Central Sn Research Articles

Novel electrocatalyst with abundant oxygen vacancies enabling efficient two-electron water oxidation reaction for H2O2 synthesis

In the realm of electrocatalytic two-electron water oxidation reaction, the quest for efficient and selective catalysts poses a significant challenge in balancing productivity and activity, hindering the decentralized generation of hydrogen peroxide (H2O2) through electrochemical means. Addressing this hurdle, our study introduces a novel approach to crafting an effective and stable electrocatalyst for the two-electron water oxidation reaction (2e-WOR). Through the synthesis of magnesium stannite tungstate from a mixture of MgSnO3 and WO3, the engineer of a material with abundant oxygen vacancies is crucial for catalytic activity. This catalyst demonstrates exceptional performance, ascribed to its distinctive oxygen vacancies proximal to the active center Sn and electronic modulation by tungsten. Notably, Mg1-xSnWO6-x700 exhibits a remarkably low overpotential of 70 mV at 10 mA cm−2, coupled with a high faradic efficiency of 84 % for 2e- WOR at 2.6 V vs. RHE, maintaining consistent performance over 35 h. Furthermore, the formation of oxygen vacancies and the associated electronic transfer underscore the novelty and promise of our material in advancing the field of two-electron WOR. In sum, our electrocatalyst presents a cost-efficient and selective solution for water oxidation, offering potential avenues for enhancing H2O2 production.

Synthesis of organotin(IV) heterocycles containing a xanthenyl group by a Barbier approach via ultrasound activation: synthesis, crystal structure and Hirshfeld surface analysis.

A series of organotin heterocycles of general formula [{Me2C(C6H3CH2)2O}SnR2] [R= methyl (Me, 4), n-butyl (n-Bu, 5), benzyl (Bn, 6) and phenyl (Ph, 7)] was easily synthesized by a Barbier-type reaction assisted by the sonochemical activation of metallic magnesium. The 119Sn{1H} NMR data for all four compounds confirm the presence of a central Sn atom in a four-coordinated environment in solution. Single-crystal X-ray diffraction studies for 17,17-dimethyl-7,7-diphenyl-15-oxa-7-stannatetracyclo[11.3.1.05,16.09,14]heptadeca-1,3,5(16),9(14),10,12-hexaene, [Sn(C6H5)2(C17H16O)], 7, at 100 and 295 K confirmed the formation of a mononuclear eight-membered heterocycle, with a conformation depicted as boat-chair, resulting in a weak Sn...O interaction. The Sn and O atoms are surrounded by hydrophobic C-H bonds. A Hirshfeld surface analysis of 7 showed that the eight-membered heterocycles are linked by weak C-H...π, π-π and H...H noncovalent interactions. The pairwise interaction energies showed that the cohesion between the heterocycles are mainly due to dispersion forces.

Trimethyltin(IV) (p-fluoro-/p‑hydroxy-/p-nitro-)benzoates and their benzimidazole complexes: X-ray structures of [Me3Sn(p-NO2C6H4CO2)]n, and [Me3Sn(p-NO2C6H4CO2). bz], DFT calculations, DNA binding, and DNA cleavage studies

