Three-dimensional Supramolecular Network Research Articles

Synthesis of 3-D co(II)-oxonate colorimetric probe for selective detection of isopropanol, Co2+, and MnO4 –

A coordination polymer (CP) based on Co(II), {[Co(Ox)(H2O)3] · 2H2O} n (KA@CP2_ARS), has been synthesized using 1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene (Timb) and potassium oxonate (OxK) at room temperature which was examined by single-crystal X-ray diffraction. KA@CP2_ARS contains a one-dimensional (1-D) helical chain that is extended through hydrogen-bonding interactions to form two-dimensional (2-D) and three-dimensional (3-D) supramolecular networks. KA@CP2_ARS demonstrates highly selective luminescent performance for IPA, Co2+, MnO4 –, and uric acid with detection limits of 0.214, 0.16, 0.076, and 0.65 ppm, respectively, among the screened analytes. KA@CP2_ARS displays strong photocatalytic activities for degrading 88.6% of methyl violet dye under ultraviolet irradiation.

Synthesis, crystal structure and characterization of two new cobalt(II) metal–organic frameworks with 1,4-bis((1h-imidazol-1-yl)methyl) benzene and 1,3,5-tris[(1h-imidazol-1-yl)methyl]benzene ligands

Two novel CoII metal–organic frameworks {[Co(BIMB)2(H2O)2](SO4)·EG·3 H2O}n (I) and {[Co(TIMB)2](SiF6)}n (II) were hydrothermally synthesized by corresponding metal salt with organic ligands 1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene (TIMB) or 1,4-bis((1H-imidazol-1-yl)methyl)benzene (BIMB). Crystal structural analysis reveals that they exhibit varied structures. Compound I contains two crystallographically unique CoII centers, each lying on an inversion center and having a slightly distorted octahedral environment. The BIMB ligands link the CoII cations to generate a three-dimensional porous framework with a 4-connected uninodal (65.8) topology. Compound II exhibits a two-dimensional sheeted metal-organic structure running parallel to the (0 0 1) plane, in which TIMB ligands join Co2+ centers having a six-coordinated octahedral structure. In the solid state, adjacent sheets are further bridged by guest SiF6 - anions via C–H…F hydrogen-bonding interactions, giving rise to a three-dimensional supramolecular network structure with a 2-nodal (3-c)2(6-c) net. The topological analysis suggests that the point Schläfli symbol of compound II is (43)2(46.66.83). In addition, their thermal stabilities have also been investigated.

Bifurcated Polymorphic Transition and Thermochromic Fluorescence of a Molecular Crystal Involving Three-Dimensional Supramolecular Gear Rotation.

The ability of molecules to move and rearrange in the solid state accounts for the polymorphic transition and stimuli-responsive properties of molecular crystals. However, how the crystal structure determines the molecular motion ability remains poorly understood. Here, we report that a three-dimensional (3D) supramolecular gear network in the green-emissive polymorph 1G of a dialkylamino-substituted anthracene-pentiptycene π-system (1) enables an unusual bifurcated polymorphic transition into a yellow-emissive polymorph (1Y) and a new green-emissive polymorph (1G*) via 3D correlated supramolecular rotation. The 90° forward correlated rotation causes the molecular conformation between the octyl and the anthracene units to change from syn to anti, the ladder-like supramolecular columns to constrict, and the gear network to disengage. This cooperative molecular motion is marked by the gradual formation of an intermediate state (1I) across the entire crystal from 170 to 230 °C, which then undergoes bifurcated (forward or backward rotation) and irreversible transitions to form polymorphs 1Y and 1G* at 230-235 °C. Notably, 1G* is similar to 1G but lacks gear engagement, preventing its transformation into 1Y. Nevertheless, 1G can be restored by grinding 1Y or 1G* or fuming with dichloromethane (DCM) vapor. This work illustrates the correlation between the crystal structure and solid-state molecular motion behavior and demonstrates how a 3D molecular gear system efficiently transmits thermal energy to drive the polymorphic transition and induce fluorochromism through significant conformational and packing changes.

Hydrogen-bonding interactions in 5-fluorocytosine-urea (2/1), 5-fluorocytosine-5-fluorocytosinium 3,5-dinitrosalicylate-water (2/1/1) and 2-amino-4-chloro-6-methylpyrimidine-6-chloronicotinic acid (1/1).

