Inorganic Clusters Research Articles

Chirality-enhanced 2D conductive polymer for flexible electronics and chiral sensing applications

Chiral two-dimensional (2D) conductive polymers, encompassing chiral, 2D, flexible, and conductive properties, constitute a novel class of material that remains largely unexplored. The infusion of chirality into 2D conductive polymers taps into the unique characteristics associated with chirality, presenting opportunities to enhance or tailor the electronic, optical, and structural properties of materials for specific technological applications. In this study, we synthesized a chiral 2D PEDOT:PMo11V nanofilm through interfacial polymerization, effectively integrating a chiral monolayer, conductive polymer, and inorganic cluster. The inclusion of inorganic cluster serves to enhance the conductivity of the resulting chiral nanofilm. Furthermore, we demonstrated the chiral nanofilm as a capable electrochemical sensor for detecting drug enantiomers. The inherent flexibility of the chiral nanofilm also lays the groundwork for the development of chiral flexible/wearable devices.

A classification scheme for inorganic cluster compounds based on their electronic structures and bonding characteristics

A novel classification scheme for inorganic cluster compounds is presented based on the characteristics of their electronic structures. In the classification scheme, five distinct categories have been introduced, including Jellium clusters, Wadian clusters, electron-precise clusters, π-donor ligated metal-metal bonded clusters, and antiferromagnetically coupled high-spin metal clusters.

Nanoscale Metal-Organic Frameworks and Nanoscale Coordination Polymers: From Synthesis to Cancer Therapy and Biomedical Imaging.

Recently, there has been significant interest in nanoscale metal-organic frameworks (NMOFs) characterized by ordered crystal structures and nanoscale coordination polymers (NCPs) featuring amorphous structures. These structures arise from the coordination interactions between inorganic metal ions or clusters and organic ligands. Their advantages, such as the ability to tailor composition and structure, efficiently encapsulate diverse therapeutic or imaging agents within porous frameworks, inherent biodegradability, and surface functionalization capability, position them as promising carriers in the biomedical fields. This review provides an overview of the synthesis and surface modification strategies employed for NMOFs and NCPs, along with their applications in cancer treatment and biological imaging. Finally, future directions and challenges associated with the utilization of NMOFs and NCPs in cancer treatment and diagnosis are also discussed.

Crystal structure and elastic and phonon properties of realgar versus pressure

Realgar, α-As4S4 (space group P21/n), is one of the best-known arsenic sulfide minerals because of its extended use in the past as a red pigment and its employment in modern times for advanced optical and electronic technological applications. From a geological perspective, the main realgar deposits are hydrothermal and epithermal, but it is also a relevant phase found between the upper mantle and Earth's crust and therefore one of the main sources of arsenic. Despite this widespread use and interest, few experimental and theoretical studies have been focused on the characterization of the structural, elastic and vibrational properties of realgar, especially their variation with pressure. Some quantities, such as the cohesive energy between the As4S4 units and the elastic moduli, have never been reported in the scientific literature. The present work deals with a density functional theory investigation of the cited properties of realgar using the recently proposed PBEh-3c method, which was devised in particular to deal with crystalline solids characterized by weak van der Waals interactions. This approach is validated against the available crystal-chemical, mechanical and spectroscopic data from previous studies, finding a generally good agreement. The equation-of-state parameters of the energy versus unit-cell volume data were V 0 = 767.13 (9) Å3, B 0 = 15.73 (8) GPa and B′ = 9.1 (2), with the bulk modulus value (B 0) in good agreement with the value obtained from the elastic tensor analysis (B = 16.1 GPa). The cohesive energy was found to be about 146.1 kJ mol–1, a value that follows the typical ones of organic crystals. The present work provides new insights into this peculiar mineral that, from a mineralogical point of view, could be considered a prototype of a heterodesmic structure made by inorganic molecular clusters.

Continuous flow synthesis of atom-precise platinum clusters.

