Synthesis, Crystal Structure, and Antimicrobial Activity of Manganese(III) and Iron(III) Complexes Derived from Similar bis-Schiff Bases

A new manganese(III) complex, [Mn(L-1)(CH3OH)(dca)] 1, and a new iron(III) complex, [Fe(L-2)(CH3OH)(NCS)] 2, for which dca is dicyanoamide anion, and L-1 and L-2 are the dianionic form of N,N-3,4-methylphenylenebis(5-methylsalicylaldimine) and N,N-bis(5-methylsalicylidene)-o-phenylenediamine, respectively, have been prepared and characterized by elemental analyses, IR, and single-crystal X-ray crystallographic determination. The crystal of complex 1 is orthorhombic: space group Pna2(1), a = 14.6557(6), b = 10.8906(5), c = 15.0536(7) angstrom, V = 2402.7(2) angstrom(3), Z = 4, R-1 = 0.0321, wR(2) = 0.0715. The crystal of complex 2 is monoclinic: space group C2/c, a = 14.6798(9), b = 11.1306(7), c = 27.831(1) angstrom, = 93.782(2)degrees, V = 4537.6(5) angstrom(3), Z = 8, R-1 = 0.0423, wR(2) = 0.1027. The bis-Schiff base ligands coordinate to the metal center through phenolate O and imine N atoms. Both the Mn and Fe atoms in the complexes are in octahedral coordination, with the equatorial donor atoms come from the Schiff base ligands, and with the axial donor atoms come from a methanol O atom and a pseudohalide N atom. The effects of the complexes on the antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans were studied.