Trigonal Bipyramidal Research Articles

Crystal structure of di-μ-chlorido-bis-{chlorido-[(-)-5,6-pinenebi-pyridine]-cobalt(II)} aqua-dichlorido[(-)-5,6-pinenebi-pyridine]cobalt(II).

The crystal structure of [Co2Cl4(C17H18N2)2][CoCl2(C17H18N2)(H2O)] or [Co(L)Cl(μ-Cl)]2[Co(L)(Cl)2(OH2)], where L is the enanti-opure bidentate ligand (-)-5,6-pinenebi-pyridine (C17H18N2), has been determined. Crystals suitable for X-ray structure analysis were obtained by slow evaporation of an ethano-lic solution containing equimolar amounts of L and CoCl2·6H2O. The CoII cations all have a coordination number of five, and in each case the coordination polyhedron is a trigonal bipyramid. The Co-N bonds lengths range from 2.037 (7) to 2.195 (7) Å, and Co-Cl bonds lengths range from 2.284 (2) to 2.509 (2) Å. The asymmetric unit contains two discrete complexes, one dinuclear and the other mononuclear. Between the two mol-ecules, two types of inter-molecular inter-actions have been evidenced: π-π stackings involving the bi-pyridine units, and O-H⋯Cl hydrogen bonds between the hydrogen atoms of the aqua ligand coordinating to the mononuclear complex and the non-bridging chlorido ligand coordinating to the dinuclear mol-ecule. These inter-actions lead to a two-dimensional supra-molecular arrangement parallel to the ab plane.

Experimental and theoretical approaches on structural, spectroscopic (FT‐IR and UV‐Vis), nonlinear optical, and molecular docking analyses for Zn (II) and Cu (II) complexes of 6‐chloropyridine‐2‐carboxylic acid

AbstractNovel transition metal‐based complexes that may be of value as biological agents and/or nonlinear optical materials, Zn (II) and Cu (II) transition metal complexes of 6‐chloropyridine‐2‐carboxylic acid (LH), were successfully synthesized. The chemical structure of each complex was characterized using X‐ray diffraction (XRD) method and FT‐IR spectroscopy. XRD and FT‐IR demonstrated that L ligand coordinate to central metal ions through the donor N and O atoms. By coordinating two H2O ligand to Zn (II) ion, a distorted octahedral complex geometry was constructed for 1. As for 2, a distorted trigonal bipyramidal coordination geometry was obtained by a H2O ligand coordination to Cu (II) ion. Theoretical studies using B3LYP/6‐311++G(d,p)‐LanL2DZ were performed to further validate the proposed structures. The molecular docking of 1 to SARS‐CoV‐2 main protease (PDB: 6LU7) gives a binding energy of −5.24 kcal/mol and inhibition constant of 144.6 μM, demonstrating that 1 is a more promising candidate to biologically active complexes than 2. The first‐order hyperpolarizability (β) parameter for 1 and 2 was calculated as 0.88 × 10−30 and 10.40 × 10−30 esu, respectively. These β values also demonstrated that 2 exhibits more effective NLO character than 1 due to the electronic configuration and coordination geometry.

Structural diversities in the Zn(II), Mn(II) and Cd(II) coordination polymers induced by metal ions and/or anions

