Nitrogen Atoms Of Ligand Research Articles

Unique Hydration/Dehydration-Induced Vapochromic Behavior of a Charge-Transfer Salt Comprising Viologen and Hexacyanidoferrate(II).

We successfully prepared and crystallographically characterized the first intermolecular charge-transfer (CT)-based vapochromic compound, (EV)(H3O)2[Fe(CN)6] (1-Wet, EV2+: 1,1'-diethyl-4,4'-bipyridine-1,1'-diium), an ethyl viologen-containing CT salt. 1-Wet, which is purple in color, is transformed into a brown powder (1-Dry) upon exposure to methanol vapor, drying over silica gel, or heating; 1-Dry returns to 1-Wet upon exposure to water vapor. These color changes are induced by hydration and dehydration, and gravimetric analyses suggest that 1-Dry is the dehydrated form of 1-Wet, namely, (EV)(H)2[Fe(CN)6]. Interestingly, desorption of water molecules from the oxonium ions in 1-Wet produces isolated protons (H+) that remain in 1-Dry as counter cations. Powder X-ray crystal structure analysis of 1-Dry reveals the presence of very short contacts between the nitrogen atoms of adjacent [Fe(CN)6]4- anions in the crystal. The isolated protons are trapped between the nitrogen atoms of cyanido ligands to form very short N···H···N hydrogen bonds. A detailed comparison of the crystal structures of 1-Wet and 1-Dry reveals that hydration and dehydration induce changes in crystal packing and intermolecular CT interactions, resulting in reversible color changes.

Surface-activated anion exchange resins for synthesis and immobilization of gold and palladium nano- and microstructures

A series of surface-activate anion exchange resins, bearing amino functionalities, were employed in processes of multiple adsorption and desorption of AuCl4−, PtCl62− and PdCl42− from solutions in 0.1 and 3mol∙L−1 HCl. The resins with ethylenediamine (EDA) and 1-(2-aminoethyl)piperazine (AEP) functionalities efficiently removed up to 100wt% of the noble metals, however, instead expected total elution, they revealed only up to 50wt% of desorption. The phenomenon was caused by the fact, that the anion exchange resins revealed an ability to reduce ionic forms of gold and palladium to their nano- and microparticles creating colloids and nanocomposites. For that reason the generated metallic forms were investigated using X-Ray Diffraction (XRD), Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM). The size of the obtained structures was in range of 50–1000nm, however, because reduction involves the transfer of an electron from a donor nitrogen it is dependent on the number of nitrogen atoms in amino ligands. A very close look at the changes in the resins' chemical structures has been taken using Fourier Transformation Infrared Spectroscopy allowing to determine a possible reason of the reduction.

Synthesis, Structures, and Antibacterial Activities of Two Methanol Coordinated Zinc Complexes with Tetradentate Bis-Schiff Bases

Two methanol coordinated zinc(II) complexes, [Zn(L1)(MeOH)] (I) and [Zn(L2)(MeOH)] (II), where L1 and L2 are the dianionic form of N,N'-bis(5-fluorosalicylidene)ethane-1,2-diamine and N,N'-bis(5-fluorosalicylidene)propane-1,2-diamine, respectively, have been synthesized and characterized by physical chemical methods and single crystal X-ray diffraction (CIF files CCDC nos. 950907 (I) and 950908 (II)). Crystallographic data for I: triclinic, P $$\bar 1$$ , a = 8.8765(8), b = 9.6577(9), c = 10.5117(9) A, α = 114.590(2)°, β = 91.648(3)°, γ = 97.114(3)°, V = 809.87(13) A3, Z = 2, R 1 = 0.0307, wR 2 = 0.0698. Crystallographic data for II: orthorhombic, Pca21, a = 22.946(2), b = 7.6942(7), c = 9.6234(8) A, V = 1699.0(2) A3, Z = 4, R 1 = 0.0320, wR 2 = 0.0676. X-ray crystal structural study indicated that the coordination environment around each zinc(II) atom in the complexes is a five-coordinated distorted pyramid in which the apical position is occupied by a methanol oxygen atom, and the basal plane is defined by the nitrogen and oxygen donor atoms of the Schiff base ligand. The antibacterial activities of the complexes were assayed.

