Dicopper(II,II) and dicopper(I,II) complexes of a series of dinucleating macrocycles

The dinucleating macrocycles H2Lm,n containing two 2,6-di(aminomethyl)-4-methylphenol entities combined through two alkane chains, (CH2)m and (CH2)n, at the amine nitrogens have been prepared for the (m,n) sets (2,3), (2,4), (2,5), (3,3) and (3,4). The dinuclear copper(II) complexes having general formula [Cu2Lm,n][ClO4]2 have been prepared. Cryomagnetic investigations (80–300 K) reveal a strong antiferromagnetic spin-exchange between the copper(II) ions within each complex (J based on ℋ=–2JS1S2 in the range –345 to –255 cm–1). The cyclic voltammograms show two reduction couples, CuIICuII–CuICuII and CuICuII–CuICuI. The comproportionation constants Kcom for the mixed-valence CuICuII complexes have been determined electrochemically. The Kcom value increase in the order of the macrocycles (L2,3)2– < (L2,4)2– < (L2,5)2– and (L3,3)2– < (L3,4)2–. The CuICuII mixed-valence state is shown to be ‘spin-trapped’(Class I) for all the complexes based on ESR spectra.

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