexes whose S1 and T1 wavefunctions are dominated by MLCT excitations tend to emit phosphorescence instead. Unlike the situation in metal-free TADF emitters, the presence of low-lying locally excited triplet states does not promote ISC. These states rather hold the danger of trapping the excitation with nonradiative deactivation being the major deactivation channel.

Graphical abstract: Understanding the luminescence properties of Cu(i) complexes: a quantum chemical perusal

Supplementary files

Article information

Article type
Paper
Submitted
03 sen 2020
Accepted
16 sen 2020
First published
16 sen 2020

Phys. Chem. Chem. Phys., 2020,22, 23530-23544

Understanding the luminescence properties of Cu(I) complexes: a quantum chemical perusal

N. Lüdtke, J. Föller and C. M. Marian, Phys. Chem. Chem. Phys., 2020, 22, 23530 DOI: 10.1039/D0CP04654J

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements