Mononuclear Gold Research Articles

Gold(I) complexes of the type [AuL{κC-2-C6H4P(S)Ph2}] [L = PTA, PPh3, PPh2(C6H4-3-SO3Na) and PPh2(2-py)]: Synthesis, characterisation, crystal structures, and In Vitro and In Vivo anticancer properties

Four new mononuclear gold (I) compounds of the type [AuL{κC-2-C6H4P(S)Ph2}] {L = PTA (1), PPh3 (2), PPh2(C6H4-3-SO3Na) (3), and PPh2(2-py) (4)} were prepared by scission of the dinuclear compound [Au2{μ-2-C6H4P(S)Ph2}2] by L or via a transmetalation reaction using the organotin reagent 2-Me3SnC6H4P(S)Ph2 and a suitable gold halide precursor. The cytotoxic potential of complexes 1–4 was evaluated against four human cancer cell lines of diverse cellular origin: cervical (HeLa), prostate (PC-3), non-small cell lung adenocarcinoma (A549), and fibrosarcoma (HT-1080). The in vitro cytotoxicity results showed that 1 demonstrated exceptional anticancer activity with IC50 values ranging from 0.08 to 3.5 μM. Complex 3, which contains a sulfonated triphenyl phosphine ligand, displayed the weakest anticancer activity with IC50 values ranging from 3.1 to >50 μM. When compared to the standard chemotherapeutic drug cisplatin, 1 displayed approximately 27-fold greater cytotoxic activity against cervical cancer cells and 3.5- and 7.5-fold greater activities against prostate and fibrosarcoma cancer cells, respectively. Additionally, 1 exhibited 3-fold selectivity for cervical cancer cells compared to non-cancerous HEK-293 cells. Mechanistic investigations revealed that 1 induced apoptosis, which was associated with elevated reactive oxygen species (ROS) and inhibition of the intracellular enzyme thioredoxin reductase. Furthermore, 1 exhibited notable antiangiogenic characteristics in an in vivo model using transgenic zebrafish Tg(fli1a:EGFP). In vivo studies using mouse xenograft models showed that complex 1 displayed superior inhibition of tumour growth (82 %) compared to the clinical drug cisplatin (29 %). Overall, these results highlight the potential of gold (I) compounds as novel antitumour agents.

Synthesis, and spectroscopic characterizations of gold(III) complexes containing nitrogen-heterocycle based pyridine derivatives as a biomolecular chelates

Three gold(III) nanostructured complexes of nicotinamide (nta), picolinic acid (pica), and isonicotinic acid (inta) were synthesized by the reacted of AuCl3 salt with nta, pica, and inta with 1:2 stoichiometry in the alcoholic medium. The solid products obtained were formulated by comparing experimental and calculated data for microanalytical (C, H, N) and metal. Both produce 1:2 compounds with metal ions. The prepared complexes were characterized by different physico-spectroscopic techniques. The FTIR, and 1H NMR spectral analysis, morphological analysis (scanning electron microscopy SEM, transmittance TEM, and X-ray powder diffraction XRD) of these complexes have been discussed. The conductive behavior of the complexes indicates that all of them behave as electrolytic behavior. The mononuclear gold(III) complexes have formulated as [Au(nta)2(Cl)2].Cl, [Au(pica)2].Cl and [Au(inta)2].Cl. The shifts of the ν(N–H) amino, ν(C=N) pyridine, and ν(C=O) carboxylic stretches have been monitored to find out the donor sites of the ligands. According to the experimental data, the three complexes can be characterized in the solid state as mononuclear, with a four-coordinate stereochemistry. KEY WORDS: Gold complex, Nicotinamide, Picolinic acid, Isonicotinic acid, Nanostructure, Spectroscopic Bull. Chem. Soc. Ethiop. 2025, 39(1), 111-121. DOI: https://dx.doi.org/10.4314/bcse.v39i1.9

