Three-dimensional Supramolecular Structure Research Articles

Bis(ethyl-enedi-ammonium) μ-ethyl-enedi-aminetetra-acetato-1κ3 O,N,O':2κ3 O'',N',O'''-bis-[tri-oxidomolybdate(VI)] tetra-hydrate.

The title compound, (C2H10N2)2[(C10H12N2O8)(MoO3)2]·4H2O, which crystallizes in the monoclinic C2/c space group, was obtained by mixing molybdenum oxide, ethyl-enedi-amine and ethyl-enedi-amine-tetra-acetic acid (H4edta) in a 2:4:1 ratio. The complex anion contains two MoO3 units bridged by an edta4- anion. The midpoint of the central C-C bond of the edta4- anion is located on a crystallographic inversion centre. The independent Mo atom is tridentately coordin-ated by a nitro-gen atom and two carboxyl-ate groups of the edta4- ligand, together with the three oxo ligands, producing a distorted octa-hedral coordination environment. In the three-dimensional supra-molecular crystal structure, the dinuclear anions, the organo-ammonium counter-ions and the solvent water mol-ecules are linked by N-H⋯Ow, N-H⋯Oedta and O-H⋯O hydrogen bonds.

Metal-induced assembly of two novel MOFs: sensitive fluorescence sensing properties and insights into mechanisms

Two new MOFs, namely, [Pb2(2-CPP)2(H2N-bpdc)]n (1) and [Cd(3-CPP)2]n (2), have been prepared by using N- and O-donor ligands and metal ions Pb2+, Cd2+ under hydrothermal conditions. The single-crystal X-ray diffraction analysis was used to measure the crystal structure. The complex 1 is one-dimensional chain structures, and it can further form two-dimensional and three-dimensional supramolecular structures through π-π stacking. The complex 2 is a two-dimensional layered structure, which can form three-dimensional supramolecular structure through π-π interaction. The synthesized MOFs exhibit ligand-based luminescence, which can be attributed to the coordination effect. Due to its excellent fluorescence properties, complex 2 can be used for selective and sensitive detection of nitro aromatic compounds (NAC) and metal ions. The results show that the complex 2 could quickly detect Cr2O72−, nitrobenzene and Fe3+ by fluorescence quenching, and had good anti-interference and cycle stability, so it was a potential chemical fluorescence sensing material. The identification mechanism of 2 is discussed by electron transfer analysis method and density functional theory (DFT) calculation.

Two new Zn(ii) coordination polymers incorporating 2-(2,6-dichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline: Synthesis and structure

Abstract Based on phenanthroline derivate ligand and Zn(ii), two novel coordination polymers, namely [Zn(L)(hta)] n (1) and {[Zn2(L)2(dhb)2]·H2O} n (2) (L = 2-(2,6-dichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, H2hta = heptanedioic acid, and H2dhb = 3,5-dinitro-2-hydroxybenzoic acid), have been synthesized under the hydrothermal condition. For 1, each hta anion bridges two Zn(ii) atoms in a tridentate mode to shape into a chain structure and through different π–π stacking interactions to form a three-dimensional supramolecular structure. The L ligand of 2 connects two neighbouring Zn(ii) atoms to give a 1D chain, which is further extended into the 2D supramolecular layer.

A new type Co(II)-based photocatalyst for the nitrofurantoin antibiotic degradation

Coordination polymers (CPs) are a special class of multidimensional materials that can be employed for the photocatalytic degradation of antibiotics in wastewater. In this paper, a new Co(II)-based coordination polymer with the molecular formula {[Co(H2L)(dpa)(H2O)]·H2O}n (1), (H4L = 1,1′:2′,1″-triphenyltetracarboxylic acid, dpa = 1,2-di(pyridin-4-yl)diazene) was synthesized and characterized. Single-crystal x-ray diffraction results showed that 1 formed a 2D layered structure, which was stacked into a three-dimensional (3D) supramolecular structure through hydrogen-bonding interactions. In addition, the results of the photocatalytic experiments showed that 1 possesses good photocatalytic activity at nitrofurantoin (NFT). The photocatalytic mechanism has been discussed in detail.

