X-ray structure determination of Ru (TPP) (CO) (Melm)·2CHCI₃

The crystal structure of (carbonyl)(1-methylimidazole)(5,10,15,20-tetraphenylporphyrinato) ruthenium(II)·2chloroform, Ru(TPP)(CO)(Melm)·2CHCl₃, an R-state model of the hemoglobin active site, has been determined. The material crystallizes in space group P2₁/c of the monoclinic system with four formula units in a cell of dimensions a = 12.733(2) Å, b = 14.535(2) Å, c = 24.921(2) Å, β = 91.15(1)° at T= 110 K. The structure has been refined to R(F) = 0.038 for 588 variables and 7458 data. The Ru-C(O) distance is 1.835(3) Å and the Ru-N_(imidazole) distance is 2.163(2) Å. This is the third reported crystal structure of a solvated Ru(TPP)(CO)(Melm) compound. It differs from the other two in a larger displacement of 0.079(1) Å of the Ru atom from the mean porphyrin plane toward the CO ligand, a shorter Ru-N_(imidazole) bond, a smaller average deviation, 0.06 Å, of atoms from the porphyrin plane, and the absence of a small ≥60° dihedral angle between the porphyrin plane and phenyl rings.