Subnanometer clusters with precise atom numbers hold immense potential for applications in catalysis, as single atoms can significantly impact catalytic properties. Typically, inorganic clusters are produced using batch processes with high dilutions, making the scale-up of these processes time-consuming and its reproducibility challenging. While continuous-flow systems have been employed for organic synthesis and, more recently, nanoparticle preparation, these approaches have only rarely been applied to cluster synthesis. In a flexible, continuous flow synthesis platform, we integrate multiple continuous stirred tank reactors (CSTR) into a cascade to synthesize clusters with a precise number of atoms, demonstrating the potential of this approach for atom precise cluster synthesis and expanding the application of continuous-flow systems beyond organic synthesis.

A tetrahedron-shaped polyoxoantimotungstate encapsulating a hexanuclear octahedral lanthanide-oxo cluster for an amperometric bromate sensor.

An inorganic hexalanthanide-oxo-cluster-encapsulated antimotungstate, K2Na3H43[Nd6(OH)6(H2O)6(B-α-SbW9O33)4]2·67H2O (1), has been successfully synthesized by a facile one-step hydrothermal reaction method. The tetrahedron-shaped two-shell {Nd6(OH)6(H2O)6(B-α-SbW9O33)4}(1a) polyanion is composed of a novel pure lanthanide-oxo {Nd6(μ3-OH)6(H2O)6} octahedron and {(B-α-SbW9O33)4} tetrahedron. After being effectively loaded onto a glassy carbon electrode (GCE) by electrostatic adsorption using polydiallyldimethyl ammonium chloride (PDDA)-functionalized multi-walled carbon nanotubes (MWCNTs), compound 1 exhibits electrochemical activity for the reduction of bromate ions with good selectivity, a high sensitivity of 186 μA mM-1 and a detection limit that has reached 1.9 μM. To the best of our knowledge, this is the first example of an amperometric bromate sensor based on Ln-containing antimotungstates, which will provide new materials for electrochemical sensors.

Rational Design of Electrocatalysts for Water Oxidation Reaction: Inspiration from Photosystem II

AbstractTo address the ever‐increasing societal demand for clean energy, electrocatalytic water splitting has attracted considerable interest for the efficient production of H2 and O2. However, the oxygen evolution reaction (OER) is inherently sluggish and poses a significant challenge to the overall water splitting process. As a result, extensive research efforts have been dedicated to pursuing various approaches in developing efficient electrocatalysts for water oxidation. The oxygen‐evolving center (OEC) of Photosystem II (PS II) is a natural model giving the prominent reference. Hence, this review discusses recent advances in the design of artificial electrocatalyst inspired by PS II. The discussion begins with a brief introduction to the fundamentals of electrocatalytic water oxidation and PS II. Subsequently, the progress of the novel electrocatalysts inspired by PS II is presented in the following two aspects: engineering various transition metal clusters to mimic the inorganic metal cluster of OEC (Mn4O5Ca), and utilizing different ligands to simulate the protein and amino acid environment around [Mn4O5Ca]. In addition to outlying the structures, catalytic activities, and corresponding mechanisms of these prepared catalysts, this present review concludes by proposing several effective development perspectives to this emerging field that warrant further investigation.

Functionalization of Dodecaborates by Mild and Efficient Pd-Catalyzed Formation of B-C Bonds with Boronic Acids.

Hybrid organic-inorganic molecules have recently received great interest due to their unique properties, which give access to their implementation in biological and material sciences. Herein, a new synthetic approach for the direct-linkage of the purely inorganic dodecaborate cluster to organic building blocks through B-C bond is established, using boronic acids as functional groups on the organic moiety, reacting under Suzuki-Miyaura coupling conditions with iodo-undecahydridododecaborate. The choices of ligand (DavePhos) and solvent (N-methylpyrrolidone for electron-poor, CD3 CN for electron-rich groups) are essential for the successful coupling. Ultimately, the newly described methodology is found to be functional-group tolerant covering a wide spectrum of substrates including electron-poor arenes.

Monodispersed Sub-1nm Inorganic Cluster Chains in Polymers for Solid Electrolytes with Enhanced Li-Ion Transport.

