Dithiocarbonate-Protected Au25 Nanorods of a Chiral D5 Configuration and NIR-II Phosphorescence.

Innovative surface-protecting ligands are in constant demand due to their crucial role in shaping the configuration, property, and application of gold nanoclusters. Here, the unprecedented O-ethyl dithiocarbonate (DTX)-stabilized atomically precise gold nanoclusters, [Au25(PPh3)10(DTX)5Cl2]2+ (Au25DTX-Cl) and [Au25(PPh3)10(DTX)5Br2]2+ (Au25DTX-Br), were synthesized and structurally characterized. The introduction of bidentate DTX ligands not only endowed the gold nanocluster with unique staggered Au25 nanorod configurations but also generated the symmetry breaking from the D5d geometry of the Au25 kernels to the chiral D5 configuration of the Au25 molecules. The chirality of Au25 nanorods was notably revealed through single-crystal X-ray diffraction, and chiral separation was induced by employing chiral DTX ligands. The staggered configurations of Au25 nanorods, as opposed to eclipsed ones, were responsible for the large red shift in the emission wavelengths, giving rise to a promising near-infrared II (NIR-II, >1000 nm) phosphorescence. Furthermore, their performances in photocatalytic sulfide oxidation and electrocatalytic hydrogen evolution reactions have been examined, and it has been demonstrated that the outstanding catalytic activity of gold nanoclusters is highly related to their stability.

Assembly of Luminescent Chiral Gold(I)-Sulfido Clusters via Chiral Self-Sorting.

Due to the ubiquity of chirality in nature, chiral self-assembly involving self-sorting behaviors has remained as one of the most important research topics of interests. Herein, starting from a racemic mixture of SEG-based (SEG=SEGPHOS) chlorogold(I) precursors, a unique chiral butterfly-shape hexadecanuclear gold(I) cluster (Au16 ) with different ratios of RSEG and SSEG ligands is obtained via homoleptic and heterochiral self-sorting. More interestingly, by employing different chlorogold(I) precursors of opposite chirality (such as RSEG -Au2 and SBIN -Au2 (BIN=BINAP)), an unprecedented heteroleptic and heterochiral self-sorting strategy has been developed to give a series of heteroleptic chiral decanuclear gold(I) clusters (Au10 ) with propellor-shape structures. Heterochiral and heteroleptic self-sorting have also been observed between enantiomers of homoleptic chiral Au10 clusters to result in the heteroleptic chiral Au10 clusters via cluster-to-cluster transformation. Incorporation of heteroleptic ligands is found to decrease the symmetry from S4 of homoleptic meso Au10 to C2 of heteroleptic chiral Au10 clusters. The chirality has been transferred from the axial chiral ligands and stored in the heteroleptic gold(I) clusters.

Coordination-Driven Tetragonal Prismatic Cage and the Investigation on Host-Guest Complexation.

A coordination-driven host has been reported to encapsulate guests by noncovalent interactions. Herein, we present the design and synthesis of a new type of prism combining porphyrin and terpyridine moieties with a long cavity. The prism host can contain bisite or monosite guests through axial coordination binding of porphyrin and aromatic π interactions of terpyridine. The ligands and prismatic complexes were characterized by electrospray ionization mass spectrometry (ESI-MS), TWIM-MS, NMR spectrometry, and single-crystal X-ray diffraction analysis. The guest encapsulation was investigated through ESI-MS, NMR spectrometry, and transient absorption spectroscopy analysis. The binding constant and stability were determined by UV-Vis spectrometry and gradient tandem MS (gMS2) techniques. Based on the prism, a selectively confined condensation reaction was also performed and detected by NMR spectrometry. This study provides a new type of porphyrin- and terpyridine-based host that could be used for the detection of pyridyl- and amine-contained molecules and confined catalysis.

Stimuli-Induced Reversible Transformation between Decanuclear and Pentanuclear Gold(I) Sulfido Complexes.

Decanuclear and pentanuclear gold(I) sulfido complexes of phenanthrene- and dibenzothiophene-based diphosphine ligands were synthesized and characterized. Unprecedented stimuli-induced reversible transformation between decanuclear and pentanuclear gold(I) sulfido complexes was observed, which could be readily monitored by NMR and UV-vis absorption spectroscopy in solution. Remarkably, the decanuclear gold(I) sulfido complex (Au10-LPh) was found to show a highly reversible transformation process, which is stable for over 10 successive cycles in solution. The stimuli-induced reversible transformation behavior of the gold(I) sulfido complexes was found to depend on the P-P bite distance of the bidentate phosphine ligands.