Under the same solvothermal conditions, nine novel coordination polymers (CPs), [Mn(L)(Cl)(H2O)] (1a), [Mn(L)(H2O)2]·(NO3) (2a), [MnL]·(HSO4)·MeCN·2H2O (3a), [Zn(L)2]·H2O (1b), [Zn(L)2] (2b and 3b), [Cd(L)]·Cl (1c), [Cd(L)(NO3)] (2c) and [CdL]·(HSO4)·2.5H2O (3c), were synthesized using a new ligand, namely 4-(2-chloroimidazo[1,2-a]pyridin-3-yl)-[2,4′-bipyridine]-6-carboxylic acid (HL). The Zn(II) CPs 1b-3b are similar 1D chains and their structures were mediated by the trigonal bipyramidal geometry of the Zn(II) cation, not by the counter-anions. However, when using Mn(II) and Cd(II) salts bearing various counter-anions (Cl−, NO3− or SO42−) as reagents, the Mn(II) (1a-3a) or Cd(II) (1c-3c) CPs do reveal different structures, which were induced by different anions acting as either a coordinated anion or a counter-anion for balancing the charge of 1a-3a or 1c-3c. When the larger NO3− anion replaced the Cl− anion, the 1D molecular box chain of 1a with a coordinated Cl− anion was changed to the 2D brickwall-type network of 2a with NO3− only as a counter-anion. However, the NO3− anion still could be coordinated to larger volume of the Cd(II) cation, leading to a 3D framework for 2c. Moreover, CPs 3a and 3c are isostructural, which could be induced by the much larger tetrahedral HSO4− counter-anion. Furthermore, the luminescent properties of the CPs have been investigated. The present work provides a promising approach to design and construct CPs or MOFs by adjusting metal salts bearing various counter-anions.

O,N,S-tris-chelating ligand scaffolds flanked with cyclohexyl or adamantyl substituents anchored with diorganotin(IV) moieties: synthesis, structures and cytotoxicity

The O,N,S-tris-chelating ligand, H2NSCN-N-C(H)ArO− constitutes an attractive scaffold in coordination chemistry and we have expanded this scaffold by installing an alkyl group of different steric hindrance. Thus, the ligand scaffolds containing O,N,S (Ln) differ with respect to the chemical link between the coordinating O atoms, which is either a phenol or a naphthol moiety and carrying a cyclohexyl or a adamantyl groups (L1, phenol and cyclohexyl; L2, naphthol and cyclohexyl; L3, phenol and adamantyl; L4, naphthol and adamantyl). Six novel diorganotin(IV)-Ln compounds 1–6 were synthesized and structurally characterized. The solid-state structures were deduced from single crystal X-ray diffraction data, and revealed the Sn(IV) cations adopting square pyramid (in 2, 3 and 4) or trigonal bipyramid (in 1, 5 and 6) geometries with coordination spheres comprising κ-N,O,S (κ-N,S in 1) ligand chelators and two methyl or phenyl groups (plus a hydrosulfide in 1) co-ligands. Solution state characterizations were achieved by detailed 1H, 13C, 15N and 119Sn NMR analysis including selected 2D experiments. In vitro cytotoxic activities of the compounds were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay against human histiocytic lymphoma U-937 cells. The IC50 values revealed better activities of diphenyltin(IV) compounds 4–6 as compared to the respective pro-ligands and doxorubicin. More importantly, compounds 4–6 demonstrated maximum inhibition in U-937 cells (IC50 = 0.47–0.99 μM), with negligible effect on human peripheral blood mononuclear cells (PBMC). Compounds 4–6 effectively inhibited cell viability event, which was confirmed by detecting cytotoxicity, Live & Dead and Lactate dehydrogenase (LDH) release assays.

Self-assembly synthesis of diorganotin complexes based on arylformylhydrazone possessing ONO donor set: anticancer activity and mechanism.

Fourteen new organotin(IV) complexes were successfully synthesized and characterized by elemental analyses, Fourier transform infrared spectroscopy (FT-IR), multinuclear (1H, 13C, and 119Sn) NMR spectroscopy, high-resolution mass spectrometry (HRMS), and X-ray single-crystal techniques. Crystallographic data showed that the complexes 1b, 2b, 3b, and 5b were macrocyclic compounds, 4b exhibited a one-dimensional spiral chain structure with distorted trigonal bipyramidal geometry, other complexes were centrosymmetric dimers, and there was an Sn2O2 four-membered ring in the middle of the molecule. In-vitro anticancer activity against the three human tumor cell lines NCI-H460, MCF-7, and HepG2 was studied, and the dibutyltin complex 5a is a more potent antitumor agent than other complexes and cisplatin. Cell apoptosis study of 5a with the highest activity on HepG2 cancer cell lines was done by flow cytometry; it was shown that the antitumor activity of 5a was related to apoptosis, and it inhibited proliferation by blocking cells in the G2/M phase. The single-cell gel electrophoresis assay results show that 5a induces DNA damage. 5a interacts with ct-DNA by intercalating the mode of interaction. UV-visible absorption spectrometry, fluorescence competitive, viscosity measurements, and gel electrophoresis results also support the intercalative mode of interaction for 5a with DNA.