Experimental and theoretical studies of trinuclear cadmium(II) complex containing pyridine ring: Synthesis, crystallographic, spectroscopic, TD/DFT calculations and Hirshfeld surface analysis

Two three-dimensional supramolecular structures of L and [Cd3L2(CH3OH)4Cl6] complex (L = 2-(6-bromopyridin-2-yl)-4-methyl-1,2-dihydroquinazoline-N3-oxide), were synthesized and characterized by X-ray crystallography and elemental analysis, as well as FT-IR, UV–Vis, and fluorescence spectroscopy. The photoluminescence behavior of the Cd(II) complex was also investigated in different solvents. X-ray diffraction analysis results revealed that the Cd(II) complex was a trinuclear hexa-coordinate structure and made up of two L, three Cd2+ metal central, four methanol and six chlorine ions. In the crystal structures, it was noteworthy that L formed an infinite 1-D chain-like, 2-D square structure, parallelogram 3-D supramolecular skeleton, whereas the Cd(II) complex formed an infinite 1-D chain-like, 2-D ladder-like configuration, and even expanding into 3-D grid-like supramolecular frameworks. Density functional theory (DFT) calculation was used to compute the optimization, molecular frontier orbital energies (HOMO and LUMO). Specifically, owing to the combination of metal orbitals and the ligand, the energy gap of the complex was less than L. Electrostatic potential (ESP) was used to analyze the reaction sites of two compounds. On the basis of optimized geometry, time-dependent DFT (TD-DFT) simulated the electronic transitions rationalized the UV–Vis spectra peaks of L and Cd(II) complex. In addition, some non-covalent interactions were quantified by Hirshfeld surface and analyzed by Interaction region indicator (IRI).

Comprehensive insights of a Salamo-like Oligo(N,O-donor) ligand and its self-assembled di-nuclear Mn(III) and tetra-nuclear Cd(II) complexes

The self-assembled di-nuclear Mn(III) & tetra-nuclear Cd(II) salamo-like oligo(N,O-donor) complexes, [Mn2(L)2(CH3OH)2]·4CH3OH (1) and [Cd4(L)2(η-OAc)2(CH3OH)2] (2) have been constructed successfully applying the measure of solvent evaporation and characterized structurally by X-ray diffraction analyses of single crystal, IR & UV visible analyses. The single crystals of the salamo-like oligo(N,O-donor) compound H3L have been obtained by wet-chemical technique, its established structure is H3L∙CH3OH. The structure of complex 1 is centrally symmetrical, and both Mn(III) atoms are hexa-coordination and have slightly distorted octahedral geometries. There are two sets of intermolecular H-bonding interactions which are connected with adjacent units of the Mn(III) complexes and form a two-dimensional network structure. For the complex 2, all of the Cd(II) atoms are also hexa-coordination and possess slightly twisted octahedral configurations. And five groups of intermolecular H-bonding interactions form a honeycomb shaped three-dimensional supramolecular structure. Additionally, the intermolecular interactions of H3L, complexes 1 and 2 have been quantified by Hirshfeld surface analysis for further study. Fluorescence emission spectra of H3L, complexes 1 and 2 were also investigated.

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.

One-pot synthesis, structural investigation, antitumor activity and molecular docking approach of two decavanadate compounds

Two bases-decavanadates coordination compounds [(C6H13N4)2][Mg(H2O)6]2[O28V10].6H2O (1) and [(C7H11N2)4][Mg(H2O)6][O28V10].4H2O (2) have been synthesized and well characterized using vibrational spectroscopy (infrared), UV–Visible analysis and single crystal X-ray diffraction technique. The formula unit, for both compounds, is composed by the decavanadate [V10O28]6−, hydrated magnesium ion, a counter anion and free water molecules. The transition metal adopts octahedral geometries in both compound (1) and (2). The existence of a multitude of hydrogen bonding interactions for both compounds provides a stable three-dimensional supramolecular structure. Optical absorption reveals a band gap energy indicating the semi-conductive nature of the compound. In this study, the cytotoxic and the anti-proliferative activities of compounds (1) and (2) on human cancer cells (U87 and MDA-MB-231) were investigated. Both compounds demonstrated dose-dependent anti-proliferative activity on U87 and MDA-MB-231 with respective IC50 values of 0.82 and 0.31 μM and 1.4 and 1.75 μM. These data provide evidence on the potential anticancer activity of [(C6H13N4)2][Mg(H2O)6]2[O28V10].6H2O and [(C7H11N2)4][Mg(H2O)2][O28V10].4H2O. Molecular docking of the compounds was also examined. Molecular docking studies were performed for both compounds against four target receptors and revealed better binding affinity with these targets in comparison to Cisplatin. Moreover, molecular docking investigations suggest that these compounds may function as potential inhibitors of proteins in brain and breast cells, exhibiting greater efficiency compared to Cisplatin.

