Synthesis and properties of iron (II) quinoline-2-carboxylates, crystal structure of trans-diaquabis(quinoline-2-carboxylato)iron (II) bis(dichloromethane) solvate

Beyond the Simple Copper(II) Coordination Chemistry with Quinaldinate and Secondary Amines

Copper(II) acetate has reacted in methanol with quinaldinic acid (quinoline-2-carboxylic acid) to form [Cu(quin)₂(CH₃OH)]∙CH₃OH (1) (quin⁻ = an anionic form of the acid) with quinaldinates bound in a bidentate chelating manner. In the air, complex 1 gives off methanol and binds water. The conversion was monitored by IR spectroscopy. The aqua complex has shown a facile substitution chemistry with alicyclic secondary amines, pyrrolidine (pyro), and morpholine (morph). trans-[Cu(quin)₂(pyro)₂] (2) and trans-[Cu(quin)₂(morph)₂] (4) were obtained in good yields. The morpholine system has produced a by-product, trans-[Cu(en)₂(H₂O)₂](morphCOO)₂ (5) (morphCOO⁻ = morphylcarbamate), a result of the copper(II) quinaldinate reaction with ethylenediamine (en), an inherent impurity in morpholine, and the amine reaction with carbon dioxide. (pyroH)[Cu(quin)₂Cl] (3) forms on the recrystallization of [Cu(quin)₂(pyro)₂] from dichloromethane, confirming a reaction between amine and the solvent. Similarly, a homologous amine, piperidine (pipe), and dichloromethane produced (pipeH)[Cu(quin)₂Cl] (11). The piperidine system has afforded both mono- and bis-amine complexes, [Cu(quin)₂(pipe)] (6) and trans-[Cu(quin)₂(pipe)₂] (7). The latter also exists in solvated forms, [Cu(quin)₂(pipe)₂]∙CH₃CN (8) and [Cu(quin)₂(pipe)₂]∙CH₃CH₂CN (9). Interestingly, only the piperidine system has experienced a reduction of copper(II). The involvement of amine in the reduction was undoubtedly confirmed by identification of a polycyclic piperidine compound 10, 6,13-di(piperidin-1-yl)dodecahydro-2H,6H-7,14-methanodipyrido[1,2-a:1′,2′-e][1,5]diazocine.

Antioxidant, tautomerism and antibacterial studies of Fe(III)-1,2,4-triazole based complexes

New Fe(III) complexes have been synthesized by the reactions of ferric nitrate with Schiff base derived from 3-substituted phenyl-4-amino-5-hydrazino-1,2,4-triazole and indoline-2,3-dione. All these complexes are soluble in DMF and DMSO; low molar conductance values indicate that they are non-electrolytes. Elemental analyses suggest that the complexes have 1:1 stoichiometry of the type [FeLn(H2O)(OH)]·xH2O. Structural and spectroscopic properties have been studied on the basis of elemental analyses, infrared spectra, (1)H and (13)H NMR spectra, electronic spectra, magnetic measurements and FAB mass spectra. FT-IR, (1)H and (13)H NMR studies reveal that the ligand (Ln) exists in the tautomeric enol form in both the states with intramolecular hydrogen bonding. Magnetic moment and reflectance spectral studies reveal that an octahedral geometry has been assigned to all the prepared complexes. FRAP values indicate that all the compounds have a ferric reducing antioxidant power. The compounds 2 and 3 showed relatively high antioxidant activity while compound 1 and 4 shows poor antioxidant power. Also good antimicrobial activities of the complexes against Staphylococcus aureus, Bacillus subtilis, Serratia marcescens, Pseudomonas aeruginosa and Escherichia coli have been found compared to its free ligands.

Antitubercular and fluorescence studies of copper(II) complexes with quinolone family member, ciprofloxacin

Four new mixed-ligand complexes of Cu(II) with ciprofloxacin (Cip) and uninegative bidentate ligands have been synthesized and characterized. The structure of mixed-ligand complexes was investigated using spectroscopic method, physicochemical and elemental analyses. The fluorescence spectra of complexes show red shift, which may be due to the chelation by the ligands to the metal ion. It enhances ligand ability to accept electrons and decreases the electron transition energy. Antimycobacterial screening of ligand and its copper compound against Mycobacterium tuberculosis shows clear enhancement in the antitubercular activity upon copper complexation.

DNA interactions and promotion in antibacterial activities of ciprofloxacin drug due to formation of mixed-ligand complexes of oxovanadium(IV)

Mixed-ligand complexes of oxovanadium(IV) of the type [VOAL]*2H(2)O [where A = ciprofloxacin and L = uninegative bidentate ligands] have been synthesized and characterized using infrared spectra, electronic spectra, magnetic measurements, elemental analyses, thermal investigation, and mass spectroscopy. Here, we tried to increase an antibacterial activity of ciprofloxacin drug due to formation of mixed-ligand complexes. The complexes were found to be more potent compare to some standard drugs, ligands and metal salt against selective gram(+ve) and gram(-ve) organisms. Binding of the complexes with DNA have been investigated by spectroscopic absorption titration and viscometric techniques. The mixed-ligand complexes show good binding ability. The cleavage efficacy has been determined using gel electrophoresis method and complexes were found to be more active compared to parental ligands and metal salt.

Synthesis and characterization of iron(II) quinaldate complexes

Treatment of iron(II) chloride or iron(II) bromide with 2 equiv of sodium quinaldate (qn = quinaldate or C(10)H(6)NO(2)(-)) yields the coordinatively unsaturated mononuclear iron(II) quinaldate complexes Na[Fe(II)(qn)(2)Cl].DMF and Na[Fe(II)(qn)(2)Br].DMF (DMF = N,N-dimethylformamide), respectively. When a similar synthesis is carried out using iron(II) triflate, a solvent-derived linear triiron(II) complex, [Fe(II)(3)(qn)(6)(DMF)(2)], with two five-coordinate iron(II) centers and a single six-coordinate iron(II) center is obtained. Each of these species has been characterized using X-ray diffraction. The vibrational features of these complexes are consistent with the observed solid-state structures. Each of these compounds exhibits an iron(II)-to-quinaldate (pi*) charge-transfer band between 520 and 550 nm. These metal-to-ligand charge-transfer bands are sensitive to substitution of the quinaldates as well as alteration of the first coordination sphere ligands. However, the (1)H NMR spectra of these paramagnetic high-spin iron(II) complexes are not consistent with retention of the solid-state structures in a DMF solution. The chemical shifts, longitudinal relaxation times (T(1)), relative integrations, and substitution of the quinaldate ligands provide a means to fully assign the (1)H NMR spectra of the paramagnetic materials. These spectra are consistent with coordination equilibria between five- and six-coordinate species in a DMF solution. Electrochemical studies are reported to place these oxygen-sensitive compounds in a broader context with other iron(II) compounds. Iron complexes of bidentate quinoline-2-carboxylate-derived ligands are germane to metabolic pathways, environmental remediation, and catalytic applications.