Oxide Ligands Research Articles

Synthesis and crystallographic characterisation of a homologous series of bis-tridentate phosphine oxide NP3O3 Fe(II), Co(II), Ni(II) and Cu(II) complexes

Despite the large numbers of mono- and bidentate phosphine oxide complexes, examples of well characterised discrete multidentate phosphine oxide transition metal complexes are relatively rare. Herein, we report the coordination chemistry of the triphosphine oxide ligand N{CH2P(O)Ph2}3 (NP3O3, 1) with a series of first row transition metals. Ligand 1 was found to form a series of bis-tridentate homoleptic complexes with Fe(II), Co(II), Ni(II) and Cu(II) salts of the type M(BF4)2·6H2O. The anion exchange reaction of BF4— for BPh4— aided in the crystallisation of three of the four complexes. X-Ray crystallographic analysis of this series: [Fe(N{CH2P(O)Ph2}3)2](BPh4)2 (2), [Co(N{CH2P(O)Ph2}3)2](BPh4)2 (3), [Ni(N{CH2P(O)Ph2}3)2](BPh4)2 (4) and [Cu(N{CH2P(O)Ph2}3)2](BF4)2 (5) confirmed either almost idealised octahedral or distorted octahedral structures and tridentate coordination of 1. Complex 5, Cu(II) d9, displayed a classic Jahn-Teller distortion showing a prominent elongation of the axial M–O bonds. All complexes were found to be paramagnetic which precluded NMR spectroscopy analysis. Magnetic susceptibility measurements on solid samples of the complexes confirmed their number of unpaired electrons and high spin states.

Phenol Oxidation by a Nickel(III)-Fluoride Complex: Exploring the Influence of the Proton Accepting Ligand in PCET Oxidation.

In order to gain insight into the influence of the H+ -accepting terminal ligand in high-valent oxidant mediated proton coupled electron transfer (PCET) reactions, the reactivity of a high valent nickel-fluoride complex [NiIII (F)(L)] (2, L=N,N'-(2,6-dimethylphenyl)-2,6-pyridinecarboxamidate) with substituted phenols was explored. Analysis of kinetic data from these reactions (Evans-Polanyi, Hammett, and Marcus plots, and KIE measurements) and the formed products show that 2 reacted with electron rich phenols through a hydrogen atom transfer (HAT, or concerted PCET) mechanism and with electron poor phenols through a stepwise proton transfer/electron transfer (PT/ET) reaction mechanism. The analogous complexes [NiIII (Z)(L)] (Z=Cl, OCO2 H, O2 CCH3 , ONO2 ) reacted with all phenols through a HAT mechanism. We explore the reason for a change in mechanism with the highly basic fluoride ligand in 2. Complex 2 was also found to react one to two orders of magnitude faster than the corresponding analogous [NiIII (Z)(L)] complexes. This was ascribed to a high bond dissociation free energy value associated with H-F (135 kcal mol-1 ), which is postulated to be the product formed from PCET oxidation by 2 and is believed to be the driving force for the reaction. Our findings show that high-valent metal-fluoride complexes represent a class of highly reactive PCET oxidants.

Coordination Compounds of 9,10‐Dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐Oxide (DOPO) Ligands: Extremely High Thermostability and Ligand Oxidation in the Solid State

Different metal phosphinates and phosphonates were obtained containing zinc, calcium and magnesium as cations by means of a salt metathesis reaction with sodium salts of DOPO and DOPO‐OH. The synthesized complexes [Zn(DOPO)2]n, [Zn(DOPO‐OH)2]n and [Ca(DOPO)2(H2O)]n are featured a polymeric structure. The open‐ring metal phosphinate coordination compound [Zn(DOPO)2]n is able to undergo a non‐reversible thermally induced oxidative cyclisation to the corresponding metal phosphonate [Zn(DOPO‐OH)2]n. The magnesium and calcium phosphinates cannot be oxidized to their corresponding metal phosphonate complexes. All organophosphorus compounds were analyzed by means of X‐ray crystallography, NMR, TGA and TDMS. The oxidative cyclisation reaction of [Zn(DOPO)2]n was investigated by DSC. Additionally, the coordination polymer [Zn(DOPO)2]n can be transformed into a molecular complex by adding nitrogen ligands such as N‐methylimidazole, whereby the phosphonate ligand changes from a bridging to a monodentate ligand. The synthesized coordination compounds exhibit very high thermostabilities of up to 520 °C.

