Organomercury(II) Complexes of Kojic Acid

Abstract

Kojic acid or 5-hydroxy-2-(hydroxymethyl)pyran-4-one (I) is an antibiotic substance produced by Aspergilli. It is known to inhibit thegrowth of E. coli and S. aureus.^1,2 Since the antibiotic activity of a drug is altered in the presence of metal ions, it was thought worthwhile to synthesise and characterise a few organomercury (11) complexes of kojic acid of the type RHgL(II) [R = C₆ H₅. o-, p-HOC₆H₄, p-AcOC₆H₄, 2-C₄H₃O (2-furyl); HL = kojic acid] and to study their activity against E. coti and P. pyocyuneu bacterial strains. This is a sequel to our investigation of metal ion-biomolecule interaction.^3–6     

Synthesis of Some Biologically Active Pyrazole, Thiazolidinone, and Azetidinone Derivatives

Pyrazole, thiazolidinone, and azetidinone derivatives were synthesized from chalcones of 4-hydroxycoumarin. The structures of all the synthesized compounds were confirmed on the basis of spectral and analytical data. The compounds were screened in vitro for their antibacterial activity against various bacterial strains.     

Thermal Studies of Cobalt(II), Nickel(II) and Copper(II) Complexes of 4-(Sulfonylazido Phenylazo) Pyrazolones

The thermal decompositions of cobalt(II), nickel(II) and copper(II) complexes of4-(3'-sulfonylazido-6'-methoxyphenylazo)-1-phenyl-3-methyl-2-pyrazolin-5-one H(D¹–SO₂N₃) and 4-(4'-sulfonylazido phenylazo)-3-phenyl-3-methyl-2-pyrazolin-5-one H(D²–SO₂N₃) were studied by thermogravimetry. The decomposition in all cases takes place along two stages. The first stage is due to the elimination of water and nitrogen molecules with the formation of tetracoordinate complexes containing nitrene reactive species[M(DSO₂N:)₂]. The second stage represents the decomposition of the material to the metal oxide. The kinetics of the decomposition were examined by using Coats–Redfern, the decomposition in all complexes was found to be first order for the first and second stages. The activation energies and other activation parameters (H^* and S^* and G^*) were computed and related to the bonding and stereochemistry of the complexes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Thermal Studies on Some Lanthanide Complexes

The new mixed ligand complexes with the formulae Zn(2-bipy)(ox), Zn(4-bipy)_1.5 (ox)H₂ O, Zn(2,4'-bipy)₂ (ox)2H₂ O, Cd(2-bipy)(ox)2H₂ O, Cd(4-bipy)₂ (ox) and Cd(2,4'-bipy)(ox)2H₂ O (2-bipy, 4-bipy, 2,4'-bipy=2,2'-, 4,4'- and 2,4'bipyridine, ox=oxalate) were prepared. The thermal decompositions of these compounds were studied by means of TG, DTG and DTA in air. During heating the complexes decompose via different intermediate products to ZnO and CdO. The Zn(II) complexes are thermally more stable than the corresponding Cd(II) complexes. The influence of nitrogen atom position in the bipyridine isomers and nature of central atom on the thermal behaviour of these complexes was discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Behaviour of Some Iron(III) Complexes with Active Therapeutically Biguanides

Two iron(III) complexes with therapeutically active biguanides - N',N'-anhydrobis-(beta-oxyethyl) biguanide (HMBig), and N',N'-dimethylbiguanide (HMetf), respectively - [Fe(HMBig)₃]Cl₃·9H₂O (I) and [Fe(HMBig)(HMetf)]Cl₃·6H₂O (II) - were synthesized and characterized through elemental analysis, electrical conductivity, IR and UV/VIS spectroscopy, measurements in magnetic field and non-isothermal analysis. In studied complexes the biguanide derivatives act as bidentate ligands through nitrogen atoms of the iminic groups. Their magnetic moments correspond to iron(III) in the spin quartet ground state. The thermal analysis evidenced an endotherm release of crystallization and coordinated water molecules. The degradation of the ligand molecules is a complex one, several processes being overlapped. The presence of biguanidic ligand increase the thermal stability of the coordination compound. The final product of both thermal decompositions is a-Fe₂O₃. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal Decomposition Kinetics of Some Metal Complexes of N,N-diethyl-n '-benzoylthiourea

