Photosensitization study of cage-like metal complexes with hexadentate ligands, tptn and tpen. Part 1. Photochemistry and spectroelectrochemistry of iron(II), cobalt(III) and nickel(II) complexes

Two hexadentate ligands, N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,3-propanediamine (tptn) and N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (tpen), were used to prepare cage-like metal complexes of Fe(II), Co(III) and Ni(II). As expected, these complexes are photochemically inert. The electrochemical behaviour of these complexes was studied by spectroelectrochemical methods. The iron(II) complexes exhibit chemical irreversibility on reduction and the nickel(II) complexes show reversible reduction behaviour. The potential of cobalt(III) complexes as photosensitizers is discussed.