Hepta-Zr-Incorporated Polyoxometalate Assembly.

Driven by the synergistic-directing effect of the lacunary fragments, [B-α-GeW9O34]10- and [B-α-GeW11O39]8-, an unprecedented hepta-Zr-substituted polyoxometalate (POM) assembly K2Na6H10(Hpy)3[SbZr7O6(OH)4(B-α-GeW9O34)2(B-α-GeW11O39)2]·28H2O (1) was made under hydrothermal condition and structurally characterized. Of which, a unique hepta-Zr cluster, [SbZr7O6(OH)4]15+ core, was built by two trilacunary [B-α-GeW9O34]10- fragments and two monolacunary [B-α-GeW11O39]8- fragments and further arranged in a mode of a vertical cross and formed a pseudo-tetrahedron geometry. Compound 1 features the first Zr7-cluster-substituted POM. Moreover, 1 is an effective heterogeneous catalyst for the catalytic oxidation of sulfides into the corresponding sulfones with H2O2, manifesting distinguished conversion, excellent yield, and desired recyclability.

Dual Emissive Gold(I)-Sulfido Cluster Framework Capable of Benzene-Cyclohexane Separation in the Solid State Accompanied by Luminescence Color Changes.

A decanuclear gold(I)-sulfido complex, [(LH)4Au10S4]Cl2 (LH-Au10S4-Cl, where LH = 4,5-bis(diphenylphosphanyl)-2H-1,2,3-triazole), assembled from the reaction of H2S with the chlorogold(I) precursor obtained from the click reaction of [dppa(AuCl)2] (where dppa = 1,2-bis(diphenylphosphino)acetylene) with NaN3, is shown to display a bright dual green and red emission in the solid state. Single crystal X-ray diffraction (SCXRD) studies indicate a gold(I) cluster-based framework assembled through intermolecular halogen···hydrogen bonds as well as other weak interactions. The framework of LH-Au10S4-Cl is found to display high stability toward solvent molecules, with capability to encapsulate solvent molecules, such as benzene and cyclohexane, inside the crystal lattice voids via a single-crystal-to-single-crystal (SCSC) transformation. With different degrees of influence on the dual green and red emission, crystalline solids of LH-Au10S4-Cl exhibit remarkable solvatochromic luminescence in the presence of benzene and cyclohexane. Notably, due to the size confinement of the lattice cavities, the LH-Au10S4-Cl solids exhibit a high selectivity (>95%) toward benzene in a mixture of equimolar concentration of benzene and cyclohexane. This work has demonstrated the promising capability of gold(I)-sulfido cluster frameworks to serve as luminescent functional materials for the separation of benzene and cyclohexane.

Stimuli-Responsive and Structure-Adaptive Three-Dimensional Gold(I) Cluster Cages Constructed via "De-aurophilic" Interaction Strategy.

Self-assembly of three-dimensional (3D) metallosupramolecular cages has drawn increasing attention for their potential to interconvert between different architectures due to the dynamic and reversible features of the coordination bond. These supramolecular transformations can provide unique approaches for the construction of stimuli-responsive supramolecular model systems to mimic biological transformation processes. While gold(I) clusters have attracted much interest due to their propensity to exhibit aurophilic interactions, the construction of 3D gold(I) cluster cages has remained a challenging and daunting task. Here, we proposed a "de-aurophilic" interaction strategy, which involves the prevention of aurophilic interaction formation between the basic [(µ3-S)Au3]+ units, to construct 3D gold(I) cluster cages. Through the judicious design of diphosphine ligands, an unprecedented class of gold(I) cluster cages with adaptive structures has been constructed. These gold(I) cluster cages are found to show intriguing stimuli-responsive structure transformation and interconversion. This work not only provides a strategy for the design and construction of novel 3D supramolecular cages based on cluster nodes but also offers a paradigm to study the stimuli-responsive structural interconversion between the unique structures of these gold(I) cluster cages.

Concentration- and Solvation-Induced Reversible Structural Transformation and Assembly of Polynuclear Gold(I) Sulfido Complexes.