Tetraphenylethene-based mononuclear aggregation-induced emission (AIE)-active mechanofluorochromism gold(I) complexes with different auxiliary ligands

In this study, a series of tetraphenylethene-containing gold(I) complexes with different auxiliary ligands have been synthesized. These complexes were characterized using a variety of techniques including nuclear magnetic resonance spectroscopy, mass spectrometry, and single crystal X-ray diffraction. Their aggregation-induced emission (AIE) behaviors were investigated through ultraviolet/visible and photoluminescence spectrum analyses, and dynamic light scattering measurements. Meanwhile, their mechanofluorochromic properties were also studied via solid-state photoluminescence spectroscopy. Intriguingly, all these mononuclear gold(I) molecules functionalized by tetraphenylethene group demonstrated AIE phenomena. Furthermore, five gold(I) complexes possessing diverse auxiliary ligands exhibited distinct fluorescence changes in response to mechanical grinding. For luminogens 2–5, their solids showed reversible mechanofluorochromic behaviors triggered by the mutual transformation of crystalline and amorphous states, while for luminogen 1, blue-green-cyan three-color solid fluorescence conversion was realized by sequential mechanical grinding and solvent fumigation. Based on this stimuli-responsive tricolored fluorescence feature of 1, an information encryption system was successfully constructed.

14-Membered Macrocyclic β-Diiminato Gold(II) - A New Member for the Gold(II) Complex Family?

The chemistry of molecular gold compounds is dominated by the oxidation states +I and +III. For the intermediate oxidation state +II with 5d9 electron configuration, dimerization or disproportionation of the gold(II) radicals is favored, so that only a few mononuclear gold(II) complexes have been isolated to date. The present study addresses the one-electron reduction of the macrocyclic gold(III) complex [AuIIIL]+ of the innocent β-diiminato ligand L2- with a 14-membered macrocycle (L2-=5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-5,7,12,14-tetraenato). Electrochemistry, spectroelectrochemistry and chemical reduction of [AuIIIL]+ monitored by UV/Vis, NMR and EPR spectroscopy together with density functional theory calculations reveal disproportionation of the initially generated but elusive gold(II) complex AuIIL and provide guidelines for prospective stable mononuclear tetraazamacrocyclic gold(II) complexes.

Computational Insights into the Photoinduced Dimeric Gold-Catalyzed Divergent Dechloroalkylation of gem-Dichloroalkanes with Alkenes.

The employment of dinuclear Au(I) catalysts in photomediated modern organic transformations has attracted significant attention over the past decade, which commonly demonstrates unique catalytic performance compared with the corresponding mononuclear gold complexes. Nevertheless, detailed mechanisms of dinuclear gold catalysis remain ambiguous, and further mechanistic understanding is highly desirable. Herein, computational studies were carried out to gain mechanistic insights into the photoinduced dinuclear gold-catalyzed divergent dechloroalkylation of gem-dichloroalkanes. Computational results suggest that a proton transfer from the additive, Hantzsch ester (HE), to the base, guanidine, could lead to an ionic pair complex, which is ready to undergo excitation under blue light irradiation to result in the corresponding triplet excited state. Then, the excited complex might undergo oxidative quenching with the dinuclear gold photocatalyst [AuI-AuI]2+, via a single-electron-transfer (SET) step to afford an unusual [Au1/2-Au1/2]+ dinuclear species. The corresponding mononuclear gold catalyst, [AuI]+, however, is not ready to enable the analogous step to give a [Au0] species, which might account for the unique characteristics of dinuclear gold catalysis. Subsequently, the formed [Au1/2-Au1/2]+ intermediate could trigger a Cl-atom transfer from dichloromethane in an inner-sphere manner to furnish a critical chloromethyl radical. Next, the resulting chloromethyl radical could attack the alkenyl moiety of substrates to generate the corresponding alkyl radicals. Then, three possible mechanistic pathways were explored to rationalize the substrate-dependent divergent transformations in this protocol. The main factors responsible for the diversified transformations were discussed.

