Luminescence Ranging from Red to Blue: A Series of Copper(I)−Halide Complexes Having Rhombic {Cu2(μ-X)2} (X = Br and I) Units with N-Heteroaromatic Ligands

Photoluminescence of Platinum(II) Complexes with Diazine-Based Ligands

In the last past twenty years, research on luminescent platinum (II) complexes has been intensively developed for useful application such as organic light emitting diodes (OLEDs). More recently, new photoluminescent complexes based on diazine ligands (pyrimidine, pyrazine, pyridazine, quinazoline and quinoxaline) have been developed in this context. This review will summarize the photophysical properties of most of the phosphorescent diazine Pt(II) complexes described in the literature and compare the results to pyridine analogues whenever possible. Based on the emission color, and the photoluminescence quantum yield (PLQY) values, the relationship between structure modification, and photophysical properties are highlighted. Tuning of emission color, quantum yields in solution and solid state and, for some complexes, aggregation induced emission (AIE) or thermally activated delayed fluorescence (TADF) properties are described. When emitting OLEDs have been built from diazine Pt(II) complexes, the external quantum efficiency (EQE) values and luminance for different emission wavelengths and in some cases, chromaticity coordinates obtained from devices, are given. Finally, this review highlights the growing interest in studies of new luminescent diazine Pt(II) complexes for OLED applications.

Synthesis and Photophysical Properties of Silver(I) Coordination Polymers Bridged by Dimethylpyrazine: Comparison of Emissive Excited States between Silver(I) and Copper(I) Congeners

Highly luminescent silver(I) coordination polymers [Ag2X2(PPh3)2(Me2pyz)]n (X = I, Br, Cl; Me2pyz: 2,5-dimethylpyrazine) were prepared together with copper congeners [Cu2X2(PPh3)2(Me2pyz)]n (X = I, Br). All the complexes showed thermally activated delayed fluorescence from the charge-transfer states in the visible region, from blue to red. The isomorphous relationship among the complexes allowed a detailed discussion of the effect of halogenido ligands and crystal packing on their luminescence energy. The relaxation in the emissive excited states (ESs) was determined to be more remarkable in silver complexes than in copper complexes despite their isomorphous structures, and the electronic effect of halogenido ligands was comparable to the effect of relaxation in emissive ESs.

Determining Factors to Understand the External Quantum Efficiency Values: Study Carried Out with Copper(I)-I and 1,2-Bis(4-pyridyl)ethane Coordination Polymers as Downshifters in Photovoltaic Modules

Downshifters refer to compounds with the capacity to absorb UV photons and transform them into visible light. The integration of such downshifters has the potential to improve the efficiency of commercial photovoltaic modules. Initially, costly lanthanide derivatives and organic fluorescent dyes were introduced, resulting in a heightened module efficiency. In a novel research direction guided by the same physicochemical principles, the utilization of copper(I) coordination compounds is proposed. This choice is motivated by its simpler and more economical synthesis, primarily due to copper being a more abundant and less toxic element. Our proposal involves employing 1,2-bis(4-pyridyl) ethane (bpe), an economically viable commercial ligand, in conjunction with CuI to synthesize coordination polymers: [CuI(bpe)]n(1), [Cu3I3(bpe)3]n(2), and [CuI(bpe)0.5]n(3). These polymers exhibit the ability to absorb UV photons and emit light within the green and orange spectra. To conduct external quantum efficiency studies, the compounds are dispersed on glass and then encapsulated with ethylene vinyl acetate through heating to 150 °C. Interestingly, during these procedural steps, the solvents and temperatures employed induce a phase transformation, which has been thoroughly examined through both experimental analysis and theoretical calculations. The outcomes of these studies reveal an enhancement in external quantum efficiency with [Cu3I3(bpe)3]n(2), at a cost significantly lower (between 340 and 350 times) than that associated with lanthanide DS complexes.

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.