Effect of Auxiliary Ligands on the Architectures of Manganese Complexes Constructed by N-Heterocyclic Ligands: Syntheses, Structures, and Properties

Two manganese complexes based on N-heterocyclic ligands, [Mn(bqdca)(2,2'-bipy)(H2O)2]n (1), Mn0.5(4,4'-bipy) (H2O)2?0.5bqdca?2H2O (2) (H2bqdca = 2, 2'-biquinoline-4, 4'-dicarboxylic acid, 2, 2'-bipy = 2, 2'-bipyridine, 4, 4'-bipy = 4, 4'-bipyridine), have been synthesized by hydrothermal methods based on Pearson?s acid-base theory and structurally characterized. In Complex 1, the Mn ions are bridged by bqdca2- anions to form one-dimensional chains, which are further linked by hydrogen bonds to generate a two-dimensional layered structure. In Complex 2, each Mn ion was coordinated by 4, 4'-bipy and water molecules to generate a mononuclear structure accompanied by bqdca2- anion balancing valences. The intermolecular hydrogen bonds can link them to construct a three-dimensional supramolecular structure. The different structures of Complexes 1 and 2 illustrate the great influence of the N-heterocyclic auxiliary ligands on the self-assembly of coordination architectures. 2,2'- bipy and 4,4'-bipy ligands all act as terminal ligands. In addition, Complexes 1 and 2 exhibit the photoluminescent emission at 455 nm and 463 nm, and 455 nm and 465 nm in the solid state, respectively, which may be attributed to intraligand transitions. The redshifts of Complexes 1 and 2 may be due to the ligand-to-metal charge transfer, comparing to the H2bqdca ligand.. KEYWORDS :Crystal structure, Manganese complex, N-Heterocyclic ligand, Photoluminesce.

A Eu coordination polymer sensor for the detection of tartrazine, folic acid, and amino acids

In this work, 3-(2,4-dicarboxyphenyl)-6-carboxypyridine (H2ppda) and 4-(4-carboxyphenyl)benzoic acid (H2bpdc) were selected to synthesize a two-dimensional layered coordination polymer, [Eu(ppda)(bpdc)0.5(C2H5OH)(H2O)]n (Eu-1). Eu-1 is further hydrogen-bonded to construct a three-dimensional supramolecular structure. It has found that Eu-1 can be used as an excellent fluorescence sensor for the determination of food additives, such as tartrazine (TA), folic acid (FA), arginine (Arg), and lysine (Lys). Eu-1 showed high sensitivity, selectivity, recyclability, and anti-interference for the detection of TA, FA, Arg, and Lys in aqueous solution. The limits of detection TA, FA, Arg, and Lys are 9.87 × 10-8 M, 3.28 × 10−8 M, 2.20 × 10-6 M, and 9.46 × 10-7 M, respectively. Notably, it is the first example of luminescent coordination polymer to identify TA in aqueous system. In the meantime, a film utilizing Eu-1 as the key component had been successfully fabricated, and exhibited a remarkable potential for the visual recognition of TA and FA. In addition, the luminescence sensing mechanisms of Eu-1 on the above analytes were investigated further in detail.

A Metal-Free Helical Covalent Inorganic Polymer: Preparation, Crystal Structure and Optical Properties.

Helical morphologies are widely observed in nature, however, it is very challenging to prepare artificial helical polymers. Especially, precisely understanding the structure information of artificial metal-free helical covalent inorganic polymers via single-crystal X-ray diffraction (SCXRD) analysis is rarely explored. Here, we successfully prepare a novel metal-free helical covalent inorganic polymer ({[Te(C6 H5 )2 ] [PO3 (OH)]}n , named CityU-10) by introducing angular anions (HOPO3 2- ) into traditional tellurium-oxygen chains. The dynamic reversibility of the reaction is realized through the introduction of organic tellurium precursor and the slow hydrolysis of polyphosphoric acid. High-quality and large-size single crystals of CityU-10 have been successfully characterized via SCXRD, where the same-handed helical inorganic polymer chains form a pseudo-two-dimensional layer via multiple hydrogen-bonding interactions. The left-handed layers and right-handed layers alternatively stack together through weak hydrogen bonds to form a three-dimensional supramolecular structure. The single crystals of CityU-10 are found to display promising optical properties with a large birefringence. Our results would offer new guidelines for designing and preparing new crystalline covalent polymers through tellurium-based chemistry.

