Thermoanalytical investigation and biological properties of zinc(II) 4-chloro- and 5-chlorosalicylates with N-donor ligands

New zinc(II) 4- and 5-chlorosalicylate complexes of general formula [Zn(X-sal)₂(L) _n (H₂O) _x ] (where X-sal?=?4-Clsalicylate, 5-Clsalicylate; L?=?N,N-diethylnicotinamide, isonicotinamide, theophylline; n?=?1, 2; x?=?0, 1, 2, 4) were prepared. The complexes were determined by elemental analysis and characterised by infrared spectroscopy. The thermal behaviour of the complexes was studied by simultaneous TG, DTG and DTA methods under dynamic air conditions. The thermal decomposition is a multi-step process. In the first step of the thermal decomposition, water is released in hydrated compounds. The anhydrous compounds start to decompose by the release of organic ligand, followed by chlorosalicylic acid, chlorophenol and carbon monoxide. The final solid product of the thermal decomposition is zinc oxide. The volatile products of the thermal decomposition were determined by mass spectrometry. The antimicrobial activities of the complexes were evaluated against selected pathogen and probiotic bacteria, yeasts and fungi strains. Bioactivities of the tested compounds are different against bacteria, yeasts and filamentous fungi. It was found that bacteria were more sensitive to the studied zinc(II) complex compounds than yeasts or filamentous fungi.     

Synthesis,thermal, spectral and biological properties of zinc(II) 4-hydroxybenzoate complexes

New zinc(II) 4-hydroxybenzoate complex compounds with general formula [Zn(4-OHbenz)₂L_n]·xH₂O, where 4-OHbenz = 4-hydroxybenzoate; L = isonicotinamide, N-methylnicotinamide, N,N-diethylnicotinamide, thiourea, urea, phenazone, theophylline, methyl-3-pyridylcarbamate; n = 2, 3; x = 0–3, 5, were synthesized and characterised by elemental analysis, thermal analysis and IR spectroscopy. The thermal behaviour of the prepared compounds was studied by TG/DTG and DTA methods in argon atmosphere. The thermal decomposition of hydrated compounds started with dehydration. During the thermal decomposition, organic ligand, carbon monoxide, carbon dioxide and phenol were evolved. The final solid product of the thermal decomposition was zinc or zinc oxide. The volatile gaseous product, solid intermediate products and the final product of thermal decomposition were identified by IR spectroscopy, mass spectrometry, qualitative chemical analyses and X-ray powder diffraction method. The antimicrobial activity of zinc(II) carboxylate compounds was tested against various strains of bacteria, yeasts and filamentous fungi (S. aureus, E. coli, C. parapsilosis, R. oryzae, A. alternata, M. gypseum). The presence of zinc in complexes led to the increase in their antimicrobial activity in comparison with free 4-hydroxybenzoic acid.     

Thermal decomposition and antimicrobial activity of zinc(II) 2-bromobenzoates with organic ligands

New zinc(II) 2-bromobenzoate complex compounds with general formula Zn(2-BrC₆H₄COO)₂·nL·xH₂O (where L = urea, nicotinamide, N-methylnicotinamide, N,N-diethylnicotinamide, isonicotinamide, phenazone n = 0–2, x = 0–2) were prepared and characterized by elemental analysis, IR spectroscopy and thermal analysis. The thermal decomposition of hydrated compounds started with dehydration process. During the thermal decomposition organic ligand, carbon dioxide and bis(2-bromophenyl)ketone were evolved. The solid intermediates and volatile products of thermal decomposition were proved by IR spectroscopy and mass spectrometry. The final solid product of the thermal decomposition heated up to 1073 K was zinc oxide. Antimicrobial activity of the prepared compounds was tested against various strains of bacteria, yeasts and filamentous fungi (E. coli, S. aureus, C. albicans, R. oryzae, A. alternate and M. gypseum). It was found that the selected bacteria were more sensitive to the studied zinc(II) complex compounds than the yeast and the filamentous fungi.     

