Twisted and Disconnected Chains: Flexible Linear Tetracuprous Arrays and a Decanuclear CuI Cluster as Blue- and Green/Yellow-Light Emitters

Defined arrays of transition metal ions embedded in tailored polydentate ligand scaffolds allow for a systematic design of their physical properties. Such molecular strings of closed-shell transition metal centers are particularly interesting for Group 11 metal ions in the oxidation state +1 if they undergo metallophilic d10···d10 contact interactions since these clusters are oftentimes efficient photoluminescence (PL) emitters. Copper is particularly attractive as a sustainable earth-abundant coinage metal source and because of the ability of several CuI complexes to serve as powerful thermally activated delayed fluorescence (TADF) emitters in molecular/organic light-emitting devices (OLEDs). Our combined synthetic, crystallographic, photophysical, and computational study describes a straight tetracuprous array possessing a centrally disconnected CuI2···CuI2 chain and a continuous helically bent CuI4 complex. This molecular helix undergoes a facile rearrangement in diethyl ether solution, yielding an unprecedented nanosized CuI10 cluster (2.9 × 2.0 nm) upon crystallization. All three clusters show either bright blue phosphorescence, TADF, or green/yellow multiband phosphorescence with quantum yields between 6.5 and 67%, which is persistent under hydrostatic pressure up to 30 kbar. Temperature-dependent PL investigations in combination with time-dependent density-functional theory (TD-DFT) calculations and void space analyses of the crystal packings complement a comprehensive correlation between the molecular structures and photoluminescence properties.

Thermally Activated Delayed Fluorescent Binuclear Copper(I) Alkynyl Complexes with Cuprophilic Interactions

Copper(I)-based thermally activated delayed fluorescence (TADF) emitters have been conceived to be promising candidates for display and lighting applications because of their multifarious structures and strong photoluminescence. Herein a string of binuclear Cu(I) complexes bearing pronounced cuprophilic interactions have been designed and synthesized. [Cu2(dppb)2(μ2-η1-C≡C-Ph)2] (1 a) and [Cu2(dppb)2(μ2-η1-C≡C-PPXZ)2] (1 b) display photoluminescence quantum yields of up to 67 % in doped films and solid states via TADF and exhibit reversible bicolor luminescence switching upon mechanical stimuli. Computational studies manifest that the metal-to-ligand charge transfer predominant transitions ensure a small energy splitting (ΔEST) between the lowest singlet (S1) and triplet (T1) excited states and cuprophilic interactions promote the spin-orbit coupling (SOC), favoring the reverse intersystem crossing (RISC) process. This study provides a new strategy for the construction of stimuli-responsive metal-based TADF materials.

Pargyline-phosphine copper(I) clusters with tunable emission for light-emitting devices

Three pargyline-phosphine copper(I) clusters, [Cu4(CC-C9H12N)3(PPh3)4](PF6) (1) and [Cu6(CC-C9H12N)4(dppy)4](X)2 (dppy = diphenyl-2-pyridylphosphine; X = PF6 for 2 and X = ClO4 for 3), were synthesized. Their structures were fully characterized using various spectroscopic methods and X-ray crystallography, which showed that the stoichiometry and nature of pargyline and phosphine ligands play an important role in tuning the structure and photophysical features of Cu(I) clusters. Interestingly, clusters 1, 2 and 3 exhibited red, orange and yellow phosphorescence with high quantum yields of 88.5%, 22.0% and 40.2%, respectively, at room temperature. Moreover, clusters 1-3 show distinct temperature-dependent emissions. The excellent luminescence performance of 1 and 3 was designed and employed for the construction of monochrome and white light-emitting devices (LEDs).

Heterometallic AuI 6 AgI 6 Macrocyclic Cluster Templated by a Supramolecular Melamine Dimer

The application of supramolecular templates in aligning atomically precise heterometal arrays is important for pursuing functional materials. Herein, we report that a bilayered supramolecular tri-deprotonated melamine dimer functions as an effective template in the construction of a heterometallic gold(I)-silver(I) macrocyclic cluster [μ6 -(C3 N6 H3 )3- ]2 -AuI 6 AgI 6 . X-ray single crystal structural analysis showed that a crown-like AuI 6 AgI 6 macrocycle is aligned around two parallelly stacked μ6 -(C3 N6 H3 )3- moieties hold together with π-π interactions. Theoretical calculations revealed that the [μ6 -(C3 N6 H3 )3- ]2 motif dominantly contributes to the near-occupied orbitals in the electronic structure, which is closely related to its luminescence properties. This work demonstrates that the supramolecular templates containing multiple symmetric binding sites may present a facile approach in the construction of functional metal clusters.

Structure and optical limiting effects of heterometallic Ag6@Ti12 and Ag8@Ti12 oxo clusters regulated by alkynyl ligands

Heterometallic Ag6@Ti12 and Ag8@Ti12 oxo clusters were prepared through a strategy of protecting polynuclear silver cores by a hollow Ti-O module. The introduction of alkyne ligands has shown significant influence on their structures and optical limiting effects.

Three in One: Three Different Molybdates Trapped in a Thiacalix[4]arene Protected Ag72 Nanocluster for Structural Transformation and Photothermal Conversion

Polyoxometalates (POMs) represent crucial intermediates in the formation of insoluble metal oxides from soluble metal ions, however, the rapid hydrolysis-condensation kinetics of MoVI or WVI makes the direct characterization of coexisted molecular species in a given medium extremely difficult. Silver nanoclusters have shown versatile capacity to encapsulate diverse POMs, which provides an alternative scene to appreciate landscape of POMs in atomic precision. Here, we report a thiacalix[4]arene protected silver nanocluster (Ag72b) that simultaneously encapsulates three kinds of molybdates (MoO4 2- , Mo6 O22 8- and Mo7 O25 8- ) in situ transformed from classic Lindqvist Mo6 O19 2- , providing more deep understanding on the structural diversity and condensation growth route of POMs in solution. Ag72b is the first silver nanocluster trapping so many kinds of molybdates, which in turn exert collective template effect to aggregate silver atoms into a nanocluster. The post-reaction of Ag72b with AgOAc or PhCOOAg produces a discrete Ag24 nanocluster (Ag24a) or an Ag28 nanocluster based 1D chain structure (Ag28a), respectively. Moreover, the post-synthesized Ag28a can be utilized as potential ignition material for further application. This work not only provides an important model for unlocking dynamic features of POMs at atom-precise level but also pioneers a promising approach to synthesize silver nanoclusters from known to unknown.

Supramolecularly Dimeric Assemble of Planar Cu13 Clusters Controlled by the Length of Spacers of Diphosphine

The controlled formation of dimeric clusters is challenging. Three copper(I) clusters, labeled as {Cu13[o-Ph(C≡C)2]6(L)4}(ClO4), were synthesized by using three different ligands, including 1,4-bis(diphenylphosphino)butane (dppb), 1,5-bis(diphenylphosphino)pentane (dpppe), and bis(diphenylphosphino)hexane (dpph). By increasing the flexibility of alkyl spacers in the diphosphine ligands, the relative positions of the phenyl rings could be optimized to achieve efficient packing with maximized intercluster interactions. In the crystal structures, cluster 1 with dppb ligands did not display interlocked structures. In contrast, cluster 2 with dpppe ligands formed supramolecularly interlocked polymers through weak π-π interactions and C-H···π interactions, while cluster 3 employing dpph ligands formed supramolecularly interlocked dimers with strong π-π interactions and C-H···π interactions. The supramolecular dimer of 3 was also evidenced by analyses through electrospray ionization mass spectrometry and transmission electron microscopy. Density functional theory calculation was used to understand the electronic structure and transitions. Supramolecularly interlocked polymers/dimers with rigid structures exhibited higher quantum efficiency. The solution of these clusters demonstrated remarkable aggregation-induced emission enhancements. This study presents unique examples of planar luminescent copper clusters, featuring the first serial dialkynyl-protected cluster. It underlines the importance of ligand flexibility in creating supramolecular cluster dimers.

Unravelling the Roles of Solvophobic Effects and π⋅⋅⋅π Stacking Interactions in the Formation of [2]Catenanes Featuring Di-(N-Heterocyclic Carbene) Building Blocks

A series of [2]catenanes has been prepared from di-NHC building blocks by utilizing solvophobic effects and/or π⋅⋅⋅π stacking interactions. The dinickel naphthobiscarbene complex syn-[1] and the kinked biphenyl-bridged bipyridyl ligand L2 yield the [2]catenane [2-IL](OTf)4 by self-assembly. Solvophobic effects are pivotal for the formation of the interlocked species. Substitution of the biphenyl-linker in L2 for a pyromellitic diimide group gave ligand L3 , which yielded in combination with syn-[1] the [2]catenane [3-IL](OTf)4 . This assembly exhibits enhanced stability in diluted solution, aided by additional π⋅⋅⋅π stacking interactions. The π⋅⋅⋅π stacking was augmented by the introduction of a pyrene bridge between two NHC donors in ligand L4 . Di-NHC precursor H2 -L4 (PF6 )2 reacts with Ag2 O to give the [Ag2 L4 2 ]2 [2]catenane [4-IL](PF6 )4 , which shows strong π⋅⋅⋅π stacking interactions between the pyrene groups. This assembly was readily converted into the [Au2 L4 2 ]2 gold species [5-IL](PF6 )4 , which exhibits exceptional stability based on the strong π⋅⋅⋅π stacking interactions and the enhanced stability of the Au-CNHC bonds.

Dicarboxylic Acids Induced Tandem Transformation of Silver Nanocluster

Structural transformation of metal nanoclusters (NCs) is of great ongoing interest regarding their synthesis, stability, and reactivity. Although sporadic examples of cluster transformations have been reported, neither the underlying transformation mechanism nor the intermediates are unambiguous. Herein, we have synthesized a flexible 54-nuclei silver cluster (Ag54) by combining soft (tBuC≡C-) and hard (nPrCOO-) ligands. The existence of weakly coordinated nPrCOO- enhances the reactivity of Ag54, thus facilitating the dicarboxylic acid to induce structural transformation. X-ray structural analyses reveal that Ag54 transforms to Ag28 cluster-based 2D networks (Ag28a and Ag28b) induced by H2suc (succinic acid) and H2glu (glutaric acid), whereas with H2pda (2,2'-(1,2-phenylene)diacetic acid), a discrete Ag28 cluster (Ag28c) is isolated. The key intermediate Ag17 that emerges during the self-dissociation of Ag54 was isolated by using cryogenic recrystallization and characterized by X-ray crystallography. The "tandem transformation" mechanism for the structure evolution from Ag54 to Ag28a is established by time-dependent electrospray ionization mass spectrometry (ESI-MS) and UV-vis spectroscopy. In addition, the catalytic activity in the 4-nitrophenol reduction follows the sequence Ag28c > Ag28b > Ag28a > Ag54 due to more bare silver sites on the surface of the Ag28 cluster unit. Our findings not only open new avenues to the synthesis of silver NCs but also shed light on a better understanding of the structural transformation mechanism from one cluster to another or cluster-based metal-organic networks induced by dicarboxylates.

Eight-Electron Superatomic Cu31 Nanocluster with Chiral Kernel and NIR-II Emission

Owing to the inherent instability caused by the low Cu(I)/Cu(0) half-cell reduction potential, Cu(0)-containing copper nanoclusters are quite uncommon in comparison to their Ag and Au congeners. Here, a novel eight-electron superatomic copper nanocluster [Cu₃₁(4-MeO-PhC≡C)₂₁(dppe)₃](ClO₄)₂ (Cu₃₁, dppe = 1,2-bis(diphenylphosphino)ethane) is presented with total structural characterization. The structural determination reveals that Cu₃₁ features an inherent chiral metal core arising from the helical arrangement of two sets of three Cu₂ units encircling the icosahedral Cu₁₃ core, which is further shielded by 4-MeO-PhC≡C^- and dppe ligands. Cu₃₁ is the first copper nanocluster carrying eight free electrons, which is further corroborated by electrospray ionization mass spectrometry, X-ray photoelectron spectroscopy and density functional theory calculations. Interestingly, Cu₃₁ demonstrates the first near-infrared (750-950 nm, NIR-I) window absorption and the second near-infrared (1000-1700 nm, NIR-II) window emission, which is exceptional in the copper nanocluster family and endows it with great potential in biological applications. Of note, the 4-methoxy groups providing close contacts with neighboring clusters are crucial for the cluster formation and crystallization, while 2-methoxyphenylacetylene leads only to copper hydride clusters, Cu₆H or Cu₃₂H₁₄. This research not only showcases a new member of copper superatoms but also exemplifies that copper nanoclusters, which are nonluminous in the visible range may emit luminescence in the deep NIR region.