Three new compounds, namely, 5-fluorocytosine-urea (2/1), 2C4H4FN3O·CH4N2O, (I), 5-fluorocytosine-5-fluorocytosinium 3,5-dinitrosalicylate-water (2/1/1), 2C4H4FN3O·C4H5FN3O+·C7H2N2O7-·H2O, (II), and 2-amino-4-chloro-6-methylpyrimidine-6-chloronicotinic acid (1/1), C6H4ClNO2·C5H6ClN3, (III), have been synthesized and characterized by single-crystal X-ray diffraction. In compound (I), 5-fluorocytosine (5FC) molecules A and B form two different homosynthons [R22(8) ring motif], one formed via N-H...O hydrogen bonds and the second via N-H...N hydrogen bonds. In addition to this interaction, a sequence of fused-ring motifs [R21(6), R33(8), R22(8), R43(10) and R22(8)] are formed, generating a supramolecular ladder-like hydrogen-bonded pattern. In compound (II), 5FC and 5-fluorocytosinium are linked by triple hydrogen bonds, generating two fused-ring motifs [R22(8)]. The neutral 5FC and protonated 5-fluorocytosinum cation form a dimeric synthon [R22(8) ring motif] via N-H...O and N-H...N hydrogen bonds. On either side of the dimeric synthon, the neutral 5FC, 5-fluorocytosinium cation, 3,5-dinitrosalicylate anion and water molecule are hydrogen bonded through N-H...O, N-H...N, N-H...OW and OW-HW...O hydrogen bonds, forming a large ring motif [R1010(56)], leading to a three-dimensional supramolecular network. In compound (III), 2-amino-4-chloro-6-methylpyrimidine (ACP) interacts with the carboxylic acid group of 6-chloronicotinic acid via N-H...O and O-H...O hydrogen bonds, generating an R22(8) primary ring motif. Furthermore, the ACP molecules form a base pair via N-H...N hydrogen bonds. The primary motif and base pair combine to form tetrameric units, which are further connected by Cl...Cl interactions. In addition to this hydrogen-bonding interaction, compounds (I) and (III) are further enriched by π-π stacking interactions.

Synthesis and crystal structure of N 1,N 2-dimethylethanedihydrazide

The title compound, N 1,N 2-dimethylethanedihydrazide, C4H10N4O2, was obtained by the methylation of oxalyl dihydrazide protected with phthalimide. The molecule is essentially non-planar with a dihedral angle between the two planar hydrazide fragments of 86.5 (2)°. This geometry contributes to the formation of a multi-contact three-dimensional supramolecular network via C—H...O, N—H...O and N—H...N hydrogen bonds.

Synthesis, Structural Characterization and Hirshfeld Surface Analysis of a Novel Cd(II) Coordination Polymer with Mixed N- and O-donor Linker

In the present study, we report the room temperature synthesis of a novel two-dimensional (2D) coordination polymer (CP) having the formula {[Cd(H-PCA)2(H2O)].0.5(H2O).0.5(CH3OH)}n (CP1), where H-PCA represents 4-pyrazolecarboxylate. The synthesis of CP1 was achieved through a one-pot reaction, involving the self-assembly of Cd(OAc)2·2H2O and the multitopic mixed N- and O-donor ligand, 4-pyrazolecarboxylic acid (H2-PCA), in methanol. This method demonstrated high yield and purity, enabling the facile production of multigram quantities of CP1 within a short timeframe. Notably, the synthetic procedure selectively deprotonates the carboxylic acid group while retaining the pyrazole moiety in its protonated form.CP1 has been thoroughly characterized using various analytical techniques, including single-crystal X-ray diffraction, FTIR spectroscopy, elemental analysis, scanning electron microscopy, thermogravimetric analysis, and powder X-ray diffraction. The structural analysis revealed that CP1 features a 3, 5-connected binodal net with the point symbol {4.5.6}{4.55.63.7}, leading to a unique –ths net topology. Through hydrogen bonding connections between adjacent 2D sheets, CP1 further extends into a three-dimensional (3D) supramolecular network due to the presence of coordinated water molecules and the protonated pyrazole group. Additionally, a 3D Hirshfeld Surface analysis accompanied by quantitative 2D fingerprint plots was also investigated to explore the intermolecular interactions.

