Using chiral ligand substituents to promote the formation of dinuclear, double-stranded iron, manganese, and zinc mesocates

The synthesis and structures of dinuclear manganese, iron, and zinc complexes of chiral di-iminodipyrromethane ligands (L) are reported. Schiff base condensation reactions between 5,5 '-diformyl-2,2 '-dipyrromethane and the chiral amines (-)- (R)-CH(Me)tBu and (+)-(R)-CH(Me)Ph result in the straight-forward synthesis of the new, chiral ligands H2L2 and H2L3, respectively. Salt elimination reactions between K2L, and divalent Mn and Fe halides, and protonolysis reactions between ZnMe2 and H2L result in the formation of the new dinuclear complexes [M-2(L)(2)]. Investigation of the structures of these compounds in solution and in the solid state reveal that chiral mesocates are formed for L = L-2, whereas for L = L-3, a racemic mixture of helicates is present. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).