Comparing organic and metallo-organic hydrazone molecular cages as potential carriers for doxorubicin delivery.

Molecular cages are three-dimensional supramolecular structures that completely wrap guest molecules by encapsulation. We describe a rare comparative study between a metallo-organic cage and a fully organic analogous system, obtained by hydrazone bond formation self-assembly. Both cages are able to encapsulate the anticancer drug doxorubicin, with the organic cage forming a 1 : 1 inclusion complex with μM affinity, whereas the metallo-organic host experiences disassembly by interaction with the drug. Stability experiments reveal that the ligands of the metallo-organic cage are displaced in buffer at neutral, acidic, and basic pH, while the organic cage only disassembles under acidic conditions. Notably, the organic cage also shows minimal cell toxicity, even at high doses, whilst the doxorubicin-cage complex shows in vitro anti-cancer activity. Collectively, these results show that the attributes of the pure organic molecular cage are suitable for the future challenges of in vivo drug delivery using molecular cages.

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.

Hydrothermal syntheses of d10-based Zn(II) and Cd(II) metal–organic frameworks for the catalysis of the Knoevenagel condensation

Metal–organic frameworks (MOFs) are compounds that feature metal clusters coordinated with organic ligands, forming impressive structures and properties. In this study, two MOFs of Zn(II) and Cd(II) were synthesized using the organic compound 5‑hydroxy-2-pyrazinecarboxylic acid, forming Zn-MOF and Cd-MOF. To better understand the intricate structures of these MOFs, single-crystal X-ray crystallography was used to characterize their respective structures. The results showed that both MOFs have complex three-dimensional supramolecular structures that are highly symmetric and contain water molecules. Additionally, topological analysis of the MOFs indicated that they have a zeolite-like structure. The Hirshfeld surfaces analysis revealed that both crystal structures could preferentially interact with other molecules through hydrogen bonds. The MOFs were found to have a direct band gap, with the energy observed to be 2.44 and 2.71 eV for the Zn-MOF and Cd-MOF systems, respectively. The hydrogen bond formation ability of the MOFs, in combination with their low band gap energy, make them highly suitable for use in the Knoevenagel condensation reaction in water. Overall, the results of this study provide important insights into the unique properties and potential applications of MOFs in diverse fields.

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 %.

An efficient Cu(II)-based MOF as electrocatalyst for oxygen reduction reaction

We have synthesized a new Cu(II)-based MOF, thatshows atwo-dimensional structure which is linked throughelaborate H-bonding interactions resultingin a three-dimensional supramolecular structure. Cyclic voltametricstudies demonstrate good electrocatalytic behaviorwith lowering the onset potential to 0.56 V. From LSV, the catalyst was found to produce high polarization current density at 0.1 V/s scan rate. The reported Cu-MOF represents an excellent Platinum group metalfree electrocatalyst that exhibits an outstanding and stable electrocatalytic activity toward 4e-reduction of O2, facilitates the catalytic process in the fuel cell in a cost-effective manner and can play a vital role in ORR.

Syntheses, structures and luminescent properties of five new Ag(I)-based coordination polymers

In this work, five Ag(I)-based coordination polymers (CPs), namely, [Ag(HL)(H2L)]n (1), [Ag(HL)(2,2′-bpy)(H2O)0.5] (2), [Ag(HL)(phen)(H2O)0.5] (3), {[Ag2(HL)2(4,4′-bpy)(H2O)2]∙H2O} (4) and [Ag(HL)(thpy)]n (5), were synthesized under hydrothermal conditions (H2L = 1-(3-carboxybenzyl)-1H-pyrazole-4-carboxylic acid, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, 4,4′-bpy = 4,4′-bipyridine and thpy = 2-(2-thienyl)pyridine). These coordination polymers were characterized by single-crystal X-ray diffraction, elemental analyses, infrared spectroscopy, thermogravimetric analyses and powder X-ray diffraction. Compound 1 displays a one-dimensional (1D) chain structure which can be further extended into a three-dimensional (3D) supramolecular structure via intermolecular hydrogen bond. In compounds 2 and 3, the binuclear zero dimensional (0D) units are extended to 3D supramolecular frameworks by intermolecular hydrogen bond and π–π stacking interaction. In compound 4, the 0D units constructed by HL− anions, 4,4′-bpy and metal ions are expanded to form a two-dimensional (2D) supramolecular network. Compound 5 shows a different 2D supramolecular structure extended from 1D chain by intermolecular hydrogen bond. The results suggest that organic ligand plays a key role in the formation of the final structures. The solid-state luminescent properties of compounds 1–5 were studied in detail. The results show that the luminescent color of compounds 1–5 can be tunable by varying excitation wavelengths.

