Vapochromic luminescence of a spin-coated copper(I) complex thin film by the direct coordination of vapour molecules

Luminescence Thermochromism of a Noncluster Copper Iodide Complex

Hybrid copper(I) halide materials are currently attracting significant attention due to their exceptional luminescence properties, offering great potential for the development of multifunctional emissive materials with, in addition, eco-friendly features. A binuclear copper iodide complex, based on the [Cu2I2L4] motif with phosphite derivatives as ligands, has been synthesized and structurally characterized. Photophysical investigations indicate that this complex displays luminescence thermochromic properties, which are characterized by a temperature-dependent change in the relative intensity of two emission bands. The high-contrast luminescence thermochromism, with an important color variation from purple to cyan, is ascribed to the thermal equilibrium of two different excited states. While thermochromism is relatively known for multimetallic complexes, the perfectly controlled thermochromism of the studied compound is unprecedented for a binuclear complex. From theoretical investigations, this original feature is due to the coordination of phosphite ligands, which induces a specific energy layout of the complex, presenting vacant orbitals of varying nature. This single-component, dual-emissive binuclear complex, displaying relevant sensitivity temperature response, presents great potential for luminescence ratiometric thermometry applications. This study underlines the relevance of the ligand engineering strategy in developing original, emissive, and sustainable copper-based materials.

A luminescent Cu2I2P2S2-type binuclear complex and its fluorescence sensing for pyridine

Luminescent CuI complexes are an important class of coordination compounds due to their relative abundance, low cost and ability to display excellent luminescence. The title Cu2I2P2S2-type binuclear complex, di-μ-iodido-bis[(thiourea-κS)(triphenylphosphine-κP)copper(I)], [Cu2I2(CH4N2S)2(C18H15P)2], conventionally abbreviated as Cu2I2TPP2TU2, where TPP and TU represent triphenylphosphine and thiourea, respectively, is described. In this complex, each CuI atom adopts a CuI2PS four-coordination mode and pairs of atoms are connected to each other by two μ2-I ligands to form a centrosymmetric binuclear cluster. It was also found that the paper-based film of this complex exhibited obvious luminescence light-up sensing for pyridine and 4-methylpyridine.

Photoluminescent copper(I) iodide alkylpyridine thin films as sensors for volatile halogenated compounds

The paper presents the fabrication and characterization of [CuI(L)]n thin films, where L represents various alkylpyridine ligands including 4-methylpyridine, 3-methylpyridine, 2-methylpyridine, 4-tbutylpyridine, 3,4-dimethylpyridine, and 3,5-dimethylpyridine. The thin films were synthesized by exposing the corresponding ligands to CuI thin films through vapor deposition. The coordination reactions occurring on the films were investigated using PXRD and time-dependent photoluminescence spectroscopy, and a comparison was made between the structures of the thin films and the corresponding powder phases. The films showed primarly blue emission (λem = 457-515 nm) and polymeric structures with excited state lifetimes ranging from 0.6 to 5.5 μs. Significantly, the studied compounds exhibited fast reversible luminescence quenching when exposed to vapors of dichloromethane and dibromomethane (15 and 30 min respectively), and the luminescence was restored upon re-exposure to the alkylpyridine ligand (after 20 min). These findings indicate that these thin films hold promise for applications as sensors (with sensitive and reversible detection capability) for volatile halogen-based compounds (VHC).

Time-resolved radioluminescence of the Cu(I) cluster Cu4I62-. Different responses to photo, X-ray, β-ray and α-particle excitation

Time-resolved radioluminescence (TRRL) properties of the Cu(I) cluster Cu4I62- upon pulsed X-ray, β-ray or α-particle excitation are described. The longer (>2 μs) TRRL component displays exponential decay comparable to pulsed UV excitation; however, temporal behaviour at shorter times indicates that high local excited state density provides an alternative decay channel.

Photoactive CuI-Cross-Linked Polyurethane Materials

Using multinuclear copper iodide complexes as cross-linking agents in a polyurethane matrix, original photoluminescent stimuli-responsive materials were synthesized. The intrinsic photoluminescence properties of the covalently incorporated copper iodide complexes are thus transferred to the materials while retaining the beneficial characteristics of the polymer host. The transparent materials exhibit room-temperature phosphorescence with emission switching properties by displaying luminescence thermochromism and solvatochromism. The luminescence thermochromism is characterized by a change in the wavelength and intensity of the emission with temperature, and the vapochromic effect presents a contrasted response of extinction or exaltation according to the nature of the solvent of exposure. By combining the luminescence characteristics of photoactive copper iodide complexes with the ease of polymer processing, the application of these luminescent materials as phosphors in LED (light-emitting diode) devices was also demonstrated. The present study shows that the use of copper iodide complexes as cross-linkers in polymeric materials is a relevant strategy to design materials with enhanced functionalities in addition to their low cost and sustainable characteristics.

Multifunctional Platform Based on a Copper(I) Complex and NaYF4:Tm3+,Yb3+ Upconverting Nanoparticles Immobilized into a Polystyrene Matrix: Downshifting and Upconversion Oxygen Sensing

This work presents an innovative approach to obtain a multifunctional hybrid material operating via combined anti-Stokes (upconversion) and Stokes (downshifting) emissions for oxygen gas sensing and related functionalities. The material is based on a Cu(I) complex exhibiting thermally activated delayed fluorescence emission (TADF) and infrared-to-visible upconverting Tm³⁺/Yb³⁺-doped NaYF₄ nanoparticles supported in a polystyrene (PS) matrix. Excitation of the hybrid material at 980 nm leads to efficient transfer of Tm³⁺ emission in the ultraviolet/blue region to the Cu(I) complex and consequently intense green emission (560 nm) of the latter. Additionally, the green emission of the complex can also be directly generated with excitation at 360 nm. Independently of the excitation wavelength, the emission intensity is efficiently suppressed by the presence of molecular oxygen and the quenching rate is properly characterized by the Stern-Volmer plots. The results indicate that the biocompatible hybrid material can be applied as an efficient O₂ sensor operating via near-infrared or ultraviolet excitation, unlike most optical oxygen sensors currently available which only work in downshifting mode.

Coordination-based vapochromic behavior of a luminescent Pt(ii) complex with potassium ions

Vapochromic Pt(ii) complexes that exhibit color and luminescence changes induced by the presence of vapor molecules have drawn considerable attention because of their potential use as vapor sensors. Generally, the vapochromic responsiveness of Pt(ii)-based complexes is difficult to envisage, because a typical molecular design facilitates the stabilization of a vapor-adsorbed form through weak intermolecular interactions. Herein, we investigate the vapochromic behavior of a Pt(ii) complex with potassium ions, which act as vapor coordination sites, by strongly stabilizing the vapor-adsorbed form. Upon exposure to N,N-dimethylacetamide and N,N-dimethylformamide vapors, the complex exhibits crystal structural transformation with luminescence spectral changes. Crystal structural analysis indicates that the vapor molecules are coordinated to the potassium ions after vapor exposure. This study suggests the possibility of inducing Pt(ii)-based vapochromic responsiveness through establishing potassium-ion-based vapor coordination sites.

A luminescent Pt(ii) complex with potassium ions was successfully synthesized and its coordination-based vapochromic behavior was investigated.

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.