Thermo-, Mechano-, and Vapochromic Dinuclear Cuprous-Emissive Complexes with a Switchable CH3CN-Cu Bond

A thermo-, mechano-, and vapochromic bimetallic cuprous-emissive complex has been reported, and the origin and application of its tri-stimuli-responsive luminescence have been explored. As revealed by single-crystal structure analysis, thermo- and vapochromic luminescence adjusted by heating at 60 °C and CH₃CN vapor fuming, accompanied by a crystalline-to-crystalline transition, is due to the breaking and rebuilding of the CH₃CN-Cu bond, as supported by ¹H nuclear magnetic resonance (NMR), Fourier-transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), thermogravimetry (TG), and time-dependent density functional theory (TD-DFT) analyses of the CH₃CN-coordinated species [Cu₂(μ-dppa)₂(μ-η¹(N)η²(N,N)-fptz)(CH₃CN)](ClO₄)·H₂O (1) and its CH₃CN-removed derivative [Cu₂(μ-dppa)₂(μ-η¹(N)η²(N,N)-fptz)](ClO₄)·H₂O (2). Luminescence mechanochromism, mixed with a crystalline-to-amorphous transition where the initial crystalline is different for 1 and 2, is mainly assigned as the destruction of the CH₃CN-Cu bonding and/or the O···HN_dppa and OH···N_triazolyl hydrogen bonds. It is also suggested that a rational use of switchable coordination such as weak metal-solvent bonding is a feasible approach to develop multi-stimuli-responsive luminescent materials and devices.

Triple-bridged helical binuclear copper(i) complexes: Head-to-head and head-to-tail isomerism and the solid-state luminescence

A family of helical dinuclear copper(i) pyridylphospholane complexes [Cu₂L₃X]X (X = BF₄^-, Cl^- and Br^-) was prepared. The family includes the first examples of this type of complex based on copper(i) chloride and copper(i) bromide. The two isomers typical of this class of compounds, namely head-to-head and head-to-tail complexes, were studied in solution by spectroscopic and optical methods, and in the solid state by X-ray diffraction. Furthermore, the solid-state luminescence of the complexes at different temperatures was studied, and the results were interpreted using quantum-chemical calculations. It was shown that the luminescence of the complexes is attributed to the ³(M + X)LCT transitions.

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

A suite of paddle-wheel shaped [Cu₂(PymPPh₂)₃(L_an)_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 (L_an = 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 + L_an)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 L_an 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.

Diverse Architectures and Luminescence Properties of Group 11 Complexes Containing Pyrimidine-Based Phosphine, N-((Diphenylphosphine)methyl)pyrimidin-2-amine

In this article, the synthesis, structural studies, and luminescence properties of Cu^I, Ag^I, and Au^I complexes of pyrimidine-based phosphine [C₄H₃N₂-2-NH(CH₂PPh₂)] (1) are described. The reactions of 1 with CuX led to the isolation of one-dimensional (1D) chain, tetranuclear ladder, or cyclic derivatives. The structural features of these complexes are greatly influenced by the metal-to-ligand ratio, reaction conditions, and CuX (X = Cl, Br or I) employed. In the case of CuCl and CuBr, one-dimensional coordination polymers [{CuCl}{C₄H₃N₂-2-NH(CH₂PPh₂)}]_∞ (2) and [{CuBr}{C₄H₃N₂-2-NH(CH₂PPh₂)}]_∞ (3) were obtained, whereas CuI afforded tetracopper complex [{CuI}₄{C₄H₃N₂-2-NH(CH₂PPh₂)}₂(NCCH₃)₂] (4) having Cu₄ ladder structure supported by P∩N-bridging coordination of 1. The reaction of 1 with AgOTf yielded unprecedented one-dimensional chain structure [{AgOTf}{C₄H₃N₂-2-NH(CH₂PPh₂)}]_∞ (5), whereas the reaction with AgBF₄ produced a 12-membered dinuclear complex, [{Ag}{C₄H₃N₂-2-NH(CH₂PPh₂)}]₂[BF₄]₂ (6), with each silver atom having a linear geometry. Gold complex [{AuCl}{C₄H₃N₂-2-NH(CH₂PPh₂)}]₂ (7) was synthesized by reacting 1 with [AuCl(SMe₂)]. Compounds 2-4 were also prepared using a pestle and mortar by grinding method in almost quantitative yield. Complex 4 with a Cu···Cu distance of 2.828(5) Å shows high luminescence due to the nonbonded metal···metal interactions.

Cu(I) complexes regulated by N-heterocyclic ligands: Syntheses, structures, fluorescence and electrochemical properties

Three mononuclear Cu(I) complexes, namely, [Cu(2-PBO)(PPh₃)₂]·ClO₄·2CH₂Cl₂ (1), [Cu(3-PBO)(PPh₃)₂(ClO₄)]·CH₂Cl₂ (2) and [Cu(PBM)(PPh₃)₂]·ClO₄ (3) (2-PBO = 2-(2'-Pyridyl)benzoxazole, 3-PBO = 2-(3'-Pyridyl)benzoxazole, PBM = 2-(2'-Pyridyl)benzimidazole, PPh₃ = triphenylphosphine) have been synthesized and characterized by elemental analyses, IR, ¹H NMR, ¹³C NMR, X-ray single crystal diffraction and thermal analysis. Photoluminescent investigation shows that complexes 1-3 exhibit distinct tunable light green (512 nm)-to-yellow (557 nm) photoluminescence by varying the N-heterocyclic ligands. Three complexes show intense 2-PBO-based yellow, 3-PBO-based light green and intense PBM-based bright green luminescence upon irradiation with a standard UV lamp (λ_ex = 254 nm) at room temperature. Moreover, the electrochemical properties of 1-3 have been investigated by cyclic voltammetry. The results suggest the frontier molecular orbits and the HOMO-LUMO energy gaps of these cuprous complexes are effectively adjusted through the introduction of different N-heterocyclic ligands, thus achieving the selective luminescence of the cuprous complexes.