TADF and X-ray Radioluminescence of New Cu(I) Halide Complexes: Different Halide Effects on These Processes

A series of complexes [Cu2X2(Pic3PO)2] (X = Cl, Br, I) based on tris(pyridin-2-ylmethyl)phosphine oxide (Pic3PO) has been synthesized. At 298 K, these compounds exhibit thermally activated delayed fluorescence (TADF) of 1(M+X)LCT type with λmax varying from 485 to 545 nm, and quantum efficiency up to 54%. In the TADF process, the halide effect appears as the emission intensification and bathochromic shift of λmax in the following order X = I < Br < Cl. Upon X-ray irradiation, the title compounds emit radioluminescence, the emission bands of which have the same shape as those at TADF, thereby meaning a similar radiative excited state. By contrast to TADF, the halide effect in the radioluminescence is reversed: its intensity grows in the order X = Cl < Br < I, since heavier atoms absorb X-rays more efficiently. These findings essentially contribute to our knowledge about the halide effect in the photo- and radioluminescent Cu(I) halide emitters.

Synthesis, Electrochemistry, Photophysics, and Photochemistry of a Discrete Tetranuclear Copper(I) Sulfido Cluster

A tetranuclear copper(I) complex, [Cu₄{μ-(Ph₂P)₂NH}₄(μ₄-S)](PF₆)₂ (1), was synthesized. It was found to display intense and long-lived phosphorescence in the solid and solution states. The lowest-energy excited state was assigned as ligand-to-metal charge transfer (LMCT) [S^2- → Cu₄] mixed with some metal-centered (ds/dp) character. In addition, the phosphorescent state of this complex was found to be quenched by pyridinium acceptors via an oxidative electron-transfer quenching process. An excited-state reduction potential of -1.74 V versus saturated salt calomel electrode was estimated through oxidative quenching studies with a series of structurally related pyridinium acceptors, indicative of its strong reducing power in the excited state. From the transient absorption difference spectrum of the tetranuclear copper(I) sulfido complex and 4-(methoxycarbonyl)-N-methylpyridinium hexafluorophosphate, in addition to the characteristic absorption of the pyridinyl radical at ca. 395 nm, two absorption bands at ca. 500 and 660 nm were also observed. The former was assigned as an LMCT absorption [S^2- → Cu₄] and the latter as an intervalence charge-transfer transition, associated with the mixed-valence species Cu^I/Cu^I/Cu^I/Cu^II.

Copper(I)-Pyrazolate Complexes as Solid-State Phosphors: Deep-Blue Emission through a Remote Steric Effect

We describe a novel manifestation of rigidochromic behavior in a series of tetranuclear Cu(I)-pyrazolate (Cu₄pz₄) macrocycles, with implications for solid-state luminescence at deep-blue wavelengths (<460 nm). The Cu₄pz₄ emissions are remarkably sensitive to structural effects far from the luminescent core: when 3,5-di-tert-butylpyrazoles are used as bridging ligands, adding a C4 substituent can induce a blue shift of more than 100 nm. X-ray crystal and computational analyses reveal that C4 units influence the conformational behavior of adjacent tert-butyl groups, with a subsequent impact on the global conformation of the Cu₄pz₄ complex. Emissions are mediated primarily through a cluster-centered triplet (³CC) state; compression of the Cu₄ cluster into a nearly close-packed geometry prevents the reorganization of its excited-state structure and preserves the ³CC energy at a high level. The remote steric effect may thus offer alternative strategies toward the design of phosphors with rigid excited-state geometries.

Halogen-induced Core Structural Evolution of Four Dinuclear Copper(Ι) Luminescent Coordination Compounds

Reaction of [Cu(CH3CN)4]ClO4 and 2-(diphenylphosphino) pyridine (dppy) along with different halogen reagents NH4X (X = Cl-, Br- and I-), four luminescent di-copper(I) coordination compounds, namely [Cu2(μ-dppy)3Cl]ClO4·H2O (1a), [Cu2(μ-dppy)3Br]ClO4 (2a), Cu2(μ-Br)2(μ-dppy)(η-dppy)2...

