Design of luminescent complexes with different Cu4I4 cores based on pyridyl phenoxarsines

A series of luminescent Cu4I4 clusters with stair-step, cubane, and octahedral geometries supported by a novel type of cyclic As,N-ligand, pyridyl-containing 10-phenoxarsines, were synthesized and characterized by NMR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction analysis. An unusual arrangement of As,N-bidentate and μ2-iodo ligands was found in the octahedral cluster. The structural diversity of the Cu(I) complexes is reflected in their photophysical properties: the phosphorescence spectra of the compounds display emission in a broad spectral range of 495-597 nm. The complex with the Cu4I4L2 stoichiometry bearing a stair-step Cu4I4 core demonstrates temperature-dependent dual emission. The luminescence properties of all complexes were rationalized by DFT calculations.

Robust and highly emissive copper(I) halide 1D-coordination polymers with triphenylarsine and a series of bridging N-heteroaromatic co-ligands

Various 1D-coordination polymers with dinuclear rhombic {Cu2X2} cores (X = Br, I) were synthesized using a spontaneous evaporation method employing triphenylarsine (AsPh3) and six types of bidentate N-heteroaromatic co-ligands. The coordination polymers exhibited intense emission even at 298 K (quantum yield: up to 0.60), and their emission color was dependent on the N-heteroaromatic co-ligand. The emission efficiencies of these coordination polymers were higher than those of the discrete complexes with AsPh3 and monodentate N-heteroaromatic co-ligands reported in our previous work. In addition, the luminescence of these coordination polymers was more resistant to mechanical stimuli than that of the discrete ones.

Pyridylarsine-based Cu(I) complexes showing TADF mixed with fast phosphorescence: a speeding-up emission rate using arsine ligands

Can arsine ligands be preferred over similar phosphines to design Cu(I)-based TADF materials? The present study reveals that arsines can indeed be superior to reach shorter decay times of Cu(I) emitters. This has been exemplified on a series of bis(2-pyridyl)phenylarsine-based complexes [Cu₂(Py₂AsPh)₂X₂] (X = Cl, Br, and I), the emission decay times of which are significantly shorter (2-9 μs at 300 K) than those of their phosphine analogs [Cu₂(Py₂PPh)₂X₂] (5-33 μs). This effect is caused by two factors: (i) large ΔE(S₁-T₁) gaps of the arsine complexes (1100-1345 cm^-1), thereby phosphorescence is admixed with TADF at 300 K, thus reducing the total emission decay time compared to the TADF-only process by 5-28%; (ii) higher SOC strength of arsenic (ζ_l = 1202 cm^-1) against phosphorus (ζ_l = 230 cm^-1) makes the k_r(T₁ → S₀) rate of the Cu(I)-arsine complexes by 1.3 to 4.2 times faster than that of their phosphine analogs. It is also noteworthy that the TADF/phosphorescence ratio for [Cu₂(Py₂AsPh)₂X₂] at 300 K is halogen-regulated and varies in the order: Cl (1 : 1) < Br (3 : 1) ≈ I (3.5 : 1). These findings provide a new insight into the future design of dual-mode (TADF + phosphorescence) emissive materials with reduced lifetimes.

Luminescent Cu4I4-cubane clusters based on N-methyl-5,10-dihydrophenarsazines

Two luminescent Cu₄I₄-cubane tetramers with N-methyl-10-(p-halogenophenyl)-5,10-dihydrophenarsazine ligands were synthesized and characterized by NMR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction analysis. The UV-Vis absorption and emission properties were studied and rationalized by DFT and time-dependent DFT calculations. The luminescence behavior was found to be rather different from that of recently reported tetranuclear copper iodide cubane clusters based on As,O-analogues - 10-(aryl)phenoxarsines. The crystalline powders of both complexes exhibit the temperature-dependent dual-band emission: the low-energy emission originates from the cluster-centered (³CC) triplet state, whereas the high-energy emission was attributed to the intraligand (³IL) triplet state.