Mechanistic Insights into Multisilver-Mediated Synergistic Activation of Terminal Alkynes

Synergistic effect extensively exists in multimetal-involved catalytic or mediated processes of group 11 metals due to their remarkable metallophilic interactions. Herein, we present a multiple synergism model for alkynyl substrates and conduct theoretical investigations on various multimetallic bonding modes and the corresponding synergistic activations. We computationally screen nine alkynyl multisilver coordination modes and sequence their reactivity shown in an intramolecular nucleophilic addition reaction by the trend of active μ₄-η¹η¹η²η² and μ₃-η¹η¹η² to the relatively inert μ₂-η¹η². The transition-state (TS) stabilization of the high-nuclearity mode mainly comes from the significant negative interaction energies between Ag_n and the substrate based on the distortion/interaction analysis. Energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV) analysis further reveals the charge-accepting reservoir effect of the polysilver moiety and the orbital match between the alkynyl group and specific spatial arrangement of silver atoms to account for this efficient activation. In addition, tests on different ligands coordinated to silver atoms show a correlation of the ligand conformation adjustability with the reactivity of the alkynyl unit, and the accommodable η² activation unit embodies a lower deformation energy than the other homonuclear synergistic modes. Privileged multiple synergistic models have been further evidenced based on on-bench experiments by isolating trisilver and tetrasilver alkynyl complexes. This study not only systematically evaluates the multimetallic synergism of different coordination modes in alkyne activation but also provides a guidance for the future design of multimetallic catalysts.

Synthesis and Full Characterization of One Organometallic Polyoxometalate-Based Copper(I)-Alkene Complex

An alkene-bridged thioether ligand (L) was designed and used for its first study within a polyoxometalate (POM) hybrid system, and a POM-based copper(I)-alkene compound [(Cu^IL)₂(P^VMo^VI₁₂O₄₀)]·(Cu^IL) (1) was isolated and characterized by X-ray crystallography. A unique alkene-coordinating N(η²-C═C)N mode of L is observed, and the Cu centers are captured by σ²,π-L in a pocket fashion, giving birth to discrete [Cu^IL]⁺ cations and [(Cu^IL)₂(P^VMo^VI₁₂)]^- anions. The ionic crystal exhibits solubility in aprotic polar solvents, and the electrospray ionization mass spectrometry is used to explore the nature of species present in the solution. It is found that the whole cluster [P^VMo^VI₁₂]^3- is completely present, and all the main peaks can be assigned to different charged fragments of the same parent cluster.

Self-Assembly of Molecular Trefoil Knots Featuring Pentadecanuclear Homoleptic AuI -, AuI /AgI -, or AuI /CuI -Alkynyl Coordination

Metal-free and metal-containing molecular trefoil knots are fascinating ensembles that are usually covalently assembled, the latter requiring the rational design of di- or multidentate/multipodal ligands as connectors. In this work, we describe the self-assembly of pentadecanuclear Au^I trefoil knots [Au₁₅ (C≡CR)₁₅ ] from monoalkynes HC≡CR (R=9,9-X₂ -fluorenyl with X=nBu, n-hexyl) and [Au^I (THT)Cl]. Hetero-bimetallic counterparts [Au₉ M₆ (C≡CR)₁₅ ] (M=Cu/Ag) were self-assembled by reactions of [Au₁₅ (C≡CR)₁₅ ] with [Cu(MeCN)₄ ]⁺ /AgNO₃ and HC≡CR. The type of pentadecanuclear trefoil knots described herein is characterized by X-ray crystallography, 2D NMR and HR-ESI-MS. [Au₉ Cu₆ (C≡CR)₁₅ ] is relatively stable in hexane; its excited state properties were investigated. DFT calculations revealed that non-covalent metal-metal and metal-ligand interactions, together with longer alkyl chain-strengthened inter-ligand dispersion interactions, govern the stability of the trefoil knot structures.