An inorganic–organic hybrid constructed from Keggin polyoxoanions and benzotriazole ligands modulated by two dinuclear silver(I) clusters

A new polyoxometalate (POM)-based inorganic–organic hybrid, [Ag4(SiMo12O40)(HBTA)8]·8H2O (1), constructed from the Keggin-type polyoxomolybdates and benzotriazole (HBTA) ligands linked by two dinuclear silver(I) clusters has been obtained and characterized by single-crystal X-ray diffraction and IR spectrum. In 1, a pair of parallel Ag2(HBTA)4 units fixed to the central [SiMo12O40]4− stick out like a barbell to support the whole structure. These clusters are extended into the wave-like layers by the strong π–π stacking interactions and hydrogen bonds. The 2D layers are further extended into a 3D supramolecular structure by means of hydrogen bonds (C4–H4⋯O10) between the nitrogen atoms of the HBTA ligands and the oxygen atoms of [SiMo12O40]4− anions. Luminescence property of 1 in CH3CN solution has been investigated. In addition, 1-CPE possesses good electrocatalytic activity toward the reduction of KNO2, H2O2 and KBrO3.

Molecular Simulation of Ionic Polyimides and Composites with Ionic Liquids as Gas-Separation Membranes.

Polyimides are at the forefront of advanced membrane materials for CO2 capture and gas-purification processes. Recently, ionic polyimides (i-PIs) have been reported as a new class of condensation polymers that combine structural components of both ionic liquids (ILs) and polyimides through covalent linkages. In this study, we report CO2 and CH4 adsorption and structural analyses of an i-PI and an i-PI + IL composite containing [C4mim][Tf2N]. The combination of molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations is used to compute the gas solubility and the adsorption performance with respect to the density, fractional free volume (FFV), and surface area of the materials. Our results highlight the polymer relaxation process and its correlation to the gas solubility. In particular, the surface area can provide meaningful guidance with respect to the gas solubility, and it tends to be a more sensitive indicator of the adsorption behavior versus only considering the system density and FFV. For instance, as the polymer continues to relax, the density, FFV, and pore-size distribution remain constant while the surface area can continue to increase, enabling more adsorption. Structural analyses are also conducted to identify the nature of the gas adsorption once the ionic liquid is added to the polymer. The presence of the IL significantly displaces the CO2 molecules from the ligand nitrogen sites in the neat i-PI to the imidazolium rings in the i-PI + IL composite. However, the CH4 molecules move from the imidazolium ring sites in the neat i-PI to the ligand nitrogen atoms in the i-PI + IL composite. These molecular details can provide critical information for the experimental design of highly selective i-PI materials as well as provide additional guidance for the interpretation of the simulated adsorption systems.

Crystal structure and characterization of new cadmium complex from 4-pyridin-carbohydrazide and 2-chlorobenzaldehyde

Reaction of 4-pyridincarbohydrazide, 2-chlorobenzaldehyde and Cd(II) ion in ethanol resulted the complex trans -[Cd(H 2 O) 4 (C 13 H 10 N 3 ClO) 2 ](NO 3 ) 2 . The title complex was characte-rized by elemental analyses, UV-Vis and IR spectroscopy. The structure of complex also was established by single crystal X-ray diffraction analysis. The [Cd(H 2 O) 4 (C 13 H 10 N 3 ClO) 2 ](NO 3 ) 2 complex has monomeric structure with monoclinic crystal system and space group of P2 1 /n , a = 7.7720(16) A, b = 17.594(4) A, c = 11.823(2) A, β = 97.29(3)° with Z = 2. The cadmium atom in the crystal structure has octahedral geometry by coordination of the two nitrogen atoms of ligand and four oxygen atoms of water molecules.

