Dicopper(I) Paddle-Wheel Complexes with Thermally Activated Delayed Fluorescence Adjusted by Ancillary Ligands

Abstract

A suite of paddle-wheel shaped [Cu2(PymPPh2)3(Lan) n ]­(PF6)2 complexes showing efficient thermally activated delayed fluorescence (TADF) has been synthesized. In these complexes, Cu­(I) ions are P,N-bridged by three diphenyl­(2-pyrimidyl)­phosphine (PymPPh2, L) ligands in a “head-to-tail” fashion, and one or both metals are also capped by the ancillary ligand (Lan = MeOH, Me2CO, MeCN, PhCN). At ambient temperature, the solid complexes emit TADF with the quantum yield of up to 85% and the lifetimes of from 9.6 to 27 μs. The ancillary ligands, whose orbitals negligibly contribute to the radiative 1(M + L + Lan)­LCT state, remarkably adjust emission energies and ΔE(S1–T1) energy splitting magnitudes of the emitters obtained. Thus, depending on structure and/or number of the Lan molecules, the emission maxima vary from 500 to 563 nm, and the ΔE(S1–T1) gaps range 550–1100 cm–1. Such tunable TADF characteristics coupled with the excellent solubility and air-stability make the complexes presented to be promising TADF materials.

P∩N Bridged Cu(I) Dimers Featuring Both TADF and Phosphorescence. From Overview towards Detailed Case Study of the Excited Singlet and Triplet States

“…This effect of combined TADF-phosphorescence emission, suited for decreasing the overall emission decay time, has already been addressed in the literature [ 50 , 51 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 ]. In particular, Cu(I) and Ag(I) dimers, in which the metal centers are linked by P∩N ligands can show this effect [ 34 , 50 , 87 , 90 , 91 , 92 , 93 , 94 , 95 ] and very probably also the complexes reported recently [ 96 ]. To evaluate the class of materials of Cu 2 X 2 (P∩N) 3 complexes (with X = Cl, Br, I), we study eight compounds with respect to their crystal structures and, especially, their emission properties at T = 300 K and 77 K, respectively.…”

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…”

Crystalline Metal‐Organic Materials with Thermally Activated Delayed Fluorescence

“…Several paddle-wheel shaped dinuclear Cu(I) complexes [Cu 2 (PymPPh 2 ) 3 (L an ) n ](PF 6 ) 2 (1L-6L) were constructed by diphenyl(2-pyrimidyl)phosphine (PymPPh 2 , L) ligands and various ancillary ligands (L an = MeOH, Me 2 CO, MeCN, PhCN) by Artem'ev et al in 2020 (Figure 18d). [76] By adjusting the structure and/or the number of the L an in [Cu 2 (PymPPh 2 ) 3 (L an ) n ](PF 6 ) 2 skeleton, the emission energy and ΔE(S 1 −T 1 ) value ranges could be controllably designed giving rise to efficient TADF. As for the solid 1L-6L, the emission maxima were located in the range of 500-563 nm with monoexponential decay lifetimes range from 9.6 to 27 µs at 300 K. For complex 1L, when decreasing temperature from 300 to 77 K, the emission band redshifted from 510 to 530 nm (Figure 18e), and decay lifetime exhibited an increase from 21 to 136 µs with QY from 65% to 99%.…”

“…The solid line represents the fit of the experimental data according to Equation (1). Reproduced with permission [76]. Copyright 2020, American Chemical Society.…”