Solvent-Controlled Condensation of [Mo2 O5 (PTC4A)2 ]6- Metalloligand in Stepwise Assembly of Hexagonal and Rectangular Ag18 Nanoclusters

Stepwise assembly starting from a preassembled metalloligand is a promising approach to obtain otherwise unattainable silver nanoclusters, but hard to be intrinsically identified due to the lack of convincing evidence to justify such a process. Herein, hexagonal and rectangular Ag₁₈ nanoclusters are constructed from the [Mo₂ O₅ (PTC4A)₂ ]^6- (H₄ PTC4A=p-phenyl-thiacalix[4]arene) metalloligand through stepwise assembly. The formation of the metalloligand is confirmed by electrospray ionization mass spectrometry, then assembled with silver ions to form two geometrically different Ag₁₈ nanoclusters in different solvents. The cyclization from the metalloligand to [(Mo₂ O₅ PTC4A)₆ ]^12- can be realized without alcohols and otherwise blocked by them. The installation of this metalloligand not only provides comprehensive understanding of how the solvents regulate the silver nanocluster structures, but also brings new insights for the controllable ligand metallization and subsequent condensation.

Co-ligand triphenylphosphine/alkynyl-stabilized undecagold nanocluster with a capped crown structure

We report the synthesis and crystal structure of novel co-ligand phosphine/alkynyl protected Au nanoclusters, with composition [Au₁₁(PPh₃)₈(C[triple bond, length as m-dash]CPh-CF₃)₂](SbF₆) (1). The gold atoms in the cluster as a capped crown structure subtend C _3v symmetry with one deriving from a central icosahedron and 10 peripheral Au atoms, and all alkynides are exclusively σ coordination bonding. The mean core diameter is about 5.1 Å and the overall van der Waals diameter can be estimated to be 20.5 Å. The optical absorbance of 1 in solution reveals characteristic peaks at 384 and 426 nm and a shoulder between 450 and 550 nm.

Recent advances in polyoxometalate-based metal-alkynyl clusters

This paper focuses on the recent advances in polyoxometalate-based metal-alkynyl clusters.

Ethynyl π-coordinated and non-coordinated mononuclear Cu(i) halide diphosphine complexes: synthesis and photophysical studies

Complexes 4 and 5 emit yellow green delayed fluorescence and complexes 1–3 and 6 and 7 show yellow green to greenish yellow prompt fluorescence.

Tetra- and hexanuclear string complexes of the coinage metals

Reaction of the PNNP ligand system N,N'-bis[(2-diphenylphosphino)phenyl]formamidinate (dpfam) featuring different coordination compartments with [AuCl(tht)], [CuMes]₅, [AgMes]₄, or [AuC₆F₅(tht)] (tht = tetrahydrothiophene) resulted in tetranuclear homo- and heterometallic coinage metal complexes, as well as a hexanuclear gold complex. All of them feature a metal string conformation. Photophysical investigation revealed a significant dependence of the photoluminescence properties on the metal composition. Below 100 K, the PL efficiency of three compounds approaches nearly 100%.

A Photoluminescent Ag10 Cu6 Cluster Stablized by a PNNP Ligand and Phenylacetylides Selectively and Reversibly Senses Ammonia in Air and Water

A photoluminescent bimetallic cluster [Ag₁₀ Cu₆ (bdppthi)₂ (C≡CPh)₁₂ (MeOH)₂ (H₂ O)](ClO₄ )₄ (1, bdppthi=N,N'-bis(diphenylphosphanylmethyl)-tetrahydroimidazole} was synthesized from the PNNP type ligand bdppthi generated in-situ. Upon excitation at 365 nm, 1 exhibited strong phosphorescent emission at 630 nm, which was selectively quenched by NH₃ in air or water. The sensing of NH₃ was rapid and recoverable, with detection limits of 53 ppm (v/v) in N₂ and 21 μmol/L (0.36 ppm, w/w) for NH₃  ⋅ H₂ O in water. Cluster 1 could potentially serve as a bifunctional chemical sensor for the efficient detection of ammonia in waste-gas and waste-water.