Exploring the structure–property relationship of ethylenediammonium hydrogen phosphite: Insights from XRD, vibrational, DFT, and biological evaluation

The interaction between the molecules of phosphonic acid (H2P(H)O3) and ethylenediamine (NH2CH2CH2NH2) reacts in an aqueous solution and results in the formation of salt molecules with two NH∙∙∙O hydrogen bonds. The calculated stabilization energy of the 1:1 salt molecule, which represents the strength of the two NH∙∙∙O hydrogen bonds, is 8.063 kcal/mol (33.735 kJ/mol). The title compound crystallizes in the centrosymmetric space group Pbca of the orthorhombic system with eight molecules per unit cell. The three-dimensional supramolecular network is formed by hydrogen bonds between every hydrogen atom in both of the NH3+ groups of the ethylenediammonium cation. Hirshfeld surfaces and two-dimensional fingerprint plots were used to analyze the interactions of ethylenediammonium cations and hydrogen phosphite anions forming a three-dimensional supramolecular structure. Practically, two types of interactions, i.e. NH∙∙∙O and H∙∙∙H, are observed for both building units, ethylenediammonium cation and the hydrogen phosphite anion, which cover 100 % of the HS surface of each unit. Density functional theory (DFT) computations of normal mode force constants and structure optimizations were employed to evaluate the molecular structure, fundamental vibrational frequencies, and vibrational band intensities. The utilization of potential energy distribution (PED) allowed for the determination of comprehensive vibrational assignments for the wave numbers. The interactions involving the charge transfers of the supramolecular unit are explained by the computed HOMO and LUMO energy gap of 5.193 eV. To prove that the EDHP has stabilized, NBO analysis has been done. NBO studies establish that strong intra and intermolecular stabilization exists between the ethylenediammonium cation and the hydrogen phosphite anion. Furthermore, to investigate the synthetic chemical EDHP as a possible drug candidate, molecular docking studies and drug-likeness evaluation have been carried out. The best binding energy of the obtained cluster is −3.85 kcal/mol. The rmsd value is found to be 1.950 (≤2 Å) which is fairly good and confirms the best superimposed docked pose. Thus Molecular docking studies reveal that EDHP molecule has a substantial binding affinity for the SARS-CoV-2 protein and can serve as a promising drug candidate. The bioavailability score of 0.55 from pharmacokinetics study suggests that EDHP may have moderate bioavailability.

A blue emission of zirconium (IV) complex based on 2, 6-pyridinedicarboxylic acid ligand: Syntheses, crystal structure, and luminescence sensing

A novel blue emission of zirconium complex, formulated as [Zr(pydc)3]·[(CH3)2NH2]2 (1), has been synthesized by using a mixture of zirconium nitrate and 2, 6-pyridinedicarboxylic acid (H2pydc). The complex 1 presents a three-dimensional supramolecular network structure due to the intermolecular NH···O, OH···O hydrogen bonds. Additionally, the crystals of 1 exhibit blue luminescence and demonstrate a highly selective and sensitive sensing capability for detection of Co2+ ions with a Ksv value of 1.22 × 104 M−1 and limit of detection (LOD) of 1.20 × 10−5 M. Furthermore, the fluorescence lifetime and quantum yield of the complex 1 is τ = 6.22 μs and Φ = 25.9 %.

Synthesis, crystal structure study, thermal, Hirshfeld surface, optical and photoluminescence properties of new organic-inorganic hybrid material: (C6H5CH2N(C2H5)3)[Cd3Cl7

