Solvent-Free Thermal Synthesis of Luminescent Dinuclear Cu(I) Complexes with Triarylphosphines

Abstract

Luminescent [CuI(pyrpy)(PR)] complexes (pyrpy = 4-pyrrolidinopyridine; PR = triphenylphosphine (1), tri- m-tolylphosphine (2), tri- p-tolylphosphine (3)) were prepared by solution reactions and a rarely reported solvent-free thermal method. X-ray structure analyses reveal that complexes composed of dinuclear {CuI} cores surrounded by two PR and two pyrpy ligands were formed. Although the melting point of pyrpy is the lowest among the organic units used in this study, the temperature required to form the luminescent dinuclear complex, prepared by the thermal synthesis method, depended strongly on the PR moiety. Two of the three complexes (1 and 3) were successfully prepared by the solvent-free thermal method. Complexes 1-3 exhibited blue emissions at around 450 nm with moderately high quantum yields (Φ) of 0.24, 0.31, and 0.51, respectively. Emission-lifetime measurements and time-dependent density functional theory (TD-DFT) calculations suggest thermally activated delayed fluorescence (TADF) in each complex. This solvent-free thermal synthesis of TADF materials represents a promising method for the preparation of luminescent layers directly onto substrates of thin-layer electronic devices, such as organic light-emitting diodes.

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…”

Largely Color-Tuning Prompt and Delayed Fluorescence: Dinuclear Cu(I) Halide Complexes with tert-Amines and Phosphines

“…Dinuclear Cu­(I) cores possess a great advantage over mononuclear core since they have a rigid structure and thus high efficiency recorded for bulky ligand chelated complexes. − However, the reported dinuclear Cu­(I) halide complexes are mainly limited to bidendate diphoshines ,− or imine and phosphine ,− ,− ligands, whereas bidentate amine and phosphine ligands are rarely reported. In comparison to the great success in green emitters, it seems that blue emitters are still a challenge to meet the requirement of full color displays and white light sources. , …”

Quantitative Solvent-Free Thermal Synthesis of Luminescent Cu(I) Coordination Polymers

“…In fact, the mechanochemical synthesis of luminescent Cu­(I) complexes has been reported as an effective technique to minimize the use of a solvent as well as to shorten the reaction time and improve the yield. − However, most mechanochemical syntheses of luminescent Cu­(I) complexes require an assisting solvent, while a washing process is necessary to remove the unreacted starting materials. We have previously reported a thermal synthesis without the use of an assisting solvent, which enabled us to synthesize luminescent Cu­(I) complexes via the melting of organic ligands to effectively promote complex formation. , However, certain amounts of organic solvent were still necessary during the washing process. Thus, in this work, we have focused on thermally stable Cu­(I) coordination polymers because of (1) the high thermal stability of the coordination polymers, which allowed the removal of any unreacted materials, mainly excess organic ligands, via evaporation by simple heating and (2) the wide tunability of the emission color, from blue to red, which was achieved in the coordination polymeric system [Cu 2 I 2 (PPh 3 )­(L)] n (PPh 3 = triphenylphosphine, L = N -heteroaromatic organic linkers). − Herein, we report the completely solvent-free mechanochemical thermal synthesis of two simple Cu­(I) coordination polymers [Cu 2 I 2 (3,3′-bpy)] n and [Cu 2 I 2 (4,4′-bpy)] n (Scheme , CuI-3 and CuI-4 , respectively; bpy = 3,3′- or 4,4′-bipyridine, respectively) with two isomeric bpy linkers.…”