A series of trimethyltin(IV) carboxylates with Sn‒O bonds: [Me3Sn(p-FC6H4CO2)] (1), [Me3Sn(p-HOC6H4CO2)] (2), [Me3Sn(p-NO2C6H4CO2)]n (3), and their benzimidazole complexes with Sn‒N bond: [Me3Sn(p-FC6H4CO2).bz] (4), [Me3Sn(p-HOC6H4CO2).bz] (5), and [Me3Sn(p-NO2C6H4CO2).bz] (6) (bz = benzimidazole) have been synthesized and characterized by elemental analysis, FT-IR, 1H, 13C, 119Sn NMR, and electrospray ionization mass spectrometric (ESI-MS) studies. The crystal structures for (3) and (6) have been authenticated by X-ray diffraction. In the crystal structure, polymeric coordination compound (3) and the monocrystal system (6) have trigonal bipyramidal geometry around the Sn centre, where most electronegative atoms occupied the axial positions, and three methyl groups occupied the equatorial positions. The gas-phase tetrahedral geometries of (1) and (2), asymmetric unit (Sc-XRD) of (3), and trigonal bipyramidal geometries of (4–6) have been optimized using the B3LYP function and LanL2Z basis, and obtained ∠C-Sn-C bond angles agree with those obtained from NMR/X-ray studies. The interaction of (1–6) with calf thymus DNA (ctDNA) has been investigated by spectroscopic titrations such as UV–visible, fluorescence, and circular dichroism (CD) titrations, and calculated binding constant values found in the 104–105 M−1 range which suggest a groove binding or electrostatic interaction between complexes and ctDNA. The gel electrophoresis studies suggest that (1–6) effectively cleaved the plasmid pBR322 DNA into three bands: the supercoiled, nicked/circular, and linear structures. The intriguing biophysical findings from the study indicate that these complexes have properties that make them strong contenders for additional research as potential anti-cancer agents.

Sustainable biodiesel production via castor oil transesterification using organotin(IV) compounds as catalysts

The rapid reduction in fossil fuel reserves and their environmental effects has caused a serious threat to humanity. Meanwhile, the exponential increase in the usage of fossil fuels demands the exploration of new energy sources. Therefore, this work was designed keeping in view the today need of the World for renewable energy source. The 4-(4-chloro-2-fluorophenylamino)-4-oxobut-2-enoic acid based organotin(IV) carboxylates were prepared and characterized by FT-IR, NMR and single crystal XRD analysis. Due to the Lewis acid character of Sn(IV) centre confirmed by DFT computational study, the synthesized compounds were used as catalysts for the transesterification of castor oil for biodiesel production. Under the optimized experimental conditions, the catalytic performance of the tested compounds was found as follow: 1 > 3 > 2 > 4 > 6 > 5 > 7. The obtained biodiesel was confirmed by FT-IR, NMR and GC–MS. The fuel properties of the obtained biodiesel were also determined and compared with American Standard (ASTM D-6751). Based on their catalytic performance, these compounds might be the potential future candidates for the expansion of catalyst systems for efficient biodiesel production from the various feedstocks.

Zeolite-catalyzed one-pot sucrose-to-HMF transformation: Ge outperforms Sn, Zr, and Al sites

The conversion of renewable compounds to versatile platform molecules over environmentally friendly heterogeneous catalysts is a major challenge. Zeolites stand as active, selective, and reusable solid catalysts for various acid-catalyzed reactions involved in the one-pot cascade transformation of polysaccharides to 5-hydroxymethylfurfural (HMF), a platform molecule opening the way to various valuable chemicals. However, the acidity-performance relationships of zeolite catalysts in HMF synthesis have not been fully elucidated. Here, we have addressed the effect of acid site nature in zeolite catalysts for sucrose-to-HMF transformation by comparing the performance of conventional Al-substituted IWW zeolite with that of Sn-, Zr-, and Ge-containing zeolite catalysts of the same structure. Ge-associated acid sites were found to exhibit superior HMF selectivity compared to Sn, Zr, and Al acid centers, while experiencing evolution into Brønsted acid centers during the catalytic run. The conversion of sucrose over germanosilicate zeolites enhances with increasing catalyst pore diameter or decreasing crystal size. Specifically, the extra-large pore Ge-UTL catalyst, featuring intersecting 14- and 12-ring pores (crystal size 10 × 20 × <1 μm), and large-pore Ge-IWW with 12-, 10- and 8-ring pores (crystal sizes of 1 μm) showed a yield of targeted HMF comparable to or even exceeding the values previously reported for homogeneous or heterogeneous catalysis (54 % after 3 h at 120 °C). Ge-IWW catalyst demonstrated reusability across a minimum of 3 catalytic runs, while in situ structural transformation precluded stable performance of Ge-UTL catalyst in the repetitive catalytic cycles. The results of this study highlight zeolites with uncharacteristic chemical compositions as active, selective, and reusable catalysts for highly demanding applications in biomass valorization.