X-ray crystal structure and theoretical study of a new dinuclear Cu(II) complex with two different geometry centers bridged with an oxo group

A new Schiff base ligand HL, 1,3-bis(2-((Z)-(2-aminoethylimino)methyl)phenoxy)ethylene di amine, has been synthesized from the reaction of a new aldehyde and ethylenediamine. After preparation the Schiff base, a new dinuclear Cu(II) complex with two different geometry for each metal ion was synthesized. Single crystal X-ray structure analysis of the complex Cu(II) showed that the complex is binuclear and all nitrogen and oxygen atoms of ligand (N4O3) are coordinated to two Cu(II) center ions. The crystal structure studying shows, a perchlorate ion has been coordinated to the two Cu(II) metal centers as bridged and another perchlorate coordinated to the one of Cu(II) ion as terminal. However, two interesting structures square pyramidal and distorted octahedral Cu(II) ions are bridged asymmetrically by a perchlorate ion and oxygen of hydroxyl group of Schiff base ligand. In addition, we had a theoretical study to have a comparison of experimental and theoretical results we determined the HOMO and LUMO orbitals.

Dihydroxo-bridged dimeric Cu(II) system containing sandwiched non-coordinating phenylacetate anion: Crystal structure, spectroscopic, anti-bacterial, anti-fungal and DNA-binding studies of [(phen)(H2O)Cu(OH)2Cu(H2O)(phen)]2L.6H2O: (HL = phenylacetic acid; phen = 1,10-phenanthroline)

This paper reports the synthesis, X-ray crystal structure, DNA-binding, antibacterial and antifungal studies of a rare dihydroxo-bridged dinuclear copper(II) complex including 1,10-phenanthroline (Phen) ligands and phenylacetate (L) anions, [Cu2(Phen)2(OH)2(H2O)2].2L.6H2O. Structural data revealed distorted square-pyramidal geometry for each copper(II) atom with the basal plane formed by the two nitrogen atoms of the phenantroline ligand and the oxygen atoms of two bridging hydroxyl groups. The apical positions are filled by the oxygen atom from a water molecule. This forms a centrosymmetric cationic dimer where the uncoordinated phenylacetate ligands serve to balance the electrical charge. The dimers interact by means of hydrogen bonds aided by the coordinated as well as uncoordinated water molecules and phenyl-acetate moieties in the crystal lattice. The binding ability of the complex with salmon sperm DNA was determined using cyclic voltammetry and absorption spectroscopy yielding binding constants 2.426 × 104 M−1 and 1.399 × 104 M−1, respectively. The complex was screened against two Gram-positive (Micrococcus luteus and Bacillus subtilis) and one Gram-negative (Escherichia coli) bacterial strains exhibiting significant activity against all the three strains. The complex exhibited significant, moderate and no activity against fungal strains Mucor piriformis, Helminthosporium solani and Aspergillus Niger, respectively. These preliminary tests indicate the competence of the complex towards the development of a potent biological drug.

Synthesis and characterization of a new nano lead(II) 0-D coordination supramolecular compound: A precursor to produce pure phase nano-sized lead(II) oxide

Nano-structure of a new 0D Pb(II) coordination supramolecular compound, [Pb4(8-Quin)6](ClO4)2(1), L=8-HQuin=8-hydroxyquinolin ligand has been synthesized by use of a sonochemical process and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FTIR) and elemental analyses. The structure of compound 1 was determined by single-crystal X-ray diffraction. The single crystal X-ray data of compound 1 implies that the Pb+2 ions are five coordinated. Each lead atom is coordinated to nitrogen and oxygen atoms of 8-hydroxyquinolin ligand. Topological analysis shows that the compound 1 is 1,2,3,4,4M12-1net. Nanoparticles of lead(II) oxide have been prepared by calcination of lead(II) coordination polymer at 500°C that were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD) and IR spectroscopy.

Synthesis, characterization, and crystal structure of a four-coordinate cobalt(II) compound incorporating bis(3,5-dimethylpyrazol-1-yl)methane and cyanate

ABSTRACTA new mononuclear cobalt(II) compound [Co(dmpzm)(NCO)2] (1) (where dmpzm = bis(3,5-dimethylpyrazol-1-yl)methane and NCO− = cyanate) has been synthesized and characterized by different physicochemical methods. Crystal structure of the compound is established by single-crystal X-ray diffraction analysis, which reveals that central cobalt(II) adopts distorted tetrahedral geometry and is coordinated by two nitrogen atoms of a bis-chelating dmpzm ligand and nitrogen atoms of two monodentate cyanate ions. Crystal structure is further stabilized by intermolecular C–H···O interactions, generating one-dimensional chain structure. The electrochemical properties of the compound were studied by cyclic voltammetric method. Room temperature magnetic susceptibility measurements reveal the presence of high-spin cobalt(II) ion in 1.