Fe1.5V2(PO4)3/C phosphate as a negative electrode material for high-rate performance lithium-ion batteries

A NaSICon-type phosphate Fe1.5V2(PO4)3/C (FVP/C) was successfully prepared and its crystal structure and electrochemical performance as a negative electrode material for lithium-ion batteries (LIBs) were investigated. The material was synthesized via a sol-gel method and calcined at 800 °C under inert atmosphere. The obtained powder crystallized in the triclinic system with P-1 space group. The structure contains two types of dioctahedral edge-sharing V2O10 groups, while distorted Fe(1)O6 octahedra and trigonal bipyramid Fe(2)O5 were evidenced. The electrochemical performance of FVP/C versus Li+/Li were evaluated in 0.01–3.0 V voltage range. FVP/C exhibited a conversion mechanism and showed good reversible capacities at both high and low rates. The discharge capacities of 463, 307 and 311 mAh g−1 were delivered at 1C, 2C, and 5C after 100 cycles. Moreover, the lithiation/delithiation mechanism in FVP/C was evidenced by Operando diffraction using synchrotron radiations and Ex situ XPS spectroscopy, conforming the amorphization of the studied phosphate and revealing that both vanadium and iron are involved in the redox process upon cycling.

Synthesis and Characterization of Solvated Lanthanide Tris(trimethylsilyl)siloxides.

In an effort to develop precursors for the production of lanthanide silicate (LnSiOx) materials, the reactions of [Ln(NR2)3] (R = SiMe3) with three equivalents of tris(trimethylsilyl)silanol (H-OSi(SiMe3)3) or H-SST) in tetrahydrofuran (THF) were undertaken. The products were crystallographically characterized as [Ln(SST)3(THF)2] (where Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu). In general, these compounds are similar to the previously reported [Gd(SST)3(THF)2] complex, where each metal center of the monomeric species is found to adopt a trigonal bipyramidal (TBP; τ = av 0.95) geometry; however, the crystallographic structure solutions for these crystals invoke a much larger unit cell that reveals the complex disorder of the axial THF ligands. Using incompletely washed H-SST, the tetrahedrally (T-4) bound [Ln(SST)3(NEt3)] (Ln-NEt3 = Pr-NEt3, Ho-NEt3; NEt3 = triethylamine) compounds were isolated from the same reaction run in toluene. Rational syntheses of amine derivatives were realized by performing the same reaction with pure H-SST in toluene containing the appropriate amine and [Ln(NR2)3] with the final products identified as [Tm(SST)3(NEt3)] (Tm-NEt3) or [Tm(SST)3(NHPr2i)] (NHPr2i = di-iso-propylamine; Tm-NHPr2i). The products isolated from reactions undertaken in pyridine (py) were identified as [Ln(SST)3(py)2] (Ln-py = Ce-py, Eu-py, and Tm-py). The Ln-py structures exhibit the larger unit cell noted for the THF derivatives with each Ln adopting a TBP (τ = av 0.98) metal center possessing equatorial SST and axial py ligands. The same reaction run in toluene led to the isolation of [(η6-tol)Tm(SST)3] (Tm-tol). Multinuclear NMR (1H and 29Si) data support the retention of the solid-state structures of all of these compounds in solution. Photoluminescent measurements of Tb, Sm, Dy, and Eu were found to display emission and lifetime profiles in the visible range due to f-f transitions, consistent with trivalent lanthanide metal centers.