Structural Evolution and Photoluminescence Quenching across the FASnI3-xBrx (x = 0-3) Perovskites.

One of the primary methods for band gap tuning in metal halide perovskites has been halide (I/Br) mixing. Despite widespread usage of this type of chemical substitution in perovskite photovoltaics, there is still little understanding of the structural impacts of halide alloying, with the assumption being the formation of ideal solid solutions. The FASnI3-xBrx (x = 0-3) family of compounds provides the first example where the assumption breaks down, as the composition space is broken into two unique regimes (x = 0-2.9; x = 2.9-3) based on their average structure with the former having a 3D and the latter having an extended 3D (pseudo 0D) structure. Pair distribution function (PDF) analyses further suggest a dynamic 5s2 lone pair expression resulting in increasing levels of off-centering of the central Sn as the Br concentration is increased. These antiferroelectric distortions indicate that even the x = 0-2.9 phase space behaves as a nonideal solid-solution on a more local scale. Solid-state NMR confirms the difference in local structure yielding greater insight into the chemical nature and local distributions of the FA+ cation. In contrast to the FAPbI3-xBrx series, a drastic photoluminescence (PL) quenching is observed with x ≥ 1.9 compounds having no observable PL. Our detailed studies attribute this quenching to structural transitions induced by the distortions of the [SnBr6] octahedra in response to stereochemically expressed lone pairs of electrons. This is confirmed through density functional theory, having a direct impact on the electronic structure.

Bisgermylene-Stabilized Stannylone: Catalytic Reduction of Nitrous Oxide and Nitro Compounds via Element-Ligand Cooperativity.

This study describes the synthesis, structural characterization, and catalytic application of a bis(germylene)-stabilized stannylone (2). The reduction of digermylated stannylene (1) with 2.2 equiv of potassium graphite (KC8) leads to the formation of stannylone 2 as a green solid in 78% yield. Computational studies showed that stannylone 2 possesses a formal Sn(0) center and a delocalized 3-c-2-e π-bond in the Ge2Sn core, which arises from back-donation of the p-type lone pair electrons on the Sn atom to the vacant orbitals of the Ge atoms. Stannylone 2 can serve as an efficient precatalyst for the selective reduction of nitrous oxide (N2O) and nitroarenes (ArNO2) with the formation of dinitrogen (N2) and hydrazines (ArNH-NHAr), respectively. Exposure of 2 with N2O (1 atm) resulted in the insertion of two oxygen atoms into the Ge-Ge and Ge-Sn bonds, yielding the germyl(oxyl)stannylene (3). Moreover, the stoichiometric reaction of 2 with 1-chloro-4-nitrobenzene afforded an amido(oxyl)stannylene (4) through the complete scission of the N-O bonds of the nitroarene. Stannylenes 3 and 4 serve as catalytically active species for the catalytic reduction of nitrous oxide and nitroarenes, respectively. Mechanistic studies reveal that the cooperation of the low-valent Ge and Sn centers allows for multiple electron transfers to cleave the N-O bonds of N2O and ArNO2. This approach presents a new strategy for catalyzing the deoxygenation of N2O and ArNO2 using a zerovalent tin compound.

Insights into the selective anticancer activity of [SnIV(L)(Cl)2(OH2)] [L =(E)-N,N-diethyl-2-(2-hydroxy-3-methoxybenzylidene)hydrazinecarbothioamide] at thiosemicarbazone appended tin(IV) site

We herein report the synthesis of a mononuclear tin(IV) complex [SnIV(L)(Cl)2(OH2)] [L = (E)-N,N-diethyl-2-(2-hydroxy-3-methoxybenzylidene)hydrazinecarbothioamide] (1). From the X-ray crystallographic characterization the molecular geometry of 1 around Sn(IV) center has been found to be distorted octahedron. The present report illustrates the selective reactivity of 1 against human lung carcinoma epithelial cell line, A549 by inducing depolarization of the mitochondrial membrane potential resulting in selective cancer cell death.

