Nuclearity Control for Efficient Thermally Activated Delayed Fluorescence in a Cu^I Complex and its Halogen-Bridged Dimer

Abstract

We report on the thermally activated delayed fluorescence (TADF) properties of a novel iodine-bridged Cu I dimeric complex and its structurally related monomer. The chemical environment around the copper centers is identical in both complexes, providing a clean comparison to understand the effect of nuclearity in Cu I emitters. Efficient room-temperature TADF (≈80% of the total emission) is observed in both compounds. Similar singlet−triplet splittings were found for the monomer and the dimer (554 and 583 cm −1 , respectively), while the dimer triplet lifetime (90.0 μs) was longer than that of the monomer (46.0 μs). Experimental findings were rationalized by time-dependent density functional theory and complete active space self-consistent field calculations, identifying key structural factors determining TADF properties such as the key role of iodine in spin−orbit coupling mixing and the importance of near degeneracies in donor and acceptor orbitals for promoting state mixing. Unavoidable modifications associated with a change in nuclearity (e.g. intermolecular interactions, molecular charge, or modification of some binding motifs) can be also designed to promote TADF performance.

TADF: Enabling luminescent copper(i) coordination compounds for light-emitting electrochemical cells

“…Most of these are neutral and are of interest for OLEDs; selected examples which have been tested in OLED configurations are shown in Scheme 3. 36,64–96…”

Understanding the internal heavy-atom effect on thermally activated delayed fluorescence: application of Arrhenius and Marcus theories for spin–orbit coupling analysis

“…In light-atom organic materials, SOC is too low to enable fast rISC. 4 The introduction of cheap and abundant heavy atoms (HAs) into organic TADF emitters seems to be the most obvious and promising way to increase SOC, 5–8 and accelerate rISC, generally referred to as a “heavy-atom effect”. 9 Undoubtedly, modification of organic emitters with the heavy atoms of groups 14–17 opens new prospects in the engineering of heavy-metal-free materials for optoelectronics.…”

“…E-mail: illia.serdiuk@ug.edu.pl; Tel: +48 58 523 22 44 b Faculty of Chemistry, University of Gdan ´sk, Wita Stwosza 63, 80-308 Gdan ´sk, Poland c Center for Supramolecular Optoelectronic Materials, Department of Materials Science and Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744, Republic of Korea † Electronic supplementary information (ESI) available: Synthetic procedures and results of analyzes, description of methods used and procedure for the determination of photophysical parameters; detailed discussion on spectral properties; details of the analysis approach based on Arrhenius and Marcus theories; computational details and theoretical prediction of ISC and rISC rate constants within rotational, vibrational, and rotational-vibronic models; animation file for the key molecular vibrations. See DOI: https://doi.org/10.1039/d2tc00476c (HAs) into organic TADF emitters seems to be the most obvious and promising way to increase SOC, [5][6][7][8] and accelerate rISC, generally referred to as a ''heavy-atom effect''. 9 Undoubtedly, modification of organic emitters with the heavy atoms of groups 14-17 opens new prospects in the engineering of heavy-metal-free materials for optoelectronics.…”

Impact of Intermolecular Non‐Covalent Interactions in a CuI8PdII1 Discrete Assembly: Conformers’ Geometries and Stimuli‐Sensitive Luminescence Properties

“…This can allow thermal population of the lowest energy excited singlet state (S 1 ) from the lowest energy triplet excited state (T 1 ), via a reverse intersystem crossing (RISC) inducing efficient radiative relaxation to the ground state and exalted solid‐state luminescence properties that occurs ideally at temperatures close to room temperature (RT). Importantly, this phenomenon is not only observed for mononuclear Cu(I) complexes but several polynuclear Cu I complexes have been also reported with enhanced solid‐state luminescent properties [5b,9n–x, 10d–j] . In such derivatives non‐covalent short intermetallic cuprophilic interactions (d(Cu−Cu) bellow ca.…”