Indium(III) and organotin(IV) 2-(methoxycarbonyl)benzenethiolates: Synthesis, structure and properties

Two compounds In(mts)3, 1 and triphenyltin(mts), 2 [where mts = 2-(methoxycarbonyl) ben- zenethiolate] were synthesized and characterized. Both the compounds crystallize in the monoclinic system; 1 with space group P21/c and 2 with space group P21/n. Molecule 1 has a distorted trigonal bipyramidal geometry around the In(III) center. In the case of 1, out of the three mts ligands, two bind (S and O) bidentately while the third one binds mainly through its S atom, whereas 2 has a tetrahedral geometry around Sn(IV) center in which the mts ligand is bonded through its S atom only. Hirshfeld analyses were carried out to understand the nature of weak interactions responsible for the deviation from the ideal geometry of both compounds. Quantum chemical calculations were carried out at the DFT level using B3LYP functional in order to get the optimized geometry and vibrational frequencies. Natural bond orbital analyses (NBO) were performed to explore hyper-conjugative interaction energies, HOMO-LUMO, and various inter and intramolecular transitions. The thermodynamic profiles and electrostatic potential surfaces of the compounds have been investigated. Bulk properties such as dielectric loss/constant and AC conductivities have also been explored.

Designing, physiochemical confirmation, evaluation of biological and in-silico potential of Triorganotin(IV) complexes

FTIR, NMR, CHN and single crystal X-ray crystallography were used to validate a series of three new triorganotin(IV) carboxylate complexes, R3Sn(L) for R = Methyl (1), n-Butyl (2) and Phenyl (3), obtained from LH = 4-[(2,5-dimethoxyphenyl)carbamoyl]butanoic acid. The coupling constant and θC-Sn-C values in solution-state NMR data suggest a 5-coordinated environment around the Sn centre. In the crystal of 1, the carboxylate is bidentate bridging leading to a zigzag chain with the Sn centre having a distorted trigonal-bipyramidal geometry. The compounds were evaluated for their interaction with salmon sperm DNA and found that they interact through an intercalative mode resulting in hypochromism and bathochromic shift as confirmed by the UV–visible spectroscopic and viscometric techniques. The findings of anti-microbial activity performed on five bacterial and two fungus strains demonstrate that some of the compounds exhibit >80% inhibition of certain bacteria and >100% inhibition of certain fungal strains. The compounds were also evaluated for cell viability tested on human embryonic kidney cell (HEC-239) and human red blood cells (RBC). The anti-cancer potential of the compounds was assessed using cis-platin as a standard against human malignant glioma U87 (MG-U87) cell lines, and 1 was shown to be the most potent (IC50: 148.979 µM) at a 50 µM dose. The DPPH anti-oxidant activity results revealed a 91% maximum scavenging activity for 1. The compounds follow the principles of drug-likeness and have good bioavailability potential, according to an in silico analysis conducted using the SwissADME webserver.

New Complexes of organotin(IV) and organosilicon(IV) with 2-{(3,4-dimethoxybenzylidene)amino}-benzenethiol: Synthesis, spectral, theoretical, antibacterial, docking studies

New series of dimethyl-, dibutyltin(IV), trimethylsilicon(IV), and phenylsilicon(IV) compounds with bidentate nitrogen and sulphur donor ligands have been synthesized with the 2-{(3,4-dimethoxybenzylidene)amino}-benzenethiol (LH), in molar ratios of 1:1 and 1:2. For structure elucidation, all produced compounds were characterized using IR, UV–vis, elemental analysis, conductance measurements, NMR (1H, 13C, 29Si, 119Sn) spectroscopy techniques. The 2-{(3,4-dimethoxybenzylidene)amino}-benzenethiol behaves as monofunctional bidentates, interacting with the tin and silicon atom via the thiolic-sulphur and azomethine-nitrogen atoms. Compound 1, 3, and 5 have a five-coordinated trigonal bipyramidal geometry surrounding the metal atoms, whereas Compound 2, 4, and 6 have deformed octahedral structures. The optimum geometrical parameters, including bond length, bond angles, HOMO, LUMO, electrophilicity index, chemical hardness, global softness, and mulliken atomic charges, were determined using density functional theory-based methods (DFT). The studied compounds and their ligands were simultaneously evaluated for antibacterial activity in-vitro and compared to streptomycin. The binding affinity of compound with bulky group and hydrogen bond acceptor groups is more in comparision of other compounds. The structure activity relationship revealed that compounds with bulky and hydrogen bond acceptor group will enhance the antibacterial activity agaisnt Staphylococcus aureus.