This work describes a new two-dimensional chlorocadmate (II) compound formulated us (C6H5CH2N(C2H5)3)[Cd3Cl7] has been synthesized by slow evaporation method at room temperature and characterized by single-crystal X-ray diffraction. Structural analysis reveals that this compound crystallizes in the triclinic system with centrosymetric P−1 space group. The molecular arrangement of the crystal displays a two-dimensional (2D) structure which consist in one (C6H5CH2N(C2H5)3)+cation and one anionic layers [Cd3Cl7]‒. The various components are interconnected through non-classical C–H…Cl hydrogen bonds, Coulombic attractions, and van der Waals interactions, which collectively secure the unity and stability of the crystal arrangement. This interaction ensemble contributes to the formation of a three-dimensional (3D) supramolecular network. The examination of the crystal structure provides a new interesting example of covalent polymeric layers of [Cd3Cl7]n. The intermolecular interactions were identified using Hirshfeld surfaces as well 2D-fingerprint plots. Furthermore, Infrared (IR) spectrum was analyzed, confirming the presence of the organic cation. Thermogravimetric analysis (TGA) reveals that the studied compound remains stable up to 266 °C. DSC thermogram shows that it undergoes two endothermic anomalies around 79.6 °C and 139 °C. Diffuse reflectance spectra (DRS) method was used to study the optical properties and shows that there is a strong absorption in the UV region for Cd hybrid. Kubelka–Munk equation has been used to calculate the band gap energy indicating that the material is a direct type (4.25 eV). Photoluminescence spectroscopy (PL) proves that the title material was well structured.

Combined Experimental and Computational Study of V-Substituted Lindqvist Polyoxotungstate: Screening by Docking for Potential Antidiabetic Activity.

In the current work, a novel vanadotungstate compound, (C6H9N2)4[V2W4O19]·2H2O (1), is isolated by a simple stepwise synthesis method and characterized by a combined experimental and computational study. Molecular docking is conducted for the first time for this kind of substituted Lindqvist polyoxometalates to elucidate for potential antidiabetic activity. Hence, the modeling results revealed a significant docking score of the reported compound to bind to the active sites of α-glucosidase with the lowest binding energy of -5.7 kcal/mol, where the standard drug acarbose (ACB) had -4.6 kcal/mol binding energy. The stability of binding was enhanced by strong H-bonding, van der Waals, and electrostatic interactions occurring in the three-dimensional (3D) supramolecular network of polyanionic vanadotungstate subunits templated with organic moieties as shown by X-ray diffraction and Hirshfeld analyses. Furthermore, density functional theory (DFT) calculations supported with photophysical measurements are also discussed to predict the most chemical and biological reactivity. In this view, the complete description of electronic and biological features of (1) is enhanced by determination of the highest occupied molecular orbital (HOMO)/least unoccupied molecular orbital (LUMO) energy, electronic density, ionization potential, electron affinity, etc. These chemical descriptors, intermolecular interactions, docking score, and binding free energy estimation are essential in understanding the reactivity of this bioactive compound offering potential inhibition of the α-glucosidase enzyme.

Enhanced photocatalytic degradation performance of new and stable 2D/3D Ln-MOFs for tetracycline under visible light

Rational design of lanthanide metal-organic frameworks (Ln-MOFs) with high stability is of great significance for multifunctional applications. Ln-MOFs have attracted extensive attention in the field of photocatalysis due to their large specific surface area and strong visible light efficiency. In this paper, two 2D/3D Ln-MOFs with different spatial configurations have been successfully synthesized under solvothermal conditions, namely [La(HL)(H2O)]n·3H2O (1), [Er(HL)·3/2(H2O)]n·3/2H2O (2), where H4L = 5-(bis(3-carboxybenzyl)amino)isophthalic acid. Their structures were determined by X-ray single crystal diffraction analysis, and further characterized by XRD analysis and IR spectroscopy. The complex 1 shows layered structure, which extends into a three-dimensional (3D) supramolecular network by π-π interactions, the complex 2 exhibit 3D network structures with a Schläfli symbol of 412·63 topologies, respectively. BET test results showed that there were carboxylic acid groups without coordination in the structure of complex 1, with abundant active sites and higher adsorption activity than complex 2, which would promote the effective contact and reaction between the photocatalyst and tetracycline (TC), thus improving the photocatalytic efficiency of complex 1. Under visible light irradiation, complex 1 showed good photocatalytic degradation of TC, and the degradation rate of TC could reach 75.54% under 120 min. This can be attributed to the effective separation of photogenerated electron-hole pairs and adsorption properties of complex 1. This study provides a new idea for MOFs as an efficient photocatalyst to degrade antibiotic pollutants.