Heterotrimetallic Precursor with 2:2:1 Metal Ratio Requiring at Least a Pentanuclear Molecular Assembly.

This work represents an important step in the quest to make heteromultimetallic molecules featuring specific metal types and complicated metal ratios. The rational design, synthesis, and characterization of a complex heterotrimetallic single-source molecular precursor for the next generation sodium-ion battery cathode material, Na2Mn2FeO6, is described. A unique pentametallic platform [MnII(ptac)3-Na-MnIII(acac)3-Na-MnII(ptac)3] (1) was derived from the known polymeric structure of [NaMnII(acac)3]∞, through a series of elaborate design procedures, such as mixed-ligand, unsymmetric ligand, and mixed-valent approaches. Importantly, the application of those techniques results in a molecule with distinctively different transition metal positions in terms of ligand environment and oxidation states. An isovalent substitution of FeIII for the central MnIII ion forms the target heterotrimetallic precursor [MnII(ptac)3-Na-FeIII(acac)3-Na-MnII(ptac)3] (3) with an appropriate metal ratio of Na:Mn:Fe = 2:2:1. The arrangement of metal ions and ligands in this pentametallic assembly was confirmed by single crystal X-ray investigation. The unambiguous assignment of the positions and oxidation states of the Periodic Table neighbors Fe and Mn in 3 has been achieved by a combination of investigative techniques that include synchrotron resonant diffraction, X-ray multiwavelength anomalous diffraction, X-ray fluorescence spectroscopy, Mössbauer spectroscopy, and gas-phase DART mass spectrometry. The heterotrimetallic single-source precursor 3 was shown to exhibit a clean decomposition pattern yielding the phase-pure P2-Na2Mn2FeO6 quaternary oxide with high uniformity of metal ion distribution as confirmed by electron microscopy.

The effects of binge alcohol exposure on tooth movement and associated root resorption in rats.

Considering the increasing prevalence of alcohol use and the growing number of orthodontic patients, some orthodontic patients might engage in binge drinking during treatment. Nevertheless, little is known about the effect of alcohol use on orthodontic treatment. Male Wistar rats were divided into ethanol and control groups (n=32). The rats received a single daily intraperitoneal injection of 20% (vol/vol) ethanol/saline solution at a dose of 3g/kg of ethanol or saline for three consecutive days, and no injection was given during the remaining four days each week. All rats received orthodontic appliances to draw the maxillary first molar mesially. The rats were sacrificed at days 14 and 28, respectively. The amount of tooth movement was measured. Root resorption area was evaluated by scanning electron microscope. Hematoxylin and eosin (H&E) staining and tartrate-resistant acid phosphatase (TRAP) staining were conducted. Immunohistochemistry staining was performed to evaluate the expressions of nuclear factor kappa B ligand (RANKL), osteoprotegerin (OPG), and inducible nitric oxide synthase (iNOS). There were no significant differences in tooth movement and root resorption between ethanol and control groups. The number of TRAP-positive cells was significantly higher in the ethanol group. The expression of RANKL was statistically increased in the ethanol group. In contrast, the expression of OPG was remarkably decreased in rats injected with ethanol. Moreover, the iNOS level was significantly up-regulated in the ethanol group. The tooth movement and root resorption in rats were not affected by binge alcohol exposure.