Thermal decomposition study and biological characterization of zinc(II) 2-chlorobenzoate complexes with bioactive ligands

New zinc(II) 2-chlorobenzoates of general formula [Zn(2-ClC₆H₄COO)₂(L)₂] (where L = caffeine—caf, urea—u, methyl-3-pyridylcarbamate—mpc, phenazone—phen, theophylline—thp) were synthesised and characterised by elemental analysis and IR spectroscopy. The thermal behaviour of the complexes was studied by TG/DTG and DTA methods in nitrogen and in air atmosphere. During the thermal decomposition of the studied compounds the release of organic ligands take place followed by the decomposition of 2-chlorobenzoate anion. The volatile decomposition intermediates were proved by mass spectrometry. Zinc oxide was found as the final product of the thermal decomposition performed up to 1,000 K. The antimicrobial activity of the zinc(II) complexes against various strains of bacteria, yeasts and filamentous fungi has been investigated. It was found that the prepared compounds decreased the growth of Staphylococcus aureus, Escherichia coli, Candida albicans, Rhizopus oryzae and Microsporum gypseum, respectively. The most resistant to all tested compounds was probiotic strain of Lactobacillus plantarum. The presence of zinc and ligands in the prepared compounds increased the inhibitory effect compared to sodium salt of prepared compounds and free ligands.     

Preparation,spectral, thermal,and biological properties of zinc(II) 4-chloro- and 5-chlorosalicylate complexes with methyl 3-pyridylcarbamate and phenazone

New zinc(II) 4-chloro- and 5-chlorosalicylate complex compounds of the general formula ((4- or 5-Cl)C₆H₃(2-OH)COO)₂Zn · L _n (where L = methyl 3-pyridylcarbamate, phenazone; n = 2, 4) were prepared and characterized by elemental analysis, thermal analysis (TG/DTG, DTA), and IR spectroscopy. During thermal decomposition, mpc, phen, chlorosalicylic acid, chlorophenol, carbon dioxide, and carbon monoxide were released. Volatile products of the thermal decomposition were confirmed by mass spectrometry. The final solid product of the thermal decomposition up to 700°C was zinc oxide or metallic zinc. Antimicrobial activity of the compounds prepared was tested against various strains of bacteria, yeasts and filamentous fungi. The highest antimicrobial effect was determined against the G⁺ bacteria S. aureus.     

Preparation,thermal decomposition,and crystal structure of Zn(II) 2-chlorobenzoate complex with nicotinamide

A new Zn(II) 2-chlorobenzoate complex, [Zn(2-ClC₆H₄COO)₂(nad)₂] (nad = nicotinamide), was synthesized and characterized by elemental analysis, infrared (IR) spectroscopy, mass spectrometry, thermal analysis, and X-ray structure determination. The mechanism of thermal decomposition of the complex was studied by TG/DTG, DTA, IR spectroscopy, and mass spectrometry. The thermal decomposition is characterized as a two-step process. Zinc oxide was found as the final product of the thermal decomposition performed up to 900°C. Mass spectrometry was used to determine the volatiles released during thermal decomposition. The IR spectrum indicates that carboxylate is coordinated to zinc in monodentate coordination. [Zn(2-ClC₆H₄COO)₂(nad)₂] crystallizes in the monoclinic system, space group Pn, a = 10.376(2) Å, b = 10.100(1) Å, c = 12.604(1) Å, β = 100.79(1)°. The zinc is tetrahedrally coordinated by two nitrogens of nicotinamide and two oxygens of 2-chlorobenzoate.     

Chemical structure and glass transition temperature of non-ionic cellulose ethers

New zinc(II) propionate complexes (CH₃CH₂COO)₂Zn·Ln·xH₂O, where n=1-2, x=0 or 2, were prepared by reaction of zinc(II) propionate with heterocyclic ligands (L=theophylline, nicotinamide, methyl-3-pyridyl carbamate) and their thermal properties were studied. The prepared complex compounds were characterized by elemental analysis and IR spectra. TG/DTG and DTA measurements of the prepared compounds were performed in the air atmosphere under dynamic conditions. The thermal decomposition can be characterized as a multi-step process. The first step is attributed to the elimination of water or N-donor ligand molecules. It is followed by the decomposition of propionate anion when diethyl ketone and carbon dioxide were released. Zinc oxide was found as a final product of the thermal decomposition of the complex compounds under study. The volatile intermediate products of the thermal decomposition of zinc(II) propionate complexes were identified by IR-spectroscopy, qualitative chemical analyses and final solid product by X-ray powder diffraction method. Moreover, IR spectra suggest monodentate coordination of propionate anion to zinc. The complexes were tested against bacteria and filamentous fungi and show both antimicrobial activity and fungistatic effect towards pathogens as well as probiotic activity towards Lactobacillus paracasei.     