Photophysical properties of homobimetallic Cu(i)–Cu(i) and heterobimetallic Cu(i)–Ag(i) complexes of 2-(6-bromo-2-pyridyl)-1H-imidazo[4,5-f][1,10]phenanthroline

The heteronuclear Cu(i)–Ag(i) complexes show dual emission bands and enhanced luminescence compared with their isostructural homobinuclear Cu(i) complexes.

Photoluminescent coordination polymer bulk glasses and laser-induced crystallization

Over centimeter-sized luminescent coordination polymer glasses were fabricated. They showed high transparency (over 80%) and strong green emission at room temperature. The glass-to-crystal transformation by laser irradiation was demonstrated.

Multi-stimulus semiconductor Cu(i)–I-pyrimidine coordination polymer with thermo- and mechanochromic sensing

The 1D-[Cu(aClpym)I]n coordination polymer behaves as an intelligent material with response to different stimuli since its emission is altered with temperature and with varying modes of pressure, making it a potential multi-response material.

Multiple stimuli triggered structural isomerization of copper iodide–pyridine crystals

Structural isomerization of copper iodide–pyridine crystals under multiple stimuli was monitored, revealing a three-step dissociation–reorganization mechanism.

Coordinated Anionic Inorganic Module-An Efficient Approach Towards Highly Efficient Blue-Emitting Copper Halide Ionic Hybrid Structures

Copper halide based organic-inorganic hybrid semiconductors exhibit great potential as light-emitting materials with excellent structural variety and optical tunability. Among them, copper halide hybrid molecular compounds with discrete inorganic modules are particularly interesting due to their high quantum efficiency. However, synthesizing highly efficient blue-emitting molecular clusters remains challenging. Here, we report a novel and facile strategy for the design and synthesis of highly luminescent copper halide hybrid structures by fabricating coordinated anionic inorganic modules in these ionic species. By using this approach, a family of strongly blue-emitting copper halide hybrid ionic structures has been prepared with high internal quantum yields up to 98 %. Strong luminescence from the combination of ionic and covalent bonds in these compounds make them ideal candidates as alternative, rare-earth-element free light-emitting materials for possible use in optoelectronic devices.

Synthesis, Structure, and Photophysical Properties of Yellow-Green and Blue Photoluminescent Dinuclear and Octanuclear Copper(I) Iodide Complexes with a Disilanylene-Bridged Bispyridine Ligand

The synthesis, structural, and photophysical investigations of CuI complexes with a disilanylene-bridged bispyridine ligand 1 are herein presented. Dinuclear (2) and ladder-like (3) octanuclear copper(I) complexes were straightforwardly prepared by exactly controlling the ratio of CuI/ligand 1. Single-crystal X-ray analysis confirmed that dinuclear complex 2 had no apparent π…π stacking whereas octanuclear complex 3 had π…π stacking in the crystal packing. In the solid state, the complexes display yellow-green (λ_em = 519 nm, Φ = 0.60, τ = 11 µs, 2) and blue (λ_em = 478 nm, Φ = 0.04, τ = 2.6 µs, 3) phosphorescence, respectively. The density functional theory calculations validate the differences in their optical properties. The difference in the luminescence efficiency between 2 and 3 is attributed to the presence of π…π stacking and the different luminescence processes.

Solid-State Structures and Photoluminescence of Lamellar Architectures of Cu(I) and Ag(I) Paddlewheel Clusters with Hydrogen-Bonded Polar Guests