Highly Oxidized States of Phthalocyaninato Terbium(III) Multiple-Decker Complexes Showing Structural Deformations, Biradical Properties and Decreases in Magnetic Anisotropy.

Presented here is a comprehensive study of highly oxidized multiple‐decker complexes composed of TbIII and CdII ions and two to five phthalocyaninato ligands, which are stabilized by electron‐donating n‐butoxy groups. From X‐ray structural analyses, all the complexes become axially compressed upon ligand oxidation, resulting in bowl‐shaped distortions of the ligands. In addition, unusual coexistence of square antiprism and square prism geometries around metal ions was observed in +4e charged species. From paramagnetic 1H NMR studies on the resulting series of triple, quadruple and quintuple‐decker complexes, ligand oxidation leads to a decrease in the magnetic anisotropy, as predicted from theoretical calculations. Unusual paramagnetic shifts were observed in the spectra of the +2e charged quadruple and quintuple‐decker complexes, indicating that those two species are actually unexpected triplet biradicals. Magnetic measurements revealed that the series of complexes show single‐molecule magnet properties, which are controlled by the multi‐step redox induced structural changes.

Highly selective transport of lithium across a supported liquid membrane

Lithium extraction is a major concern in view of the increase in battery manufacturing. Separation of lithium from associated sodium is still a challenging task due to the similar chemical behavior of these alkali metals. Lithium sources such as salt brines or seawater usually contain large amounts of sodium which requires a high selectivity for the lithium extraction process. In this study, we demonstrate the application of a supported liquid membrane (SLM) with very high selectivity for the separation of lithium from sodium. A synergistic extraction system made of heptafluoro-dimethyloctanedione (HFDOD) and tri-n-octylphosphine oxide (TOPO) ligands diluted in dodecane was selected based on its extraction efficiency (>99 % of lithium extracted) and selectivity for lithium over sodium (separation factor ca.400). Several experimental parameters were studied using a SLM made of HFDOD and TOPO (initial lithium concentration and sodium to lithium concentration ratio in the feed aqueous phase, HFDOD: TOPO ratio in the organic phase). It was found that high lithium permeation rates can be obtained even for low lithium concentrations and high sodium concentration. Membrane stability was evaluated and found to be poor, i.e. significant loss of performances was observed after one cycle of use, due to the leakage of the organic phase and change in HFDOD: TOPO ratio into it. The SLM system designed is suitable for the extraction of lithium from lowly concentrated solutions such as brines and seawater.

Unravelling the Chemistry of the [Cu(4,7-Dichloroquinoline)2Br2]2 Dimeric Complex through Structural Analysis: A Borderline Ligand Field Case

Large dark prismatic crystals (P 1 ¯ ) consisting of closely packed centrosymmetric [Cu(4,7-dichloroquinoline)2]2Br4 binuclear units are formed when 4,7-dichloroquinoline (DCQ, C9H5NCl2) binds copper(II). Cu2+ adopts a strongly distorted square pyramidal coordination geometry, perturbed by electrostatic interactions with two axial μ–Br ligands acting as highly asymmetric bridges. It is shown that, as electronic states of ligands are higher in energy than the metal ones, antibonding orbitals bear significant ligand-like character and electronic charge is partially transferred from inner-sphere coordinated halogen atoms to copper. Overall, the title compound sits on the Hoffman’s border between main group and transition chemistry, with non-negligible contributions of the ligands to the frontier orbitals. The relative energy placement of metal and ligand states determines an internal redox process, where the metal is slightly reduced at the expense of partial oxidation of the bromide ligands. In fact, the crystal structure is partially disordered due to the substitution of some penta-coordinated Cu(II) centers with tetra-coordinated Cu(I) ions. The geometry of the complex is rationalized in terms of electrostatic-driven distortions from an ideal octahedral prototype. Implications on the reactivity of Cu(II)–quinoline complexes are discussed.