The organic-inorganic interfaces can enhance Li+ transport in composite solid-state electrolytes (CSEs) due to the strong interface interactions. However, Li+ non-conductive areas in CSEs with inert fillers will hinder the construction of efficient Li+ transport channels. Herein, CSEs with fully active Li+ conductive networks are proposed to improve Li+ transport by composing sub-1nm inorganic cluster chains and organic polymer chains. The inorganic cluster chains are monodispersed in polymer matrix by a brief mixed-solvent strategy, their sub-1nm diameter and ultrafine dispersion state eliminate Li+ non-conductive areas in the interior of inert fillers and filler-agglomeration, respectively, providing rich surface areas for interface interactions. Therefore, the 3D networks connected by the monodispersed cluster chains finally construct homogeneous, large-scale, continuous Li+ fast transport channels. Furthermore, a conjecture about 1D oriented distribution of organic polymer chains along the inorganic cluster chains is proposed to optimize Li+ pathways. Consequently, the as-obtained CSEs possess high ionic conductivity at room temperature (0.52mScm-1 ), high Li+ transference number (0.62), and more mobile Li+ (50.7%). The assembled LiFePO4 /Li cell delivers excellent stability of 1000 cycles at 0.5C and 700 cycles at 1C. This research provides a new strategy for enhancing Li+ transport by efficient interfaces.

Apparent symmetry rising induced by crystallization inhibition in ternary co-crystallization-driven self-assembly

The concept of apparent symmetry rising, opposite to symmetry breaking, was proposed to illustrate the unusual phenomenon that the symmetry of the apparent morphology of the multiply twinned particle is higher than that of its crystal structure. We developed a unique strategy of co-crystallization-driven self-assembly of amphiphilic block copolymers PEO-b-PS and the inorganic cluster silicotungstic acid to achieve apparent symmetry rising of nanoparticles under mild conditions. The triangular nanoplates triply twinned by orthogonal crystals (low symmetry) have an additional triple symmetry (high symmetry). The appropriate crystallization inhibition of short solvophilic segments of the block copolymers favors the oriented attachment of homogeneous domains of hybrid nanoribbons, and consequently forms kinetic-controlled triangular nanoplates with twin grain boundaries.

A Thiol-Michael Approach Towards Versatile Functionalized Cyclic Titanium-Oxo Clusters.

In expanding our research activities of superlattice engineering, designing new giant molecules is the necessary first step. One attempt is to use inorganic transition metal clusters as building blocks. Efficient functionalization of chemically precise transition metal clusters, however, remains a great challenge to material scientists. Herein, we report an efficient thiol-Michael addition approach for the modifications of cyclic titanium-oxo cluster (CTOC). Several advantages, including high efficiency, mild reaction condition, capability of complete addition, high atom economy, as well as high functional group tolerance were demonstrated. This approach can afford high yields of fully functionalized CTOCs, which provides a powerful platform for achieving versatile functionalization of precise transition metal clusters and further applications.

A High-Rigidity Organic-Inorganic Metal Halide Hybrid Enabling Reversible and Enhanced Self-Trapped Exciton Emission under High Pressure.

Zero-dimensional organic-inorganic metal halide hybrids provide ideal bulk-crystal platforms for exploring the pressure engineering of electron-phonon coupling (EPC) and self-trapped exciton (STE) emission at the molecular level. However, the low stiffness of inorganic clusters hinders the reversible tuning of these physical properties. Herein, we designed a Sb3+-doped metal halide with a high emission yield (89.4%) and high bulk modulus (35 GPa) that enables reversible and enhanced STE emission (20-fold) under pressure. The high lattice rigidity originates from the corner-shared cage-structured inorganic tetramers and ring-shaped organic ligands. Further, we reveal that the pressure-enhanced emission regime below 4.5 GPa is owing to the lattice hardening and preferably EPC strength reducing, while the pressure-insensitive emission regime within 4.5-8.5 GPa results from the enhanced intercluster Coulombic attraction force that resists intracluster compression. These results provide insights into the structure-property relation and molecular engineering of zero-dimensional metal halides toward wide-band and pressure-sensitive light sources.

Reversible Thermochromism and Stable Resistance Switching Behaviors Based on a Co(III)-Complex-Linked Polyoxoniobate.