Synthesis, crystal structures and anticancer activities of Cu(II), Zn(II) and Cd(II) complexes containing bis(2-pyridyl)-di(4-methoxyphenyl)ethene

Three new complexes of Cu(II), Zn(II) and Cd(II) with bis(2-pyridyl)-di(4-methoxyphenyl)ethene (KT1), bis(µ2-chloro)-dichloro-bis(2-(2,2-di(4-methoxyphenyl)-1-(pyridin-2-yl)vinyl)pyridine)-di-copper(II) (CuKT1), dichloro-2-(2,2-di(4-methoxyphenyl)-1-(pyridin-2-yl)vinyl)pyridine-zinc(II) (ZnKT1) and hexakis(µ2-chloro)-dichloro-tetrakis(2-(2,2-di(4-methoxyphenyl)-1-(pyridin-2-yl)vinyl)pyridine)-tetra-cadmium(II) (CdKT1) were synthesized and characterized by IR spectroscopy, 1H NMR spectroscopy and single-crystal X-ray diffraction. The results reveal that ZnKT1 is a mononuclear complex, while CuKT1 and CdKT1 are binuclear and tetranuclear complexes, respectively. The central metal ions are surrounded by two N atoms of bis(2-pyridyl)-di(4-methoxyphenyl)ethene and Cl− ions including pendant and bridged ones. In the ZnKT1 complex, a distorted tetrahedral geometry is formed with Zn(II) as central ion and two chloride ions plus two nitrogen atoms of KT1 as surrounding atoms. CuKT1 is a binuclear complex with two square pyramids formed around the two Cu(II) ions. CdKT1 is a tetranuclear complex with two Cd(II) cations having coordination number six (distorted octahedral geometry) and the other two having coordination number five (distorted trigonal-bipyramidal geometry). The anticancer activity tests on four cancer cell lines, including KB, Hep-G2, Lu and MCF-7, show that ZnKT1 and CuKT1 are active against Hep-G2 and Lu but do not considerably damage KB and MCF-G7. CuKT1 has a considerable effect on two cancer cell lines, Hep-G2 and Lu, with IC50 values of 16(2) and 13(1) μM, respectively. CdKT1 exhibits excellent activity against all four cancer cell lines, with IC50 values ranging from 3.5(2) to 8.8(5) μM, which are lower than those of cisplatin. These complexes exhibit low cytotoxic activity on the normal cell line HEK-293A with IC50 values ranging from 10(1) to 74(5) µM.

Syntheses, structure, DNA docking and antimicrobial studies of copper(II) complexes with diethylenetriamine and N-bidentate ligands