Exploring the Coordination Properties of Phosphonium‐Functionalized N‐Heterocyclic Carbenes Towards Gold

AbstractGold(I) complexes with N‐heterocyclic carbene ligands functionalized with a pendant phosphonium moiety were synthesized by simple procedures. In particular, the simple addition of LiBr salt in the reaction media allows the formation of the NHC gold(I) mononuclear complexes, whilst in the absence of excess bromide ions the deprotonation of the methylene group in alpha position to the phosphonium group occurs, allowing the isolation of the dinuclear complexes with two C,C‐bridging NHC‐phosphonium ylide ligands. The complexes were characterized in solution with NMR spectroscopy and ESI‐MS spectrometry, as well as in the solid state by means of single crystal X‐ray diffraction analysis. Mononuclear gold(III) species were also isolated by Br2 oxidative addition to the mononuclear gold(I) species and fully characterized. Preliminary results of the biological effects on MCF7 cancer cells are also reported.

Au⋅⋅⋅H−C Interactions Support a Robust Thermally Activated Delayed Fluorescence (TADF) Gold(I) Complex for OLEDs with Little Efficiency Roll‐Off and Good Stability

AbstractThe practical use of luminescent mononuclear gold(I) complexes as optoelectronic materials has been limited by their inferior stability. Herein we demonstrate a strategy to improve the stability of gold(I) complexes which display thermally activated delayed fluorescence (TADF). A highly rigid and groove‐like σ‐donating aryl ligand has been used to form dual Au⋅⋅⋅H−C hydrogen bonds. The secondary metal‐ligand interactions have been authenticated by single‐crystal structure, NMR spectroscopy and theoretical simulations. The TADF AuI complex exhibits appealing emission properties (photoluminescence quantum yield=76 %; delayed fluorescence lifetime=1.2 μs) and much improved thermal and photo‐stability. Vacuum‐deposited organic light‐emitting diodes (OLEDs) show promising electroluminescence with a maximum external quantum efficiency (EQE) over 23 % and negligible efficiency roll‐off even at 10 000 cd m−2. An estimated LT50 longer than 77 000 h with initial luminance of 100 cd m−2 reveals good operational stability. This work suggests a way for design of stable luminescent gold(I) complexes.

Au⋅⋅⋅H-C Interactions Support a Robust Thermally Activated Delayed Fluorescence (TADF) Gold(I) Complex for OLEDs with Little Efficiency Roll-Off and Good Stability.

The practical use of luminescent mononuclear gold(I) complexes as optoelectronic materials has been limited by their inferior stability. Herein we demonstrate a strategy to improve the stability of gold(I) complexes which display thermally activated delayed fluorescence (TADF). A highly rigid and groove-like σ-donating aryl ligand has been used to form dual Au⋅⋅⋅H-C hydrogen bonds. The secondary metal-ligand interactions have been authenticated by single-crystal structure, NMR spectroscopy and theoretical simulations. The TADF AuI complex exhibits appealing emission properties (photoluminescence quantum yield=76 %; delayed fluorescence lifetime=1.2 μs) and much improved thermal and photo-stability. Vacuum-deposited organic light-emitting diodes (OLEDs) show promising electroluminescence with a maximum external quantum efficiency (EQE) over 23 % and negligible efficiency roll-off even at 10 000 cd m-2 . An estimated LT50 longer than 77 000 h with initial luminance of 100 cd m-2 reveals good operational stability. This work suggests a way for design of stable luminescent gold(I) complexes.