Hot carriers perspective on the nature of traps in perovskites

Amongst the many spectacular properties of hybrid lead halide perovskites, their defect tolerance is regarded as the key enabler for a spectrum of high-performance optoelectronic devices that propel perovskites to prominence. However, the plateauing efficiency enhancement of perovskite devices calls into question the extent of this defect tolerance in perovskite systems; an opportunity for perovskite nanocrystals to fill. Through optical spectroscopy and phenomenological modeling based on the Marcus theory of charge transfer, we uncover the detrimental effect of hot carriers trapping in methylammonium lead iodide and bromide nanocrystals. Higher excess energies induce faster carrier trapping rates, ascribed to interactions with shallow traps and ligands, turning these into potent defects. Passivating these traps with the introduction of phosphine oxide ligands can help mitigate hot carrier trapping. Importantly, our findings extend beyond photovoltaics and are relevant for low threshold lasers, light-emitting devices and multi-exciton generation devices.

Immobilization and activation of cobalt-amine catalyst on NH4OH-treated activated carbon for ethylene dimerization

Catalytic dimerization of ethylene (C2H4) to butene (C4H8) utilizes homogenous catalysts composed of transition metal molecular complexes in the presence of a co-catalyst or Ni, Rh or Cr supported heterogeneous catalysts. Recently, a heterogeneous cobalt catalyst supported on NH4OH-treated carbon (Co/NC) has gained attention. However, the structure of the active site, the identity of the active phase, the role of NH4OH treatment and the effect of thermal activation have remained elusive. Herein, in situ Raman spectroscopy showed the absence of crystalline cobalt oxide phases, such as CoO or Co3O4, in the working catalyst. An intense Raman band at 810 cm−1 was detected in the as-synthesized catalyst, which corresponds to μCo-peroxo species formed via auto-oxidation of the [Co(NH3)x]2+ sites during the drying step. UV–vis DRS absorbance bands at ∼286, 340 and 560 nm indicated that a mixture of octahedral Co3+ and Co2+ is present in the as-synthesized catalyst. During thermal treatment in inert atmosphere, the 265 and 810 cm−1 Raman bands diminished signifying the reduction of μCo-peroxo sites, with the oxidation of some NH3 ligands to N2O(g), indicated by an IR doublet at ∼2225 cm−1. UV–vis DRS during thermal treatment corroborated the reduction of Co3+ to Co2+, with Co2+ sites coordinated in a tetrahedral fashion, as indicated by a new absorbance band at ∼600−700 nm. The presence of the immobilized pseudo-tetrahedral [Co(NH3)x]2+ molecular complexes active for dimerization is proposed as an alternative to previous reports that attribute olefin dimerization activity to crystalline cobalt oxide phase in this catalyst. Steady-state catalytic test results at 1 bar, 80 °C, 5.0 % C2H4 at 10 sccm, 0.3 g catalyst show that model catalyst containing crystalline cobalt oxides (Co/C) exhibited similar initial butene productivity to the [Co(NH3)x]2+ containing Co/NC catalyst, but suffered sharper deactivation due to the irreversible olefin deposition on Co3+ sites.

Site Isolation of Catalytically Active Mn(III)-Porphyrin into Porous Materials

Porous materials (PMs) including porous coordination polymers (PCPs), metal–organic frameworks (MOFs), porous organic polymers (POPs), and polymers with intrinsic microporosity (PIMs), have received much attention and they often show novel and/or enhanced performances in wide range of applications such as catalysis, separation, gas storage, drug delivery, biosensing, and imaging. Although they can be successfully obtained by controlling the growth conditions, their fabrication is still a major challenge because of lack of information regarding the crucial factors for the precise control of particles during the synthesis. Furthermore, the translation of building blocks into well-defined structures, whose properties and functions are regulated in the building block level, still remains very challenging. In this regard, metalloporphyrins would be good building blocks for the construction of such functional materials witnessed by a wide range of molecular architectures, such as molecular boxes, self-assembled arrays, CPs and MOFs with various applications. Particularly, Mn(III)- and Fe(III)-containing metalloporphyrins are often used to fabricate various functional molecular architectures and to mimic the extraordinary behavior of enzymes in both homogeneous and heterogeneous catalytic systems.In the case of homogeneous catalysis, these materials have frequent trouble with fast catalytic degradation because of µ-oxo dimer formation or ligand oxidation. To avoid the catalyst degradation, the heterogenization of homogeneous catalysts, such as immobilization and/or site-isolation of homogeneous catalysts using supporters are widely used alternative strategies. In this regard, I like to present the preparations and heterogeneous catalytic uses of Mn(III)–porphyrin in various porous materials (PMs).