A series of mononuclear heteroleptic copper(II) complexes with diethylenetriamine (DETA) and bidentate N-donor ligands, [Cu(DETA)(5,6-DMPhen)](ClO4)21, [Cu(DETA)(4,7-DMPhen)](ClO4)2, 2, [Cu(DETA)(3,4,7,8-TMPhen)](BPh4)2, 3, [Cu(DETA)(8-AQ)](ClO4)2, 4, [Cu(DETA)(2-AMP)](ClO4)2, 5, [Cu(DETA)(2-AEP)](ClO4)2, 6, [Cu(DETA)(1,2-DACH)](ClO4)2, 7 and [Cu(DETA)(1,3-DAP)](ClO4)2, 8, with biologically relevant N-donor ligands 5,6-dimethyl-1,10-phenanthroline (5,6-DMPhen), 4,7-dimethyl-1,10-phenanthroline (4,7-DMPhen), 3,4,7,8-tetramethyl-1,10-phenanthroline (3,4,7,8-TMPhen), 8-aminoquinoline (8-AQ), 2-aminomethylpyridine (2-AMP), 2-aminoethylpyridine (2-AEP), 1,2-diaminocyclohexane (1,2-DACH) and 1,3-diaminopropane (DAP) respectively. All the complexes (1–8) were structurally determined by a single-crystal X-ray diffraction technique and characterized by CHN, UV–Vis, FT-IR, and ESI-MS. X-ray analysis revealed that the geometry around the copper center in all complexes (1–8) is distorted trigonal bipyramidal. All complexes strongly bind with ct-DNA via groove/electrostatic interactions. Their binding with DNA was supported by UV–Vis and CD spectral studies. Docking studies revealed that copper(II) complexes containing aromatic N-donor ligands (5,6-DMPhen, 4,7-DMPhen, 3,4,7,8-TMPhen & 8-AQ) have a stronger binding affinity than complexes with aliphatic N-donor ligands (2-AMP, 2-AEP, 1,2-DACH & DAP) towards DNA. All complexes exhibited good antibacterial activity against American standard ATCC Escherichia coli (ATCC 25922) and clinically isolated Escherichia coli (E1) bacterial strains.

Evolution of Bonding and Magnetism via Changes in Valence Electron Count in CuFe2–xCoxGe2

A series of solid solutions, CuFe2-xCoxGe2 (x = 0, 0.2, 0.4, 0.8, and 1.0), have been synthesized by arc-melting and characterized by powder X-ray and neutron diffraction, magnetic measurements, Mössbauer spectroscopy, and electronic band structure calculations. All compounds crystallize in the CuFe2Ge2 structure type, which can be considered as a three-dimensional framework built of fused MGe6 octahedra and MGe5 trigonal bipyramids (M = Fe and Co), with channels filled by rows of Cu atoms. As the Co content (x) increases, the unit cell volume decreases in an anisotropic fashion: the b and c lattice parameters decrease while the a parameter increases. The changes in all the parameters are nearly linear, thus following Vegard's law. CuFe2Ge2 exhibits two successive antiferromagnetic (AFM) orderings, corresponding to the formation of a commensurate AFM structure, followed by an incommensurate AFM structure observed at lower temperatures. As the Co content increases, the AFM ordering temperature (TN) gradually decreases, and only one AFM transition is observed for x ≥ 0.2. The magnetic behavior of unsubstituted CuFe2Ge2 was found to be sensitive to the preparation method. The temperature-dependent zero-field 57Fe Mössbauer spectra reveal two hyperfine split components that evolve in agreement with the two consecutive AFM orderings observed in magnetic measurements. In contrast, the field-dependent spectra obtained for fields ≥2 T reveal a parallel arrangement of the moments associated with the two crystallographically unique metal sites. Electronic band structure calculations and chemical bonding analysis reveal a mix of strong M-M antibonding and non-bonding states at the Fermi level, in support of the overall AFM ordering observed in zero field. The substitution of Co for Fe reduces the population of the M-M antibonding states and the overall density of states at the Fermi level, thus suppressing the TN value.

Trigonal Bipyramidal Rhodium(I) Methyl and Phenyl Complexes: Precursors of Oxidative Methyl and Phenyl Radical Generation

The new complexes [Rh(Me)(trop3P)] (2) and [Rh(Ph)(trop3P)] (3) (trop = 5H-dibenzo[a,d]cyclohepten-5-yl) were synthesised by addition of organolithium reagents (MeLi and PhLi) to the parent pentacoordinated chloride complex [RhCl(trop3P)]. The compounds have a trigonal bipyramidal structure with olefin-only ligands in the equatorial position and the methyl or phenyl substituent in the axial position. Oxidation of complexes 2 and 3 leads to the liberation of methyl and phenyl radicals, which were indirectly detected by reaction with common spin trapping reagents.