A 3D Co(III)-complex hybrid polyoxoniobate framework Na10(H2O)36[Co2(phen)2(4,4'-bipy)(Nb6O19)2]·19H2O (1) has been constructed from [Co2(phen)2(4,4'-bipy)(Nb6O19)2]10- dimer units and 2D inorganic Na-O cluster layers. The Co(III) centers are coordinated with {Nb6O19}, 4,4'-bipy and phen simultaneously. The [Co2(phen)2(4,4'-bipy)(Nb6O19)2]10- fragments link the Na-O cluster layers to generate a 3D metal complex-modified hybrid polyoxoniobate framework with π-π interactions between phenanthroline rings. Compound 1 shows reversible thermochromic behavior resulting from electron transfer from {Nb6O19} to 4,4'-bipy and subsequent formation of radical products, which is first observed in polyoxoniobates. Furthermore, the compound exhibits stable nonvolatile storage behavior and rewritable resistive switching with a low switching voltage (1.12 V) and high current on/off ratio (1.18 × 103) along with stable cyclic performance during stability test for 200 cycles. Charge-transfer mechanism has been studied by analyzing the relationship between current and voltage in the process of resistance switching.

Designed Tetranuclear Iron-oxo Clusters with Redox Activity for High-Performance Lithium Storage.

Polyoxometalates (POMs) are considered as promising catalysts with unique redox activity at the molecular level for energy storage. However, eco-friendly iron-oxo clusters with special metal coordination structures have rarely been reported for Li-ion storage. Herein, three novel redox-active tetranuclear iron-oxo clusters have been synthesized using the solvothermal method with different ratios of Fe3+ and SO4 2- . Further, they can serve as anode materials for Li-ion batteries. Among them, cluster H6 [Fe4 O2 (H2 O)2 (SO4 )7 ]⋅H2 O, the stable structure extended by SO4 2- with a unique 1D pore, displays a specific discharge capacity of 1784 mAh g-1 at 0.2 C and good cycle performance (at 0.2 C and 4 C). This is the first instance of inorganic iron-oxo clusters being used for Li-ion storage. Our findings present a new molecular model system with a well-defined structure and offer new design concepts for the practical application of studying the multi-electron redox activity of iron-oxo clusters.

A Short Review on Photoluminescent Properties of Hybrid Metal Organic Framework

Metal organic frameworks (MOFs) are three dimensionally arranged compounds of bridged organic ligands coordinately bonded with inorganic cluster. The large surface area with large pore volume of MOFs introduces wide application in catalysis field. With accurate combination of organic and inorganic bridging units we can alter the chemical, thermal stability as well as its porosity. Luminescence is the one of the most important properties exhibited by Metal organic frameworks (MOFs). This luminescent property of MOFs is highly sensitive for guest interaction due to which they are used in the detection of various toxic substances, organic pollutants. Based on their high sensitivity and selectivity they are applied in the field of sensors, different environmental applications, various clean energies, optoelectronic devices, medical and biological applications.

Electron-Donor Functional Groups, Band Gap Tailoring, and Efficient Charge Separation: Three Keys To Improve the Gaseous Iodine Uptake in MOF Materials.