Synthesis and Photophysical Properties of Symmetrical Mononuclear Gold(I)-N-Heterocyclic Carbene Complexes

Seven new mononuclear gold(I)-N-heterocyclic carbene (NHC) complexes, [bis(1-butyl-3-alkylbenzimidazolium)gold(I)] hexafluorophosphate (alkyl = methyl, ethyl, butyl, pentyl, hexyl, heptyl, benzyl), 1–7 were reported. All these complexes were successfully synthesized through transmetalation method of their respective silver(I)-NHC complexes, proved by elemental analyses, FTIR, 1H, 13C NMR and single crystal X-ray diffraction analyses. All the 13C NMR spectra of the complexes showed singlet peaks in the range of 189.0–191.2 ppm, belong to the carbene carbon that directly bonded with gold(I) ion, thus, suggesting the successful formation of gold(I)-NHC complexes. The single crystal X-ray diffraction data of 3 shows the presence of bis-NHC mononuclear complex with the chemical formula of [NHC-Au-NHC]·PF6 (NHC = 1,3-bisbutylbenzimidazol-2-ylidene ligand). At room temperature, complex 3 emits weak blue emission under UV light radiation. The photoluminescence study of 3 in solid state shows the excitation and emission spectra at 360 and 460 nm at room temperature while 306 and 406 nm at 77 K, respectively. With the aurophilic interaction excluded, these bands are attributed to metal-to-ligand transfer charge (MLCT) and ligand-centered π-π* transitions. The luminescence of 3 becomes more intense at 77 K compared to room temperature, with the large blue shift of the emission bands.

Tetranuclear Dicationic Aurophilic Gold(I) Catalysts in Enyne Cycloisomerization: Cooperativity for a Dramatic Shift in Selectivity.

In comparison to mononuclear gold Lewis acid catalysts, digold complexes and dual-gold catalysis have illustrated a distinct and powerful potential for the activation of carbon-carbon multiple bonds. Herein, this concept is pushed further by designing novel tetranuclear gold(I) dicationic complexes structurally supported by strongly stabilizing constraint diphosphinoferrocenyl ligands and attractive closed-shell Au⋅⋅⋅Au aurophilic interactions. The use of a molecularly-defined tetranuclear dicationic aurophilic gold(I) precatalyst for the selectivity-challenging cycloisomerization of low-substituted 1,6-enynes favors the formation with high selectivity of strained azabicyclo[4.1.0]hept-4-enes - even in the complete absence of activating/orienting substituents on alkyne and olefin reactive functions. This selectivity is not achieved by the reported phosphine- and carbene-stabilized mono- and dinuclear cationic gold(I) complexes, including the ones formed from the same ligands. More importantly this selectivity differs also from nanoparticles and heterogeneous gold catalysts reported to date. DFT studies correlated to experimental mechanistic investigations support an unprecedented "cluster-like" reactivity from polynuclear cooperation at the origin of this peculiar selectivity where the aurophilic interactions preexist, and pre-organize, gold cluster reactive intermediates.

Synthesis and structural characterization of new gold(I) complexes as bioactive and antitumor agents

New mononuclear gold(I) complexes based on 1-thiocarbamoyl-3,5-diaryl-pyrazoline ligands were synthesized and structurally characterized using X-ray crystallography, 13C and 1H NMR studies, and elemental analysis combined with FT-IR and UV-Vis spectroscopy. Complexes 1–3 were prepared in good yields and characterized by X-ray diffraction as neutral mononuclear complexes of the [Au(L)Cl] type with linear coordination geometry around AuI atoms. The UV-Vis absorption profiles of the compounds prepared exhibited two strong absorption bands between 225 and 400 nm, attributed to HOMO → LUMO electronic transitions of the (M + X)LCT type (charge transfer excitations arising from metal plus halogen to ligand) and mixed XLCT + IL type (charge transfer excitations arising from halogen to ligand plus intraligand), based on DFT studies. Assayed for antitumor activity against B16-F10 murine melanoma cells, 4 T1 murine mammary carcinoma cells, and a normal BHK-21 baby hamster kidney cells line, complexes 1–3 exhibited higher bioactivity and selectivity than their respective free ligands. The preliminary results showed these complexes to be good candidates for the development of new metallodrugs based on gold(I) compounds.

