Polynuclear manganese amino acid complexes.

The reaction of MnCl(2).4H(2)O with DL-valine (Val) in MeOH in the presence of Et-saoH(2) (2-hydroxypropiophenone oxime) and NEt(4)OH forms the complex [Mn(III)(3)Mn(IV)(2)O(2)(CH(3)O)(Et-sao)(6)(Val)].Val.1.5H(2)O (1.Val.1.5H(2)O) in very good yields. A similar reaction of MnCl(2).4H(2)O with Glycine (Gly) in MeOH in the presence of saoH(2) (salicylaldoxime) and Ca(OH)(2) yields the complex [Mn(III)(3)O(sao)(3)(Gly)Cl(MeOH)(3)].1.87 MeOH.0.13H(2)O (2.1.87 MeOH.0.13H(2)O). Replacing saoH(2) with Me-saoH(2) (2-hydroxyethanone oxime) and Gly with HPABA (para-aminobenzoic acid) in the presence of CH(3)ONa in MeOH forms the complex [Mn(6)O(2)(PABA)(2)(Me-sao)(6)(MeOH)(4)(H(2)O)(2)].2[Mn(6)O(2)(PABA)(2)(Me-sao)(6)(MeOH)(2)].11 MeOH (3.11 MeOH) in moderate yields. Magnetic studies for 1 and 2 reveal the presence of both ferromagnetic and antiferromagnetic interactions, leading to S = 2 ground states for both complexes. Complexes 1 and 2 represent the first examples of polynuclear manganese complexes with any naturally occurring alpha-amino acid, while 3 is the first structurally characterised example of a manganese para-aminobenzoate complex.