Main Avenues in Gold Coordination Chemistry

In this contribution, we provide an overview of the main avenues that have emerged in gold coordination chemistry during the last years. The unique properties of gold have motivated research in gold chemistry, and especially regarding the properties and applications of gold compounds in catalysis, medicine, and materials chemistry. The advances in the synthesis and knowledge of gold coordination compounds have been possible with the design of novel ligands becoming relevant motifs that have allowed the preparation of elusive complexes in this area of research. Strong donor ligands with easily modulable electronic and steric properties, such as stable singlet carbenes or cyclometalated ligands, have been decisive in the stabilization of gold(0) species, gold fluoride complexes, gold hydrides, unprecedented π complexes, or cluster derivatives. These new ligands have been important not only from the fundamental structure and bonding studies but also for the synthesis of sophisticated catalysts to improve activity and selectivity of organic transformations. Moreover, they have enabled the facile oxidative addition from gold(I) to gold(III) and the design of a plethora of complexes with specific properties.

Heterometallation of Photoluminescent Silver(I) Sulfide Nanoclusters Protected by Octahedral Iridium(III) Thiolates

The recently-increasing interest in coinage metal clusters stems from their photophysical properties, which are controlled via heterometallation. Herein, we report homometallic Ag^I ₄₆ S₁₃ clusters protected by octahedral fac-[Ir(aet)₃ ] (aet=2-aminoethanethiolate) molecules and their conversion to heterometallic Ag^I ₄₃ M^I ₃ S₁₃ (M=Cu, Au) clusters. The reactions of fac-[Ir(aet)₃ ] with Ag⁺ and penicillamine produced [Ag₄₆ S₁₃ {Ir(aet)₃ }₁₄ ]²⁰⁺ ([1]²⁰⁺ ), where a spherical Ag^I ₄₆ S₁₃ cluster is covered by fac-[Ir(aet)₃ ] octahedra through thiolato bridges. [1]²⁰⁺ was converted to [Ag₄₃ M₃ S₁₃ {Ir(aet)₃ }₁₄ ]²⁰⁺ ([1^M ]²⁰⁺ ) with an Ag^I ₄₃ M^I ₃ S₁₃ cluster by treatment with M⁺ , retaining its overall structure. [1]²⁰⁺ was photoluminescent and had an emission band ca. 690 nm that originated from an S-to-Ag charge transfer. While [1^Cu ]²⁰⁺ showed an emission band with a slightly higher energy of ca. 650 nm and a lower quantum yield, the emission band for [1^Au ]²⁰⁺ shifted to a much higher energy of ca. 590 nm with an enhanced quantum yield.

Unprecedented [d9]Cu[d10]Au coinage bonding interactions in {Cu(NH3)4[Au(CN)2]}+[Au(CN)2]- salt

The X-ray structure of the {Cu(NH₃)₄[Au(CN)₂]}⁺[Au(CN)₂]^- salt is reported showing an unprecedented [d⁹]Cu[d¹⁰]Au coinage bond. The physical nature of the interaction has been studied using DFT calculations, including the quantum theory of atoms-in-molecules, the noncovalent interaction plot and the natural bond orbital analysis, revealing the nucleophilic role of the [d¹⁰]Au metal and the electrophilic role of [d⁹]Cu metal.

Heterometallic Coinage Metal Acetylenediide Clusters Showing Tailored Thermochromic Luminescence

Acetelyenediide (C₂ ^2- ) species have been encapsulated in bimetallic and trimetallic clusters: [(AuL)₆ Ag₇ (C≡C)₃ ](BF₄ )₇ (2) and [(AuL)₆ AgCu₆ (C≡C)₃ ](BF₄ )₇ (3), L=phenylbis(2-pyridyl)phosphine (PPhpy₂ ). Single-crystal X-ray diffraction analysis revealed that they are isostructural and six silver atoms in 2 are replaced with copper in 3. Both clusters have a trefoil skeleton, which can be viewed as three trigonal bipyramidal (LAu-C≡C-AuL)M₂ Ag (M=Ag/Cu) motifs sharing a common silver atom. TDDFT calculations showed Cu-doping significantly increases the energy level of (C₂ -Cu)-involved occupied orbital, thus inducing interesting transition coupling of dual-emission at low temperature. This work not only provides a strategy for constructing heterometallic clusters, but also shows the prospect for pursuing novel thermochromic luminescent materials by incorporating multi-congeneric metal components.

