Mononuclear Copper(I) 3-(2-pyridyl)pyrazole Complexes: The Crucial Role of Phosphine on Photoluminescence

Abstract

A series of emissive Cu(I) cationic complexes with 3-(2-pyridyl)-5-phenyl-pyrazole and various phosphines: dppbz (1), Xantphos (2), DPEPhos (3), PPh3 (4), and BINAP (5) were designed and characterized. Complexes obtained exhibit bright yellow-green emission (ca. 520–650 nm) in the solid state with a wide range of QYs (1–78%) and lifetimes (19–119 µs) at 298 K. The photoluminescence efficiency dramatically depends on the phosphine ligand type. The theoretical calculations of buried volumes and excited states explained the emission behavior for 1–5 as well as their lifetimes. The bulky and rigid phosphines promote emission efficiency through the stabilization of singlet and triplet excited states.

Synthesis of a New Dinuclear Cu(I) Complex with a Triazine Ligand and Diphenylphosphine Methane: X-ray Structure, Optical Properties, DFT Calculations, and Application in DSSCs

“…The calculated spectrum displays two additional bands at 363 nm (f = 0.0565) and 359 nm (f = 0.0449), which are assigned to HOMO-3→LUMO+3/HOMO-6→LUMO and HOMO-10→LUMO/HOMO-6→LUMO transitions, respectively. These transitions imply that intramolecular charge transfer takes place [29,30,58]; the band at 363 nm can be related to the broad experimental absorption band found at 338 nm (ε = 26,700 M −1 cm −1 , Figure 5 and Figure S10) and has an LLCT character. The experimental band centered at 286 nm (ε = 56,700 M −1 cm −1 ) was assigned to π→π* transitions, having an LLCT character.…”

Tetranuclear Copper(I) and Silver(I) Pyrazolate Adducts with 1,1′-Dimethyl-2,2’-bibenzimidazole: Influence of Structure on Photophysics

“…Modifying pyrazoles with the introduction of pyridine yields chelating ligands. In this case, mixed-ligand mononuclear metal complexes with chelating or bridging bisphosphines have been obtained [ 47 , 48 ].…”

Visible-emitting Cu(i) complexes with N-functionalized benzotriazole-based ligands

“…37 A wide variety of further examples involving azoles from pyrazoles to tetrazoles was reported. 9,38–53 The four coordinated complex [Cu(bis(2-(diphenylphosphino)phenyl)ether)(5-(2-pyridyl)tetrazolate)] was deeply studied also from a computational point of view, focusing the attention on the ISC process. 54…”

“…37 A wide variety of further examples involving azoles from pyrazoles to tetrazoles was reported. 9,[38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] The four coordinated complex [Cu(bis(2-(diphenylphosphino)phenyl)ether)(5-(2-pyridyl)tetrazolate)] was deeply studied also from a computational point of view, focusing the attention on the ISC process. 54 Despite its renowned versatility, benzotriazole is not commonly used as a ligand for the preparation of luminescent transition metal complexes.…”