Thermogravimetry (TG) and differential thermal analysis (DTA) were performed on the complexes with general formula (M(DEBT)_n (where M =Fe, Co, Ni, Cu or Ru; n =2, or 3 and DEBT=N,N-diethyl-N'-benzoylthiourea). Derivative thermogravimetric (DTG) curves were also recorded in order to obtain decomposition data on the complexes. The complexes of Fe(III), Co(II), Ni(II), Cu(II) and Ru(III) displayed two- or three-stage decomposition patterns when heated in a dynamic nitrogen atmosphere. Mass loss considerations relating to the decomposition stages indicated the conversion of the complexes to the sulfides or to the corresponding metal alone (Cu, Ru, NiS, CoS or FeS). Mathematical analysis of the TG and DTG data showed that the order of reaction varied between 0.395 and 0.973. Kinetic parameters such as the decomposition energy, the entropy of activation and the pre-exponential factor are reported. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and Thermal Studies of 2,4'-bipyridyl Complexes of Manganese(II) Salts

2,4'-Bipyridyl (2,4'-bipy or L) complexes of Mn(II) with the formulae MnL₂X₂·2H₂O (X_–=Cl, Br, NCS, NO₃), MnLSO₄·5H₂O and MnL₄(ClO₄)₂·2H₂O were synthesized and characterized via the IR spectra and magnetic, and conductivity measurements. The nature of the Mn(II)-ligand coordination is discussed. The thermal decompositions of these compounds were studied in air atmosphere. The mode of decomposition depends on the anion present, but the final product in all cases is Mn₃O₄. Some of the intermediates (MnL₂Cl₂, MnLCl₂, MnL₂Br₂, MnL₂(NCS)₂ and MnLSO₄) formed during the pyrolysis are isomeric with 2,2'-bipy and 4,4'-bipy complexes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Thermal Analysis of Manganese(II) Complexes With L-proline and L-hydroxyproline

The thermal decomposition reactions of manganese(II) complexes with L-proline and 4-hydroxy- L-proline were studied. The Mn(II) proline complex loses the water molecule at 40–95°C and then, heated above 250°C it decomposes in several steps to manganese oxide. The most appropriate kinetic equations for dehydration process are the geometrical R2 or R3 ones. They give a value of activation energy, E of about 95 kJmol^–1. The Mn(II) hydroxyproline complex loses the water molecules in two stages (70–110 and 110–230°C) and next it decomposes to manganese oxide in several steps. The R3 or D3 (three-dimensional diffusion) models are the most appropriate for the first stage of dehydration (E is about 155 kJ mol^–1). The second step of dehydration is limited by D3 mechanism (E=52 kJ mol^–1). This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition kinetics and mechanism of Cu(II), Zn(II) and Cd(II) complexes derived from fluorenone anthranilic acid

Copper(II), zinc(II) and cadmium(II) complexes of the Schiff base, fluorenone anthranilic acid were prepared and characterized by elemental analysis, magnetic measurements, conductivity experiments and electronic and infrared spectral studies. The thermal decomposition kinetics and mechanism of these chelates was studied from TG data.     

Physicochemical Studies and Thermal Decomposition Kinetics of Co(II), Ni(II), Cu(II) and Zn(II) Complexes of Citronellal Anthranilic Acid

Cobalt(II), nickel(II), copper(II) and zinc(II) complexes of two new Schiff-bases, citronellal anthranilic acid and citronellal-5-bromoanthranilic acid have been synthesized. On the basis of spectral, magnetic and thermal data, octahedral structure was assigned to all complexes [ML₂(H₂O)₂]. Thermal decomposition of these complexes was studied by TG. Kinetic parameters, viz activation energy, E, pre-exponential factor, A, and order of reaction, n, were calculated from the TG curves using mechanistic and non-mechanistic integral equations. This revised version was published online in July 2006 with corrections to the Cover Date.     