Influence of the Reaction Conditions in the Crystal Structures of Zn(II) and Ni(II) Coordination Compounds with a Dissymmetric Bis(Thiosemicarbazone) Ligand

The new ligand HMeATSM, derived from condensation of 2-3-butanedione with 4-methyl-3-thiosemicarbazide and 2,4-dimethyl-3-thiosemicarbazide, has been synthesized. Its reactivity with nickel(II) and zinc(II) nitrates was explored and the resulting complexes were thoroughly characterized by elemental analysis, conductivity, mass spectrometry, IR, 1H and 13C NMR spectroscopies and their structures were confirmed by single-crystal X-ray diffraction. The results showed that the complex [Ni(MeATSM)]NO3 1 is formed under every reaction condition. In contrast, the reaction with zinc(II) nitrate depends on the temperature and the presence of LiOH·H2O, leading to the obtaining of complexes [Zn(MeATSM)(OH2)](NO3) 2 and [Zn(Me2TS)2(OH2)](NO3)2 3. The crystal structures of complexes 1 and 2 show that the dissymmetric ligand acts as a N2S2 tetradentate monoanionic ligand. The structural preferences of the metals also determine the structure of the complexes: whereas nickel(II) is in a square-planar environment, the zinc atom prefers a distorted square-base pyramid geometry imposed by the coordination mode and the planarity of the bis(thiosemicarbazone) ligand. In contrast, in complex 3, containing two bidentate Me2TS ligands, the Zn(II) is in a trigonal bipyramid arrangement. In all the complexes, the nitrate ion is not coordinated to the metal and acts as a counterion.

Exploiting the Multifunctionality of M2+/Imidazole-Etidronates for Proton Conductivity (Zn2+) and Electrocatalysis (Co2+, Ni2+) toward the HER, OER, and ORR.

This work deals with the synthesis and characterization of one-dimensional (1D) imidazole-containing etidronates, [M2(ETID)(Im)3]·nH2O (M = Co2+ and Ni2+; n = 0, 1, 3) and [Zn2(ETID)2(H2O)2](Im)2, as well as the corresponding Co2+/Ni2+ solid solutions, to evaluate their properties as multipurpose materials for energy conversion processes. Depending on the water content, metal ions in the isostructural Co2+ and Ni2+ derivatives are octahedrally coordinated (n = 3) or consist of octahedral together with dimeric trigonal bipyramidal (n = 1) or square pyramidal (n = 0) environments. The imidazole molecule acts as a ligand (Co2+, Ni2+ derivatives) or charge-compensating protonated species (Zn2+ derivative). For the latter, the proton conductivity is determined to be ∼6 × 10–4 S·cm–1 at 80 °C and 95% relative humidity (RH). By pyrolyzing in 5%H2–Ar at 700–850 °C, core–shell electrocatalysts consisting of Co2+-, Ni2+-phosphides or Co2+/Ni2+-phosphide solid solution particles embedded in a N-doped carbon graphitic matrix are obtained, which exhibit improved catalytic performances compared to the non-N-doped carbon materials. Co2+ phosphides consist of CoP and Co2P in variable proportions according to the used precursor and pyrolytic conditions. However, the Ni2+ phosphide is composed of Ni2P exclusively at high temperatures. Exploration of the electrochemical activity of these metal phosphides toward the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) reveals that the anhydrous Co2(ETID)(Im)3 pyrolyzed at 800 °C (CoP/Co2P = 80/20 wt %) is the most active trifunctional electrocatalyst, with good integrated capabilities as an anode for overall water splitting (cell voltage of 1.61 V) and potential application in Zn–air batteries. This solid also displays a moderate activity for the HER with an overpotential of 156 mV and a Tafel slope of 79.7 mV·dec–1 in 0.5 M H2SO4. Ni2+- and Co2+/Ni2+-phosphide solid solutions show lower electrochemical performances, which are correlated with the formation of less active crystalline phases.

