Polyoxometalate Complexes Research Articles

Polyoxometalate‐Incorporated Supramolecular Self‐Assemblies: Structures and Functional Properties

AbstractAs a family of functional inorganic clusters, polyoxometalates (POMs) were introduced into hybrid self‐assemblies with the assistance of the supramolecular interaction with diverse organic cationic molecules, which reinforced both the processibility and functionality of the POMs. This method not only improved the surface properties of the POMs, but also provided excellent amphiphilic building blocks for the construction of advanced self‐assembled nanostructures. In this review, we summarize the fundamental aspects of surfactant‐encapsulated POMs (SEPs) and the most recent progress in potential applications of SEPs and the related POM‐containing systems (hybrids composed of POMs and polymers and other cationic molecules beyond surfactants). The functionalization of such organic/inorganic hybrids in self‐assembled systems is also described. Furthermore, perspectives regarding self‐assemblies and possible applications of POM complexes with synergetic interactions between organic and inorganic components are outlined.

Efficient Light-Driven Carbon-Free Cobalt-Based Molecular Catalyst for Water Oxidation

The abundant-metal-based polyoxometalate complex [Co(4)(H(2)O)(2)(PW(9)O(34))(2)](10-) is a hydrolytically and oxidatively stable, homogeneous, and efficient molecular catalyst for the visible-light-driven catalytic oxidation of water. Using a sacrificial electron acceptor and photosensitizer, it exhibits a high (30%) photon-to-O(2) yield and a large turnover number (>220, limited solely by depletion of the sacrificial electron acceptor) at pH 8. The photocatalytic performance of this catalyst is superior to that of the previously reported precious-metal-based polyoxometalate water oxidation catalyst [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(γ-SiW(10)O(36))(2)](10-).

Quantum chemical characterization of the generation of high-valent oxoruthenium species of Keggin type polyoxometalates: electronic structure and bonding features

High-valent transition-metal-substituted Keggin-type polyoxometalates (POMs) are active and robust oxidation catalyst. The important oxidized intermediates of these POM complexes are very difficult to be characterized by using the experimental method, and thus no detail information is available on such species. In the present paper, density functional theory (DFT) calculations have been carried out to characterize the electronic structures of a series of mono-ruthenium-substituted Keggin-type POMs. We find that the aquaruthenium(II/III/IV) species possess d(xy)(2)d(xz)(2)d(yz)(2), d(xy)(2)d(xz)(2)d(yz)(1), and d(xy)(2)d(xz)(1)d(yz)(1) electronic configuration, respectively, and hydroxyl/oxoruthenium(IV/V/VI) species possess d(xy)(2)d(xz)(1)π*(yz)(1), d(xy)(2)π*(xz)(1)π*(yz)(1), d(xy)(1)π*(xz)(1)π*(yz)(1), and d(xy)(1)π*(xz)(1)π*(yz)(0) electronic configuration, respectively. Mulliken spin population shows that spin density is localized on the ruthenium center in aquaruthenium(II/III/IV) POM complexes, and the RuO(a) unit in hydroxyl/oxoruthenium(IV/V/VI) POM complexes. The O(a) atom has substantial radical character in oxoruthenium(IV/V) species, and the radical character of the O(a) atom are significantly weakened in the oxoruthenium(VI) species. The relevant energy of the important Ru-O(a)π*-antibonding unoccupied orbitals with high RuO(a) compositions of oxoruthenium(IV/V/VI) POM complexes decrease in the order: oxoruthenium(IV) > oxoruthenium(V) > oxoruthenium(VI). The pH-independent multiple reduction energies for Ru(III/II), Ru(V/IV), and Ru(VI/V) couples are calculated, which is in agreement with the experimental data.

