β-Octafluorinated tetrakis(ethoxycarbonyl)porphyrin

Tetrakis(alloxycarbonyl)porphyrin and its β-octafluoro-substituted derivatives were synthesized via Lindsey method and transformed to their zinc complexes.Single crystal X-ray structures of corresponding Zn(Ⅱ) porphyrins revealed that β-octafluorination will give more compactness of porphyrin moieties in the crystal structure owing to the hydrogen bonding interactions involving β-fluorine atoms.An unusual six-coordinated Zn(Ⅱ) was found via intramolecular coordination of oxygen atom of meso-substituents with central Zn(Ⅱ).     

1，2-环己二羧酸及芳香含氮配体的双核镉、锰配合物的合成和晶体结构

用水热法合成了两种新的配合物[Cd2(e,e-trans-chdc)2(bipy)2(H2O)2].H2O(1)和[Mn2(e,a-cis-chdc)2(phen)2(H2O)2].2H2O(2)(chdc=1,2-环己二羧酸,bipy=2,2′-联吡啶和phen=1,10-邻菲咯啉),用X-射线单晶衍射分析确定了配合物的晶体结构。配合物1和2均为双核分子。配合物1中,2个镉髤离子由2个1,2-环己二羧酸根以e,e-trans配位方式桥联,每个镉髤离子与1个2,2′-联吡啶的2个氮原子、2个1,2-环己二羧酸根的4个氧原子及1个水分子中的氧原子配位,形成了单帽变形三棱柱构型。配合物2中,2个锰髤离子由2个1,2-环己二羧酸根以e,a-cis配位方式桥联,每个锰髤离子与1个1,10-邻菲咯啉的2个氮原子、2个1,2-环己二羧酸根的3个氧原子及1个水分子中的氧原子配位,形成了畸变的八面体构型。配合物1和2分子之间都存在π-π堆积和O-H…O、C-H…O弱作用,进而将双核分子连接成三维超分子网络结构。配合物的荧光均来自于配体的荧光。     

Formation of six-coordinated silicon in calcium phosphosilicate xerogels assisted by polyols at low temperature and pressure

Silicon is usually found to be four-coordinated when neighbored with oxygen. Six-coordinated silicon is only seen in samples at very specific composition or made at high temperature/pressure. In this study,we managed to synthesize calcium phosphosilicate xerogels containing six-coordinated silicon with the help of polyols by sol–gel method, without the need of treatment at high temperature or high pressure.Both phosphorus precursors and polyols were found to be essential for the formation of six-coordinated silicon species; in the absence of either species, only normal four-coordinated silicon was observed under otherwise identical conditions. Samples containing six-coordinated silicon sites were found to release silicon species faster than those without six-coordinated silicon sites upon dissolved in water,suggesting that six-coordinated silicon species have higher reactivity toward hydrolysis.     

A screened hybrid density functional study on energetic complexes: Alkaline-earth metal carbohydrazide perchlorates

The molecular geometries, electronic structures and stabilities of a series of alkaline-earth metal carbohydrazide perchlorates were investigated using the Heyd–Scuseria–Ernzerhof (HSE) screened hybrid density functional. The results show that Be and Mg complexes have six-coordinated octahedron features, as previously reported for the transition metal complexes. However, Ca, Sr and Ba complexes have additional coordinated oxygen atoms from the perchlorate ion. Detailed NBO analyses indicate that the metal–ligand interactions are essentially ionic and play an important role in the stabilities of these energetic complexes. The donor–acceptor interactions result in a reduction of occupancies of σ_C=O and σ_N–H bond orbitals, and also their subsequent impact on bond length and bond order.     

Synthesis and spectral study of biologically active macrocyclic complexes of divalent transition metal ions

The condensation reaction of succinyldihydrazide with glyoxal in the presence of divalent metal ions (1: 1: 1) results in the formation of the complexes of type [M(C₆H₈N₄O₂)X₂], where M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and X = Cl⁻, NO₃⁻, CH₃COO⁻. The complexes have been characterized with the aid of elemental analyses, conductance measurements and electronic, NMR, infrared spectral studies. On the basis of these studies, a six-coordinated distorted octahedral geometry in which two nitrogen and two carbonyl oxygen atoms are suitably placed for coordination toward metal ion, has been proposed for all the complexes. The complexes were tested for their in vitro antibacterial activity. Some of the complexes showed remarkable antibacterial activities against some selected bacterial strains.     

