Coordination Studies of Bis-Strapped-Hanging-Carboxylate Porphyrins. X-ray Characterization of a Five-Coordinate Iron(II) Complex with a Built-in Axial Base
journal contributionposted on 2010-04-05, 00:00 authored by Ismail Hijazi, Thierry Roisnel, Marc Fourmigué, Jean Weiss, Bernard Boitrel
The comparison of two series of preorganized strapped porphyrins, derived from both the αβαβ and ααββ conformers of meso-tetrakis(aminophenyl)porphyrin, and the coordination studies of their affinity for O2 are reported. Both series of ligands bear a proximal built-in axial base and a polar distal side defined by either a hanging malonyl ester or a hanging malonic acid residue. In the αβαβ model, the carboxylic acid groups are maintained in an apical location at a fixed distance from the distal oxygen atom of iron-bound O2. A particular emphasis is placed on the ααββ series, for which the crystal structure of the five-coordinate (S = 2) iron(II) ester complex was determined. In this series, the distal strap can adopt either a tilted conformation or a vertical position over the FeII core, allowing changes in the distance between the carboxylic groups and the bound O2.