Preparation, Structure, and Imaging of Luminescent SiO2 Nanoparticles by Covalently Grafting Surfactant-Encapsulated Europium-Substituted Polyoxometalates

A novel route to the preparation of luminescent silica nanoparticles and coloration for living cells was demonstrated in this article. A europium-substituted polyoxometalate was encapsulated by a hydroxyl-group-terminated double-chain quaternary ammonium cation through an ion replacement process, yielding an organic-inorganic complex with core-shell structure bearing hydroxyl groups located at the periphery. The introduction of -OH groups not only increased the solubility of the complex in polar solvents but also caused it to embed into the inner matrix of silica nanoparticles covalently and be well-dispersed through an in situ sol-gel reaction with tetraethyl orthosilicate. Elemental analysis and spectral characterization confirmed the formation of prepared complexes with the anticipated chemical composition. Scanning and transmission electron microscopy images illustrated the size change of luminescent nanoparticles with smooth surfaces and well-dispersed polyoxometalate complexes inside of the silica matrix. X-ray photonic spectra and ζ-potential measurements revealed the chemical association between the silica matrix and the complex. Luminescent spectral characterization indicated the well-retained photophysical property of Eu-substituted polyoxometalate in silica nanoparticles. The surface amino-modified silica nanoparticles were applied to cell coloration, and the dyed Hela cells were observed through laser confocal fluorescence microscopy.

Smart Self‐Assemblies Based on a Surfactant‐Encapsulated Photoresponsive Polyoxometalate Complex

Smart Self‐Assemblies Based on a Surfactant‐Encapsulated Photoresponsive Polyoxometalate Complex

Smart Self‐Assemblies Based on a Surfactant‐Encapsulated Photoresponsive Polyoxometalate Complex

Licht und Form: Ein tensidverkapseltes Polyoxometallat (POM) mit organischen Seitenketten wurde synthetisiert, indem photoresponsive Azobenzolgruppen an einen Anderson-POM-Cluster angeknüpft wurden. Diese Hybridkomplexe ändern bei Bestrahlung infolge einer Photoisomerisierung ihre Form, was zu reversiblen Morphologieänderungen ihrer Aggregate führt.

Self‐Assembly and Structural Evolvement of Polyoxometalate‐Anchored Dendron Complexes

A cationic dendritic molecule that has alkyl chains has been synthesized and employed to encapsulate anionic polyoxometalates through electrostatic interactions. The prepared surfactant-encapsulated polyoxometalate (SEP) complexes were used as building blocks to fabricate self-assemblies in solution and the solid state. Monodispersion, lamellar, and columnar assemblies of SEP complexes have been characterized in detail. With increasing the number of peripheral cationic dendrons on inorganic clusters, the SEPs undergo changes from globular assemblies to monodispersions in solution and from lamellar assemblies to hexagonal columnar structures in the solid state, depending on the amounts of cationic dendrons in the complexes. The structural evolvement was simulated through consideration of the size and shape of the cationic dendron and polyanionic clusters, and the experimental results are in good agreement with the interpretation of the simulations. The present research demonstrates a new kind of dendritic complex and provides a route for controlling their assembling states by simply alternating the number of cationic dendrons in the complexes.

Structural, Magnetic, EPR, and Electrochemical Characterizations of a Spin-Frustrated Trinuclear CrIIIPolyoxometalate and Study of Its Reactivity with Lanthanum Cations

The asymmetric Cr(III) polyoxometalate complex Cs(10)[(gamma-SiW(10)O(36))(2)(Cr(OH)(H(2)O))(3)] x 17 H(2)O (1) has been synthesized in water under atmospheric pressure from the trinuclear precursor [Cr(3)(CH(3)COO)(7)(OH)(2)] and the divacant ligand [gamma-SiW(10)O(36)](8-). Complex 1 is built up of two [gamma-SiW(10)O(36)](8-) Keggin units sandwiching a trinuclear {(Cr(III)(OH)(H(2)O))(3)} fragment where the paramagnetic centers are bridged by three mu-OH ligands forming a nearly isosceles triangle. The magnetic properties of this spin-frustrated system have thus been interpreted considering a 2-J Hamiltonian showing that the Cr(III) ions are antiferromagnetically coupled and that 1 possesses an S = 3/2 ground state with an S = 1/2 first excited state located at 11 cm(-1). These results have been confirmed by EPR spectroscopy measurements (Q-band), which have also enabled the quantification of the electronic parameters characterizing the quadruplet spin ground state. The magnitude of the magnetic exchange interactions and the nature of the ground state are discussed in light of previously reported isosceles triangular S = 3/2 clusters. UV-visible and electrochemical studies have shown that 1 is stable in aqueous media in a 1-7 pH range. This stability is chemically confirmed by the study of the reactivity of 1 with La(III) cations, which has allowed the isolation of the Cs(4)[(gamma-SiW(10)O(36))(2)(Cr(OH)(H(2)O))(3)(La(H(2)O)(7))(2)] x 20 H(2)O compound (2). Indeed, during the synthetic process of this 3d-4f system, the integrity of the [(gamma-SiW(10)O(36))(2)(Cr(OH)(H(2)O))(3)](10-) building unit constituting 1 is maintained despite the high oxophilic character of the La(III) ions. The single crystal X-ray diffraction study of 2 has revealed that in the solid state the rare earth cations connect these subunits, affording a 3d-4f double-chain monodimensional system.