Metal-organic frameworks (MOFs) have been largely investigated worldwide for their use in the capture of radioactive iodine due to its potential release during nuclear accident events and reprocessing of nuclear fuel. The present work deals with the capture of gaseous I2 under a continuous flow and its subsequent transformation into I3- within the porous structures of three distinct, yet structurally related, terephthalate-based MOFs: MIL-125(Ti), MIL-125(Ti)_NH2, and CAU-1(Al)_NH2. The synthesized materials exhibited specific surface areas (SSAs) with similar order of magnitude: 1207, 1099, and 1110 m2 g-1 for MIL-125(Ti), MIL-125(Ti)_NH2, and CAU-1(Al)_NH2, respectively. Because of that, it was possible to evaluate the influence of other variables over the iodine uptake capacity─such as band gap energies, functional groups, and charge transfer complexes (CTC). After 72 h of contact with the I2 gas flow, MIL-125(Ti)_NH2 was able to trap 11.0 mol mol-1 of I2, followed by MIL-125(Ti) (8.7 mol mol-1), and by CAU-1(Al)_NH2 (4.2 mol mol-1). The enhanced ability to retain I2 in the MIL-125(Ti)_NH2 was associated with a combined effect between its amino group (which has a great affinity toward iodine), its smaller band gap (2.5 eV against 2.6 and 3.8 eV for CAU-1(Al)_NH2 and MIL-125(Ti), respectively), and its efficient charge separation. In fact, the presence of a linker-to-metal charge transfer (LMCT) mechanism in MIL-125(Ti) compounds separates the photogenerated electrons and holes into the two distinct moieties of the MOF: the organic linker (which stabilizes the holes) and the oxy/hydroxy inorganic cluster (which stabilizes the electrons). This effect was observed using EPR spectroscopy, whereas the reduction of the Ti4+ cations into the paramagnetic Ti3+ species was evidenced after irradiation of the pristine Ti-based MOFs with UV light (<420 nm). In contrast, because CAU-1(Al)_NH2 exhibits a purely linker-based transition (LBT)─with no EPR signals related to Al paramagnetic species─it tends to exhibit faster recombination of the photogenerated charge carriers as, in this case, both electrons and holes are located over the organic linker. Furthermore, the transformation of the gaseous I2 into In- [n = 5, 7, 9, ...] intermediates and then into I3- species was evaluated using Raman spectroscopy by following the evolution of their respective bands at about 198, 180, and 113 cm-1. This conversion─which is favored by an effective charge separation and smaller band gaps─increases the I2 uptake capacity of the compounds by creating specific adsorption sites for these anionic species. In fact, because the -NH2 groups act as an antenna to stabilize the photogenerated holes, both In- and I3- are adsorbed into the organic linker via an electrostatic interaction with these positively charged entities. Finally, changes regarding the EPR spectra before and after the iodine loading were considered to propose a mechanism for the electron transfer from the MOFs structure to the I2 molecules considering their different characteristics.

Quantum size effect to induce colossal high-temperature energy storage density and efficiency in polymer/inorganic cluster composites.

Polymer dielectrics need to operate at high temperatures to meet the demand of electrostatic energy storage in modern electronic and electrical systems. The polymer nanocomposite approach, an extensively proved strategy for the performance improvement, encounters the bottleneck of reduced energy density and poor discharge efficiency beyond 150°C. Here, we report a polymer/metal oxide cluster composite prepared based on the "site isolation" strategy. Capitalizing on the quantum size effect, the bandgap and surface defect states of the ultra-small inorganic clusters (2.2nm diameter) are modulated to markedly differ from the regular-sized nanoparticles. Experimental results in conjunction with computational simulation demonstrate that, the presence of ultra-small inorganic clusters can introduce more abundant, deeper traps in the composite dielectric with respect to the conventional polymer/nanoparticle blends. Unprecedented high-temperature capacitive performance including colossal energy density (6.8 Jcm-3 ), ultra-high discharge efficiency (95%) and superior stability at different electric field frequencies, are achieved in these polymer/cluster composites up to 200°C. Along with the advantages in material preparation (inexpensive precursors and one-pot synthesis), such polymer/inorganic cluster composite approach is promising for high-temperature dielectric energy storage in practical power apparatus and electronic devices. This article is protected by copyright. All rights reserved.

Chitosan decorated zirconium metal-organic framework for collaborative adsorption and photocatalytic degradation of methylene blue and methyl orange