Two hexanuclear paddlewheel-like clusters appending six carboxylic-acid pendants have been isolated with the inclusion of polar solvent guests: [Cu₆(Hmna)₆]·7DMF (1·7DMF) and [Ag₆(Hmna)₆]·8DMSO (2·8DMSO), where H₂mna = 2-mercaptonicotininc acid, DMF = N,N’-dimethylformamide, and DMSO = dimethyl sulfoxide. The solvated clusters, together with their fully desolvated forms 1 and 2, have been characterized by FTIR, UV–Vis diffuse reflectance spectroscopy, TG-DTA analysis, and DFT calculations. Crystal structures of two solvated clusters 1·7DMF and 2·8DMSO have been unambiguously determined by single-crystal X-ray diffraction analysis. Six carboxylic groups appended on the clusters trap solvent guests, DMF or DMSO, through H-bonds. As a result, alternately stacked lamellar architectures comprising of a paddlewheel cluster layer and H-bonded solvent layer are formed. Upon UV illumination (λ_ex = 365 nm), the solvated hexasilver(I) cluster 2·8DMSO gives intense greenish-yellow photoluminescence in the solid state (λ_PL = 545 nm, Φ_PL = 0.17 at 298 K), whereas the solvated hexacopper(I) cluster 1·7DMF displays PL in the near-IR region (λ_PL = 765 nm, Φ_PL = 0.38 at 298 K). Upon complete desolvation, a substantial bleach in the PL intensity (Φ_PL < 0.01) is observed. The desorption–sorption response was studied by the solid-state PL spectroscopy. Non-covalent interactions in the crystal including intermolecular H-bonds, CH⋯π interactions, and π⋯π stack were found to play decisive roles in the creation of the lamellar architectures, small-molecule trap-and-release behavior, and guest-induced luminescence enhancement.

Largely Color-Tuning Prompt and Delayed Fluorescence: Dinuclear Cu(I) Halide Complexes with tert-Amines and Phosphines

Luminescent copper(I) halide complexes with bi- and tridentate rigid ligands have gained wide research interests. In this paper, six tetracoordinate dinuclear copper(I) halide complexes, Cu₂X₂(ppda)₂ [ppda = 2-[2-(dimethylamino)phenyl(phenyl)phosphino]-N,N-dimethylaniline, X = I (1), Br (2), Cl (3)] and Cu₂X₂(pfda)₂ [pfda = 2-[2-(dimethylamino)-4-(trifluoromethyl)phenyl(phenyl)phosphino]-N,N-dimethyl-5-trifluoromethylaniline, X = I (4), Br (5), Cl (6)], were successfully prepared and systematically characterized on their structures and photophysical properties. Complexes 1-5 have a centrosymmetric form with a planar Cu₂X₂ unit, and complex 6 has a mirror symmetry form with a butterfly-shaped Cu₂X₂. Solid complexes 1, 4, and 5 emit delayed fluorescence at room temperature, intense blue to greenish yellow (λ_max = 443-570 nm) light, and their peak wavelengths are located at 443-570 nm with microsecond lifetimes (τ = 0.4-19.2 μs, Φ_PL = 0.05-0.48). Complexes 2, 3, and 6 show prompt fluorescence, very weak yellowish green to yellow (λ_max = 534-595 nm) emission with peak wavelengths at 534-595 nm, and lifetimes in nanoseconds (τ = 4.4-9.3 ns, Φ_PL < 0.0001). (Metal + halide) to ligand and intraligand charge transitions are the main origin of the emission of the complexes. Solution-processed, complex-4-based nondoped and doped devices emit yellow green light with CIE coordinated at (0.41, 0.51), a maximum EQE up to 0.17%, and luminance reaching 75.52 cd/m².

Synthesis and Photophysical Properties of Emissive Silver(I) Halogenido Coordination Polymers Composed of {Ag2X2} Units Bridged by Pyrazine, Methylpyrazine, and Aminopyrazine

Luminescent silver(I) coordination polymers having a {Ag₂(μ-X)₂} rhombic core (X = I, Br) were prepared using pyrazine (pyz), methylpyrazine (Mepyz), and aminopyrazine (ampyz) as bridging ligands. Photophysical measurements show that the complexes were strongly luminescent in the solid state at room temperature; further, the emissive excited state of the pyz and Mepyz complexes was a triplet charge-transfer (³CT) excited state, similar to that of their copper(I) congeners, whereas that of the ampyz complex was a intraligand (³IL) excited state. The energy of the ³CT excited state of a silver halogenido complex was revealed to be ca. 5000 cm^-1 higher than that of the corresponding copper complex.