Synthesis,biological and physicochemical properties of Zinc(II) salicylate and 5-chlorosalicylate complexes with theophylline and urea

New zinc(II) salicylate complex compounds of general formula (X-C₆H₃-2-(OH)COO)₂Zn · L_n · xH₂O (where X = H, 5-Cl; L = theophylline, urea; n = 2, 4; x = 1, 2, 4) were prepared and their thermal, spectral and biological properties were studied. It was found that the thermal decomposition of hydrated compounds starts with the release of water. During the thermal decomposition of anhydrous compounds, the release of salicylic acid, theophylline, urea, CO₂, H₂O and C₆H₅Cl takes place. Zinc oxide was found as the final product of the thermal decomposition heated up to 900 °C. The complexes were tested against bacteria, yeasts and filamentous fungi. The highest biological activity show 5-chlorosalicylate compounds.     

Thermal,structural and optical properties of Al2CoO4-Crocoite composite nanoparticles used as pigments

Novel zinc(II) complex compounds of general formula Zn(C₆H₅COO)₂·L₂ (where L=caffeine (caf) and urea (u)) were synthesized and characterized by elemental analysis and IR spectroscopy. The thermal behaviour of the complexes was studied during heating in air by thermogravimetry. It was found that the thermal decomposition of the anhydrous Zn(II) benzoate compounds with bioactive ligands was initiated by the release of organic ligands at various temperatures. On further heating of the compounds up to 400°C the thermal degradation of the benzoate anions took place. Zinc oxide was found as the final product of the thermal decomposition of all zinc(II) benzoate complex compounds heated to 600°C. Results of elemental analysis, infrared spectroscopy, mass spectroscopy and thermogravimetry are presented.     

Synthesis, spectroscopic, thermal characterization, and antimicrobial activity of miconazole drug and its metal complexes

Metal complexes having the general composition [MCl₂(H₂O)₂(L)₂]·yH₂O (where y?=?1?C3, M?=?Mn(II), Cu(II), Co(II), Ni(II), and Zn(II) and L?=?miconazole drug?=?MCNZ) and [MCl₂(H₂O)₂(L)₂]Cl·3H₂O (where M?=?Cr(III) and Fe(III)) have been synthesized. All the synthesized complexes were identified and confirmed by elemental analyses, IR, diffused reflectance, and thermal analyses (TG and DTA) techniques as well as molar conductivity and magnetic moment measurements. The molar conductance data reveals that bivalent metal complexes are non-electrolytes while Cr(III) and Fe(III) complexes are electrolytes and of 1:1 type. IR spectral studies reveal that MCNZ is coordinated to the metal ions in a neutral unidentate manner with N donor site of the imidazole-N. On the basis of magnetic and solid reflectance spectral studies, an octahedral geometry has been assigned for the complexes. Detailed studies of the thermal properties of the complexes were investigated by thermogravimetry (TG) and differential thermal analyses (DTA) techniques and the activation thermodynamic parameters are calculated using Coats?CRedfern method. The free MCNZ drug and its complexes were also evaluated against bacterial species (P. aeruginosa, S. aureus, B. subtilis, E. Coli) and fungi (A. fumigatus, P. italicum, and C. albicans) in vitro. The activity data show that the metal complexes have higher biological activity than the parent MCNZ drug.     

Thermal investigations of nickel–zinc ferrites formation from malate coordination compounds

Nickel–zinc ferrites have been synthesized via thermal decomposition of polynuclear coordination compounds containing as ligand the anion of malic acid, namely (NH₄)[Fe₂NixZn_1–x(C₄H₄O₅)(OH)₃]·nH₂O (x =0.25, 0.5 and 0.75, n=3 and 5). A comparison between the thermal behaviour of the studied polynuclear coordination compounds is inferred. Fe₂NixZn_1–xO₄ (n=0.25, 0.5 and 0.75) ferrites with mean particle sizes of 65–85 Å and free from other phases are formed after a heating treatment of only one hour at 500°C.     