A novel Ag3L2 coordination cage derived from a tripodal oxazoline ligand: synthesis, structure and catalysis

Coordination cages have attracted considerable attention recently due to the well-defined cavities and varied potential applications in different fields. In this work, a new tripodal oxazoline-based ligand with C3 symmetry, tris(4-(4,5-dihydrooxazol-2-yl)phenyl)amine (TOPA), was synthesized and employed to constitute coordination cage compounds. By the reaction of TOPA and AgPF6 at room temperature, a novel M3L2-type crystalline coordination cage complex was obtained with the formula of {[Ag3(TOPA)2]·(PF6)3}(1). In this complex, the adjacent two ligands coordinated with three Ag+ ions to form a coordination cage and these cages further generate the three-dimensional (3D) supramolecular networks through noncovalent interactions including hydrogen bond, C-H…π and F…Ag interactions. Moreover, cage complex 1 exhibited good catalytic performance in the cyclopropanation of styrene with methyl 2-diazo-2-(4-methoxyphenyl)acetate.

2-[(E)-(2-carboxybenzylidene) amino] ethan ammonium-like amino acid zwitterions: crystal structure, functional studies and its molecular dynamic simulation study with drug target receptors

The novel synthetic amino acid-like zwitterion containing imine bond ionic compound 2-[(E)-(2-carboxy benzylidene) amino] ethan ammonium salt, C10H12N2O2, was synthesized. Computational functional characterization is now being used to predict novel compounds. Here, we report on a titled combination that has been crystallizing in orthorhombic space group Pcc2 with Z = 4. The zwitterions form centrosymmetric dimers to polymeric supramolecular network via intermolecular N—H… O hydrogen bonds between the carboxylate groups and ammonium ion. The components are linked by ionic (N+–H–O−) and hydrogen bonds (N+–H–O), forming a complex three-dimensional supramolecular network. Further, molecular computational docking characterization study was performed with compound against multi-disease drug target biomolecule of anticancer target molecule of HDAC8 (PDB ID 1T69) receptor and antiviral molecular target protease (PDB ID 6LU7) to evaluate the interaction stability, conformational changes and to get insights into the natural dynamics on different timescales in solution. Highlights The novel zwitter ionic amino acid compound 2-[(E)-(2-carboxybenzylidene) amino] ethan ammonium salt, C10H12N2O2. The crystal structure determined for this compound illustrates the presence of intermolecular ionic N+–H–O− and N+–H–O hydrogen bonds between the carboxylate groups and ammonium ion, which influence the formation of a complex three-dimensional supramolecular polymeric network. Molecular docking studies helps to understand the conformational stability and interaction stability The novel molecule can be considered for anticancer treatment.

Photoactive hourglass-type M{P 4Mo 6} 2 networks for efficient removal of hexavalent chromium

The exploration of high-efficiency photocatalysts to drive the conversion of highly toxic heavy metal hexavalent chromium (Cr(VI)) in wastewater to low-toxic trivalent chromium (Cr(III)) is of great significance for purifying water that contains emerging contaminants. Herein, four hourglass-type phosphomolybdate-based hybrid networks—(H₂bpe)₂[M(H₂O)₃]₂{M[P₄Mo₆O₃₁H₇]₂}·8H₂O <strong>(</strong>M = Mn for <strong>1</strong>, Co for <strong>2</strong>) and (Hbpe)(H₂bpe)Na[M(H₂O)₃]₂{M[P₄Mo₆O₃₁H₇]₂}·9H₂O <strong>(</strong>M = Mn for <strong>3</strong>, Co for <strong>4</strong>; {M[P₄Mo₆O₃₁H₇]₂}⁸⁻ (abbr. M{P₄Mo₆}₂); bpe = 1,2-di(4-pyridyl)ethylene)—were hydrothermally synthesized as heterogeneous photocatalysts for Cr(VI) reduction. A structural analysis showed that the four hybrids <strong>1</strong>–<strong>4</strong> exhibited two-dimensional inorganic sheet-like structures with a 3,6-connected <i>kgd</i> topology built of hourglass phosphomolybdate clusters having different central metal ions, which further interacted with organic bpe cations via abundant hydrogen-bonding interactions to extend the structure to a three-dimensional (3D) supramolecular network. The four hybrids displayed excellent redox properties and wide visible-light absorption. When used as heterogeneous photocatalysts, hybrids <strong>1</strong>–<strong>4</strong> exhibited excellent photocatalytic activity for Cr(VI) reduction under 10 W white light irradiation, with reduction rates of 91% for <strong>1</strong>, 74% for <strong>2</strong>, 90% for <strong>3,</strong> and 71% for <strong>4</strong>, respectively, within 80 min. The Cr(VI) reduction reaction over hybrids <strong>1</strong>–<strong>4</strong> followed the pseudo first-order kinetics model with reaction rate constants <i>k</i> of 0.0237 min⁻¹ for <strong>1</strong>, 0.0143 min⁻¹ for <strong>2</strong>, 0.0221 min⁻¹ for <strong>3</strong> and 0.0134 min⁻¹ for <strong>4</strong>, respectively. The Mn{P₄Mo₆}₂-based hybrids <strong>1</strong> and <strong>3</strong> showed better photocatalytic performance than the Co{P₄Mo₆}₂-based hybrids <strong>2</strong> and <strong>4</strong>, along with excellent recycle stability. This mechanism study shows that the different central metals M in the M{P₄Mo₆}₂ cluster have a considerable impact on photocatalytic performance due to their regulation effect on the electronic structure. This work provides evidence for the important role of the central metal in hourglass-type phosphomolybdate in the regulation of photocatalytic performance, and it brings inspiration for the design of highly efficient photocatalysts based on polyoxometalates.