Mononuclear aggregation-induced emission (AIE)-active gold(I)-isocyanide phosphors: Contrasting phosphorescent mechanochromisms and effect of halogen substitutions on room-temperature phosphorescence nature

Developing phosphors with long-lifetime (millisecond scale or even longer) solid state room temperature phosphorescence (RTP) feature has attracted considerable attention. However, to date, stimuli-responsive phosphors with RTP nature are still rare due to the absence of effective guidelines for the exploitation of luminophors synchronously possessing stimuli-responsive and RTP characteristics. In this work, a series of mononuclear gold(I) complexes are reported. All these complexes exhibit various solid-state RTP properties, and phosphor 1-Cl exhibits long-lived RTP behavior. The effect of halogen atoms on the RTP nature of these complexes is investigated in detail. Furthermore, the introduction of different types of halogen atoms can effectively regulate the phosphorescent mechanochromism phenomena of these gold(I)-containing complexes. In addition, these phosphors display typical aggregation-induced emission (AIE) effect except for phosphor 5-CCl, which lacks hydrogen-bonding interactions compared with the other four phosphors. This work will be very helpful to the development of mechanical-force-responsive AIE phosphors with lasting RTP.

A Radical Chain: Mononuclear “Gold Only” Photocatalysis

AbstractWe herein report an unprecedented reactivity of mononuclear gold catalysts acting as classical catalysts and at the same time as active partners in a radical chain mechanism, whereby gold is the only catalyst. The mechanism of the photo‐induced photosensitizer‐free “gold only”‐catalyzed cross coupling was studied in detail – experimentally and theoretically – based on the reaction between arylboronic acids and aryldiazonium salts. With a systematic set of stoichiometric experiments under various conditions and analytic methods, we could show that this mechanism is initiated by an aryl radical formed in the presence of blue LEDs and MeOH. This aryl radical enters the catalytic cycle to oxidize gold(I) to gold(II). Single electron transfer from gold(II) to the aryldiazonium salt then gives the cationic gold(III) complex by formation of a chain‐supporting aryl radical which then is enabled to start a new cycle by oxidation of gold(I) without the need for irradiation. At least every 432 cycles of the radical chain, a new chain‐initiating radical has to restart the radical chain. Eventually, the boronic acid is activated by the BF4− anion to transmetalate to gold(III), and reductive elimination delivers the desired product.magnified image

New mononuclear gold(III) complexes: Synthesis, characterization, kinetic, mechanistic, DNA/BSA/HSA binding, DFT and molecular docking studies

Five new gold(III) complexes, with general formula [Au(NN)Cl2]+ for complexes 1–3 and [Au(NN)2]3+ for complexes 4–5 (where NN is 3-((2-((5-phenyl-1H-pyrazol-3-yl)methoxy)naphthalene-3-yloxy)methyl)-5-phenyl-1H-pyrazole – L1, (3-((2-((5-phenyl-1H-pyrazol-3-yl)methoxy) phenoxy)methyl)-5-phenyl-1H-pyrazole – L2, (3-((2-((5-naphthalen-2-yl)-1H-pyrazol-3-yl)methoxy)phenoxy)methyl)-5-(naphthalen-3-yl)-1H-pyrazole – L3), were synthesized and characterized by elemental analysis, 1H NMR, IR, UV–Vis, ESI-MS and conductometry. Also, ligand L2 was characterized by X-ray analysis. Stability of complexes in water and in Hepes buffer was confirmed by UV–Vis. Kinetics and mechanism of the substitution reactions of 1–3 with guanosine-5′-monophosphate (5′-GMP), glutathione (GSH) and.l-Methionine (l-Met) were studied by stopped-flow technique. Obtained results have shown that complex 1 is the most reactive, while the reactivity of the nucleophiles decreases in order: GSH > 5′-GMP > l-Met. Calculated values of the entropy of activation support an associative mechanism. Redox stability of complexes 1–3 was investigated in the presence of the same biomolecules by cyclic voltametry. Obtained voltammograms showed reduction of gold(III) up to gold(0). DNA binding studies in the presence of ethidium bromide (EB) and 2-(4-hydroxyphenyl)-5-[5-(4-methylpipera-zine-1yl)-benzimidazo-2-yl]-benzimidazole (HOE) were performed by UV–Vis, fluorescence spectroscopy and viscosity measurements, in order to assess the binding mode. The results showed that gold(III) complexes interact with calf-thymus (CT-DNA) via covalently binding mode rather than via intercalation. Also, all complexes shown high values of binding constants for the interactions with bovine serum albumin (BSA) and human serum albumin (HSA). Furthermore, the binding studies with CT-DNA and BSA/HSA were supported by molecular docking. The strong connection between structure and reactivity of gold(III) complexes toward biologically important molecules was confirmed.