A type of crystalline porous material known as zirconium metal-organic frameworks (UiO-66) is made up of organic carboxylate ligands and inorganic zirconium clusters. The UiO-66 has consistent pore sizes, large porosities, exceptional adsorption capabilities, and particular functional groups for increasing dye adsorption. This study reports the synthesis of Zirconium metal-organic framework (UiO-66) and chitosan composite of zirconium metal−organic framework (CS/UiO-66) for potential adsorption of methyl orange (MO) and methylene blue (MB) dyes from the aqueous media and additional, excellent photodegradation capability of the synthesized material towards selected dyes. The synthesized materials were successfully characterized for structural, morphological, surface and thermogravimetrical analysis. The exclusion of dyes onto the CS/UiO-66 followed the trend MB (2321 mg/g) > MO (900 mg/g) respectively. The maximum sorption and degradation capacity of the CS/UiO-66 were increased by 5–10 times after its composite with chitosan (CS) and the affinity of the dyes towards the different adsorbents followed the sequence CS/UiO-66 > UiO-66 > CS which is parallel to their surface properties. The negative values of the entropy i.e., − 382 for MB and − 249 for MO affirmed the controlled versatility of the MO, and MB onto CS/UiO-66 whereas the isosteric heat of adsorption i.e., − 201 kJ/mol for MB and − 153 kJ/mol for MO illustrated the exothermicity of the adsorption process. The intraparticle diffusion and Richenberge kinetic models demonstrated that pore diffusion dominates in the adsorption of MB while film diffusion has a greater involvement in the MO adsorption of CS/UiO-66. Moreover, the photocatalytic degradation study indicated that the pH and H2O2 play a significant part in the deprivation of dyes. While GC-MS analysis revealed that the photocatalytic degradation of MB resulted in the formation of six TPs. The toxicity of these TPs of MB was evaluated by ECOSAR program and the results showed that the TPs were less toxic than the parent MB molecule.

Playing with [{Mo6Bri6Sei2}(CN)a6]4− Cluster Building Blocks and Mn(salen)+ Nodes for the Crystal Engineering of Inorganic Coordination Polymers

AbstractWe present here the syntheses and structural characterizations of inorganic polymeric cluster compounds, Cs[Mn(salen)]3[{Mo6Br6Se2}(CN)6] (1) and (H3O)(TBA)[Mn(salen)]2[{Mo6Br6Se2}(CN)6] (2) (TBA=tetrabutylammonium ((n‐C4H9)4N+)), built‐up from [{Mo6Br6Se2}(CN)6]4− molecular building blocks and Mn(salen)+ complexes (salen = salen = N,N′‐bis(salicylidene)ethylenediamine). The nature of additional counter cations (i. e. Cs+ or TBA+) enables to control the interactions between the [{Mo6Br6Se2}(CN)6]4− building blocks and the Mn(salen)+ groups. Thus, 1 was obtained by slow diffusion of a methanol solution of K2Cs2[{Mo6Br6Se2}(CN)6] cluster compound into a methanol solution of Mn(salen)ClO4. 2 was obtained in a similar way but after the addition of tetrabutylammonium bromide into the solution of Mn(salen)ClO4. 1 is a bimetallic 3D coordination compound ( ) and 2 is a bimetallic 2D compound ( ). Structural correlations between 1 and 2 are discussed and compared with relevant examples found in the literature.

Carbazole Derivative Doped Polyoxometalate Inorganic Clusters as Hole Transport Layer to Enhance the Photovoltaic Performance of Organic Solar Cells

Polyoxometalate inorganic clusters (PICs) as a kind of environmentally friendly material can potentially act as an effective hole transport layer (HTL) in organic solar cells (OSCs) due to their thermally stable, low-cost, easily soluble, and excellent redox properties. However, their low conductivity often limits the applications in high-efficiency OSCs. Here, we use a carbazole derivative (2PACz) to modify the bivalent tin (Sn2+) doped phosphomolybdic acid (H3PMo12O40) (termed HPMO-Sn) to further increase the conductivity. The resulted HPMO-Sn:2PACz HTL displays an improved hole transport ability, enhanced conductivity, increased exciton dissociation efficiency, and low nonradiative energy loss in OSCs. As a result, OSCs employing HPMO-Sn:2PACz as the HTL and PM6:Y6 as the active layer exhibit higher power conversion efficiency (17.62%) than those using HPMO-Sn (efficiency: 16.40%) or PEDOT:PSS (efficiency: 16.45%) as the HTL with enhanced open-circuit voltage and fill factor. Our results provide an effective method to elevate the conductivity of PICs and demonstrate the possibility of using the modified PICs as an effective HTL to achieve high-efficiency OSCs.