Metal ion complexes are playing an increasing role in the development of antimicrobials. We review here the antimicrobial properties of cobalt coordination complexes in oxidation state 3+. In addition to reviewing the cobalt complexes containing polydentate donor ligands, we also focus on the antimicrobial activity of the homoleptic [Co(NH3)6]3+ ion.
Kinetics, stoichiometry, and products of the oxidation of trimethoprim (TMP), one of the most commonly detected antibacterial agents in surface waters and municipal wastewaters, by ferrate(VI) (Fe(VI)) were determined. The pH dependent second-order rate constants of the reactions of Fe(VI) with TMP were examined using acid-base properties of Fe(VI) and TMP. The kinetics of reactions of diaminopyrimidine (DAP) and trimethoxytoluene (TMT) with Fe(VI) were also determined to understand the reactivity of Fe(VI) with TMP. Oxidation products of the reactions of Fe(VI) with TMP and DAP were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Reaction pathways of oxidation of TMP by Fe(VI) are proposed to demonstrate the cleavage of the TMP molecule to ultimately result in 3,4,5,-trimethoxybenzaldehyde and 2,4-dinitropyrimidine as among the final identified products. The oxidized products mixture exhibited no antibacterial activity against E. coli after complete consumption of TMP. Removal of TMP in the secondary effluent by Fe(VI) was achieved.
Reactions of primary and secondary amine complexes [(η5‐C5H5)Re(NO)(PPh3)(NHRR')]+ TfO− [2; R/R' = H/H (a), H/CH3 (b), H/C6H5 (d), CH3/CH3 (f), CH2CH2CH2CH2 (h)] with nBuLi give amido complexes (η5‐C5H5)Re(NO)(PPh3)(NRR') (1) in quantitative NMR yields. Although 1 d can be isolated in pure form, 1 f is converted upon workup into a dimeric bridging bis(amido) complex, cis‐[(η5‐C5H5)Re(NO){μ‐N(CH3)2}]2. The crystal structure of 1 d exhibits a pyramidal amido nitrogen atom. The diastereotopic methyl groups in 1 f readily exchange, as assayed by variable‐temperature NMR. Complexes 1 a, f react with TfOH to regenerate 2a, f, and with TfOR” to give the corresponding alkylated amine complexes. The basicities and nucleophilicities of the amido nitrogen atoms are shown to be greater than those of organic amines.
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