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

Transition metal complexes of the PPO/POP ligand: variable coordination chemistry and photo-luminescence properties

In the current work the tautomeric equilibrium between tetraphenyldiphosphoxane (Ph₂P-O-PPh₂, POP) and tetraphenyldiphosphine monoxide (Ph₂P-P(O)Ph₂, PPO) in the absence and presence of transition metal precursors is investigated. Whereas with hard transition metal ions, such as Fe(II) and Y(III), PPO-type complexes, such as [FeCl₂(PPO)₂] (1) and [YCl₃(THF)₂(PPO)] (2), are formed, softer transition metals ions tend to form so-called coordination stabilised tautomers of the POP ligand form, such as [Cu₂(MeCN)₃(μ₂-POP)₂](PF₆)₂ (3), [Au₂Cl₂(μ₂-POP)] (4), and [Au₂(μ₂-POP)₂](OTf)₂ (5). The photo-optical properties of the PPO- and POP-type transition metal complexes are investigated experimentally using photo-luminescence spectroscopy, whereby the presence of metallophillic interactions was found to play a crucial role. The dinuclear copper complex [Cu₂(MeCN)₃(μ₂-POP)₂](PF₆)₂ (3) shows a very interesting thermochromic behavior and intense photo-luminescence with remarkable phosphoresence lifetimes at 77 K, which can probably be attributed to short intramolecular Cu-Cu distances.

Synthesis, structure and photophysical properties of two tetranuclear copper(I) iodide complexes based on acetylpyridine and diphosphine mixed ligands

Two copper(I) iodide tetramers, namely, [μ₂-1,3-bis(diphenylphosphanyl)propane-κ²P:P']di-μ₃-iodido-di-μ₂-iodido-[1-(pyridin-3-yl)ethan-1-one-κN]tetracopper(I) dichloromethane disolvate, [Cu₄I₄(C₆H₇NO)₂(C₂₇H₂₆P₂)₂]·2CH₂Cl₂ (CuL³), and [μ₂-1,3-bis(diphenylphosphanyl)propane-κ²P:P']di-μ₃-iodido-di-μ₂-iodido-[1-(pyridin-4-yl)ethan-1-one-κN]tetracopper(I), [Cu₄I₄(C₆H₇NO)₂(C₂₇H₂₆P₂)₂] (CuL⁴), have been synthesized from reactions of CuI, 1,3-bis(diphenylphosphanyl)propane (dppp) and 3- or 4-acetylpyridine (3/4-acepy). The complexes were characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction (XRD), powder XRD and photoluminescence spectroscopy. Both complexes possess a stair-step [Cu₄I₄] cluster structure with a crystallographic inversion centre located in the middle of a Cu₂I₂ ring (Z' = 1/2). The dppp ligands each adopt a bidentate coordination mode that bridges two Cu^I centres on one side of the [Cu₄I₄] cluster and the acepy ligands act as terminal ligands. The solid-state samples of similar complexes show highly efficiency thermally activated delayed fluorescence (TADF) at room temperature. At ambient temperature, both CuL³ and CuL⁴ exhibit photoluminescence, with a maximum emission in the region 560-580 nm and with short emissive decay times, but only phosphorescence was observed at 77 K. The narrow gaps between the higher lying singlet state and the triplet state, ΔE(S₁ - T₁), also confirm the presence of TADF. Structure analysis and consideration of photoluminescence indicates that the position of the acetyl group on the heterocyclic ligand has an obvious influence on the structural arrangement, on intermolecular interactions and on the observed photophysical properties.

Efficiently luminescent mononuclear copper iodide complexes with sterically hindered iminephosphine chelating ligands

Cu(i) complexes realize high luminescence properties due to steric hindrances of the ligands and synergistic heavy atom (Cu and I) effects.