Cu(I)-I-2,4-diaminopyrimidine Coordination Polymers with Optoelectronic Properties as a Proof of Concept for Solar Cells

Two coordination polymers with formulas [CuI(dapym)]_n and [Cu₂I₂(dapym)]_n (dapym = 2,4-diaminopyrimidine) have been synthesized in water at room temperature. According to the stoichiometry used, mono (1D) and the two-dimensional (2D) structures can be obtained. Both are made up of Cu₂I₂ double chains. Their high insolubility in the reaction medium also makes it possible to obtain them on a nanometric scale. Their structural flexibility and short Cu-Cu distances provoke interesting optoelectronic properties and respond to physical stimuli such as pressure and temperature, making them interesting for sensor applications. The experimental and theoretical studies allow us to propose different emission mechanisms with different behaviors despite containing the same organic ligand. These behaviors are attributed to their structural differences. The emission spectra versus pressure and temperature suggest competencies between different transitions, founding critical Cu₂I₂ environments, i.e., symmetric in the 1D compound and asymmetric for the 2D one. The intensity in the 2D compound's emission increases with decreasing temperature, and this behavior can be rationalized with a structural constriction that decreases the Cu-Cu and Cu-I distances. However, compound 1D exhibits a contrary behavior that may be related to a change of the organic ligand's molecular configuration. These changes imply that a more significant Π-Π interaction counteracts the contraction in distances and angles when the temperature decreased. Also, the experimental conductivity measurements and theoretical calculations show a semiconductor behavior. The absorption of the 1D compound in UV, its intense emission at room temperature, and the reduction to nanometric size have allowed us to combine it homogeneously with ethyl vinyl acetate (EVA), creating a new composite material. The external quantum efficiency of this material in a Si photovoltaic mini-module has shown that this compound is an active species with application in solar cells since it can move the photons of the incident radiation (UV region) to longer wavelengths.

Crystal Structures and Phosphorescent Properties of Group 14 Dipyridinometalloles and Their Copper Complexes

We recently reported dipyridinosilole (DPyS) and dipyridinogermole (DPyG) as π-conjugated units that show low-temperature phosphorescence. A copper complex of DPG shows solid-state phosphorescence at room temperature. In this work, we prepared diphenyldipyridinostannole (DPySn1). Its optical and electrochemical properties were investigated and compared with those of DPyS1 and DPyG1 with the same phenyl substituents. DPySn1 showed the most red-shifted phosphorescence at 520 nm at 77 K in the solid-state, which is likely due to the intermolecular Sn-pyridine interaction that was confirmed by single-crystal X-ray diffraction. Copper complexes of DPyS1 and DPySn1 were also prepared and it was found that the phosphorescence of these dipyridinometallole-copper complex solids was red-shifted in the order of DPySn1-Cu (617 nm)<DPyG1-Cu (624 nm)<DPyS1-Cu (645 nm). Single-crystal X-ray diffraction studies were performed for DPyS1-Cu and DPySn1-Cu complexes. DPyS1-Cu showed a double-chained polymeric ladder-like structure with Cu₄ I₄ cluster units and DPySn1-Cu possessed a single chain polymeric structure with Cu₂ I₂ units, analogous to DPyG1-Cu.

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.

Quantitative Thermal Synthesis of Cu(I) Coordination Polymers That Exhibit Thermally Activated Delayed Fluorescence