多相酶膜反应器合成生物活性二肽

生物活性肽;多相酶膜反应器合成生物活性二肽     

Crystal Structure of Cu(hfac)2 Complexes with Organomercury Binitroxide

The organomercury biradical HgL₂ (L is deprotonated 4,4,5,5-tetramethyl-2-imidazoline-3-oxide-1-oxyl) is capable of performing the bridging function for design of multinuclear heterospin systems. This paper describes synthesis and crystal structure of HgL₂ and the first multinuclear complexes of Cu(hfac)₂ with HgL₂.     

分子生物色谱用于中药活性成分筛选及质量控制方法的研究

报道了近期工作进展,首先阐述了分子生物色谱的基本原理及特点,然后介绍了分子生物色谱对多种中药、不同产地的同种中药活性成分谱图模式的比较,结合已有的工作对活性成分筛选方法、相互作用研究、质量控制方法发展做了细致的说明,并讨论了其发展方向及前景。     

Thermal Studies of Copper(II) Squarate Complexes of Diamines in the Solid State

CuL₂C₄O₄ [L=ethane-1,2-diamine (en)], CuL₂C₄O₄⋅2H₂O [L=N-methylethane-1,2-diamine (meen), N-ethylethane-1,2-diamine (eten),N-propylethane-1,2-diamine (pren), N-methyl-N’-ethylethane- 1,2-diamine (meeten) andpropane-1,2-diamine (pn)], CuL₂C₄O₄⋅0.5H₂O [L=N,N’-dimethylethane- 1,2-diamine (dmeen)], CuL₂C₄O₄⋅4H₂O [L=propane-1,2-diamine (pn)]and CuL₂C₄O₄⋅H₂O[L=2-methylpropane-1,2-diamine (ibn)] have been synthesized by the addition of respective diamine to finely powdered CuC₄O₄⋅2H₂O and their thermal studies have been carried out in the solid state. Cu(en)₂C₄O₄ upon heating loses one molecule of diamine with shar pcolour change yielding Cu(en)C₄O₄ which upon further heating transforms to unidentified products. All aquated-bis-diamine species [CuL₂C₄O₄⋅2H₂O, CuL₂C₄O₄⋅0.5H₂O and CuL₂C₄O₄⋅H₂O] upon heating undergo deaquation–anation reaction in the solid state showing thermochromism and transform to CuL₂C⁴O₄, which revert on exposure to humid atmosphere (RH ∼90%). All the squarato bis-diamine species, CuL₂C₄O₄, on further heating transform to unidentified products through the formation of CuLC₄O₄ as intermediates. The mono diamine species, have been isolated pyrolytically in the solid state and can be stored in a desiccator as well as in open atmosphere. They are proposed to be polymeric. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Studies of N-phenylethane-1,2-diamine Complexes of Nickel(II) in the Solid State

[NiL₃]X₂ (where L=N-phenylethane-1,2-diamine and X=I⁻ and ClO₄ ⁻), [NiL₂X₂] (X is Cl⁻, Br⁻, NCS⁻, 0.5SO₄ ²⁻ or 0.5SeO₄ ²⁻) and [NiL₂(H₂O)₂](NO₃)₂ have been synthesized from solution and their thermal study has been carried out in the solid phase. [NiL₂Cl₂] upon heating undergoes irreversible endothermic phase transition (142–152°C, ΔH=0.35 kJ mol⁻¹) without showing any visual colour change. This phase transition is assumed to be due to conformation changes of the diamine chelate rings. NiLCl₂ and NiL_2.5I₂ have been prepared pyrolytically from [NiL₂Cl₂] and [NiL₃]I₂ respectively in the solid state. [NiL₂(H₂O)₂](NO₃)₂ upon heating undergoes deaquation-anation reaction without showing any visual colour change. [NiL₂X₂] (X is Cl⁻, Br⁻, NCS⁻), [NiL₂(H₂O)₂](NO₃)₂ and [NiL₂(NO₃)₂] possess trans-octahedral configuration, whereas, [NiL₂X₂] (X is 0.5SO₄ ²⁻ or 0.5SeO₄ ²⁻) are having cis-octahedral configuration. Amongst the complexes, only NiLCl₂ shows unusually high (5.1 BM at 27°C) magnetic susceptibility value. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Thermal Stability of Ciprofloxacin Complexes with Magnesium(II), Zinc(II) and Cobalt(II)

