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The present work deals with a class I mixed valence trinuclear complex [ Co II ( μ -OAc ) 2 ( μ -L ) 2 Co 2 III ( NCS ) 2 ] ( 1 ) formed by partial aerial oxidation (H 2 L = 1,7-bis(2-hydroxyphenyl)-2,6-diazahepta-1,6-diene). The terminal Co III N 3 O 3 centres exhibit a uniform facial arrangement of both N 3 and O 3 donor sets and the Co II centre is coordinated to six oxygen atoms. Variable temperature magnetic susceptibility measurement reveals that the intermediate Co(II) paramagnetic centre undergoes a very weak spin exchange ( θ = −6.39 K, antiferromagnetic) interaction with the two terminal Co(III) diamagnetic centres over the range 300–2 K. A three line EPR spectra at 4 K was characterized with highly anisotropic g tensors and the one line broad spectra at 300 K indicates the strong influence of temperature on the metal spin states, consistent with a high spin Co(II) complex. Two anodic responses appeared at +0.85 (Co 2+ → Co 3+ , reversible) and +1.7 V (Co 3+ → Co 4+ , irreversible) corresponding to one and two electron transfer oxidation respectively. Another reversible signal attributed to Co 3+ → Co 2+ reduction occurred at −0.5 V, associated with a two electron stoichiometry. Compound 1 reacted with hydrazine to form a square planar orange-red [Co II (L)] species, 2 . Inter conversion between 1 and 2 involves electron exchange coupled with proton transfer. |
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