3-羟基肉桂酸构筑的锌(Ⅱ)和镉(Ⅱ)配合物的合成、晶体结构和荧光性质

用水热法合成得到2个配合物,{[ML₂(bipy)(H₂O)₂]·2bipy}_n(M=Cd 1,Zn 2;HL=3-羟基肉桂酸,bipy=4,4′-联吡啶),并对它们进行了红外分析、元素分析,热重分析和单晶结构分析。配合物1和2为异质同晶,单斜晶系,P2/c空间群。中心金属M为六配位,相邻的M^Ⅱ通过4,4′-联吡啶桥联形成沿b轴延伸的一维链状结构,此外还存在未配位的4,4′-联吡啶作为客体分子位于链与链之间。通过对配合物1和2的固态荧光测试表明,它们在绿光区均显示发光效应。     

Synthesis,characterization and cytotoxicity of fluorescent organotin complexes of terpyridine derivatives

Five organotin complexes of terpyridine derivatives were synthesized and characterized. The mononuclear Sn（IV） complexes were six-coordinated adopting a distorted octahedral coordination geometry. A brief outline of the fluorescence spectra and the in vitro cytotoxicity of the Sn（IV） complexes have been given.     

Synthesis and characterization of new dioxomolybdenum(VI) complexes of ONS donor Schiff bases derived from thiosemicarbazide,S-methyldithiocarbazate,S-benzyldithiocarbazate ando-hydroxy-aromatic aldehydes/ketones

Summary Syntheses of several new dioxomolybdenum(VI) complexes with composition MoO₂L · MeOH (where LH₂ = Schiff base derived from salicylaldehyde, 2-hydroxy-1-naphthaldehyde,o-hydroxyacetophenone,o-hydroxybenzophenone, pyridoxal and thiosemicarbazide,S-methyldithiocarbazate orS-benzyldithiocarbazate) are reported. The complexes have been characterized by elemental analysis, i.r., n.m.r. and electronic spectra, conductance, molecular weight and magnetic susceptibility measurements. The complexes are monomers, nonelectrolytes, diamagnetic and six-coordinated. The Schiff bases behave as dibasic tridentate ligands and coordinate through phenolic oxygen, thioenolic sulphur and azomethine nitrogen atoms. The complexes have acis-O=Mo=O structure as evidenced by the presence of two strong bands at 880–915 and 925–955 cm^–1. All of the complexes exhibit a band atca. 25000 cm^–1 due to the ligand to metal charge transfer transition.     

Reaction of nitrogen dioxide with iron tetraphenylporphyrinate nitro complex containing the trans-1-methylimidazole ligand

Electron and IR spectroscopy, as well as the data on the isotopic analog ¹⁵NO₂, were used for the studies of the reaction of nitrogen dioxide (NO₂) with thin layers of the six-coordinated Fe^III-porphyrin nitro complex with trans-1-methylimidazole ligand Fe(TPP)(1-MeIm)(NO₂) (TPP is the meso-tetraphenylporphyrinate dianion), which is a heme-modelling system. It was shown that, like in the case of the five-coordinated nitrite complex, additional portions of NO₂ promote the nitrite-to-nitrate transformation, accompanied by the evolution of NO. The reaction leads to the formation in the layer of five- and six-coordinated Fe-porphyrin nitrate complexes and a small amount of imidazole complexes Fe^III(TPP)(1-MeIm)₂ with the outersphere nitrate anion. The latter complex became predominate after treatment of this layer with additional portion of 1-methylimidazole.     

Preparation and study of pyridothienopyrazines and their Ruthenium(II) complexes: a new family of bidentate ligands

The Friedländer condensation of 3-aminothieno[2,3-b]pyrazine-2-carboxaldehyde with either methyl ketones or carbocyclic and heterocyclic ketones leads to a family of new bidentate ligands containing a pyridothienopyrazine coordinating unit. Complexation with [Ru(bpy)₂Cl₂] affords the corresponding six-coordinated Ru(II) complexes. The structures were analyzed by ¹H NMR spectroscopy, which shows shielding effects reflecting significant interligand π-stacking interaction in the complexes. The photophysical properties of the ligands and their metallic complexes have been also examined.     

含硅二烃基锡(Ⅳ)邻菲咯啉配合物的合成及结构表征

1980年,Crowe等人首次报道了六配位有机锡(Ⅳ)配合物R2SnX2L2(R=烷基或苯基;X=F,C l,Br,I或NCS;L为含O或N的有机配体)对P388淋巴白血病细胞有抑制活性[1]。以后人们合成许多二烃基锡配合物,并对基作了广泛的研究[2,3]。结果表明,二烃基锡化合物的抗肿瘤活性主要取决于烃基,混合二烃基锡化合物毒性较高,使它们的应用受到一定的限制。在药物分子中,某个碳原子被硅取代,称为硅药(Sila-drug),其特点是能降低毒性,有时也能提高药效[6]。因此,开展对含硅有机锡化合物进行研究,对于探讨分子中引入硅原子后对有机锡化合物性质的影响有一定的…     

Solid–solid synthesis,characterization, thermal decomposition and antibacterial activities of zinc(II) and nickel(II) complexes of glycine–vanillin Schiff base ligand