Thermal study of zinc(II) salicylate complex compounds with bioactive ligands

Five new complex compounds of general formula Zn(Hsal)_2·L₂·nH₂O (where Hsal=OHC₆H₄COO^-, L=thiourea (tu), nicotinamide (nam), caffeine (caf), theobromine (tbr), n=2-4), were prepared and characterized by chemical analysis, IR spectroscopy and studied by methods of thermal analysis (TG/DTG, DTA). It was found that the thermal decomposition of hydrated compounds starts with the release of water molecules. During the thermal decomposition of anhydrous compounds the release of organic ligands take place followed by the decomposition of salicylate anion. Zinc oxide was found as the final product of the thermal decomposition heated up to 800°C. RTG powder diffraction method, IR spectra and chemical analysis were used for the determination of products of the thermal decomposition. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis,crystal structures,thermal properties,and DNA-binding studies of transition metal complexes with imidazole ligands

A new series of complexes of transition metal (Cu, Zn, Ni) perchlorate with imidazole have been synthesized and characterized by elemental analysis, infrared (IR), UV-Vis spectroscopy, and single-crystal X-ray diffraction. Based on elemental and spectral data, the complexes are M(C₃H₄N₂) _x (ClO₄)₂ (M?=?Cu, Zn, x?=?4; M?=?Ni, x?=?6; C₃H₄N₂?=?imidazole). The crystal structures of Cu(C₃H₄N₂)₄(ClO₄)₂ (1) and Zn(C₃H₄N₂)₄(ClO₄)₂ (2) show metals surrounded by four nitrogens of imidazole, while the nickel complex Ni(C₃H₄N₂)₆(ClO₄)₂ (3) has six nitrogens of imidazole. Intra- and inter-molecular hydrogen bonds exist between hydrogen of imidazole and oxygen of perchlorate. The thermal stabilities of 1, 2, and 3 at different heating rates (β?=?5°C?min^?1, 10°C?min^?1, and 15°C?min^?1) show that all the complexes exhibit two thermal decomposition stages; the sequence of thermal stability is 2?>?1?>?3. 1, 2, 3, and imidazole display DNA binding ability, ascertained by UV-Vis titration.     

Preparation of non-valence compounds of zinc(II) with 1,2- and 1,4-benzenedicarboxylic acids via self-assembly

Nanostructured non-valence compounds based on coordination compounds of zinc(II) with phthalic and terephthalic acids have been prepared. The purity and composition of prepared compounds have been elucidated from X-ray diffraction analysis, IR spectroscopy, elemental analysis, and thermogravimetry studies; thermal decomposition of the non-valence compounds has been studied as well. The prepared self-assembled compounds are co-precipitated with one water molecule and 1.5 acetic acid molecules per unit of the dicarboxylic acid: [Zn₄(OH)₆·o-C₆H₄(COO)₂]·H₂O·1.5CH₃COOH and [Zn₄(OH)₆·p-C₆H₄(COO)₂]·H₂O· 1.5CH₃COOH.     

Thermal study of zinc(II) 4-chlorosalicylate complex compounds with bioactive ligands

Three new complex compounds of general formula Zn{4-ClC₆H₃-2-(OH)COO}₂⋅L₂⋅nH₂O (where L=thiourea (tu), nicotinamide (nam), caffeine (caf), n=2,3), were prepared and characterized by chemical analysis, IR spectroscopy and their thermal properties were studied by TG/DTG, DTA methods. It was found that the thermal decomposition of hydrated compounds starts with the release of water molecules. During the thermal decomposition of anhydrous compounds the release of organic ligands take place followed by the decomposition of salicylate anion. Zinc oxide was found as the final product of the thermal decomposition performed up to 650°C. RTG powder diffraction method, IR spectra and chemical analysis were used for the determination of products of the thermal decomposition.     

Thermal,Spectral and Antimicrobial Properties of New Zinc(II) Isobutyrate Compounds: Part I. Papaverine,Phenazone

Zinc carboxylate complexes with N-donor ligands exhibit antimicrobial and antifungal effects. The preparation and thermal properties of complex compounds Zn(isobut)₂ and Zn(isobut)₂L(isobut=(CH₃)₂CHCOO^–, L=papaverine — pap, phenazone — phen) are described in this paper. The newly synthesized compounds were characterized by elemental analysis, IR spectroscopy and TG/DTG, DTA methods.During the thermal treatment it was found that the release of organicligands (pap, phen) was followed by pyrolysis of zinc(II) isobutyrate. (C₃H₇)₂CO and CO₂ were found as gaseous products and zinc oxide as the final product of thermal decomposition. Gaseous and solid products of thermal decomposition were confirmed by chemical analysis, IR spectra and X-ray powder diffraction.This revised version was published online in November 2005 with corrections to the Cover Date.     