Dimerization of a mononuclear gold(I) complex to its corresponding dinuclear complex containing a cyclophane-NHC ligand

A mononuclear AuI-NHC complex was synthesized in good yield via the reaction of KAuCl4 with an imidazolium-linked cyclophane salt in the presence of a mild base. The new complex was fully characterized by 1H and 13C NMR spectroscopy and mass spectrometry. The 1H NMR studies, supported by DFT analysis, show how the mononuclear AuI-NHC complex dimerizes to its corresponding dinuclear AuI-NHC analogue slowly in solution (DMSO or CH3CN). The thermodynamic properties show a distinctive preference for dinuclear Au formation over that of the monomer. We have also discussed the unconventional structural contrast between the experimental and computational geometrical analysis of the dinuclear AuI-NHC complex.

AcridineN‐Heterocyclic Carbene Gold(I) Compounds: Tuning from Yellow to Blue Luminescence

The synthesis and the luminescence features of three gold(I)-N-heterocyclic carbene (NHC) complexes are presented to study how the n-alkyl group can influence the luminescence properties in the crystalline state. The mononuclear gold(I)-NHC complexes, [(L1 )Au(Cl)] (1), [(L2 )Au(Cl)] (2), and [(L3 )Au(Cl)] (3) were isolated from the reactions between [(tht)AuCl] and corresponding NHC ligand precursors, [N-(9-acridinyl)-N'-(n-butyl)-imidazolium chloride, (L1 .HCl)], [N-(9-acridinyl)-N'-(n-pentyl)-imidazolium chloride, (L2 .HCl)] and [N-(9-acridinyl)-N'-(n-hexyl)-imidazolium chloride, (L3 .HCl)]. Their single-crystal X-ray analysis reveals the influence of the n-alkyl groups on solid-state packing. A comparison of the luminescence features of 1-3 with n-alkyl substituents is explored. The molecules 1-3 depicted blue emission in the solution state, while the yellow emission (for 1), greenish-yellow emission (for 2), and blue emission (for 3) in the crystalline phase. This paradigm emission shift arises from n-butyl to n-pentyl and n-hexyl in the crystalline state due to the carbon-carbon rotation of the n-alkyl group, which tends to promote unusual solid packing. Hence n-alkyl group adds a novel emission property in the crystalline state. Density Functional Theory and Time-Dependent Density Functional Theory calculations were carried out for monomeric complex, N-(9-acridinyl)-N'-(n-heptyl)imidazole-2-ylidene gold(I) chloride and dimeric complex, N-(9-acridinyl)-N'-(n-heptyl)imidazole-2-ylidene gold(I) chloride to understand the structural and electronic properties.

Synthesis of N-heterocyclic carbene gold(I) complexes.

