The six-coordinate Co(III) porphyrin, [Co(Im)2(TPP)][OAc]·H2O·CHCl3, was prepared accidentally and has been characterized by a complete structural analysis. The material crystallizes with two formula units in space group Ci 1-P1 of the triclinic system in a cell of dimensions a = 13.055 (8) Å, b = 17.239 (7) Å, c = 11.807 (8) Å, α = 105.94 (3)°, β = 91.97 (3)°, and γ = 107.49 (3)°. The asymmetric unit consists of two half cations, so that there are two independent cations in the cell, each with a crystallographically imposed center of symmetry. The Co-N (of imidazole) axial bond length averages 1.93 (2) Å. Comparison of the present structure with that of the Co(NH3)6 3+ion enables us to estimate a minimum approach distance of a histidine to the plane of the porphyrin ring. This minimal approach distance is an essential factor in estimating the movement of the proximal histidine group toward the mean plane of the porphyrin ring upon oxygenation of cobalt-substituted hemoglobin.
ASJC Scopus subject areas
- Colloid and Surface Chemistry