Homo- and hetero-metallophilicity-driven synthesis of highly emissive and stimuli-responsive Au(i)–Cu(i) double salts

Discrete complex salts having Au···Au and Au···Cu interactions were obtained as three crystalline polymorphs exhibiting various emission colors with high efficiency. Solvent vapor caused crystal-to-crystal transition, changing the emission color.

Keep it tight: a crucial role of bridging phosphine ligands in the design and optical properties of multinuclear coinage metal complexes

Copper subgroup metal ions in the +1 oxidation state are classical candidates for aggregation via non-covalent metal-metal interactions, which are supported by a number of bridging ligands. The bridging phosphines, soft donors with a relatively labile coordination to coinage metals, serve as convenient and essential components of the ligand environment that allow for efficient self-assembly of discrete polynuclear aggregates. Simultaneously, accessible and rich modification of the organic spacer of such P-donors has been used to generate many fascinating structures with attractive photoluminescent behavior. In this work we consider the development of di- and polynuclear complexes of M(i) (M = Cu, Ag, Au) and their photophysical properties, focusing on the effect of phosphine bridging ligands, their flexibility and denticity.

Efficient Blue Phosphorescence in Gold(I)-Acetylide Functionalized Coinage Metal Bis(amidinate) Complexes

The synthesis of linear symmetric ethynyl- and acetylide-amidinates of the coinage metals is presented. Starting with the desilylation of the complexes [{Me3 SiC≡CC(NDipp)2 }2 M2 ] (Dipp=2,6-diisopropylphenyl) (M=Cu, Au) it is demonstrated that this compound class is suitable to serve as a versatile metalloligand. Deprotonation with n-butyllithium and subsequent salt metathesis reactions yield symmetric tetranuclear gold(I) acetylide complexes of the form [{(PPh3 )AuC≡CC(NDipp)2 }2 M2 ] (M=Cu, Au). The corresponding Ag complex [{(PPh3 )AuC≡CC(NDipp)2 }2 Ag2 ] was obtained by a different route via metal rearrangement. All compounds show bright blue or blue-green microsecond long phosphorescence in the solid state, hence their photophysical properties were thoroughly investigated in a temperature range of 20-295 K. Emission quantum yields of up to 41 % at room temperature were determined. Furthermore, similar emissions with quantum yields of 15 % were observed for the two most brightly luminescent complexes in thf solution.

Emissive Supramolecular Systems Based on Reversible Bond Formation and Noncovalent Interactions

Noncovalent interactions and reversible bond formations are widely seen in natural systems for the construction of sophisticated molecular systems that perform various biological processes. Inspired by the natural systems, luminescent supramolecular systems constructed by coordination-driven self-assembly and homometallic metal-metal interations have been studied increasingly. These supramolecular systems show fascinating luminescent behaviors that are not observed from single components. This review summarizes our progress in the development of two types of unique luminescent supramolecular systems. The mononuclear Pt(II) complex units can sandwich coinage metal ions to form heteropolynuclear complexes involving heterometallic metal-metal interactions. A close proximity of the two or three different metal ions by the noncovalent forces lead to orbital overlapping among the coinage metal ions and the Pt(II) complex units, showing emission color change accompanied with structural transformation and reversible metal binding behaviors. Emissive host-guest systems consisting of mononuclear metal complexes and a hydrogen-bonded capsule are also developed, that show a unique encapsulation-induced emission enhancement (EIEE) behavior.

Polynuclear organometallic clusters: synthesis, structure, and reactivity studies

This feature article highlights our recent advances in the controllable synthesis of carbon-centered polynuclear organometallic clusters: from synthesis to transformation, reactivity and mechanism.

The Self-Assembly of [{Ag3(C≡CtBu)2}n]n+ Building Units into a Template-Free Cuboctahedron and Anion-Encapsulating Silver Cages

We describe the controlled synthesis of silver acetylide clusters based on a simple polymeric [Ag₃L₂]⁺ (L = -C≡C^tBu) building block. A linear one-dimensional polymeric structure shows alternating pyramidal motifs and is the basic repeating unit forming discrete molecular cages (pentamers [X⊂Ag₁₅L₁₀]⁴⁺ and hexamers [PF₆⊂Ag₁₈L₁₂]⁵⁺) obtained by incorporating suitable templates. These motifs and a rare template-free cuboctahedral [Ag₁₂L₈]⁴⁺ cluster (tetramer) were crystallographically characterized.