Definition of Redox Centers in Reactions of Lithium Intercalation in Li3RuO4 Polymorphs.

Cathodes based on layered LiMO2 are the limiting components in the path toward Li-ion batteries with energy densities suitable for electric vehicles. Introducing an overstoichiometry of Li increases storage capacity beyond a conventional mechanism of formal transition metal redox. However, the role and fate of the oxide ligands in such intriguing additional capacity remain unclear. This reactivity was predicted in Li3RuO4, making it a valuable model system. A comprehensive analysis of the redox activity of both Ru and O under different electrochemical conditions was carried out, and the effect of Li/Ru ordering was evaluated. Li3RuO4 displays highly reversible Li intercalation to Li4RuO4 below 2.5 V vs Li+/Li0, with conventional reactivity through the formal Ru5+-Ru4+ couple. In turn, it can also undergo anodic Li extraction at 3.9 V, which involves O states to a much greater extent than Ru. This reaction competes with side processes such as electrolyte decomposition and, to a much lesser extent, oxygen loss. Although the associated capacity is reversible, reintercalation unlocks a different, conventional pathway also involving the formal Ru5+-Ru4+ couple despite operating above 2.5 V, leading to chemical hysteresis. This new pathway is both chemically and electrochemically reversible in subsequent cycles. This work exemplifies both the challenge of stabilizing highly depleted O states, even with 4d metals, and the ability of solids to access the same redox couple at two very different potential windows depending on the underlying structural changes. It highlights the importance of properly defining the covalency of oxides when defining charge compensation in view of the design of materials with high capacity for Li storage.

Enantioselective Twofold C−H Annulation of Formamides and Alkynes without Built‐in Chelating Groups

AbstractTwofold C−H annulation of readily available formamides and alkynes without built‐in chelating groups was achieved. Ni−Al bimetallic catalysis enabled by a bulky BINOL‐derived chiral secondary phosphine oxide (SPO) ligand proved to be critical for high reactivity and high selectivity. This reaction uses readily available formamides as starting materials and provides a concise synthetic pathway to a broad range of chiral ferrocenes in 40–98 % yield and 93–99 % ee.

Enantioselective Twofold C-H Annulation of Formamides and Alkynes without Built-in Chelating Groups.

Twofold C-H annulation of readily available formamides and alkynes without built-in chelating groups was achieved. Ni-Al bimetallic catalysis enabled by a bulky BINOL-derived chiral secondary phosphine oxide (SPO) ligand proved to be critical for high reactivity and high selectivity. This reaction uses readily available formamides as starting materials and provides a concise synthetic pathway to a broad range of chiral ferrocenes in 40-98 % yield and 93-99 % ee.

The Influence of the Ligand in the Iridium Mediated Electrocatalyic Water Oxidation.