As a new environmentally friendly route for synthesizing thermally activated delayed-fluorescence (TADF) Cu(I) complexes, we successfully and quantitatively synthesized strongly emissive Cu(I) coordination polymers [Cu₂I₂(PR₃)₂(n,n'-bpy)]_∞ (CuIR-n, R = Ph, Tol; n = 3, 4; bpy = bipyridine) via the quick thermal reaction of three starting materials (CuI, PR₃, and bpy organic ligands) for 1 h in the absence of a solvent. Powder X-ray diffraction and thermogravimetric analyses revealed that melting of the organic ligands significantly promoted the coordination polymerization reaction, and the stoichiometry of three starting materials was crucial to quantitatively affording CuIR-n. Notably, the photophysical properties of CuIR-n obtained by the thermal reaction were almost the same (emission wavelength, quantum yield, and lifetime) as that obtained by generally used solution reactions, probably because CuIR-n was thermally stable enough to prevent the thermal damage and to improve the crystallinity in the heating process. The emission origin of CuIR-n was assignable to TADF at 298 K and phosphorescence at 77 K originating from the metal-to-ligand charge-transfer excited state effectively mixed with the halide-to-ligand charge transfer ((M+X)LCT) state. Thus, the thermal reaction in the melted ligand could be a promising environmentally friendly method for producing TADF Cu(I) luminophores.

Synthetic Strategies, Reactivity and Applications of 1,5-Naphthyridines

This review covers the synthesis and reactivity of 1,5-naphthyridine derivatives published in the last 18 years. These heterocycles present a significant importance in the field of medicinal chemistry because many of them exhibit a great variety of biological activities. First, the published strategies related to the synthesis of 1,5-naphthyridines are presented followed by the reactivity of these compounds with electrophilic or nucleophilic reagents, in oxidations, reductions, cross-coupling reactions, modification of side chains or formation of metal complexes. Finally, some properties and applications of these heterocycles studied during this period are examined.

Zinc(II) complexes with aromatic nitrogen-containing heterocycles as antifungal agents: Synergistic activity with clinically used drug nystatin

Three novel Zn(II) complexes, [ZnCl₂(qz)₂] (1), [ZnCl₂(1,5-naph)]_n (2) and [ZnCl₂(4,7-phen)₂] (3), where qz is quinazoline, 1,5-naph is 1,5-naphthyridine and 4,7-phen is 4,7-phenanthroline, were synthesized by the reactions of ZnCl₂ and the corresponding N-heterocyclic ligand in 1:2 molar ratio in ethanol at ambient temperature. The characterization of these complexes was done by NMR, IR and UV-Vis spectroscopy, and their crystal structures were determined by single-crystal X-ray diffraction analysis. Complexes 1 and 3 are mononuclear species, in which Zn(II) ion is tetrahedrally coordinated by two nitrogen atoms belonging to two qz or 4,7-phen ligands, respectively, and by two chloride anions, while complex 2 is a 1D coordination polymer that contains 1,5-naph as bridging ligand between two metal ions. In agar disc-diffusion assay, complexes 1-3 manifested good inhibitory activity against two investigated Candida strains (C. albicans and C. parapsilosis), while not inducing toxic effects on the healthy human fibroblast cell line (MRC-5). This activity was not fungicidal, as revealed by the broth microdilution assay, however complex 3 showed the ability to modulate Candida hyphae formation, which is an important process during infection and showed significant synergistic effect with clinically used antifungal polyene nystatin.

Semiconducting crystalline inorganic-organic hybrid metal halide nanochains

One-dimensional (1D) inorganic-organic metal halide hybrids at the molecular level, which can be considered as arrays of nanochains isolated by organic components, have shown remarkable optical and electric properties. This review summarizes their reported structural types and shows how to modify their band gaps and optical and electric properties.

Structural Diversity of Copper(I) Cluster-Based Coordination Polymers with Pyrazine-2-thiol Ligand