Surfactant‐Encapsulated Polyoxometalates as Immobilized Supramolecular Catalysts for Highly Efficient and Selective Oxidation Reactions

A type of interesting immobilized supramolecular catalysts based on surfactant-encapsulated polyoxometalates has been developed for oxidation reactions. Through a sol-gel process with tetraethyl orthosilicate, hydroxyl-terminated surfactant-encapsulated polyoxometalate complexes have been covalently and uniformly bound to a silica matrix with unchanged complex structure. The formed hybrid catalysts possess a defined hydrophobic nano-environment surrounding the inorganic clusters, which is conducive to compatibility between the polyoxometalate catalytic centres and organic substrates. The supramolecular synergy between substrate adsorption, reaction, and product desorption during the oxidation process has been found to have an obvious influence on the reaction kinetics, with the activity of the catalyst being greatly improved. The supramolecular catalysts performed effectively in the selective oxidation of several different kinds of organic compounds, such as alkenes, alcohols, and sulfides, and the main products were the corresponding epoxides, ketones, sulfoxides, and sulfones. More significantly, the catalyst could be easily recovered by simple filtration, and the catalytic activity was well retained for at least five cycles. Finally, the present strategy has proved to be a general route for the fabrication of supramolecular hybrid catalysts containing common polyoxometalates suitable for various purposes.

Covalent Dispersion of Surfactant-Encapsulated Polyoxometalates and In Situ Incorporation of Metal Nanoparticles in Silica Spheres

In this paper, we have exhibited a novel strategy for the construction of polyoxometalate (POM) and metal nanoparticle (MNP) integrated silica spheres. To introduce MNPs into the POM embedded silica spheres, we employed the controllable in situ synthesis of MNPs through the photoreduction property of POMs that were pre-incorporated into silica spheres. Through electrostatic encapsulation with hydroxyl-terminated cationic surfactants, the POM polyanions with photoinduced redox property formed surfactant encapsulated clusters first. The complex was then grafted into a silica matrix by means of a co-condensation with hydrolyzed tetraethoxylsilicane covalently, and stable silica spheres containing surfactant-encapsulated POMs were obtained. The dispersion and the concentration of POM complex in the silica spheres can be tuned in a quite large extent, where the structure and property of POMs were maintained. In addition, the POMs can be photochromically changed to the reduced state through the irradiation with UV light. The well-dispersed POMs in a hydrophobic microenvironment within the hybrid spheres can be used as reductants for the in situ synthesis of MNPs. More significantly, the size and content of MNPs were tuned by controlling the experiment condition and the possible locations of both POMs and MNPs were characterized by IR, XPS, TEM and Raman spectra. The hybrid silica spheres combining both POMs and MNPs may provide potential applications in catalysis and antibacterial materials.

Syntheses of PAM microgel surfacely covered with alkyl quaternary ammonium surfactant/Keggin‐type polyoxometalate complexes