Thermal behaviour of ZINC(II) carboxylate complexes with methyl-3-pyridyl carbamate

Four new complex compounds were prepared by reaction of zinc carboxylate and methyl-3-pyridyl carbamate. The synthesized complex compounds of the general formula (RCOO)₂ZnL₂ (RCOO^-= HCOO^- (form), CH₃COO^- (ac), CH₃CH₂CH₂COO^- (but), (CH₃)₂CHCOO^- (isobut), L= methyl-3-pyridyl carbamate (mpc)) were characterized by chemical analysis, IR spectroscopy and studied by methods of thermal analysis (TG/DTG, DTA). CH₂O, CO₂, (CH₃)₂CO, (C₃H₇)₂CO were found as volatile products of thermal decomposition. ZnO was found as final product of thermal decomposition of the prepared complexes heated up to 700°C. Mass spectroscopy, X-ray powder diffraction method, IR spectra and chemical analysis were used for the determination of the thermal decomposition products. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal properties of solid complexes with biologically important heterocyclic ligands

Thermogravimetry (TG), derivative thermogravimetry (DTG) and infrared (IR) spectroscopy have been applied to the investigation of the thermal behaviour and structure of the compounds [Cu(2-Clbz)₂(nia)₂(H₂O)₂] (I), [Cu(2-Clbz)₂(nia)₂]·H₂O (II), [Cu(2-Brbz)₂(nia)₂]·2H₂O (III), [Cu(2-Brbz)₂(nia)₂(H₂O)] (IV), where 2-Clbz and 2-Brbz?=?2-chloro- and 2-bromobenzoate anions, nia?=?nicotinamide, H₂O?=?water molecules. Thermal decomposition of all studied compounds proceeds in three steps. Heating the compounds first results in a release of non-coordinated and/or coordinated water molecules. The final product of thermal decomposition was CuO. The thermal stability of the complexes can be ordered in the sequence: I<IV<III<II. Nicotinamide is coordinated to Cu(II) through the nitrogen atom of the heterocyclic ring. IR data suggest the unidentate coordination of benzoate anions to Cu(II) in complexes I, IV and bidentate coordination in complexes II and III.     

A new method of synthesis of BiFeO<Subscript>3</Subscript> prepared by thermal decomposition of Bi[Fe(CN)<Subscript>6</Subscript>]·4H<Subscript>2</Subscript>O

In order to investigate the formation of the multiferroic BiFeO₃, the thermal decomposition of the inorganic complex Bismuth hexacyanoferrate (III) tetrahydrate, Bi[Fe(CN)₆]·4H₂O has been studied. The starting material and the decomposition products were characterized by IR spectroscopy, thermal analysis, laboratory powder X-ray diffraction, and microscopic electron scanning. The crystal structures of these compounds were refined by Rietveld analysis. BiFeO₃ were synthesized by the decomposition thermal method at temperature as low as 600 °C. There is a clear dependence of the type and amount of impurities that are present in the samples with the time and temperature of preparation.     

Thermal stability of new zinc acetate-based complex compounds

New zinc acetate based complex compounds (of general formula Zn(CH₃COO)₂·1?2L·nH₂O) containing one or two molecules of urea, thiourea, coffeine and phenazone were prepared namely: Zn(CH₃COO)₂·2.5H₂O, Zn(CH₃COO)₂·2u·0.5H₂O, Zn(CH₃COO)₂·tu·0.5H₂O, Zn(CH₃COO)₂·2tu, Zn(CH₃COO)₂·cof·2.5H₂O, Zn(CH₃COO)₂·2cof·3.5H₂O, Zn(CH₃COO)₂·2phen·1.5H₂O. The compounds were characterized by IR spectroscopy, chemical analysis and thermal analysis. Thermal analysis showed that no changes in crystallographic modifications of the compounds take place during (heating in nitrogen before) the thermal decompositions. The temperature interval of the stability of the prepared compounds were determined. It was found that the thermal decomposition of hydrated compounds starts by the release of water molecules. During the thermal decomposition of anhydrous compounds in nitrogen the release of organic ligands take place followed by the decomposition of the acetate anion. Zinc oxide and metallic zinc were found as final products of the thermal decomposition of the zinc acetate based complex compounds studied. Carbon dioxide and acetone were detected in the gaseous products of the decomposition of the compounds if ZnO is formed. Carbon monoxide and acetaldehyde were detected in the gaseous products of the decomposition, if metallic Zn is formed. It is supposed that ZnO and Zn resulting from Zn acetate complex compounds here studied, possess different degree of structural disorder. Annealing takes place by further heating above 600°C.