The thermal behaviour of Mg(II), Zn(II) and Co(II) compounds of ciprofloxacin was studied by thermogravimetry (TG) and differential thermal analysis (DTA) in order to determine or to confirm some structural characteristics of substances. The complexes decompose in two steps: dehydration and pyrolytic decomposition of the anhydrous complexes to form metal oxide or metal fluoride. The dehydration process of one magnesium(II) compound takes place in two steps suggesting a marked difference in the bonding of water molecules. The different bonding mode of the ciprofloxacin molecules in both magnesium compounds leads to different residues of the thermal decompositions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electrometric Studies on the Ternary Complexes of M(II) With Chlorpromazine and Some Amino Acids

 The stability constants for the binary M(II)- chlorpromazine hydrochloride (CPZ) and the ternary complexes M(II)-chlorpromazine-amino acid, have been studied using pH-measurements. The amino acids (aa) are: glycine, glutamic acid, histidine and the metal ions are: Cu(II), Zn(II), Co(II), Ni(II) and UO₂(II). All experiments were carried out in the presence of 0.1 mol dm⁻³ KNO₃. The resulting stability constants of the binary and the ternary complexes were compared. It was observed that the stability of the ternary complexes-except for glutamic acid – are lower than of the binary ones. Received October 22, 1998. Revision March 14, 1999.     

Thermal Behaviour of Copper(II) Complexes of Haloaspirinates

Complexes of Cu(II) with substituted o-acetoxy benzoic acids (5-haloaspirines, X-asp) with and without pyridine (py), of composition [Cu₂(X-asp)₄] and [Cu(X-asp)₂(py)₂ ] have been synthesized and characterized. Electronic and vibrational spectroscopic data of these complexes are reported. Its thermal behaviour was investigated by thermogravimetry and differential thermal analysis. In all complexes, the haloaspirinate ligands decompose in two or three steps, starting with the break up of the coordinated acetoxy groups. CuO is obtained as the final pyrolysis residue in all cases. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Analysis of Manganese(II) Complexes With Glycine

The thermal decomposition behaviour of the manganese(II) complexes with glycine: Mn(gly)Cl₂(H₂O)₂, Mn(gly)₂Cl₂, Mn(gly)Br₂(H₂O)₂, Mn(gly)₂Br₂(H₂O)₂ was investigated by means of TG-DTG-DTA, Hi-Res-TA and DSC techniques. The evolved gas analysis was carried out by means of the coupled TG-FTIR system. Heating of the complexes results first in the release of water molecules. Next, the multi-stage decomposition process with degradation of glycine ligand occurs. Water, carbon dioxide and ammonia were detected in the gaseous products of the complexes decomposition. The temperature of NH₃ evolution from the complexes is higher than from free glycine. The final residue in the air atmosphere is Mn₂O₃ which transforms into Mn₃O₄ at 930°C. In a nitrogen atmosphere, the complexes decompose into MnO. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Decomposition of Mg(II) Complexes with Ronicol

The thermal decomposition of the complexes Mg(Clac)₂ (ron)₂ ×3H₂ O(I), Mg(Cl₂ ac)₂ (ron)₂ ×3H₂ O(II) and Mg(Cl₃ ac)₂ (ron)₂ ×3H₂ O(III), where Clac =ClCH₂ COO^- , Cl ₂ ac =Cl₂ CHCOO^- , Cl ₃ ac =Cl₃ CCOO^- and ron =3-pyridylcarbinol (ronicol) had been investigated in air atmosphere in temperature range 20–1000°C by means of TG and DTA. The composition of the complexes and the solid state intermediate and resultant products of thermolysis had been identified by means of elemental analysis and complexometric titration. The possible scheme of destruction of the complexes is suggested. The final product of the thermal decomposition was MgO. The thermal stability of the complexes can be ordered in the sequence: I<III<II. IR data suggest that ronicol was coordinated to Mg(II) through the nitrogen atom of its heterocyclic ring. This revised version was published online in July 2006 with corrections to the Cover Date.