AbstractThe composite microspheres of poly(lacrylamide) microgels (PAM) surfacely covered with [2‐(methacryloyloxy)ethyl]dodecyldimethylammonium (MEDDAB)‐tungstophosphate (HPW) complexes (MEDDAB‐HPW) were synthesized by using ion‐exchange reaction between MEDDAB located within the porous PAM microgels and HPW in aqueous solution. The morphology and component of the composite microspheres were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis, respectively. The results indicated that PAM/MEDDAB‐HPW composite microsphere with different hierarchical surface structures could be obtained by controlling the weight ratio of MEDDAB to HPW in the microgels and cross‐linking degree of PAM microgels. Although the surface morphologies of the composite microspheres prepared in different conditions were different, a general feature was that the composite microspheres have the core‐shell structure and the wrinkly surface covered with the particles of MEDDAB‐HPW complexes. The formation of the wrinkly surface is attributed to the difference in shrinkage between inside and outside of PAM microgel frameworks due to deposition of MEDDAB‐HPW on the surface, and the formation of MEDDAB‐HPW small particles originates from the reaction between MEDDAB aggregation and HPW. For this composite microsphere, PAM hydrogel core is suitable to store water‐soluble substances, and the shell composed of the surfactant/Keggin‐type polyoxometalate complexes is not only amphiphilic but also catalytic. Additionally, PAM/MEDDAB‐HPW composite microspheres with big size and MEDDAB‐HPW particles with small size make the composite microspheres not only easy for separation but also beneficial for catalysis. This material provides an example to construct microreactors with new structure used in diphase catalytic reaction. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Organic−Inorganic Hybrid Supramolecular Gels of Surfactant-Encapsulated Polyoxometalates

A new type of hybrid supramolecular gel derived from a synergetic self-assembling of organic and inorganic components has been prepared through encapsulating a series of polyoxometalate (POM) clusters with ammonium surfactants bearing two alkyl chains. Among the general organic solvents we employed, some of surfactant-encapsulated POM (SEP) complexes readily gel with nonpolar solvents. Proper alkyl chain density, alkyl chain length, and shape of POM are proven to be favorable for fabricating stable SEP gels based on the results of critical gelation concentration and transition temperature from gel to solution. In addition, the shape of POM influences the aggregation morphologies of SEPs, stripes and spheres in gel phases, as confirmed by polarizing optical microscopic and scanning electron microscopic images. X-ray diffractions reveal that all the SEPs in gel states possess similar lamellar aggregation structures with POM layer inside and alkyl chain bilayers shielding from the nonpolar solvent on both sides. The combination of solvent effect, electrostatic, and dipole interaction is thought to be responsible for the formation of SEP gels.

Micro-patterned polystyrene surfaces directed by surfactant-encapsulated polyoxometalate complex via breath figures

In this paper, surfactant-encapsulated polyoxometalate complex, (DODA)9[EuW10O36] (SEC-1), is applied to functionalize the breath figure holes of polystyrene (PS) film via a straightforward, one-step process by doping SEC-1 into PS solution. Accompanied with the self-organization of the water droplets, amphiphilic SEC-1 is found to self-assemble at the PS solution–water droplet interface to stabilize the water droplets, and it effectively enhances the order of the PS microporous film. Highly ordered PS microporous film in which SEC-1 accumulates on the internal surfaces of the holes with an ordered and tight lamellar structure was obtained. The film exhibits intense red emission under ultraviolet light excitation deriving from SEC-1. Ag and Fe2O3 nanoparticles have been successfully introduced into the microporous structure through different ways. This new method is also suitable for other polymers, and the polyoxometalates with applicable properties could be readily applied to functionalize the holes of polymer microporous films.

Hydrogen-Bonding-Induced Supramolecular Liquid Crystals and Luminescent Properties of Europium-Substituted Polyoxometalate Hybrids

Eu-containing polyoxometalates, Na9EuW10O36, K11Eu(PW11O39)2, and K13Eu(SiW11O39)2, were electrostatically canned by a cationic surfactant, N-[12-(4-carboxylphenoxy)dodecyl]-N-dodecyl-N,N-dimethylammonium bromide, through the replacement of counterions, and the resulting surfactant-encapsulated polyoxometalate complexes were characterized in detail by elemental analysis as well as IR and NMR spectra. The carboxyls bearing in the complexes were confirmed existing in the dimer state through intermolecular hydrogen bonding, which leads to stable and reversible thermotropic liquid crystal properties of these complexes. The results of differential scanning calorimetry, polarized optical microscopy, and X-ray diffraction revealed that these complexes underwent smectic mesophases during the heating and cooling cycles. These complexes displayed intrinsic luminescence both in the amorphous powder states and in their mesophases. The photophysical properties showed the dependence on the existing states of samples, and the quantum yields of the complexes in the liquid crystalline structures are higher than the corresponding amorphous powders. The present investigation provides an example for developing hydrogen-bonding-induced polyoxometalate-containing hybrid liquid crystal materials with intrinsic luminescence.

