Synthesis, Characterization And Photophysical Properties Of Razolopyridine Cuprous Complexes

There has been considerable research interest in luminescent metal complexes owing to their promising potential in materials science.Continuing efforts have been devoted to the development of metal-based phosphors with emission colors in the whole visible region and the most representative examples are d⁶-and d⁸-metal complexes of the third-row transition metal series such as Os,Ir and Pt.However,because of the high cost and limited availability of these precious metals,more attention has been paid to develop inexpensive alternatives in the past two decades.Recently,copper?I?system has become a class of important emissive metal complexes due to their promising application perspectives in optoelectronic devices and the high relative abundance and environmental friendliness of copper.In this aspect,heteroleptic Cu???complexes have been most extensively investigated,particularly copper?I?-diimine-phosphine complexes.To achieve smart photofunctional materials,we have focused on copper?I?complexes that based on azolyl and diphosphine ligands.Along this line of research,we developed several new class of cuprous complexes.1.A new series of bimetallic Cu???complexes 1-5 triply bridged by a monoanionic or charge-neutral functionalized 3-?2?-pyridyl?-1,2,4-triazole in a?-?¹?N?,?²?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???species with an eight-membered Cu2C2P4 ring of{Cu??-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???ions is four-coordinated,in a highly distorted N2P2 tetrahedral environment and the other is three-coordinated,in a distorted N2P trigonal planar arrangement.All these Cu???complexes exhibit a comparatively weak low-energy absorption in CH2Cl2 solution,ascribed to the charge-transfer transitions with appreciable¹MLCT contribution,as suggested by 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 the5-site of the 1,2,4-triazolyl ring markedly influences the proton activity of the1,2,4-triazolyl-NH,thus leading to the formation of both singly and doubly charged bimetallic Cu???species regulated by the NH?N?conversion,resulting from NH deprotonation of the 1,2,4-triazolyl ring.2.AnewneutralbimetallicCu???complexwithNH-deprotonated5-trifluoromethy-3-?2?-pyridyl?pyrazolate and 1,2-bis?diphenylphosphino?ethane ligands has been synthesized and characterized.Interestingly,its CH2Cl2-solvated crystalline sample exhibits a reversible and highly selective luminescence vapochromism to CH2Cl2 vapor by its templated lattice space,which is not observed in its non-solvated crystalline sample that obtained in 1,2-dichloroethane,chloroform,or acetone solutions.Such a special interesting vapochromic luminescence behavior originates from the weak C-H···?intermolecular interactions between the[{Cu?pyfpz?}2??-dppe?2]molecules and solvate CH2Cl2 molecules enclosed in the crystal lattice of crystalline 6??CH2Cl2.Additionally,this new neutral bimetallic Cu???complex exhibits a thermally activated delayed fluorescence?TADF?with radiative lifetime at ambient temperature.3.Four new tetranuclear Cu???complexes 7-10 were obtained by methylated and NH-deprotonated 2-?1H-tetrazol-5-yl?-pyridine with bis?diphenylphosphino?methane.These complexes show luminescence mechanochromism with a color change from blue to green upon the application of mechanical force.Powder X-ray diffraction reveal that the changed phase of complexes 7-10 are the main cause of luminescence mechanochromism.Furthermore,after the absorption of methanol or ethanol vapor to the ground samples,the original blue emissive and crystalline states are restored.Therefore,the luminescence color conversion processes are fully reversible.It suggests that the mechanochromism transitions which represent switching between the crystalline and amorphous phases are likely to be driven by stacking mode and Cu···Cu distances changes.