A series of polynuclear gold(I) sulfido complexes of bis(diphenylphosphino)amine ligands has been synthesized and characterized. A rather small variation in the conformation of the bis(diphenylphosphino)amine ligands has led to distinct differences in the identity of the polynuclear gold(I) sulfido complexes formed. Unprecedented concentration-dependent and solvation-dependent reversible cluster-to-cluster transformation between a dodecanuclear gold(I) sulfido complex (LMe-Au12) and a hexanuclear gold(I) sulfido complex (LMe-Au6) has been observed. The transformation process has been monitored not only by 1H and 31P{1H} NMR spectroscopy but also by UV-vis absorption spectroscopy and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) in the solution state. This work has provided a simple approach to achieve structure modulation of gold(I) sulfido complexes and an understanding of supramolecular transformations via external stimuli.

Heterochiral Self-Discrimination-Driven Supramolecular Self-Assembly of Decanuclear Gold(I)-Sulfido Complexes into 2D Nanostructures with Chiral Anions-Tuned Morphologies.

Chiral self-recognition and self-discrimination are of vital importance to biological processes. In this work, 2D regular rhombic nanocrystals (RS-NC) were fabricated through heterochiral self-discrimination between chiral polynuclear gold(I)-sulfido complex enantiomers, [(R-BINAP)4 Au10 S4 ]Cl2 (R-Au10 ) and [(S-BINAP)4 Au10 S4 ]Cl2 (S-Au10 ), in MeOH without the need for any surfactants or templates. The monitoring of nanocrystals (NCs) formation by TEM and DLS has uncovered the self-assembly process and shape evolution of the NCs and revealed a screw-dislocation dictated spiral growth of the rhombic NCs. Upon addition of chiral anions, the morphology of the gold NCs was found to change from rhombic to strip and quasi-hexagonal nanosheets, arising from reverse and rotational layer-by-layer stacking to give the bilayer NCs. By applying a high temperature, rhombic gold nanoisland films were obtained from the rhombic NCs. The current study has provided a simple strategy towards the construction of regular geometric 2D NCs as well as their chiral anion-tuned and reverse and rotational stacking-determined morphology change by heterochiral self-discrimination.

Diphosphine-Stabilized Small Gold Nanoclusters: From Crystal Structure Determination to Ligation-Driven Symmetry Breaking and Anion Exchange Properties.

A new class of small gold nanoclusters with molecular characteristics has been constructed using 1,1'-bis(diphenylphosphino)ferrocene (dppf) as the stabilizing ligand. The identities of the small gold nanoclusters have been fully characterized by NMR, electrospray ionization mass spectrometry, elemental analysis, and single-crystal X-ray diffraction analysis. Octa- and undecagold clusters are found to display different UV-vis absorption behavior. The ligation of the bidentate ligands and halides or pseudohalides has resulted in the symmetry breaking of these nanoclusters with C1 symmetry. The small gold nanoclusters with different coordinating halides or pseudohalides show distinct reactivities and stabilities in ligand/anion exchange experiments. The current research has provided insights into the origin of chirality in the diphosphine-stabilized small gold nanoclusters.

Thermodynamic-Driven Self-Assembly: Heterochiral Self-Sorting and Structural Reconfiguration in Gold(I)-Sulfido Cluster System.

By employing chiral precursors, a new class of chiral gold(I)-sulfido clusters with unique structures has been constructed. Interestingly, pure enantiomers of the precursors are found to self-assemble into chiral hexa- and decanuclear clusters sequentially, while a racemic mixture of them has resulted in heterochiral self-sorting of an achiral meso decanuclear cluster. Chirality has determined not only the symmetry and structures but also the photophysical behaviors of these clusters. The racemic mixture of decanuclear clusters undergoes rearrangement and heterochiral self-sorting to give a meso decanuclear cluster. The thermodynamic-driven heterochiral self-sorting of gold(I) clusters provides a means to develop controlled self-assembly that may be of relevance to the understanding of chirality in nature.

Photoinduced isomerization-driven structural transformation between decanuclear and octadecanuclear gold(I) sulfido clusters.

Upon photoirradiation, isomerization of the ligands, 1,2-bis(diphenylphosphino)ethene (dppee) from the cis to the trans form in polynuclear gold(I) sulfido clusters, led to the structural transformation of the decagold(I) cluster to the octadecagold(I) cluster. Both polynuclear µ3-sulfido gold(I) clusters have been fully characterized by NMR, mass spectrometry, elemental analysis, and single crystal X-ray diffraction analysis. The transformation process could be readily detected and monitored by UV-vis absorption, emission, and (31)P NMR spectroscopy in solution. Supported and driven by Au(I)···Au(I) bonding interactions, the nuclearity and symmetry of these clusters were largely different from each other, resulting in completely distinct photophysical features.