Facile synthesis of silver alkynide cluster and coordination polymers using picolinic acid as a co-ligand

We describe five 1D-coordination polymers and two discrete silver clusters consisting of alkynides and picolinic carboxylates as co-ligands. In some cases, DMSO or EtOH further solvated the structural motifs. Utilising the sterically demanding tri-isopropylsilyl acetylene afforded a tridecanuclear cluster that possessed an unprecedented core with a silver center surrounded by six octahedrally arranged silver atoms.

Ultrasonic-assisted fabrication of thin-film electrochemical detector of H2O2 based on ferrocene-functionalized silver cluster

A novel ferrocene-functionalized silver cluster (FcAgCs) has been designed and synthesized with the assistant of ultrasound treatment and fully characterized by single crystal spectroscopy, IR, UV-Vis, XRD, TGA, NMR, CV and elemental analyses. Ultrasound synthesis method facilitates and accelerates synthesis of this amazing structure and plays a vital role in the synthesis of this special cluster. Single-crystal X-ray analysis reveal that the cluster can be described as a cationic [(dppf)₂Ag₄(CC^tBu)₂(CH₃OH)₂]²⁺ (dppf = 1,1'-bis(diphenylphosphino)ferrocene) species consisted of four rhombic silver atom and two isolated BF₄^- counter anions. Thermal stability greater than 200 °C and solution CV results show that the title cluster is sufficiently stable and suitable for the fabricating of FcAgCs/ITO thin-films and exploring as electrochemical responding materials. Based on its properties, we use it to prepare thin-films on ITO substrate by spin coating method. Verification of synthesis, thickness, uniformity and stability of the fabricated FcAgCs/ITO thin-films were characterized and confirmed by UV, XRD, SEM and the scotch tape adhesion peel test. Moreover, we use this FcAgCs/ITO thin-film electrode as thin-film electrochemical detector which shows sensitive and quick response in the detection of H₂O₂.

Synthesis and Reactivity of an Early-Transition-Metal Alkynyl Cubane Mn4 C4 Cluster

While the coordination chemistry of monometallic complexes and the surface properties of extended metal particles are well understood, the control of metal nanocluster formation has remained challenging. The isolation of discrete metal clusters provides an especially rare snapshot at the nanoscale of cluster growth. The synthesis and full characterization of the first early-transition-metal alkynyl cubane and the first μ³ -alkynyl Mn₃ motif are reported.

Linear Copper Complex Arrays as Versatile Molecular Strings: Syntheses, Structures, Luminescence, and Magnetism

The defined linear arrangement of metal atoms in discrete coordination complexes or polymers is still one of the most intriguing challenges in synthetic chemistry. These chain arrangements are of fundamental importance, because of their potential applications as molecular wires and single molecule magnets (SMM) in microelectronic devices on a molecular scale. Oligonuclear Group 11 metal complexes with suitable bridging ligands, specifically those that are based on copper as the first choice of a cheap precursor coinage metal, are of particular interest in this regard. This is due to the superior luminescence properties of these linear clusters that often show d¹⁰ ⋅⋅⋅d¹⁰ interactions in their molecular structures. The combination of Cu^I with heavier coinage metal ions results in tunable emissive arrays that are also stimuli-responsive. Thus, both linear multinuclear Cu^I and linear heteropolymetallic Cu^I /Ag^I as well as Cu^I /Au^I clusters are excellent candidates for applications in molecular/organic light-emitting devices (OLEDs). Alternatively, paramagnetic multinuclear cupric arrays are prominent as potential molecular wires with enhanced magnetic properties through multiple coupled d⁹ centers. This Review covers the whole range of linear multinuclear assemblies of cuprous and cupric ions in complexes and coordination polymers, their syntheses, photophysical behavior, and magnetic properties. Moreover, recent advances in the rapidly progressing field of hetero-Cu^I /Ag^I and Cu^I /Au^I molecular strings are also discussed.