Lipophilic hexadentate gallium, indium and iron complexes of new phenolate-derivatized cyclohexanetriamines as potential in vivo metal-transfer reagents

Abstract

1,3,5-Tris(5-substituted salicylamino)cyclohexanes (H₃L; R = H, NO₂ or OMe) have been synthesized by Schiff-base condensation between cis-1,3,5-triaminocyclohexane and a substituted salicylaldehyde, followed by reduction with KBH₄. Reaction of these compounds with gallium(III), indium(III) and iron(III) salts gave neutral six-co-ordinate N₃O₃ complexes of type [ML](M = Ga, In or Fe). The complexes have been characterized by a combination of infrared, ¹H and ¹³C-{¹H} NMR and mass spectroscopy. The distribution coefficients between octan-1-ol and water indicate that the complexes are lipophilic. The electronic absorption spectra of the high-spin iron(III) complexes show ligand-to-metal charge-transfer bands in the 450–500 nm range. The structures of five of the complexes have been confirmed by single-crystal X-ray crystallography.