Addition reaction-induced cluster-to-cluster transformation: controlled self-assembly of luminescent polynuclear gold(I) µ3-sulfido clusters.

Unprecedented addition reaction-induced gold(I) cluster-to-cluster transformation has been observed in the present work. Reaction of the chlorogold(I) precursor, [vdpp(AuCl)2] (vdpp = vinylidenebis(diphenylphosphine)) containing the diphosphine with unsaturated C═C bond, with H2S resulted in a series of polynuclear gold(I) µ3-sulfido clusters bearing Au(I)···Au(I) interactions; the identities of which have been fully characterized by NMR, electrospray-ionization mass spectrometry, elemental analysis, and single crystal X-ray diffraction analysis. Diverse research methods, including UV-vis absorption, (1)H NMR, and (31)P NMR spectroscopy, were employed to detect and monitor the transformation and assembly processes. Supported by single crystal structures, the existence of Au(I)···Au(I) bonding interactions sustains the diverse array of sophisticated polynuclear cluster structures and endues them with rich luminescence features.

Self-assembly of [M8L4] and [M4L2] fluorescent metallomacrocycles with carbazole-based dipyrazole ligands.

Fluorescent carbazole-based dipyrazole ligands (H(2)L(1-4)) were employed to coordinate with dipalladium corners ([(phen)(2)Pd(2)(NO(3))(2)](NO(3))(2), [(dmbpy)(2)Pd(2)(NO(3))(2)](NO(3))(2), or [(15-crown-5-phen)(2)Pd(2)(NO(3))(2)](NO(3))(2), where phen = 1,10-phenanthroline and dmbpy = 4,4'-dimethyl-2,2'-bipyridine, in aqueous solution to afford a series of positively charged [M(8)L(4)](8+) or [M(4)L(2)](4+) multimetallomacrocycles with remarkable water solubility. Their structures were characterized by (1)H NMR spectroscopy, electrospray ionization mass spectrometry, and elemental analysis and in the cases of 1·8BF(4)(-) ([(phen)(8)Pd(8)L(1)(4)](BF(4))(8)), and 3·4BF(4)(-) ([(phen)(4)Pd(4)L(2)(2)](BF(4))(4)) by single-crystal X-ray diffraction analysis. Complexes 3-8 are square-type hybrid metallomacrocycles, while complexes 1 and 2 exhibit folding cyclic structures. Interestingly, in single-crystal structures of 1·8BF(4)(-) and 3·4BF(4)(-), BF(4)(-) anions are trapped in the dipalladium clips through anion-π interaction. The luminescence properties and interaction toward anions of these metallomacrocycles were discussed.

Supramolecular cuboctahedra with aggregation-induced emission enhancement and external binding ability.

Beyond the AIE (aggregation-induced emission) phenomenon in small molecules, supramolecules with AIE properties have evolved in the AIE family and accelerated the growth of supramolecular application diversity. Inspired by its mechanism, particularly the RIV (restriction of intramolecular vibrations) process, a feasible strategy of constructing an AIE-supramolecular cage based on the oxidation of sulfur atoms and coordination of metals is presented. In contrast to previous strategies that used molecular stacking to limit molecular vibrations, we achieved the desired goal using the synergistic effects of coordination-driven self-assembly and oxidation. Upon assembling with zinc ions, S1 was endowed with a distinct AIE property compared with its ligand L1, while S2 exhibited a remarkable fluorescence enhancement compared to L2. Also, the single cage-sized nanowire structure of supramolecules was obtained via directional electrostatic interactions with multiple anions and rigid-shaped cationic cages. Moreover, the adducts of zinc porphyrin and supramolecules were investigated and characterized by 2D DOSY, ESI-MS, TWIM-MS, UV-vis, and fluorescence spectroscopy. The protocol described here enriches the ongoing research on tunable fluorescence materials and paves the way towards constructing stimuli-responsive luminescent supramolecular cages.

Synthesis and anion sensing of water-soluble metallomacrocycles.