Electrochemical water oxidation is the bottleneck of electrolyzers as even the best catalysts, iridium and ruthenium oxides, have to operate at significant overpotentials. Previously, the position of a hydroxyl on a series of hydroxylpicolinate ligands was found to significantly influence the activity of molecular iridium catalysts in sacrificial oxidant driven water oxidation. In this study, these catalysts were tested under electrochemical conditions and benchmarked to several other known molecular iridium catalysts under the exact same conditions. This allowed us to compare these catalysts directly and observe whether structure–activity relationships would prevail under electrochemical conditions. Using both electrochemical quartz crystal microbalance experiments and X-ray photoelectron spectroscopy, we found that all studied iridium complexes form an iridium deposit on the electrode with binding energies ranging from 62.4 to 62.7 eV for the major Ir 4f7/2 species. These do not match the binding energies found for the parent complexes, which have a broader binding energy range from 61.7 to 62.7 eV and show a clear relationship to the electronegativity induced by the ligands. Moreover, all catalysts performed the electrochemical water oxidation in the same order of magnitude as the maximum currents ranged from 0.2 to 0.6 mA cm–2 once more without clear structure–activity relationships. In addition, by employing 1H NMR spectroscopy we found evidence for Cp* breakdown products such as acetate. Electrodeposited iridium oxide from ligand free [Ir(OH)6]2– or a colloidal iridium oxide nanoparticles solution produces currents almost 2 orders of magnitude higher with a maximum current of 11 mA cm–2. Also, this deposited material contains, apart from an Ir 4f7/2 species at 62.4 eV, an Ir species at 63.6 eV, which is not observed for any deposit formed by the molecular complexes. Thus, the electrodeposited material of the complexes cannot be directly linked to bulk iridium oxide. Small IrOx clusters containing few Ir atoms with partially incorporated ligand residues are the most likely option for the catalytically active electrodeposit. Our results emphasize that structure–activity relationships obtained with sacrificial oxidants do not necessarily translate to electrochemical conditions. Furthermore, other factors, such as electrodeposition and catalyst degradation, play a major role in the electrochemically driven water oxidation and should thus be considered when optimizing molecular catalysts.

Peptide-capped functionalized Ag/Au bimetal nanoclusters with enhanced red fluorescence for lysosome-targeted imaging of hypochlorite in living cells

Bioimaging probes for monitoring intracellular reactive oxygen species have important implications for cell biology research. Herein, we developed peptide-capped silver/gold nanoclusters (peptide@Ag/Au NCs) for lysosome-targeted imaging of hypochlorite (ClO−). The peptide@Ag/Au NCs were synthesized via a one-pot method using peptide as both a template and a reducing agent. The fluorescence intensity and absolute quantum yield of peptide@Ag/Au NCs were much higher than those of peptide-capped gold nanoclusters and silver nanoclusters. In the presence of ClO−, the fluorescence of peptide@Ag/Au NCs was quenched, accompanied by a redshift due to ClO−-induced oxidation of the peptide ligand and decreased Ag content in Ag/Au NCs. The relative fluorescence intensity F0/F had favourable linearity for ClO− concentrations in the range 0.1–100 μmol/L (R2 = 0.9954), with a detection limit (LOD) of 80 nmol/L. The lysosome-targeted peptide@Ag/Au NCs were applied to detect ClO− in lysosomes in living cells via fluorescence imaging.

Towards a Stronger Halogen Bond Involving Astatine: Unexpected Adduct with Bu3PO Stabilized by Hydrogen Bonding

The halogen bond is a powerful tool for the molecular design and pushing the limits of its strength is of major interest. Bearing the most potent halogen-bond donor atom, astatine monoiodide (AtI) was recently successfully probed [Nat. Chem. 2018, 10, 428-434]. In this work, we continue the exploration of adducts between AtI and Lewis bases with the tributylphosphine oxide (Bu3 PO) ligand, revealing the unexpected experimental occurrence of two distinct chemical species with 1:1 and 2:1 stoichiometries. The 1:1 Bu3 PO⋅⋅⋅AtI complex is found to exhibit the strongest astatine-mediated halogen bond so far (with a formation constant of 10(4.24±0.35) ). Quantum chemical calculations unveil the intriguing nature of the 2:1 2Bu3 PO⋅⋅⋅AtI adduct, involving a halogen bond between AtI and one Bu3 PO molecular unit plus CH⋅⋅⋅O hydrogen bonds chelating the second Bu3 PO unit.

