The structure of the iron(III) “capped” porphyrin, [5,10,15,20-[pyrromellitoyltetrakis(o-(oxyethoxy)phenyl)]-porphyrinato]chloroiron(III), FeCl(C2-Cap), has been determined from single-crystal, X-ray diffraction data collected at −150 °C. The material crystallizes as the trichloroform solvate, FeCl(C2-Cap)·3CHCl3, in space group C5 2h-P21/c of the monoclinic system with four formula units in a cell of dimensions a = 14.473 (5) Å, b = 19.514 (9) Å, c = 22.830 (11) Å, β = 101.61 (2)°, V= 6316 Å3. The structure was described by 396 variables, and at convergence of the full-matrix, least-squares refinement the values of R and Rw (on F, 9897 data having F0 2 > 3σ(F0 2)) are 0.065 and 0.078. The chloro ligand is outside the “cap” and the iron atom is above the mean plane of the porphyrin core away from the “cap”. The geometry about the iron atom is typical for FeCl(porphyrin) systems, with Fe−Cl = 2.242 (1) Å and with Fe 0.46 Å above the mean N4 plane and 0.47 Å above the mean 24-atom porphyrin plane. The porphyrin itself is slightly nonplanar, with the mean displacement from the least-squares plane being 0.076 Å and the maximum displacement being 0.208 Å. Although the conformations of the side chains that link porphyrin to “cap” are distinctly different from those found in the related free-base porphyrin, H2(C2-Cap), the “cap” to porphyrin distances are very similar in the two structures. The separations between the centroids of the phenyl “cap” and respectively those of the four pyrrole nitrogen atoms and the 24-atom porphyrin skeleton are 4.03 and 4.01 Å in FeCl(C2-Cap) and 3.86 and 3.96 Å in H2(C2-Cap). These separations are too small to accommodate O2 or CO within the cap and imply considerable flexibility of these “capped” porphyrins in solution where binding of O2 or CO to FeII(C2-Cap) systems occurs.
ASJC Scopus subject areas
- Colloid and Surface Chemistry