Luminescence Properties of Copper(I) Coordination Complexes

Copper(I) coordination complexes exhibit a rich array of photophysical behaviours driven by their electronic structure and ligand environment. In these compounds, luminescence often arises from metal-to-ligand charge transfer (MLCT) or ligand-centred excited states, and may manifest as prompt fluorescence, phosphorescence or thermally activated delayed fluorescence (TADF). The low spin–orbit coupling of copper compared with heavier metals is counterbalanced by strategic ligand design—particularly with diimine, phosphine and N-heterocyclic carbene donors—to achieve small singlet–triplet energy gaps that facilitate reverse intersystem crossing. Structural rigidity, π-stacking and steric protection against non-radiative decay are key to high photoluminescence quantum yields and prolonged excited-state lifetimes. These features underpin applications in organic light-emitting diodes (OLEDs), light-emitting electrochemical cells (LECs), sensing and photocatalysis, offering a sustainable alternative to noble-metal emitters and enabling tunable emission across the visible spectrum through judicious ligand modification.

Research from Nature Portfolio

Carbene–metal–amide complexes of copper(I) bearing electronically tuned ligands have been shown to deliver efficient and stable deep-blue emission in OLED architectures. By introducing trifluoromethyl-substituted carbenes, researchers achieved sky-blue to deep-blue photoluminescence from charge-transfer states with external quantum efficiencies exceeding 20 % in both host-free and host-guest devices. The high thermal stability and resistance to aggregation of these emitters allowed fabrication of vacuum-processed and solution-processed diodes with peak efficiencies up to 20.9 % and enhanced operational lifetimes. Analysis of the relative energies of charge-transfer and locally excited triplet states informed design principles for next-generation blue emitters, demonstrating that fine adjustment of ligand electronics can control emission colour and stability without sacrificing radiative rates.

Luminescence Properties of Copper(I) Coordination Complexes publication trend

The graph below shows the total number of articles in luminescence properties of copper(i) coordination complexes across all publications each year (not limited to Nature Index journals).

Technical terms

Metal-to-ligand charge transfer (MLCT): An excited state in which an electron is transferred from a metal-centred orbital to a ligand-centred orbital.

Thermally activated delayed fluorescence (TADF): A mechanism whereby triplet excitons are thermally upconverted to singlets, enabling delayed fluorescence at room temperature.

Intersystem crossing (ISC): A non-radiative transition between electronic states of different spin multiplicity, typically singlet to triplet or vice versa.

Photoluminescence quantum yield: The ratio of the number of photons emitted to the number of photons absorbed by a material.

References

1. Deep‐Blue and Fast Delayed Fluorescence from Carbene–Metal–Amides for Highly Efficient and Stable Organic Light‐Emitting Diodes. Advanced Materials (2024).
2. Thermally Activated Delayed Fluorescence (TADF) Materials Based on Earth‐Abundant Transition Metal Complexes: Synthesis, Design and Applications. Advanced Science (2024).
3. Direct observation of intersystem crossing in a thermally activated delayed fluorescence copper complex in the solid state. Science Advances (2016).
4. Shine bright or live long: substituent effects in [Cu(N^N)(P^P)] + -based light-emitting electrochemical cells where N^N is a 6-substituted 2,2′-bipyridine. Journal of Materials Chemistry C (2016).