The self-assembly of (TMEDA)Pd(NO(3))(2) or (TMEDA)Pt(NO(3))(2) (where TMEDA = N(1),N(1),N(2),N(2)-tetramethylethane-1,2-diamine) and anthracene- or ferrocene-based diimidazole ligands (L(1-3)) in aqueous solution affords a series of positively charged [M(2)L(2)](4+) dimetallomacrocycles. Their structures were characterized by (1)H NMR and electrospray ionization mass spectrometry and in the cases of {[(TMEDA)Pd](2)L(1)(2)}(NO(3))(4) (1), {[(TMEDA)Pd](2)L(1)(2)}(PF(6))(4) (1a), and {[(TMEDA)Pd](2)L(3)(2)}(NO(3))(4) (4) by single-crystal X-ray diffraction analysis. Interestingly, the NMR spectra of 1 and 1a revealed that the difference of their structures, as confirmed by X-ray diffraction analysis, was that a NO(3)(-) of 1 was encapsulated inside the cavity of the basket-shaped metallomacrocycle by C-H···O hydrogen bonds, while PF(6)(-) of 1a was bound outside by C-H···F hydrogen bonds. The fluorescence titration experiment exhibited the formation of 1:1 host-guest complexation for anthracene-based positively charged [M(2)L(2)](4+)-type metallomacrocycles with NO(3)(-). The interactions between metallomacrocycles and various anions were investigated via fluorescence titration and cyclic voltammetry studies, respectively.

Self-assembly and host-guest interaction of metallomacrocycles using fluorescent dipyrazole linker with dimetallic clips.

By employing diimine ligands coordinated dimetallic clips ([(bpy)2Pd2(NO3)2](NO3)2 or [(phen)2Pd2(NO3)2](NO3)2, where bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline) as the corner and anthracene-, naphthalene-, and benzene-based dipyrazolate dianions as the linker, a series of positively charged metallomacrocycles ([M4L2]4+ or [M8L4]8+) have been synthesized through a directed self-assembly method in aqueous solution. Every macrocycle has a cavity to bind solvent molecules or anions. The structures were characterized by elemental analysis, 1H and 13C NMR, electrospray ionization mass spectrometry, and single crystal X-ray diffraction analysis for compound 1 x 4 PF6(-) (1 = {[(bpy)Pd]4L(1)2}4+), 3 x 4 PF6(-) x 8 CH3CN x H2O (3 = {[(bpy)Pd]4L(2)2}4+), and 7 x 4 PF6(-) x 6 H2O (7 = {[(bpy)Pd]4L(5)2}4+). The 1:1 host-guest complexation for anthracene-based dipyrazolate-bridged macrocycles with aromatic guests was investigated via UV-vis and fluorescent titration.

Self-assembly of a neutral luminescent Au(12) cluster with D(2) symmetry.

The preparation and characterization of luminescent neutral Au(12) shuttle-like complexes is reported which shows a cyclic framework consisting of twelve gold(i) ions arranged in a closed ring via non-covalent Au(i)Au(i) interactions to give a chiral D(2) symmetrical structure.

Self-assembly of metallomacrocycles with dipyrazole ligands and anion sensing of [Pd4Fe2] macrocycle with ferrocene-based dipyrazole ligand.

By employing dipalladium corners [(bpy)(2)Pd(2)(NO(3))(2)](NO(3))(2) or [(phen)(2)Pd(2)(NO(3))(2)](NO(3))(2) (where bpy = 2,2'-bipyridine and phen = 1,10-phenanthroline) to bridge ferrocene-based dipyrazole ligand (L(1)) and m-phenylene-based dipyrazole ligands (L(2-3)) in aqueous solution, a series of positively-charged [M(4)L(2)](4+) metallomacrocycles were obtained. Their structures were characterized by (1)H NMR, electrospray ionization mass spectrometry (ESI-MS), elemental analysis, and single crystal X-ray diffraction analysis for 1·4NO(3) ({[(bpy)Pd](4)L(1)(2)}(NO(3))(4)) and 4·4NO(3) ({[(phen)Pd](4)L(2)(2)}(NO(3))(4)). In their single crystal structures, NO(3)(-) anions are located at the dipalladium corners by C-H...O hydrogen bonds. Importantly, the anion-sensing properties of ferrocene functionalized [Pd(4)Fe(2)] hetero-metallomacrocycle 1 were investigated in acetonitrile by SWV, CV and NMR analysis, showing promise for Br(-) sensing.

Self-assembly of nano-sized neutral metal-organic macrocycles from bis(ß-diketone) ligands.

It's hip to be square: Self-assembly of bis(ß-diketone) linkers with 90° or 120° angles and square-planer-coordinated divalent copper ions gives rise to the formation of nano-sized M(4)L(4)-type neutral metal-organic supramolecular macrocycles, which show promise towards encapsulating solvent or guest molecules.