New tetrahedral zinc halide Schiff base complexes: Synthesis, crystal structure, theoretical, 3D Hirshfeld surface analyses, antimicrobial and thermal studies

A new bidentate Schiff base ligand named as N,N′-bis((E)-3-phenylallylidene)butane-1,4-diamine (L) and three its zinc halide complexes were synthesized and characterized by FT-IR, 1H NMR, 13C NMR and UV–Vis spectroscopy. The crystal structure of zinc bromide and iodide complexes were characterized using single crystal X-ray diffraction. The two structures are isomorphous, crystallizing in the monoclinic crystal system with space group C2/c with closely similar unit cell dimensions. In these complexes, the Zn(II) ion is in the center of a distorted tetrahedral environment completed by two iminic nitrogen atoms of Schiff base ligand and two halide anions. The analysis of crystal structures shows that intermolecular interactions such as CH⋯halogen, π⋯π and CH⋯π interactions have effective role in stabilization of complexes structure. Intermolecular interactions were more analyzed using 3D Hirshfeld surface analysis and corresponding 2D fingerprint plots. Furthermore, structural optimization by DFT calculations at the B3LYP/LANL2DZ level have been performed and then compared with the experimental data. Time-dependent density functional theory (TDDFT) has been also used to calculate the electronic transitions of molecules at B3LYP/LANL2DZ level using the optimized ground-state geometries. NBO analysis was applied for investigation of intra and inter-molecular bonding and conjugative interaction in molecular systems. Schiff base ligand and their zinc complexes have been screened for their antibacterial and antifungal activities by disc diffusion method. Thermal behaviors of all compounds were studied by TG/DTG analysis data. Also, nanostructures of zinc complexes were synthesized by sonochemical method and characterized by FT-IR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). ZnO nanoparticles were simply prepared by calcination of zinc iodide complex as new precursor at 600°C.

The First Characterized Coordination Compounds of Macrocyclic Ligands Including Incorporated Tetrazole Rings

The macrocyclic binuclear tetrazole, 2,2,5,5-tetramethyl-12-oxa-1,6,7,8,16,17,18,19-octaazatricyclo[13.2.1.16,9]nonadeca-7,9(19),15(18),16-tetraene (L), reacts with copper(II) chloride or copper(II) tetrafluoroborate hexahydrate to give complexes [Cu3Cl6L2] (1) or [CuL2(H2O)2](BF4)2(H2O) (2), respectively. According to single crystal X-ray analysis, both complexes were found to be coordination polymers. In the crystal structure of complex 1, there are neutral linear bibridged trinuclear units Cu3Cl6, in which the copper atoms are linked together by double chlorine bridges. Neighboring Cu3Cl6 units are bonded to each other by two bridging macrocyclic ligands L due to coordination bonds Cu–N between terminal copper atoms of Cu3Cl6 units and the tetrazole ring nitrogen atoms of ligands L to form polymeric chains. In complex 2, the copper atom is bonded to three ligands L via the tetrazole ring nitrogen atoms, and to two water molecules, with formation of a square-pyramidal coordination of the metal. In this complex, one of two independent ligands L shows monodentate coordination, whereas another ligand plays the role of a bridge between two neighboring copper atoms being responsible for formation of polymeric cationic chains [CuL2(H2O)2]n2n+. A complex system of hydrogen bonds connects the chains and the anions BF4– into a three-dimensional network. The temperature-dependent magnetic susceptibility measurements of complex 1 revealed that the copper(II) ions were ferromagnetically coupled showing a coupling constant J of 50 cm–1.

