Bonding Ability of Isopthalic Acid-bis(thiosemicarbozone) to Manganese and Cobalt Metal Ions: Preparation, Spectral Investigation, Computational and in vitro Antipathogenic Screening

Manganese and cobalt complexes have been designed and prepared with a tetradentate ligand i.e. isopthalic acid-bis(thiosemicarbozone) (IPBT), which bind to metal ions via donor atoms present in ligand. Different spectroscopic techniques viz. nuclear magnetic resonance, infra red, mass, electronic spin resonance and analytical studies have been used to determine the chemical composition of synthesized IPBT and its Mn(II) and Co(II) complexes. The spectroscopic data exposed that IPBT behaves in a tetradentate (N2S2) mode by having ability to bind with metal ions through N2S2 atoms. An octahedral structure for manganese and cobalt complexes has been suggested on the basis of spectroscopic as well as analytical studies. The ligand (IPBT) and its metal(II) complexes have been screened to determine their antipathogenic activity against some selective microorganisms S. aureus, P. aeruginosa, E. coli, A. niger, M. phasolina and P. glomerata. In this experimental work, well diffusion and poisoned food techniques have been introduced for screening purpose and as standard drugs neomycin and chlorothalonil have been used. Data for antipathogenic screening exposed that metal complexes exerted higher activity towards all examined microbes (bacteria and fungi) even than ligand.

Aerobic Oxidation Reactivity of Well-Defined CoII and CoIII Aminophenol Complexes

This article describes the synthesis and reactivity studies of three cobalt complexes bearing aminophenol-derived ligands without nitrogen substitution: CoII(tBu2APH)2(tBu2AP)2 (1), Co2III(tBu2APH)2(tBu2AP)2(μ-tBu2BAP)2 (2), and CoIII(tBu2AP)3 (3) (tBu2APH = 2-amino-4,6-di-tert-butylphenol, tBu2AP = 2-amino-4,6-di-tert-butylphenolate, μ-tBu2BAP = bridging 2-amido-4,6-di-tert-butylphenolate). Stoichiometric reactivity studies of these well-defined complexes demonstrate the catalytic com-petency of both CoII and CoIII complexes in the aerobic oxidative cyclization of tBu2APH with tert-butyl isonitrile. Reactions with O2 reveal the aerobic oxidation of CoII complex 1 to generate the CoIII species 2 and 3. UV-visible time-course studies and EPR spectroscopy indicate that this oxidation proceeds through a ligand-based radical intermediate. These studies repre-sent the first example of well-defined cobalt-aminophenol complexes that participate in catalytic aerobic oxidation reactions and highlight a key role for a ligand radical in the oxidation sequence.

cis-1,4 Selective Coordination Polymerization of 1,3-Butadiene and Copolymerization with Polar 2-(4-Methoxyphenyl)-1,3-butadiene by Acenaphthene-Based α-Diimine Cobalt Complexes Featuring Intra-Ligand π-π Stacking Interactions

Highly cis-1,4 selective (up to 98%) coordination–insertion polymerization of 1,3-butadiene (BD) has been achieved herein using acenaphthene-based α-diimine cobalt complexes. Due to the presence of intra-ligand π-π stacking interactions, the complexes revealed high thermostability, affording polybutadiene products in high yields. Moreover, all of the obtained polymers possessed a relatively narrow molecular weight distribution as well as high molecular weight (up to 92.2 × 104 Dalton). The molecular weights of the resultant polybutadienes could be finely tuned by varying polymerization parameters, including temperature, Al/Co ratio, etc. Moreover, the copolymerization of butadiene with polar monomer 2-(4-methoxyphenyl)-1,3-butadiene (2-MOPB) was also successfully realized to produce a type of polar cis-1,4 polybutadiene (cis-1,4 content: up to 98.1%) with a range of 2-MOPB content (0.46–1.83%). Water contact angle measurements indicated that the insertion of a polar monomer into a polymer chain could significantly improve the polymer’s surface property.