The zinc(II) and nickel(II) complexes of glycine–vanillin Schiff base were synthesized by one-step solid–solid reaction at room temperature. The composition and structure of the complexes were characterized by elemental analyses, Fourier transform infrared spectra (FTIR), X-ray powder diffraction (XRD), and thermogravimetry and differential scanning calorimetry (TG–DSC). The crystal structure of the complexes belongs to monoclinic system with the lattice parameters: a = 0.6807 nm, b = 1.3818 nm, c = 1.2011 nm, β = 95.80° for [Zn(C₁₀H₉O₄N)(H₂O)₃], and a = 0.7457 nm, b = 1.3331 nm, c = 1.2560 nm, β = 91.89° for [Ni(C₁₀H₉O₄N)(H₂O)₃]·1.5H₂O. The experimental results indicate that the zinc and nickel ions are all six-coordinated by imino nitrogen, carboxylic oxygen, and phenolic oxygen from the Schiff base ligand, and oxygen from three coordinated water molecules, respectively. The possible pyrolysis reactions in the thermal decomposition processes of the complexes and the experimental and calculated percentage mass loss are also given. The two complexes have the most intense antibacterial activities against Escherichia coli.     

Preparation and Characterization of Dioxotungsten (VI) Complexes of Schiff Bases Derived from Salicylaldehydes and O-Aminothiophenol

Several dioxotungsten(VI) complexes of the type WO₂L and WO₂L.X (where LH₂ = Schiff base derived from o-aminothiophenol and salcylaldehyde, 5-chlorosalicylaldehyde, 5-bromosalicylaldehyde, and X = dimethyl formamide, dimethyl sulfoxide or pyridine) have been prepared and characterized by elemental analysis, electrical conductance, magnetic and spectral measurements. These complexes are non-electrolyte, diamagnetic, six-coordinated and possess an octahedral geometry.     

Structural features of some organotin(IV) complexes of semi- and thio-semicarbazones

Some five- and six-coordinated di and tri-n-butyl tin(IV) semi- and thio-semi carbazates have been synthesized. The characterization of these complexes, by IR, NMR (¹H, ¹³C, ¹¹⁹Sn), ¹¹⁹Sn), ¹¹⁹Sn Mössbauer and Mass spectroscopies along with X-ray diffraction, reveals that complexes of biionic ligands of the type Bu₂Sn L″ are five-coordinated having trigonal bipyramidal geometry. However, complexes of monoionic ligands of the type Bu₂SnL′₂ are six-coordinated in a distorted cis-octahedral geometry and Bu₃SnL′ are five-coordinated with a trigonal bipyramidal structure. X-ray structural studies on the compound Bu₂Sn(O.C₆H₄.CH:N.N.CS.NH₂), show that it crystallizes in a monoclinic lattice with a = 16.90 Å, b = 9.71 Å, c = 8.60 Å, and β = 103°45′.     

Manganese(II) complexes of substituted thio-and selenosemicarbazones of 2-acetylpyridine: E.s.r., magnetic and electronic spectral studies

Summary Manganese(II) bis(ligand) complexes of substituted thiosemicarbazones and selenosemicarbazones derived from 2-acetylpyridine of general formula [MnL₂] (where L=deprotonated ligand) have been synthesized and characterised by elemental analyses, electronic spectra in solution, i.r. spectra, magnetic measurements and e.s.r. spectra recorded in polycrystalline state and in solution at room temperature and 77K. The terdentate character of the ligands in all the complexes is inferred from i.r. spectra. The electronic spectra along with e.s.r. spectra suggest an octahedral environment around the manganese(II). The metal-ligand bonds are moderately covalent. Thus all the complexes reported here are six-coordinated and high-spin octahedral.     

Reactivity of oxo-rhenium precursor trans-ReOCl3(OPPh3)(SMe2) with diaza heterocyclic congeners: Synthesis and spectroscopic characterization of mono and dinuclear compounds

The treatment of ReOCl₃(OPPh₃)(SMe₂) with an appropriate amount of [1,3]- and [1,4]-diaza heterocyclic ligands N  N (were N  N = pyrimidine (pym) and pyrazine (pyz)) in boiling acetonitrile under different reaction conditions yielded either the mononuclear ReOCl₃(OPPh₃)(pym) (1), ReOCl₃(OPPh₃)(pyz) (2) or dinuclear compounds [ReOCl₃(OPPh₃)]₂(μ-pym) (3), [ReOCl₃(OPPh₃)]₂(μ-pyz) (4). The new complexes were characterized in solution by means of NMR, IR, FIR, and UV–Vis spectroscopic methods. The molecular and crystal structures of 1, 3 and 4 were also determined by X-ray crystallography. All complexes adopt distorted octahedral geometries, with similar donor atoms arrangement, were axial positions are taken by terminal oxygen and triphenylphosphine oxide molecules. The equatorial planes are occupied by three chloride ligands and one nitrogen atom of the diaza ligand. The dinuclear complexes 3 and 4 comprise two equivalent six-coordinated monomeric units. Two halves of the dimer molecule are rotated about the Re–N  N–Re fragment: thus, an N-heterocyclic ring is stacked with two adjacent phenyl rings belonging to two triphenylphosphine oxide ligands. The preliminary results concerning the reactivity of the dimeric complexes point to their relative inertness in attempted further substitution towards synthesis of polynuclear complexes.     