In Situ Oxidation of Pyridyl-Dihydrobenzoimidazoquinazoline and the Synthesis of a Highly Luminescent Cd(II) Coordination Polymer: A Promising Candidate for Mutagenic Nitroaromatic Detection and Device Fabrication.

Pyridyl-substituted imidazoquinoline, a potent fluorescent framework, is advantageous to architect multifunctional coordination networks for sensing and fabricating emergent electrical conductors. In this work, a Cd(II)-based one-dimensional (1D) coordination polymer (1D CP), [Cd(glu)2(pbiq)2(H2O)]n (1), [H2glu = glutaric acid and pbiq = 4-(6-(pyridin-4-yl)benzo[4,5]imidazo[1,2-c]quinazoline)], has been structurally confirmed by single-crystal X-ray crystallography. The H-bonding and π···π interactions built a three-dimensional (3D) supramolecular structure that strongly emits at 416 nm in acetonitrile suspension. Potentially intrusive nitroaromatics (NAs) and trinitrophenol (TNP) selectively quench the strong emission of 1, and the highest quenching is noted in the case of TNP. A detection limit (limit of detection (LOD)) of 1.51 × 10-7 M for TNP is determined. The band gap (3.31 eV) of 1 recognizes semiconducting behavior, and an electronic device is fabricated. The correlation of current vs voltage (I-V plot) reveals a substantial non-ohmic electrical conductivity of 1 (Λ: 1.10 × 10-5 S m-1) along with a low energy barrier (ΦB: 0.69), and the series resistance (Rs) becomes 6.21 kΩ.

Two Proton Conductive Coordination Polymers Constructed by an Unprecedented Structural Transformation of a Phosphine-Based Tricarboxylate Ligand

The phosphine-based tricarboxylate 2-(3,3′-dioxo-1λ5-1,1′-(3H,3′H)-spirobi[2,1-benzoxaphosphol]-1-yl)benzoic acid (L) has been intensely studied due to its unique configuration and readily oxidizable phosphorus center. However, the coordination of L with metals have been largely ignored in the field of coordination polymers (CPs). Herein, we report two CPs, [Zn3(L1)2(dib)2(H2O)]·9H2O (1) and [Cu3(L2)2(dib)2]·3H2O (2) (H3L1 = tris(2-carboxyphenyl)phosphine oxide, H3L2 = 2,2′-phosphinico-dibenzoic acid, dib = 1,4-di(1H-imidazol-1-yl)butane), synthesized based on L. Strikingly, despite the initial use of L, the structures of 1 and 2 reveal that L undergoes two unprecedented in situ structural changes after coordination with the metal ion. In 1, L is transformed to the phosphine oxide derivative L1, while in 2, it is transformed to the phosphinic acid derivative L2. With the aid of the flexible ligand dib, the one-dimensional (1D) chain structure of 1 and three-dimensional (3D) supramolecular structure of 2 were constructed. For 1 and 2, especially in 1, there are abundant hydrogen bonds between the framework and the lattice water molecules, which are conducive to the formation of excellent hydrophilic channels and the transport of protons. Electrochemical experimental results show that 1 and 2 exhibit high proton conductivities (σ) of more than 10–4 S cm–1 over a wide temperature range of 303–353 K and low activation energies (Ea) at 98% relative humidity. Compared with the σ value of the initial ligand L (3.12 × 10–5 S cm–1), the best σ values of 1 and 2 are improved by 28 times and 6 times, respectively, and Ea is also reduced from 0.39 to 0.13 eV for 1 and 0.12 eV for 2. This is the first report of proton-conducting polymers based on a phosphine-based carboxylate ligand, involving two in situ structural transitions of the ligand.

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.