Atomic layer deposition of cobalt phosphate from cobaltocene, trimethylphosphate, and O2 plasma

Electrodeposited cobalt phosphate has been reported in the literature as a robust alternative to noble metal-based electrocatalysts for the O2 evolution reaction. In parallel, atomic layer deposition (ALD) has been acknowledged as a key technology for the preparation of thin films for energy applications. With the present work, the authors have addressed the preparation of cobalt phosphate thin films by a plasma-assisted ALD process. The process developed consists of cobaltocene (step A) and trimethyl phosphate (step C) exposures alternated by O2 plasma (steps B and D) in an ABCD fashion. The process shows a linear growth with a growth per cycle of 1.12 ± 0.05 Å at 300 °C and no nucleation delay. The ALD saturation behavior has been demonstrated for each dosing step, and the process shows minimal inhomogeneity on 100 mm diameter wafers in terms of film thickness (<1.0%) and refractive index (<0.5%). The chemical characterization of the layers deposited shows that the composition is close to the stoichiometric (Co3.1P2O8.3 for a deposition temperature of 200 °C) and the oxidation states of cobalt and phosphorus and agrees with those reported in the literature. The cobalt-to-phosphorous ratio has been found to correlate with the values of absorption coefficient (k) and refractive index (n) of the layers. Furthermore, the authors have gained insights into the surface reactions occurring during each ALD step by quadrupole mass spectrometry investigation. The results suggest that cobaltocene undergoes associative adsorption and the cyclopentadienyl ligands are removed during subsequent O2 plasma exposure. Moreover, the authors have indirectly identified cyclopentadienone as an intermediate of the oxidation and removal of cyclopentadienyl ligand. On the other hand, the trimethyl phosphate dosing is characterized by chemisorption via the elimination of methanol.

Photoresponsive Propeller-like Chiral AIE Copper(I) Clusters.

A pair of propeller-like chiral trinuclear CuI clusters (R/S-Cu3) with unique photoinduced fluorescence enhancement were prepared. R/S-Cu3 showed intense variable luminescence after UV light irradiation, which was attributed to the stepwise oxidation of ligand in the clusters. It exhibited typical aggregation-induced emission (AIE) (αAIE =17.3). Mechanism studies showed that metal cluster-centered (MCC) and triplet metal-to-ligand charge-transfer (3 MLCT) processes are the origin of the luminescence; the processes are regulated by a restriction of intramolecular motions mechanism in a different state. The chiral structure and AIE feature endow R/S-Cu3 with remarkable circularly polarized luminescence (glum =2×10-2 ) in the aggregated state. It shows good capability for producing reactive oxygen species. This work enriches the kinds of atomically precise AIE clusters, gains insight into their luminescence mechanism, and offers the prospect of application in multifunctional materials.

Photoresponsive Propeller‐like Chiral AIE Copper(I) Clusters

AbstractA pair of propeller‐like chiral trinuclear CuI clusters (R/S‐Cu3) with unique photoinduced fluorescence enhancement were prepared. R/S‐Cu3 showed intense variable luminescence after UV light irradiation, which was attributed to the stepwise oxidation of ligand in the clusters. It exhibited typical aggregation‐induced emission (AIE) (αAIE=17.3). Mechanism studies showed that metal cluster‐centered (MCC) and triplet metal‐to‐ligand charge‐transfer (3MLCT) processes are the origin of the luminescence; the processes are regulated by a restriction of intramolecular motions mechanism in a different state. The chiral structure and AIE feature endow R/S‐Cu3 with remarkable circularly polarized luminescence (glum=2×10−2) in the aggregated state. It shows good capability for producing reactive oxygen species. This work enriches the kinds of atomically precise AIE clusters, gains insight into their luminescence mechanism, and offers the prospect of application in multifunctional materials.