A linear correlation of p-band center with the performance of electrochemical CO2 reduction revealed by Sn single-atom catalysts

The correlation between p-orbital energy level and catalytic activity of electrochemical CO2 reduction reaction (ECRR) is rarely reported, but significantly desired for further design of highly effective main group single-atom catalysts (SACs). Herein, a series of Sn-SACs (Sn-N3S1, Sn-N3P1, Sn-N3B1, and Sn-N4) were developed as a model system to explore structure-activity relationships of main group SACs for ECRR. Coordination environment regulation could upshift the p-band center of Sn, facilitating the adsorption of intermediates and improving the catalytic activity. Sn-N3S1 with the most positive p-band center shows a 100 % Faradaic efficiency of CO (FECO), superior over that of Sn-N4 and other reported SACs. Notably, the catalytic performance of Sn-SACs shows a linear relationship with p-band center of Sn, indicating a high applicability of p-band center as a descriptor for catalytic performance. This work provides a new way to boost ECRR by lowering the p-orbital energy level of main group metal.

Vacancy–assisted exposed Sn atoms enhancing NO2 room temperature sensing of SnSe2 nanoflowers

NO2 is a hazardous gas extremely harmful to the ecosystem and human health, so effective detection of NO2 is critical. SnSe2 is a promising candidate for gas sensors owing to its unique layered configuration that facilitates the diffusion of gas molecules. Here, ultrathin self–assembled nanoflowers F–SnSe2 rich in defects were synthesized by a simple solvothermal method. It exhibits excellent gas sensing performances for NO2 at room temperature (25 °C), with a high gas sensing response of 8.6 for 1 ppm NO2 and a lower detection limit as low as 200 ppb, capable of sensitively detecting ppb–level NO2. DFT calculations revealed that the presence of Se vacancies assists the central Sn atoms to break through the shielding effect of the surface Se atoms and become exposed active sites. The higher reactivity leads to more charge transfer and higher adsorption energy, which strongly promoted the adsorption of NO2. This work verifies the important role of vacancies for the exposed active sites and provides new guidance for defect engineering to modulate the gas sensing performances of SnSe2.

Polymorphism and Structural Variety in Sn(II) Carboxylate Coordination Polymers Revealed from Structure Solution of Microcrystals.

The crystal structures of four coordination polymers constructed from Sn(II) and polydentate carboxylate ligands are reported. All are prepared under hydrothermal conditions in KOH or LiOH solutions (either water or methanol-water) at 130-180°C and crystallize as small crystals, microns or less in size. Single-crystal structure solution and refinement are performed using synchrotron X-ray diffraction for two materials and using 3D electron diffraction (3DED) for the others. Sn2 (1,3,5-BTC)(OH), where 1,3,5-BTC is benzene-1,3,5-tricarboxylate, is a new polymorph of this composition and has a three-dimensionally connected structure with potential for porosity. Sn(H-1,3,5-BTC) retains a partially protonated ligand and has a 1D chain structure bound by hydrogen bonding via ─COOH groups. Sn(H-1,2,4-BTC) contains an isomeric ligand, benzene-1,2,4-tricarboxylate, and contains inorganic chains in a layered structure held by hydrogen bonding. Sn2 (DOBDC), where DOBDC is 2,5-dioxido-benzene-1,4-dicarboxylate, is a new polymorph for this composition and has a three-dimensionally connected structure where both carboxylate and oxido groups bind to the tin centers to create a dense network with dimers of tin. In all materials, the Sn centers are found in highly asymmetric coordination, as expected for Sn(II). For all materials phase purity of the bulk is confirmed using powder X-ray diffraction, thermogravimetric analysis, and infrared spectroscopy.

Identification of paramagnetic centers in irradiated Sn-doped silicon dioxide by first-principles.