Preparation, crystal structure, time-dependent density theory and properties of a novel organic-inorganic hybrid up-conversion luminescence tetranuclear complex

A novel up-conversion luminescence tetranuclear sodium complex [Na4(5-(carboxymethyl 2-oxo-propyl) amino isophthalic acid)(H2O)9] is synthesized by a solvothermal reaction, and its crystal structure is determined by single-crystal X-ray diffraction. The title complex crystallizes as a triclinic system with the P [Formula: see text] space group and exists as an isolated tetranuclear complex. Numerous intermolecular hydrogen bonds and van der waals forces form a three-dimensional supramolecular network. Solid-state diffuse reflectance data show that there is a wide optical band gap of 2.91 eV. The solid-state photoluminescence spectrum reveals that the complex shows an up-conversion emission in the blue region of the light spectrum. Time-dependent density functional theory calculations reveal that this emission can be attributed to ligand-to-ligand charge transfer.

Synthesis, crystal structure and proton conductivity of one Cu(II) coordination complex based on 2,2′-bipyridine-4,4′-diphosphonic acid

One proton-conductive Cu(II) coordination complex [Cu(H3L)Cl]n, in which H4L = 2,2′-bipyridine-4,4′-diphosphonic acid, was synthesized under hydrothermal condition. The product was structurally characterized by elemental analyses, infrared spectroscopy, and single-crystal X-ray diffraction analyses. The result of single-crystal X-ray diffraction analyses revealed that along c direction Cu2+ and Cl− atoms are joined together to be one infinite zigzag chain [CuCl]∞+. In b direction, adjacent [CuCl]∞+ chains are linked by [H3L]- ligands to be 2D layer. Along a direction, via hydrogen bonds of exposed phosphonic groups, 2D layers are stacked to be three-dimensional supramolecular network. This complex exhibits good proton conductivities 1.97 × 10−3–4.32 × 10−3 S cm−1 at 100 °C in the relative humidity range 35–98%. Moreover, at room temperature, the PXRD and TG analyses were employed to characterize the complex.

The investigation of two bis(phenoxo)-acetate-bridged binuclear nickel(II) complexes driven by different alcohol solvents

Two solvent-induced bis(phenoxo)-acetate-bridged binuclear Ni(II) complexes, [Ni2(L)(µ-OAc)(CH3OH)] (1) and [Ni2(L)(µ-OAc)(H2O)] (2), were synthesized with a bis(salamo)-like ligand H3L and Ni(OAc)2·4H2O in two different alcohol solvents (methanol and ethanol). Complexes 1 and 2 were described by elemental analyses, single crystal X-ray diffraction, IR spectra, UV–vis spectra and fluorescence spectra. Complexes 1 and 2 have analogous crystal structures, but the non-covalent interactions are distinct. The one-dimensional chain of 1 is formed by π–π interactions, and the three-dimensional supramolecular network structure of 2 is formed by intermolecular hydrogen bonding interactions. In addition, fluorescence experiments indicated that the fluorescence of 1 and 2 undergoe a significant quenching compared to H3L. Intermolecular forces were investigated using Hirshfeld surface analysis. DFT calculations showed that 1 and 2 have high chemical reactivity and low kinetic stability.