Quantum chemical study on the coordination environment of the catalytic zinc ion in matrix metalloproteinases

X-ray analyses of matrix metalloproteinases (MMPs) have shown that the catalytic zinc ion (Zn1) can bind to one to three water molecules in addition to three conserved histidine residues. To estimate the relative stability of the possible Zn1 coordination structures in the active site of the MMPs, we carry out computational analyses on the coordination environment of the Zn1 ion in the gelatinase A enzyme (or matrix metalloproteinase 2; MMP-2). Four-, five-, and six-coordinated complexes representative of the Zn1 site are fully characterized by means of quantum mechanical (QM) methodologies. On one hand, B3LYP/LACVP* minimizations of various cluster models of the MMP-2 active site show that the trigonal bipyramidal geometry is energetically favored in the gas phase and that continuum solvent effects stabilize preferentially the tetrahedral complexes. On the other hand, B3LYP/OPLS-AA hybrid QM/molecular mechanical calculations in the solvated catalytic domain of the MMP-2 enzyme complemented with electrostatic Poisson-Boltzmann calculations show that the mature enzyme presents most likely a Zn1 ion coordinated by three histidine residues and two water molecules, while the active site glutamic acid is negatively charged. In consonance with X-ray diffraction data, other possible Zn1 configurations, a six-coordinated structure with Zn1-water as well as four- and five-coordinated complexes with a Zn1-bound hydroxide, are predicted to be very close in energy.     

Metal complexes of pyrimidine-derived ligands—V. Co(II) and Cu(II) complexes with 6-guanidino-2,4-dimethyl-1,3-diazine and 6-phenylguanidino-2,4-dimethyl-1,3-diazine

The synthesis and physicochemical characterization of Co(II) and Cu(II) complexes of the title ligands are reported. Effective magnetic moment values and electronic diffuse-reflectance and solution spectral features along with ligand field parameters classify the Co(II) and Cu(II) complexes as six-coordinated. Vibrational spectral data furnish meaningful information regarding the bonding sites of the title ligands.     

Dioxomolybdenum(VI) complexes derived from tridentate hydrazone ligands: Synthesis,characterization, crystal structures,and antibacterial activity

A pair of structurally similar dioxomolybdenum(VI) complexes with general formula [MoO₂(L)(MeOH)] (L = L¹ = N’-(3,5-dibromo-2-hydroxybenzylidene)-2-hydroxybenzohydrazide for I, L = L² = N’-(3,5-dibromo-2-hydroxybenzylidene)-2-methylbenzohydrazide for II), have been prepared and characterized by elemental analysis, IR spectra, and single crystal X-ray determination (CIF files CCDC nos. 917823 (I) and 917824 (II)). The hydrazone ligands coordinate to the Mo atoms through phenolate oxygen, imine nitrogen, and enolic oxygen atoms. The Mo atom in each complex is six-coordinated in an octahedral geometry. The crystals of the complexes are stabilized by hydrogen bonds. The complexes and the ligands were assayed for antibacterial activities against three Gram-positive bacterial strains (B. subtilis, S. aureus, and S. faecalis) and three Gram-negative bacterial strains (E. coli, P. aeruginosa, and E. cloacae) by MTT method. As a result, the complexes showed effective antimicrobial activity against the microorganisms tested.     

Synthesis and spectral studies of transition metal complexes with 1,5:11,15-dimetheno-2,4,10,12-tetramethyl-[1,5,9,13]-tetraazahexadeca-1,3,5,6,10,11,13,15,16,20-decene a sixteen-membered tetradentate macrocyclic ligand

Complexes of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Pd(II), Pt(II), Ru(III) and Ir(III) with a sixteen-membered 1,5:11,15-dimetheno-2,4,10,12-tetramethyl-[1,5,9,13]-tetraazahexadeca-1,3,5,6,10,11,13,15,16,20-decene macrocyclic ligand have been synthesized. These complexes are characterized by magnetic moment, infrared, electronic, EPR and mössbauer spectral studies. All of complexes were found to have six-coordinated octahedral geometry and are of the high spin type except for the Pd(II) and Pt(II) complexes which are four coordinate, square planar and diamagnetic.