Synthesis, characterization and cation-induced dimerization of new aza-crown ether-appended metalloporphyrins

Abstract

New metalloporphyrins bearing one or two aryl-aza-crown ether moieties at meso-positions have been synthesized using a palladium catalyzed amination reaction and fully characterized by spectral techniques. X-Ray structural data have been presented for the zinc and copper complexes of mono-substituted aza-crown ether appended metalloporphyrins. UV-Vis and ¹H NMR spectroscopic studies showed that addition of K⁺ cations to a solution of monomeric aza-crowned porphyrins in CHCl₃/MeOH led to cation-induced dimerization of these porphyrins, whereas addition of Na⁺ cations yielded a monomeric complex. Axial coordination of the exobidentate ligand (DABCO) to zinc complexes of aza-crowned porphyrins and following binding metal ions led to formation of sandwich complexes with high stability constants.