LAUSR

Abstract Two new cobalt(III) six-coordinated complexes, [CoIII(TpivPP)Cl(py)].THF (1) [TpivPP is α,α,α,α-tetrakis(o-pivalamidophenyl)porphyrin known as the picket fence porphyrin and THF is tetrahydrofuran] and [CoIII(TpivPP)Cl(4,4′-byp)].2H2O (2) (4,4′-bpy is 4,4′-bipyridine), have been synthesized and characterized by UV–Vis, IR, 1H NMR and MS spectroscopy. The UV–Vis data confirmed the creation of hexa-coordinated Co(III)-meso-porphyrin complexes by the red shifted Soret bands of these derivatives. The proton NMR spectra of 1 and 2 clearly indicated that these derivatives are cobalt(III) diamagnetic porphyrin complexes. The molecular structures of these two Co(III) derivatives were determined by X-ray single-crystal analysis. The Co(III) cations, chlorido ligands and nitrogen atoms of the pyridine and the pyridyl moieties lie on a two-fold axis of symmetry. The equatorial plane is formed by four nitrogen atoms of the porphyrin core of 1 and 2, whereas the apical positions are occupied by the chlorido ligands and the nitrogen atoms of the pyridine ligand and the pyridyl group of the 4,4′-bipyridine ligand of compounds 1 and 2 respectively. In the crystal packing of 1 and 2, the [CoIII(TpivPP)Cl(L)] (L = pyridine or 4,4′-bipyridine) molecules are arranged in one-dimensional chains parallel to the [0 1 0] direction, and voids are located between these chains. Gram-positive and Gram-negative bacteria have been tested against the starting materials and complexes 1 and 2. The results show that the cobalt(III) porphyrin derivatives are highly effective compared to the H2TpivPP free base porphyrin and that 1 and 2 derivatives have a higher growth inhibition against Escherichia coli and Bacillus subtilis bacteria.