Quantum chemical modeling of valence tautomeric adducts of CoII bischelates with pyrene-4,5-diimines

Quantum chemical study of mixed-ligand (1: 1) adducts of tetracoordinated cobalt complexes (diketonates, bis-aminovinylketonates, and bis-salicylaldiminates) with pyrene-4,5-diimines using density functional theory (DFT B3LYP*/6-311++G(d,p)) revealed compounds possessing valence tautomeric properties. The mechanisms of intramolecular electron transfer accompanied by changing magnetic properties of the complexes under consideration were studied. It was shown that the variation of substituents at the nitrogen atoms of the diimine ligand and the donor groups in the cobalt bischelate, as well as the annulation of five- and six-membered rings to the azomethine fragment exerts a considerable influence on the stability of the formed adducts and the energy difference between their low- and high-spin isomers.

Temperature dependent CO2 behavior in microporous 1-D channels of a metal-organic framework with multiple interaction sites

The MOF with the encapsulated CO2 molecule shows that the CO2 molecule is ligated to the unsaturated Cu(II) sites in the cage using its Lewis basic oxygen atom via an angular η1-(OA) coordination mode and also interacts with Lewis basic nitrogen atoms of the tetrazole ligands using its Lewis acidic carbon atom. Temperature dependent structure analyses indicate the simultaneous weakening of both interactions as temperature increases. Infrared spectroscopy of the MOF confirmed that the CO2 interaction with the framework is temperature dependent. The strength of the interaction is correlated to the separation of the two bending peaks of the bound CO2 rather than the frequency shift of the asymmetric stretching peak from that of free CO2. The encapsulated CO2 in the cage is weakly interacting with the framework at around ambient temperatures and can have proper orientation for wiggling out of the cage through the narrow portals so that the reversible uptake can take place. On the other hand, the CO2 in the cage is restrained at a specific orientation at 195 K since it interacts with the framework strong enough using the multiple interaction sites so that adsorption process is slightly restricted and desorption process is almost clogged.

Molecular Design for Single-molecule Magnetism of Lanthanide Complexes

This review highlights the effective design criteria for lanthanide single-molecule magnets, which show strong magnetic blocking temperature up to 60 K. Increase in the anisotropy barrier and decrease in the quantum magnetization are attainable by controlling the ligand field, local molecular symmetry related to the coordination geometry of the complex, and magnetic dipole–dipole interactions between the lanthanide ions. With recent advances in this field, a new 2-coordinate complex, which is predicted to show a blocking temperature of more than 77 K, is also introduced. The existence of a proton in the nitrogen atom of porphyrin ligands quenches the single-molecule magnet because of the destruction of the symmetry, which can be possibly overlooked because of the disorder of the position of the proton in the crystals.

Synthesis, photophysical properties and structures of organotin-Schiff bases utilizing aromatic amino acid from the chiral pool and evaluation of the biological perspective of a triphenyltin compound

Five new organotin(IV) complexes of compositions [Me2SnL1] (1), [Me2SnL2]n (2), [Me2SnL3] (3), [Ph3SnL1H]n (4) and [Ph3SnL3H] (5) (where L1=(2S)-2-((E)-((Z)-4-hydroxypent-3-en-2-ylidene)amino)-3-(1H-indol-3-yl)propanoate, L2=(2S)-(E)-2-((2-hydroxybenzylidene)amino)-3-(1H-indol-3-yl)propanoate and L3=(2S)-(E)-2-((1-(2-hydroxyphenyl)ethylidene)amino)-3-(1H-indol-3-yl)propanoate were synthesized and spectroscopically characterized. The crystal structures of 1–4 were determined. For the dimethyltin derivative 2, a polymeric chain structure was observed as a result of a long Sn∙∙∙O contact involving the exocyclic carbonyl oxygen-atom from the tridentate ligand of a neighboring Sn-complex unit. The tin atom in this complex has a distorted octahedral coordination geometry, in which the long Sn-O bond is almost trans to the tridentate ligand nitrogen-atom. In contrast, the dimethyltin(IV) complexes 1 and 3 displayed discrete monomeric structures where the tin atom has distorted trigonal-bipyramidal geometry with the two coordinating L oxygen atoms defining the axial positions. On the other hand, 4 is a chain polymer in the solid state. The ligand-bridged Sn atoms adopt a trans-Ph3SnO2 trigonal-bipyramidal configuration with equatorial phenyl groups. A carboxylato oxygen atom from one and the hydroxyl oxygen of the successive ligand in the chain occupy the axial positions.The solution structures were predicted by the use of 119Sn NMR chemical shifts. The photophysical properties of the complexes were investigated in the solid and in solution. The triphenyltin(IV) compound 4 was tested in detail ex vivo against A375 (human melanoma) cell line, exhibiting an IC50 value of 261nM to induce cell death as assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay without significant alteration of cytolysis as determined by lactate dehydrogenase (LDH) assay. Compound 4-mediated potent cell death was also determined by Live and Dead assay and caspase-mediated cleavage of poly-ADP ribose polymerase (PARP). Potent cell death activity was not observed in primary cells, like blood-derived peripheral mononuclear cells (PBMC). Compound 4 inhibited the diphenyl hexatriene (DPH) binding to cells and decreased the micro viscosity in a dose-dependent manner. Additionally, the ability of 4 and cyclodextrin (CD) to interact was determined by molecular modelling.

