Synthesis, structure, and photophysics of copper(i) triphenylphosphine complexes with functionalized 3-(2'-pyrimidinyl)-1,2,4-triazole ligands.

A series of new mononuclear and dinuclear copper(i) triphenylphosphine complexes with functionalized 3-(2'-pyrimidinyl)-1,2,4-triazole ligands have been synthesized and characterized, in which functionalized 3-(2'-pyrimidinyl)-1,2,4-triazole adopts neutral mono- and bis-chelating coordination modes and a mono-anionic bis-chelating binding manner due to the 1,2,4-triazolyl-NH deprotonation. All these Cu(i) complexes display a relatively weak low-energy absorption in a CH2Cl2 solution, ascribed to the charge-transfer transitions with appreciable MLCT character, as suggested by TD-DFT analyses. These Cu(i) complexes are all emissive in solution and in the solid state at ambient temperature, and their luminescence properties can be well modulated via the addition of the second {Cu(PPh3)2} unit and modification of 3-(2'-pyrimidinyl)-1,2,4-triazole involving the N-H deprotonation and the substituent variation of the 1,2,4-triazolyl ring. It is also demonstrated that introducing the trifluoromethyl group into the 1,2,4-triazolyl ring is helpful for enhancing the solid-state luminescence properties of the 1,2,4-triazole-based Cu(i) complexes, whereas the introduction of the tert-butyl group into the 1,2,4-triazolyl ring, the 1,2,4-triazolyl-NH deprotonation, and the use of the pyrimidinyl ring instead of the pyridyl ring are all unfavorable.

Luminescent Three- and Four-Coordinate Dinuclear Copper(I) Complexes Triply Bridged by Bis(diphenylphosphino)methane and Functionalized 3-(2'-Pyridyl)-1,2,4-triazole Ligands.

A new series of bimetallic Cu(I) complexes 1-5 triply bridged by a monoanionic or charge-neutral functionalized 3-(2'-pyridyl)-1,2,4-triazole in a µ-η1(N),η2(N,N) tridentate binding mode and two bis(diphenylphosphino)methane (dppm) ligands have been synthesized. Complexes 1-5 are singly or doubly charged dinuclear Cu(I) species with an eight-membered Cu2C2P4 ring of {Cu(µ-dppm)2Cu} unit, in which 3 and 4 adopt the boat-boat conformation, while 1, 2, and 5 display the chair-boat form. In these dimeric copper(I) complex cations, one of the two Cu(I) ions is four-coordinated, in a highly distorted N2P2 tetrahedral environment and the other is three-coordinated, in a distorted NP2 trigonal planar arrangement. All these Cu(I) complexes exhibit a comparatively weak low-energy absorption in CH2Cl2 solution, ascribed to the charge-transfer transitions with appreciable 1MLCT contribution, as suggested by time-dependent density functional theory (TDDFT) analyses. Complexes 1-5 display good emission properties in both solution and solid states at ambient temperature, which are well-modulated via structural modification of 3-(2'-pyridyl)-1,2,4-triazole, including the alteration of the substituent type (-CF3, -H, -CH3, and -C(CH3)3) and position (ortho-, meta-, and para-position). Furthermore, the variation of the substituent (-CF3 and -C(CH3)3) on the 5-site of the 1,2,4-triazolyl ring markedly influences the proton activity of the 1,2,4-triazolyl-NH, thus leading to the formation of both singly and doubly charged bimetallic Cu(I) species regulated by the NH ↔ N- conversion, resulting from NH deprotonation of the 1,2,4-triazolyl ring.