We present a first-principles investigation of Sn paramagnetic centers in Sn-doped vitreous silica based on calculations of the electron paramagnetic resonance (EPR) parameters. The present investigation provides evidence of an extended analogy between the family of Ge paramagnetic centers in Ge-doped silica and the family of Sn paramagnetic centers in Sn-doped silica for SnO2concentrations below phase separation. We infer, also keeping into account the larger spin-orbit coupling of Sn atoms with respect to Ge atoms, that a peculiar and highly distorted three-fold coordinated Sn center (i.e. the Sn forward-oriented configuration) should give rise to an orthorhombic EPR signal of which we suggest a fingerprint in the EPR spectra recorded by Chiodiniet al(2001Phys. Rev.B64073102). Given its structural analogy with theEα'and Ge(2) centers, we here name it as the 'Sn(2) center'. Moreover, we show that the single trapped electron at a SnO4tetrahedron constitutes a paramagnetic center responsible for the orthorhombic EPR signal reported in Chiodiniet al(1998Phys. Rev.B589615), confuting the early assignment to a distorted variant of the Sn-E' center. We hence relabel the latter orthorhombic EPR signal as the 'Sn(1) center' due to its analogy to the Ge(1) center in Ge-doped silica.

TRIPHENYLTIN (IV) GLUTARATES: SYNTHESIS, FT-IR AND MÖSSBAUER STUDIES

Four new adducts catena-O,O′-glutaratotriphenylstannate, [(Me4N)2O2C(CH2)3CO2×4SnPh3Cl] (1), [(Me4N)2O2C(CH2)3CO2×3SnPh3Cl] (2), [(SnPh3)2O2C(CH2)3CO2×SnPh3Cl] (2′) and [(Cy2NH2)2O2C(CH2)3CO2×SnPh3Cl] (3), have been isolated from the reactions carried out in solution. The compounds have been characterized by FT-IR and Mössbauer spectroscopies except for 2’ whose structure is proposed on the basis of FT-IR data. Overall, the spectra studies sheew existence of several caracteristic bands such as υ (C=O), υ (CO2–), υ (Sn–O), υ (Sn–Cl), vibrations of glutarate ions, and the intense doublet showing the presence of phenyl groups. In the solid state, the suggested structures are discrete or of infinite chain. In this work, the geometry at Sn centers, trigonal bipyramidal or tetrahedral, is ascertained by the Mössbauer parameters. The glutarate ions exhibit a monodentate, tridentate or tetradentate coordination behavior towards the Sn atoms.

Syntheses and exploration of the catalytic activities of organotin(IV) compounds.

Six organotin(IV) compounds (1-6) have been synthesized by reaction of the polydentate pro-ligands H3L and H2L, respectively, with the corresponding diorganotin chlorides. All of the compounds were characterized by FT-IR spectroscopy, 1H, 13C{1H}, and 119Sn (1H) NMR spectroscopy, HRMS spectrometry, and single-crystal X-ray diffraction. The solid-state structures show that all of the compounds are monomeric (except compound 3) and contain a penta-coordinated tin atom. Compound 3 is a dimer with two hexa-coordinated tin atoms. Compounds 1-3 contain a non-coordinated hydroxymethyl group. All of the compounds have been screened for their catalytic efficacy in the synthesis of 1,2 disubstituted benzimidazoles using o-phenylenediamine and aldehyde derivatives. It has been observed that both the Lewis acidic Sn(IV) centre and the hydroxymethyl group (hydrogen bond donor) catalyse the reactions with a product yield of up to 92%.

Accelerating σ-Bond Metathesis at Sn(II) Centers.

Molecular main-group hydride catalysts are attractive as cheap and Earth-abundant alternatives to transition-metal analogues. In the case of the latter, specific steric and electronic tuning of the metal center through ligand choice has enabled the iterative and rational development of superior catalysts. Analogously, a deeper understanding of electronic structure-activity relationships for molecular main-group hydrides should facilitate the development of superior main-group hydride catalysts. Herein, we report a modular Sn-Ni bimetallic system in which we systematically vary the ancillary ligand on Ni, which, in turn, tunes the Sn center. This tuning is probed using Sn L1 XAS as a measure of electron density at the Sn center. We demonstrate that increased electron density at Sn centers accelerates the rate of σ-bond metathesis, and we employ this understanding to develop a highly active Sn-based catalyst for the hydroboration of CO2 using pinacolborane. Additionally, we demonstrate that engineering London dispersion interactions within the secondary coordination sphere of Sn allows for further rate acceleration. These results show that the electronics of main-group catalysts can be controlled without the competing effects of geometry perturbations and that this manifests in substantial reactivity differences.