Theoretical studies on nitrido ruthenium (VI) porphyrin and high valent ruthenium nitrido derivatives of Keggin typical polyoxometalate ([PW11O39{RuVIN}]4−): electronic structures and bonding features

In the present paper, the electronic structures and bonding features between the ruthenium atom and nitrido ligand of known nitrido ruthenium (VI) porphyrin and hexavalent ruthenium nitrido derivative of Keggin typical polyoxometalate (POM) have been investigated by using density functional theory (DFT) calculations and natural bond orbital (NBO) analysis. The results show that the Keggin POM complex and porphyrin complex have the Ru[triple bond]N triple bond, the NBO calculations yield a nitrido ligand charge close to zero in both complexes because of the charge transfer from the rich-electron nitrido ligand to the ruthenium center. The molecular orbitals predict that the ruthenium porphyrin complex would generate oxidized species with no change in the oxidation state of the metal center; however, the ruthenium center of the POM complex would be oxidized in a one-electron-oxidation process because of the different HOMO character, and moreover, the spin unrestricted calculations confirm this prediction made by molecular orbital analysis. On the other hand, both complexes have the same reduced center, the RuN unit, and the one-electron-reduction process weakens the bonding interaction between the ruthenium atom and nitrido ligand for both complexes because the antibonding LUMO is occupied. Compared with the porphyrin complex, the POM complex possesses a higher RuN composition and lower energy pi* antibonding orbital according to gas-phase and solvent calculations.

Composite microspheres with PAM microgel core and polymerisable surfactant/polyoxometalate complexes shell

The composite microspheres of poly(acrylamide) microgels (PAM) surfacely covered with [3-(acryloylamino)propyl]dodecyldimethyl ammonium-tungstophosphate complexes (APDDAB-PWA) were synthesized by using an ion-exchange reaction between APDDAB located within the porous PAM microgels and PWA in aqueous solution. The morphology and component of the composite microspheres were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis, respectively. The results indicated that PAM/APDDAB-PWA composite microsphere with different hierarchical surface structures could be obtained by controlling the weight ratio of APDDAB to PAM microgels, cross-linking degree of PAM microgels, the amount of PWA reacted with APDDAB in PAM/APDDAB, and solvent-washing process. Although the surface morphologies of the composite microspheres in detail were different, a general feature was of the core-shell structure and the wrinkly surface covered with APDDAB-PWA particles. The formation of the wrinkly surface is attributed to the difference in shrink between inside and outside of PAM microgel frameworks, and the formation of APDDAB-PWA small particles originates from the reaction between APDDAB aggregation and PWA. This composite microsphere with PAM hydrogel core is suitable to store water-soluble substances, and the shell composed of the surfactant/Keggin-type polyoxometalate complexes is not only amphiphilic but also catalytic. Additionally, PAM/APDDAB-PWA composite microspheres with big size and APDDAB-PWA particles with small size make the composite microspheres not only easy for separation but also beneficial for catalysis. These properties have been verified by the application of PAM/APDDAB-PWA composite microspheres to the deep desulfurization of fuel oil. This material provides an example to construct microreactors with new structure used in diphase catalytic reaction.

Probing the 5f electrons in a plutonyl(vi) cluster complex

We report the structural, spectroscopic and preliminary magnetic characterisation of a tri-metallic plutonyl(VI) polyoxometalate complex, K(11)[K(3)(PuO(2))(3)(GeW(9)O(34))(2)] x 12 H(2)O.

Controllable vesicular structure and reversal of a surfactant-encapsulated polyoxometalate complex

An organic–inorganic complex, surfactant-encapsulated polyoxometalate (DDDA)9EuW10O36, demonstrates reversible self-assembly behavior in organic solvents and water. This hybrid complex can spontaneously organize into inverse vesicles by simply dispersing it in an organic solvent. Interestingly, by dissolving the water-insoluble complex in a water-miscible organic solvent such as ethanol and subsequently addition of water, it could be transferred into aqueous solution and the inverse vesicles in the organic solvent transformed into a regular bilayer structure in water. The vesicular aggregate, which had a regular structure, was studied by dynamic light scattering and transmission electron microscopy, as well as X-ray diffraction. The structural transformation was proved by zeta potential analysis and X-ray photoelectron spectroscopy, and the process was followed by 1H NMR. These results provide the first example of aggregation behavior in this kind of complex, which is different from that exhibited by well known amphiphilic molecules with polar and non-polar ends, in water. Moreover, the reverse process, from a regular bilayer to inverse vesicles, can be conveniently carried out by simply extracting the complex from water into the organic phase. The results described may provide new opportunities in performing catalytic and biomimetic functions of polyoxometalates.