An Unsaturated Four-Coordinate Dimethyl Dimolybdenum Complex with a Molybdenum-Molybdenum Quadruple Bond.

We describe the synthesis and the molecular and electronic structures of the complex [Mo2 Me2 {μ-HC(NDipp)2 }2 ] (2; Dipp=2,6-iPr2 C6 H3 ), which contains a dimetallic core with an Mo-Mo quadruple bond and features uncommon four-coordinate geometry and has a fourteen-electron count for each molybdenum atom. The coordination polyhedron approaches a square pyramid, with one of the molybdenum atoms nearly co-planar with the basal square plane, in which the trans coordination position with respect to the Mo-Me bond is vacant. The other three sites are occupied by two trans nitrogen atoms of different amidinate ligands and the methyl group. The second Mo atom occupies the apex of the pyramid and forms an Mo-Mo bond of length 2.080(1) Å, consistent with a quadruple bond. Compound 2 reacts with tetrahydrofuran (THF) and trimethylphosphine to yield the mono-adducts [Mo2 Me(μ-Me){μ-HC(NDipp)2 }2 (L)] (3⋅THF and 3⋅PMe3 , respectively) with one terminal and one bridging methyl group. In contrast, 4-dimethylaminopyridine (dmap) forms the bis-adduct [Mo2 Me2 {μ-HC(NDipp)2 }2 (dmap)2 ] (4), with terminally coordinated methyl groups. Hydrogenolysis of complex 2 leads to the bis(hydride) [Mo2 H2 {μ-HC(NDipp)2 }2 (thf)2 ] (5⋅THF) with elimination of CH4 . Computational, kinetic, and mechanistic studies, which included the use of D2 and of complex 2 labelled with 13 C (99 %) at the Mo-CH3 sites, supported the intermediacy of a methyl-hydride reactive species. A computational DFT analysis of the terminal and bridging coordination of the methyl groups to the Mo≣Mo core is also reported.

Synthesis, X-ray structure, spectroscopic (IR, NMR) analysis and DFT modeling of a new polymeric Zinc(II) complex of cystamine, [Zn(Cym-Cym)Cl2

A novel polymeric Zn–cystamine complex, [Zn(Cym-Cym)Cl2]n (1) was obtained by the reaction of ZnCl2 and the disulfide bridged cystamine dihydrochloride ligand (Cym-Cym·2HCl) in the presence of 1,2-diaminoethane (en). A similar reaction of the corresponding monomeric thiol, cysteamine hydrochloride (CymH·HCl) yielded a tetrameric cyclic complex, [Zn4Cym4Cl4] (2). The X-ray diffraction analysis revealed that each zinc atom in 1 is coordinated by two nitrogen atoms of the bridging Cym-Cym ligands and two chloride ions, which complete the tetrahedral environment of Zn(II). During the reaction the cystamine ligand retained the disulfide linkage and the sulfur atoms remained uncoordinated. Combined experimental and theoretical IR, 1H, and 13C NMR spectroscopic studies of the isolated ligands and their complexes, 1 and 2 were applied to derive structure-spectra correlation for the complexes. The assignment of the solid state IR spectra of 1 and 2 was performed by means of periodic DFT modeling and frequency calculations using DFT/PAW-PBE methodology. The vibrational modes sensitive to the N- and S ligand coordination to Zn(II) and to the type of the coordination polyhedron were determined. The C–S stretching vibrations were assumed to be the characteristic modes for prediction of different binding behavior of the CS donor group in complexes 1 and 2. The 13C NMR data are able to distinguish the ligand N-binding to Zn(II) in 1 and S-binding in 2.