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.

Reaction of Bi(NO3)3 with quinoxaline in the presence of HI. Synthesis of 5,6,7,8-tetranitro-1,2,3,4-tetrahydroquinoxaline-2,3-diol by serendipity: Crystal structure, Hirshfeld and optical study of a novel energetic compound

Treatment of an acetone solution of Bi(NO3)3 with quinoxaline (Qx) in the presence of hydroiodic acid produces in moderate yield the crystallographically characterized 1D-polymeric salt-like iodobismutate [(Qx-H+)BiI4]n (1), whose negative charge is balanced by mono-protonated quinoxalinium counterions. The main product is an unusual tetra(nitrated) quinoxaline derivative, namely 5,6,7,8-tetranitro-1,2,3,4-tetrahydroquinoxaline-2,3-diol (2), which was formed accidently under mild reaction conditions. The molecular structure of this organic compound 2 was determined by single-crystal X-ray diffraction and its strong intermolecular interactions giving rise to a supramolecular three-dimensional network were assessed by IR spectroscopy and a Hirshfeld surface analysis. Structural analysis reveals that the crystal structure is supported essentially by O‒H···O and N‒H···O intermolecular hydrogen bonds and additionally stabilized by N‒O···π interactions. The ground-state molecular structure of this novel organic heterocycle has been optimized by DFT calculation. The optical band gap, caused by intramolecular charge transfer (ICT) from the 1,2,3,4-tetrahydroquinoxaline-2,3-diol fragment to the nitro groups, has been estimated to be 2.04 eV. High density, positive heat of formation and very good thermal stability according to thermal analysis by TGA, DTA and DSC characterize tetranitro compound 2 as energetic material.

Polyoxotungstate-based supramolecular complexes as multifunctional electrocatalysts for sensing water contaminants

Electrochemical detection of water contaminants driven by polyoxometalate-based materials provides a promising approach for environmental safety and diseases prevention. Herein, three polyoxotungstate-based supramolecular complexes were synthesized with formulas of [Cd3(H2O)2(trz)6][HSiW12O40]2·17H2O (1), [Cd(imi)6]2[SiW12O40]·24H2O (2), [Himi]4[SiW12O40]·H2O (3), (Htrz ​= ​1-H-1,2,4-triazole; imi ​= ​Imidazole), which were employed as multifunctional sensors for the detection of various contaminants in water. Structural analysis showed that in compound 1, the trinuclear cadmium cluster [Cd3(Htrz)6]6+ links [SiW12O40]4- anion to form a dumbbell-shaped fragment, which interacts with each other via abundant hydrogen bonds to extend the structure into three-dimensional supramolecular network. In compound 2, the windmill-shaped [Cd(imi)6]2+ cations interact with [SiW12O40]4- anion via electrostatic interactions and hydrogen bonding to form 3-D supramolecular structure. Compound 3 displays an ‘inorganic core-organic hell’ hybrid supramolecular structure constructed by [SiW12O40]4- anion cluster and four protonated organic [Himi]+ cations. Three compounds as electrochemical sensors exhibited favorable electrocatalytic activities for the detection of hexavalent chromium Cr(VI), NO2− and H2O2 with remarkable anti-interference capacity. As for the determination of Cr(VI), compound 1 shows the lowest limit of detection (LOD) of 0.86 ​μM and high sensitivity of 39.3 ​μA ​mM−1 among three compounds, which meets the WHO standard for the minimum concentration of Cr(VI) in drinking water (less than 0.962 ​μM). Moreover, the LODs of compound 1 towards NO2− and H2O2 detection are 3.74 ​μM and 1.39 ​μM along with sensitivities of 4.81 ​μA ​mM−1 for NO2− ion and 37.2 ​μA ​mM−1 for H2O2, respectively. This work provides some important insights into the design of efficient POMs-based electrochemical sensors for environmental applications.