Europium(III) Reduction and Speciation within a Wells−Dawson Heteropolytungstate

The redox speciation of Eu(III) in the 1:1 stoichiometric complex with the alpha-1 isomer of the Wells-Dawson anion, [alpha-1-P 2W 17O 61] (10-), was studied by electrochemical techniques (cyclic voltammetry and bulk electrolysis), in situ XAFS (X-ray absorption fine structure) spectroelectrochemistry, NMR spectroscopy ( (31)P), and optical luminescence. Solutions of K 7[(H 2O) 4Eu(alpha-1-P 2W 17O 61)] in a 0.2 M Li 2SO 4 aqueous electrolyte (pH 3.0) show a pronounced concentration dependence to the voltammetric response. The fully oxidized anion and its reduced forms were probed by Eu L 3-edge XANES (X-ray absorption near edge structure) measurements in simultaneous combination with controlled potential electrolysis, demonstrating that Eu(III) in the original complex is reduced to Eu(II) in conjunction with the reduction of polyoxometalate (POM) ligand. After exhaustive reduction, the heteropoly blue species with Eu(II) is unstable with respect to cluster isomerization, fragmentation, and recombination to form three other Eu-POMs as well as the parent Wells-Dawson anion, alpha-[P 2W 18O 62] (6-). EXAFS data obtained for the reduced, metastable Eu(II)-POM before the onset of Eu(II) autoxidation provides an average Eu-O bond length of 2.55(4) A, which is 0.17 A longer than that for the oxidized anion, and consistent with the 0.184 A difference between the Eu(II) and Eu(III) ionic radii. The reduction of Eu(III) is unusual among POM complexes with Lindqvist and alpha-2 isomers of Wells-Dawson anions, that is, [Eu(W 5O 18) 2] (9-) and [Eu(alpha-2-As 2W 17O 61) 2] (17-), but not to the Preyssler complex anion, [EuP 5W 30O 110] (12-), and fundamental studies of materials based on coupling Eu and POM redox properties are still needed to address new avenues of research in europium hydrometallurgy, separations, and catalysis sciences.

Self-Assembled Monolayers of CH3COS− Terminated Surfactant-Encapsulated Polyoxometalate Complexes

Self-assembled monolayers (SAMs) on gold surfaces based on three kinds of acetylthio-surfactant-encapsulated polyoxometalate clusters (thio-SECs) terminated with multiple CH(3)COS- groups, (NC(26)H(55)S(CO)CH(3))(6)H(2)[Co(H(2)O)CoW(11)O(39)], (NC(26)H(55)S(CO)CH(3))(13)H(3)[Co(4)(H(2)O)(2)(P(2)W(15)O(56))(2)], and (NC(26)H(55)S(CO)CH(3))(13)[Fe(4)(H(2)O)(2)(P(2)W(15)O(56))(2)]Br, have been prepared, which is representative of a general methodology to fabricate polyoxometalate-based SAMs. Thio-SECs self-assembled into monolayers on gold surfaces through the hydrolysis of CH(3)COS- groups and the subsequent formation of S-Au bonds, which was confirmed by grazing angle infrared spectroscopy, X-ray photoelectron spectroscopy, and ellipsometric and scanning tunneling microscopy (STM) measurements. Furthermore, the SAMs of the thio-SECs possess closely packed structures, and the local short-range order is clearly observed in the magnified STM image. We have also investigated the electrochemical behavior of SAMs of thio-SECs by cyclic voltammetry in detail, and the redox potential of the original polyoxometalates has been well retained. The electrochemical signals of the SAMs are very weak because of the small moiety of thio-SECs that are electrochemically accessible in the cyclic voltammetry experiments. The polyoxometalate-modified electrodes that we prepared are not only highly ordered in the local short range but also stable in electrochemical cycling because of the multiple S-Au bonds of thio-SECs on the gold substrates that aid in the construction of functional materials such as electrochemical and electrocatalytic devices.