Synthesis, molecular structure, spectroscopic characterization and antibacterial activity of the Co(III) (chlorido)(pyridine) and (chlorido)(4,4′-bipyridine) “picket fence” porphyrin complexes

Two new cobalt(III) six-coordinated complexes, [CoIII(TpivPP)Cl(py)].THF (1) [TpivPP is α,α,α,α-tetrakis(o-pivalamidophenyl)porphyrin known as the picket fence porphyrin and THF is tetrahydrofuran] and [CoIII(TpivPP)Cl(4,4′-byp)].2H2O (2) (4,4′-bpy is 4,4′-bipyridine), have been synthesized and characterized by UV–Vis, IR, 1H NMR and MS spectroscopy. The UV–Vis data confirmed the creation of hexa-coordinated Co(III)-meso-porphyrin complexes by the red shifted Soret bands of these derivatives. The proton NMR spectra of 1 and 2 clearly indicated that these derivatives are cobalt(III) diamagnetic porphyrin complexes. The molecular structures of these two Co(III) derivatives were determined by X-ray single-crystal analysis. The Co(III) cations, chlorido ligands and nitrogen atoms of the pyridine and the pyridyl moieties lie on a two-fold axis of symmetry. The equatorial plane is formed by four nitrogen atoms of the porphyrin core of 1 and 2, whereas the apical positions are occupied by the chlorido ligands and the nitrogen atoms of the pyridine ligand and the pyridyl group of the 4,4′-bipyridine ligand of compounds 1 and 2 respectively. In the crystal packing of 1 and 2, the [CoIII(TpivPP)Cl(L)] (L=pyridine or 4,4′-bipyridine) molecules are arranged in one-dimensional chains parallel to the [010] direction, and voids are located between these chains. Gram-positive and Gram-negative bacteria have been tested against the starting materials and complexes 1 and 2. The results show that the cobalt(III) porphyrin derivatives are highly effective compared to the H2TpivPP free base porphyrin and that 1 and 2 derivatives have a higher growth inhibition against Escherichia coli and Bacillus subtilis bacteria.

Syntheses and characterizations of the cyanide-bridged heteronuclear polymeric complexes with 2-ethylimidazole

Three new cyano-bridged heteronuclear polymeric complexes, [Cu( etim ) 3 Ni(CN) 4 ] n , {[Zn( etim ) 3 Ni(CN) 4 ]∙H 2 O} n and [Cd( etim ) 2 Ni(CN) 4 ] n ( etim = 2-ethylimidazole, hereafter abbreviated as Cu–Ni– etim , Zn–Ni– etim and Cd–Ni– etim ) have been prepared in powder form and characterized by FT-IR and Raman spectroscopies, thermal (TG, DTG and DTA) and elemental analyses. The spectral features of the complexes suggest that the Ni(II) ion is four coordinate with four cyanide-carbon atoms in a square planar geometry, whereas the Cu(II) and the Zn(II) ions of the Cu–Ni– etim and the Zn–Ni– etim complexes are completed by nitrogen atoms of two cyano groups of [Ni(CN) 4 ] 2- coordinated to the adjacent M(II) ions and three nitrogen atoms of the etim ligands. The Cd(II) ion of the Cd–Ni– etim complex is six-coordinate, completed with the two nitrogen atoms of the etim ligands and the four nitrogen atoms from bridging cyano groups. Polymeric structures of the Cu–Ni– etim and the Zn–Ni– etim complexes are 1D coordination polymer, while complex the Cd–Ni– etim presents a 2D network. The thermal decompositions in the temperature range 30–700 °C of the complexes were investigated in the static air atmosphere. KEY WORDS : Tetracyanonickelate(II) complex, 2-Ethylimidazole complex, Cyanide-bridged complex, Vibration spectra, Thermal analysis Bull. Chem. Soc. Ethiop. 2016 , 30(2), 263-272. DOI: http://dx.doi.org/10.4314/bcse.v30i2.10