N-heterocyclic carbene gold(I) chloride and hydroxide complexes are regularly used as synthons to access various oxygen-, nitrogen- or carbon-bound gold complexes. They are also widely employed as efficient catalysts in addition reactions of hydroelements to unsaturated bonds and in several rearrangement and decarboxylation protocols. Here we describe the multigram synthesis of the most common mononuclear N-heterocyclic carbene gold(I) chloride complexes bearing the N,N'-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) and N,N'-bis(2,6-bis(diphenylmethyl)-4-methylphenyl)imidazol-2-ylidene (IPr*) ligands. Their synthesis is achieved through the straightforward and practical weak base approach in a total time of 4-5 h. This straightforward methodology is conducted under air and possesses considerable advantages over alternative routes, such as the use of a sustainable reaction solvent, minimal amounts of a mild base and commercially available or easily obtained starting materials. Additionally, we describe the synthesis of the mononuclear gold(I) hydroxide complex bearing the IPr ligand, using the state-of-the-art method requiring 24 h. Finally, the improved synthesis of the dinuclear gold(I) hydroxide complex [{Au(IPr)}2(μ-OH)][BF4] is described (~3 h). All procedures can be performed by researchers with standard training and lead to high yields (76-99%) of microanalytically pure bench-stable materials.

Light in Gold Catalysis.

Within the wide family of gold-catalyzed reactions, gold photocatalysis intrinsically features unique elementary steps. When gold catalysis meets photocatalysis, a valence change of the gold center can easily be achieved via electron transfer and radical addition, avoiding the use of stoichiometric sacrificial external oxidants. The excellent compatibility of radicals with gold catalysts opens the door to a series of important organic transformations, including redox-neutral C-C and C-X coupling, C-H activation, and formal radical-radical cross-coupling. The photocatalysis with gold complexes nicely complements the existing photoredox catalysis strategies and also opens a new avenue for gold chemistry. This review covers the achieved transformations for both mononuclear gold(I) catalysts (with and without a photosensitizer) and dinuclear gold(I) photocatalysts. Various fascinating methodologies, their value for organic chemists, and the current mechanistic understanding are discussed. The most recent examples also demonstrate the feasibility of both, mononuclear and dinuclear gold(I) complexes to participate in excited state energy transfer (EnT), rather than electron transfer. The rare applications of gold(III) photocatalysts, both homogeneous and heterogeneous, are also summarized.

Dinuclear gold catalysis.

Gold chemistry has developed extensively in the past decade, and a dozen good reviews have been presented discussing this progress. Few however have paid close attention to the progress in organic synthesis of dinuclear gold-catalysis. A dinuclear gold catalyst is defined here as a gold complex with two gold centers linked by a bidentate ligand. With theoretical analysis and some representative studies in recent years, this comprehensive review highlights the particular properties of dinuclear gold-complexes, especially aurophilic interactions, and systematically summarizes the recent achievements of dinuclear gold-catalyzed coupling reactions, asymmetric catalysis, and photocatalysis, where dinuclear gold catalysts tend to show a greater advantage than the mononuclear gold catalysts.

Carbazole-modified gold(I) complexes with different substituents: Aggregate-induced luminescence change, various solid-state phosphorescence, temperature-dependent phosphorescence, and contrasting mechanoluminochromic characteristics

Three carbazole-containing isocyano-bridged mononuclear gold(I) complexes with different substituents are reported. The complexes display an aggregate luminescence change effect involving a color change from blue to yellow-green. In the solid state, luminogens 1–3 exhibit varying room-temperature phosphorescence involving blue, light yellow, and yellow emissions. In contrast, at 77 K, the gold(I) phosphors 1–3 display stronger (blue-green or yellow-green depending on the phosphor) phosphorescence with longer luminescence lifetimes. In addition, the solid-state phosphorescence of 1–3 is adjusted by moderate mechanical stimulus. More specifically, phosphor 1 shows reversible high-contrast mechanoluminochromic behavior involving interconversion between blue and yellow-green luminescence and phosphor 2 shows reversible mechanoluminochromism phenomenon involving luminescent interconversion between light yellow and light green. In contrast, solid-state phosphor 3 displays an irreversible mechanoluminochromism phenomenon—a strong yellow-green luminescence is observed after grinding. Subsequent treatment with dichloromethane vapor results in a blue-emitting sample.