Articles written in Journal of Chemical Sciences

    • Self-assembled discrete and polymeric cobalt(II) complexes of a carboxylate appended tripodal tetradentate ligand: reactivity with aerial dioxygen or aqueous hydrogen peroxide


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      Three new cobalt(II) complexes [Co(μ2-L)]3(ClO4)3.2H2O, 1, [Co(L)(NO3)], 2 and {[Co(μ2-L)(MeOH)](BPh4).(MeOH)}n, 3 are prepared where L stands for 2-(bis(pyridin-2-ylmethyl)amino)acetate. Single crystal X-ray diffraction analysis confirmed the trinuclear core for 1, and 1-D polymericstructure for 3. It is proposed that these complexes are largely mononuclear in solution state. Reactivity of thecomplexes with aerial dioxygen, in presence of Et3N, invariably produced a common complexed cation[Co(L)(pic)]+ where pic stands for picolinate. The novelty of the finding is in terms of the presence of bothintact ligand (i.e L) and a fragment of the ligand (i.e. pic) in the same complex. Crystal structures of theisolated complexes [Co(L)(pic)](ClO4), 4a and [Co(L)(pic)](NO3), 4b confirmed the solid state structures.The Co(II) center of a complex is oxidized to Co(III) and the bound ligand moiety afforded a picolinate unit(due to oxidative Cpicolyl-Namine bond cleavage). The picolinate unit then connects with another molecule of aCo(III) complex containing L in its original form. Oxidation of a representative complex using H2O2 alsoresulted [Co(L)(pic)]+, but a stable binuclear dihydroxo bridged Co(III) complex [Co(L)(μ2-OH)]2(ClO4)2, 5was formed when controlled amount of H2O2 (1 equiv) was employed.

      Synopsis: Three new Co(II) complexes of 2-(bis(pyridin-2-ylmethyl)amino)acetate (L) are prepared. Reactivity of the complexes with aerial dioxygen, in presence of Et3N, invariably produced Co(III) complexes having the common complexed cation [Co(L)(picolinate)]+. Picolinate is generated due to the oxidative cleavage of bound L.

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