Cobalt(II)-disulfide compounds with the unusual PF2O2– anion. ligand-dependent redox conversion to a cobalt(III)-thiolate complex

Herein we describe the synthesis of the cobalt(II) disulfide compounds [CoII2(LxSSLx)(μ–PO2F2)2](PF6)2 and [CoII2(LxSSLx)(NO3)4] (x = 1: di-2-(bis(2-pyridylmethyl)amino)-ethyl disulfide; x = 2: di-2-((6-methyl-2-pyridylmethyl)(2-pyridylmethyl)amino)-ethyl disulfide). The crystal structures show the cobalt(II) centers in [CoII2(LxSSLx)(μ-PO2F2)2](PF6)2 to be in distorted octahedral geometries, whereas in [CoII2(L1SSL1)(NO3)4] the geometries are distorted trigonal bipyramidal. The cobalt(II) centers in [CoII2(LxSSLx)(PO2F2)2](PF6)2 are coordinated by three nitrogen and one sulfur donor atom of the disulfide ligand, and two oxygen atoms of two bridging difluoridophosphate anions. The cobalt(II) centers in [CoII2(L1SSL1)(NO3)4] are coordinated by three nitrogen donors of the ligand and three oxygen atoms of one monodentate and one bidentate nitrate anion, the latter two oxygen atoms together occupying one of the equatorial sites of the trigonal bipyramid. It was found that the dinuclear compound [CoII2(L1SSL1)(PO2F2)2](PF6)2 is stable as such in methanol and dichloromethane solution, but in acetonitrile redox conversion occurs forming the cobalt(III) thiolate compound [CoIII(L1S)(MeCN)2]2+. The compound [CoII2(L1SSL1)(NO3)4] and the disulfide compounds of the ligand L2SSL2 do not show this redox conversion and remain in the disulfide form in all investigated solvents.

On the HOMFLY polynomials of even trigonal bipyramid links

On the HOMFLY polynomials of even trigonal bipyramid links

Synthesis, characterization, and biological evaluation of eight new organotin(IV) complexes derived from (1R, 2S) ephedrinedithiocarbamate ligand

The synthesis of eight new organotin derivatives containing ephedrine-substituted dithiocarbamate ligands [R3Sn(ephedtc)] 2–5. 2: R = Me; 3: R = Bu; 4: R = Cy; 5: R = Ph and [R2Sn(ephdtc)2] 6–9. 6: R = Me; 7: R = Bu; 8: R = t-Bu; 9: R = Ph is reported. The complexes were obtained from sodium ephedrinedithiocarbamate [Na(ephedtc)] 1 and the corresponding tri-organotin(IV) chlorides, R3SnCl 2–5 or di-organotin(IV) dichlorides, R2SnCl26–9. They were characterized by elemental analysis, IR, and NMR spectroscopy (1H, 13C, and 119Sn). The infrared spectra (solid-state) suggest that the Sn(IV) is coordinated to the ligand ephedtc, through the two sulfur atoms in an anisobidentate coordination mode. In solution, the 119Sn NMR indicates the coordination numbers: tetracoordinated for 2–4, pentacoordinate for 5, and hexacoordinated for 6–9. The single-crystal X-ray diffraction analysis of 4 reveals an anisobidentate coordination mode with a trigonal bipyramid distorted geometry around the Sn(IV). All compounds except 2, show inhibition in at least one bacterial strain, and 7 and 9 have the best antibacterial activity, mainly in the clinically isolated strains.

Synthesis, crystal structures and urease inhibition of copper, nickel and zinc complexes derived from 4-chloro-2-((pyridin-2-ylmethylene)amino)phenol

A series of copper, nickel and zinc complexes, [CuClL] (1), [CuBrL] (2), [NiL2] (3), [ZnL2] (4) and [Zn2I2L2] (5), where L is the deprotonated form of 4-chloro-2-((pyridin-2-ylmethylene)amino)phenol, have been synthesized and characterized by elemental analysis, IR and UV-Vis spectra. The structures of the complexes were further confirmed by single crystal X-ray diffraction. The Cu ions in 1 and 2 are in square planar coordination. The Ni and Zn ions in 3 and 4 are in octahedral coordination. The coordination of the Zn ions in centrosymmetric complex 5 is between square pyramidal and trigonal bipyramidal. The copper complexes have excellent urease inhibitory activity.