Six novel copper(I) cluster-based coordination polymers (CPs) [Cu₉(pzt)₇Cl₂]_n (1), [Cu₂(pzt)Cl]_n (2), [Cu₄(pzt)₃Br]_n (3), [Cu(pzt)]_n (4), [Cu₄(pzt)₃I]_n (5), and [Cu₇(pzt)₆I]_n (6) were solvothermally synthesized using Hpzt (Hpzt = pyrazine-2-thiol) ligand and well-characterized by elemental analysis, infrared (IR) spectroscopy, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction (SCXRD). Six CPs exhibit either 2D (4 and 6) or 3D (1-3, and 5) network based on diverse multinuclear {Cu_xS_y} clusters. The structural evolutions of 1-6 are greatly influenced by types of metal halides and the ligand-to-metal molar ratio used in the reaction. Among them, compound 1 displays interesting temperature-dependent photoluminescence arising from triplet cluster-centered (³CC) excited state from the cluster metal core. Compounds 1-6 also exhibit photocurrent responses upon visible-light illumination (λ = 420 nm) in the order 6 > 5 > 3 > 1 > 4 > 2. This work not only shows the structural diversity of {Cu_xS_y} clusters-based CPs but also provides an interesting insight into structural modulation using crystal engineering concept.

Chemical modification utilizing a terminal structure exposed on the specific surface of polymer-metal complex nanocrystals

It has been difficult to selectively modify the surface of molecular crystals by chemical reactions because they usually have no reaction points on their surfaces. In this paper, focusing on the unique nanocrystal surface of the polymer metal complex (PMC) [{Cu₂(μ-Br)₂(PPh₃)₂}(μ-bpy)]_n having an exposed reactive terminal chain, we successfully modified the surface of PMC nanocrystals (NCs) through an alkylation reaction. Interestingly, after the alkylation reaction, the luminescence spectrum of PMC NCs blue-shifted, and the luminescence quantum yield increased. PMC NCs with a large specific surface area showed optically peculiar or characteristic properties compared with the corresponding bulk crystals. PMC NCs have high potential as a new class of luminescent materials due to their surface effect.

We modified the surface of polymer metal complex nanocrystals (PMC NCs) with the alkylation reaction by utilizing coordinatively unsaturated bipyridine ligands exposed on the (010), and successfully changed the luminescence properties of PMC NCs.

Copper(i) halide polymers derived from tris[2-(pyridin-2-yl)ethyl]phosphine: halogen-tunable colorful luminescence spanning from deep blue to green

A series of isostructural 1D coordination polymers bearing stair-step [Cu₄X₄] modules is reported. At ambient temperature, they feature bright halogen-modulated colorful luminescence spanning from deep blue to green.

QM/MM studies on luminescence mechanism of dinuclear copper iodide complexes with thermally activated delayed fluorescence

The QM/MM method is employed to investigate the photophysical mechanism of two dinuclear copper iodide complexes with thermally activated delayed fluorescence (TADF). The S1-T1 energy differences (ΔE ST) in these two complexes are small enough so that repopulating the S1 state from T1 becomes energetically allowed. Both forward and reverse intersystem crossing (ISC and rISC) processes are much faster than the corresponding radiative fluorescence and phosphorescence processes [k ISC (108 s-1) > k F r (106 s-1), k rISC (105 s-1) > k P r (103 s-1)]. The faster rISC process than the phosphorescence emission enables TADF. Moreover, the diphosphine ligands are found to play an important role in regulating the electronic structures and thereto the radiative and nonradiative rate constants. The present work rationalizes experimental phenomena and helps understand the intrinsic luminescence properties. The obtained insights could be useful for tuning the luminescence performance of dicopper-based luminescence materials.

Diaquabis[4-(dimethylamino)pyridine-κN 1]bis[2-(1,3-dioxo-2,3-dihydro-1H-isoindol-2-yl)acetato-κO 1]cobalt(II)

In the mononuclear title complex, [Co(C10H6NO4)2(C7H10N2)2(H2O)2], the CoII ion is located on an inversion centre and has a distorted octahedral coordination geometry of type CoN2O4 by two N atoms from the two 4-(dimethylamino)pyridine (DMAP) ligands, two carboxylate O atoms from the two deprotonated N-phthaloylglycine (Nphgly) ligands [systematic name: 2-(1,3-dioxo-2,3-dihydro-1H-isoindol-2-yl)acetate] and two coordination water molecules. In the crystal, O—H...O, C—H...O hydrogen bonds and π–π stacking interactions link the molecules into the supramolecular structure.