Heme coenzymes are of great importance in biological systems, and as such have been investigated extensively by chemists. In hemoglobin, the iron is in the ferrous state, whereas it is in the ferric state in cytochromes and methemyoglobin. A great number of experimental results have been reported over the past three decades concerning the axial ligation properties of metalloporphyrins with S, O, P and N bases. Iron porphyrins containing axial ligands can be high or low spin, depending upon the

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... emperature and the nature of the axial ligand. In general, the central metal-nitrogen skeleton is square pyramidal in high-spin complexes and square planer in low-spin complexes. 1 We previously 2 reported on the synthesis of new heme analogues with phenylcyanamide ligands. The reaction of Fe(oep)Cl (1) with excess TlL in dichloromethane yields (2) ( Fig. 1) , where oep is octaethylporphyrin and L is 2,4dimethylphenylcyanamide. Here, we report on the structure of Fe(oep)L (2). The Fe atom is five-coordinated to four N atoms of the porphyrin ring and to one N atom of a phenylcyanamide group. The compound is characterized by an average Fe-N bond length of 2.064 Å. The average displacement of the iron(III) atom from the mean porphinato core is 0.43 Å. The crystallization of [Fe(oep)(2,4Me2pcyd)] at room temperature by the diffusion of hexane into its saturated dichloromethane solutions yielded black plate crystals. [Fe(oep)(2,4Me2pcyd)] was crystallized in the triclinic system with the P1 space group. Measurements were made on a Bruker X8 APEX diffractometer using graphite-monochromated Mo Ka radiation (l = 0.71073 Å) by the w scan mode at a temperature of -100 ± 0.1˚C to a maximum 2q value of 56.2˚. A total of 37887 reflections were collected to give 9308 independent X-ray Structure Analysis Online The molecular structure of the title compound, [Fe(oep)(2,4-Me2pcyd)] (where oep is dianion of octaethylporphyrin and 2,4-Me2pcyd is 2,4-dimethylphenylcyanamide), was determined by single-crystal X-ray diffraction. Crystal data: crystal system, triclinic; space group, P1 and Z = 2, a = 12.3969 (8) Å, b = 13.8021(9)Å, c = 14.1594(9)Å, a = 61.093(3)˚, b = 68.734(3)˚, g = 71.950(4)˚, R1 = 0.046; wR2 = 0.094 for all data. Fig. 1 A chemical structure of 2. Table 1 The crystal data, experimental details of [Fe(oep)(2,4Me2pcyd)] CCDC 701197 Formula = C45H53N6Fe Formula weight = 733.78 Temperature = 173.0(1) Crystal system: triclinic space group: P1 Z = 2 a = 12.3969(7)Å a = 61.093(3)b = 13.8021(7)Å b = 68.734(2)c = 14.1594(12)Å g = 71.950(4)V = 1949.4(2)Å 3 Dx = 1.250 g/cm 3 No. of re ection used = 9308 (Rint = 0.027) 2qmax = 56.2R 1 = 0.046 wR2 = 0.094 Crystal size: 0.10 ¥ 0.30 ¥ 0.35 mm F(0 0 0) = 782.00 Goodness-of-t = 1.04 (D/s)max = 0.001 (Dr)max = 0.50 e.Å -3 (Dr)min = -0.25 e.Å -3 Measurement: Bruker X8 APEX II diffractometer with graphite monochromated Mo-Ka radiation. Program system: Bruker SAINT software package Structure determination: direct methods (SHELXS) Re nement: full-matrix least-squares re nement on F 2