Main group tin single atom catalyst supported by C5N monolayer for oxygen evolution reactions

Single atom catalysts (SACs) supported by carbonaceous materials present extraordinary activity for oxygen evolution reaction (OER), which usually contain transition metal atoms serving as active sites. However, when it turns to the SACs containing main group metal atoms, the OER performance is believed to be significantly decreased. We here proposed a strategy of designing SACs with p-block element of Sn as active sites, which exhibit excellent OER performance without nitrogen coordination of the metal centers. Density functional theory calculations demonstrate that atomically dispersed Sn atoms supported by the metallic monolayers of C5N can efficiently catalyze OER, of which the Sn center coordinated with four C atoms give rise to low overpotential of 0.54 V comparable or even lower than those given by the transition-metal-based SACs. Moreover, correlation between the overpotentials and some intrinsic properties of SACs, which demonstrates that the OER performance is not strongly correlated with the charge state of Sn atoms and Sn-N/C bond length. This study paves a new way of theoretically designing SACs containing main group elements toward OER or even broader range of electrochemical reactions.

Novel 3-(2-thienyl) acrylic acid bridge di-triphenyltin(IV) {[(Ph)3SnCl)2COO]-[Et3NH]+, [(Ph)3SnCl2)]-[Et3NH]+} complex: XRD/HSA-interactions, physicochemical, thermal and POM/antifungal evaluation

The coordination reaction of Ph3SnCl with (E)-3-(thiophen-2-yl)acrylic acid as simple –COOH acid ligand in (Et)3N medium leads to formation of {[(Ph)3SnCl)2COO]-[Et3NH]+,[(Ph)3SnCl2)]−[Et3NH]+} complex matrix in high yield for the first time. FT-IR, UV–Vis, EDX, and a single XRD were used to characterize the prepared complex. Moreover, the complex was crystallized in the triclinic system P-1 with [a = 12.5191(4); b = 13.5491(5); c = 21.9805(8); α = 100.2790(10); β = 99.1470 (10) and γ = 100.4390(10)] the lattice cell parameters. The resulting environment of each Sn(IV) centers are a distorted trigonal bipyramid geometry where the ligand carboxylate part connected both Sn(IV) centers via O,O-bi-chelate mode trans to the Cl anions, meanwhile, the thiophen part was not coordinated to Sn(IV) anymore. Moreover, only Cl…H H-bonds with nonclassical mononuclear and classical binuclear type of interactions were recorded. Computationally, the Cl…..H predominant interactions were confirmed by Hirschfeld Surface Analysis (HSA). TG of the complex was evaluated under open atmosphere. The complex’s antifungal activity against the pathogenic Fusarium oxysporum f.sp. albedins (FOA) showed more activity compared by the free ligand. Furthermore, POM theory was applied to evaluate the bioactivity and explain the experimental result of desired material against fungal.

Direct Synthesis of Two-Dimensional SnSe and SnSe2 through Molecular Scale Preorganization.

Two-dimensional tin monoselenide (SnSe) and tin diselenide (SnSe2) materials were efficiently produced by the thermolysis of molecular compounds based on a new class of seleno-ligands. Main group metal chalcogenides are of fundamental interest due to their layered structures, thickness-dependent modulation in electronic structure, and small effective mass, which make them attractive candidates for optoelectronic applications. We demonstrate here the synthesis of stable tin selenide precursors by in situ reductive bond cleavage in the dimeric diselenide ligand (SeC2H4N(Me)C2H4Se)2 in the presence of SnCl4. New molecular precursors [SnIV(SeC2H4N(Me)C2H4Se)2], [SnIVCl2(SeC2H4N(Me)C2H4Se)], and [SnIV(SC2H4N(Me)C2H4S)(SeC2H4N(Me)C2H4Se)] were thoroughly characterized by multinuclear magnetic resonance studies and single-crystal X-ray diffraction analysis that revealed the Sn(IV) center to be octahedrally coordinated by two tridentate dianionic chelating ligands or trigonally pyramidally coordinated by one chelating ligand and two chlorido ligands. Preorganization of metal-selenium bonds in both compounds offered direct and reproducible synthetic access to two-dimensional tin chalcogenides (SnSe and SnSe2) via simple adjustment of the pyrolysis temperature. Additionally, SnSe2 and SnSxSe2-x particles could be successfully synthesized by microwave-assisted decomposition of the molecular precursors, which was unambiguously corroborated by both experimental and computational analyses that explained the formation of a selenium rich SnSxSe2-x phase from a single molecular precursor containing both Sn-Se and Sn-S bonds.

