The synthesis and characterization of mononuclear manganese(II), dinuclear manganese(III) and copper(II) complexes

Mononuclear Mn (II) complexes of Mn(L1)2(ClO4) 2 (C1) (L1 = (6-Methyl-2-pyridylmethyl)(2-pyridylmethyl)amine), Mn(L2)2(ClO4)2 (C2) (L2 = bis(2-pyridylmethyl)(2-methylbenzyl)amine), and Mn(L3)(H2O)(CH3CN)(ClO4)2 (C3) (L3 = (bis(2-pyridylethyl)(6-methyl-2 pyridylmethyl)amine) were synthesized and characterized. Cyclic voltammetry experiments showed irreversible anodic peaks at Ep = 1.9 V for C1 and Ep1 = 1.1 V, Ep2 = 1.6 V for C2 vs. Ag/AgCl. Cyclic voltammetric experiments showed anodic peak of 1.93 V and cathodic peak at 1.67 V for C3.;Mononuclear Mn (III) complexes of Mn (III)(L4)2(ClO4 ) (L4 = (2-pyridylethyl)(2-hydroxybenzyl)amine) (C4) and Mn (III)(L5)2(ClO4) (L5 = (2-pyridylethyl)(5-methoxy-2-hydroxybenzyl)amine) (C5) were synthesized and characterized. Both the Mn (III) complexes are prepared from the reaction of the Mn (II) complexes and dioxygen. The Mn (III) complex C4 epoxidizes cyclohexene to cyclohexene oxide in 19% yield, while that of complex C5 does not.;Dioxo-bridged dinuclear Mn (III) complexes of Mn (III)2(L6)(μ-O) 2(ClO4)2.2CH3NO2 ( C6) (L6 = (2-pyridylethyl)(bis(6-methyl-2-pyridylmethyl))amine) and Mn2 (III)(L7)2(μ-O)2(ClO4) 2 (C7) (L7 = tris(6-methyl-7-pyridylmethyl)amine) were synthesized from the reaction of the Mn (II) complexes of L6 and L7 with H 2O2. The crystal structures of both C6 and C7 show di-octahedral complexes with di-μ-oxo bridge in which the axial 6-methyl groups on the pyridyl ring are trans to each other. The cyclic voltammograms in acetonitrile show two quasi-reversible peaks at E1/2 1.733 V and 0.86 V for C7 and 1.344 and 0.553 V corresponding to IV,IV/IV,III and IV,III/III,III processes. E1/2 potential increased upon increasing the number of methyl groups at the 6th position on the pyridyl of the tripodal ligands from n = 0–3 for tpa (tris(2-pyridylmethyl)amine) parent and from n = 0–2 Etpa((2-pyridylethyl)bis(2-pyridylmethyl)amine) parent dioxo Mn (III) complexes.;Dinuclear Cu(II) complexes of Cu2(II)(L8)2(H 2O)2(ClO4)2 (C8) (L8 = (2-pyridylmethyl)(2-hydroxybenzyl)amine), Cu2(II)(L4)2(ClO 4)2.2CH3NO2 (C9) (L4 = (2-pyridylethyl)(2-hydroxybenzyl)amine). Cu2(II)(L9)2(H 2O)2(ClO4)2 (C10) (L9 = (6-methyl-2-pyridylmethyl)(2-hydroxybenzyl)amine), Cu2(II)(L10) 2(ClO4)2 (C11) (L10 = (6-methyl-2-pyridylethyl)(2-hydroxybenzyl)amine). Cu2(L11O)(μ-OH)(ClO4)2 (C12) (L11 = 1,3-bis[N-(6-methyl-2-pyridylethyl)formamidoyl]benzene), and Cu 2(L12O)(μ-OH)(ClO4)2 (C13) (L12 = 1,3-bis[N methyl,N-(2-pyridylethyl)methyl]benzene) were synthesized and characterized. Dinuclear complexes of C12 and C13 were prepared from the reaction of dinuclear Cu(I) complexes of respective ligands with dioxygen. The aromatic ring was hydroxylated in both complexes as a result of oxygen reaction. Adding one methyl group to C8 resulted in drop in E1/2 potential by 0.296 V adding one methyl group on C9 resulted in drop of E1/2 by 0.4475 V.