Cyclic voltammetry electrodeposition of self-standing Ni–Fe–Sn ternary alloys for accelerating alkaline hydrogen evolution

Designing cost-effective and high-efficiency non-noble electrocatalysts for the hydrogen evolution reaction (HER) remains a significant challenge for electrochemical water splitting to store clean and renewable energy. Herein, we have developed Ni–Fe–Sn electrocatalysts grown on Ni foam (Ni–Fe–Sn@NF) for the HER through a simple and facile synthetic route of cyclic voltammetry electrodeposition. The optimized Ni–Fe–Sn electrocatalysts possess excellent electrocatalysis toward hydrogen evolution with a low overpotential of 103 mV at a current density of 10 mA cm−2, together with a small Tafel slope value of 97.4 mV·dec−1 in 1 M KOH. The electrocatalyst also features excellent stability even after 2000 cycles and strong durability after 50 h under alkaline condition. The high HER performance can be attributed to the moderately optimized electronic structure of the Ni, Fe, and Sn center and bind-free nature of the electrode, which facilitates electron transfer and speeds up reaction kinetics. Moreover, the improved electrochemical surface area also enhances the performance on hydrogen production. This strategy presents a facile and simple tactic for the synthesis of noble-metal-free electrocatalysts with excellent HER performance.

Tin(IV) Halides Zero-dimensional based Inorganic-Organic Hybrid Materials: Crystal Structures and Hirshfeld Surface Analysis

Two tetramethylguanidinium halostannate inorganic-organic hybrid compounds was isolated and structurally investigated by single crystal X-ray crystallography and Hirshfeld surface analysis. The compound [(C6H14N3)2SnCl6] (1), crystallizes in the orthorhombic space group Fddd with Z = 8 / Z’ = 0.25, a = 7.3474(3) Å, b = 22.3678(8) Å, c = 28.4908(10) Å and V = 4682.3(3) Å3. The compound [(C6H14N3)2SnBr6] (2), crystallizes in the orthorhombic space group Fddd with Z = 8 / Z’ = 0.25, a = 7.5767(5) Å, b = 23.0591(17) Å, c = 29.008(2) Å and V = 5068.0(6) Å3. The isolation of 1 undergoes a redox process from Sn(II) to Sn(IV) in solution and in a non-controlled atmosphere. Both compounds 1 and 2 describe TMG+ ions with a central carbon atom in a trigonal–planar fashion. With respect to this CN3 plane, the pairs of di­methyl­ammonium groups are twisted by 13.70 (8) and 32.21 (8)° for 1, 14.88 (13) and 31.95(13)° for 2. The SnX6 dianions evidence a slightly distorted octahedron (Oh) about Sn centre for hybrids 1 and 2. Within the structures of the hybrid materials 1 and 2, N-H···Cl inter-species hydrogen bonding patterns between the inorganic stannate and the organic entities give rise a one-dimensional chain, wherein inorganic and organic species alternate. The propagation of the chain generates rings. The weak C-H···X hydrogen bonds formed from the methyl groups to adjacent tetramethylguanidinium-stannate chains result in a supramolecular three-dimensional hydrogen-bonded network. The Hirshfeld surface analysis shows existence of both strong and weak hydrogen bonding interactions. Inspection of 1 and 2 by the Hirshfeld surface analysis, show isostructural behavior. Hybrids 1 and 2 are the first crystal reports of a tetramethylguanidinium tetra- or hexa-halostannate.