Spin Transition in a Manganese(III) Porphyrin Cation Radical, Its Transformation to a Dichloromanganese(IV) Porphyrin, and Chlorination of Hydrocarbons by the Latter

Abstract

Chemical oxidation of (TMP)Mn(III)(Cl) (TMP = the tetramesitylporphyrinato dianion) by Fe(ClO(4))(3) leads to the porphyrin-oxidized product (TMP(*)(+))Mn(III)(ClO(4))(2). Magnetic measurements and EPR spectroscopy show that the total spin of the complex changes from S = (5)/(2) at high temperature to S = (3)/(2) at low temperature. Ligand exchange of the perchlorato ligands in (TMP(*)(+))Mn(III)(ClO(4))(2) by chloride anions is accompanied by a change of the oxidation site from porphyrin to metal, resulting in (TMP)Mn(IV)(Cl)(2). This high-valent-metal complex can effect chlorine atom transfer to olefins, as well as to dimedone and chlorodimedone, natural substrates of chloroperoxidases.

Reaction profile of the last step in cytochrome P-450 catalysis revealed by studies of model complexes

“…The changes in the contact shifts as a function of axial ligands are described as reflecting competition between X and porphyrin as electron donors to the metal: as the p-donor strength of X increases, the extent of porphyrin ] metal donation decreases, resulting in a decreased shift of the pyrrole-Hs. Thus, the b-pyrrole-CH chemical shifts for XpF P , Cl P , AcO P , ClO 4 P are P20.8, P21.8, P22.3, P35.5 ppm, respectively, in (TMP)Mn-X [47] and P19.7, P22.3, P21.8, P36.0 ppm, respectively, in (TPP)Mn-X complexes [57]. Similarly, the results collected in Table 2 support a relative p-donor strength series in the 1-X complexes of: Cl P`A cO P F P ptrif P`M eOH`ClO 4 P .…”

“…The preparation and full characterization of both (TMP c 7)Mn III (ClO 4 ) 2 and (TMP)Mn IV (Cl) 2 are reported in a separate recent publication [47].…”

“…The (TMP c 7)Mn III (ClO 4 ) 2 complex was prepared by oxidation of (TMP)Mn III (ClO 4 ) with Fe(ClO 4 ) 3 and identified by comparison of its spectroscopic characteristics to those previously reported. Treatment of (TMP c 7)Mn III (ClO 4 )2 with tetraethylammonium chloride resulted in a color change from green to red, and the isolated product was characterized as (TMP)Mn IV (Cl) 2 by various spectroscopic methods [47].…”

Spin crossover in[MnIII(pyrol)3tren]probed by high-pressure and low-temperature x-ray diffraction

“…We have investigated by single crystal X-ray diffraction the temperature and pressure dependencies of the structural properties of the mononuclear [Mn III (pyrol) 3 tren] complex which is one among the very few Mn(III) SCO systems identified 10,11 . This compound whose crystal structure determined at room temperature revealed a Mn III N 6 core is known to exhibit a very abrupt spin transition from HS ( 5 E) to LS ( 3 T 1 ) around 44 K 12,13 .…”

Epoxidation Catalysis by a Manganese Corrole and Isolation of an Oxomanganese(V) Corrole

“…Interestingly, both the green color and the UV/Vis spectrum of [Mn(tpfc)] (Figure 1 a) are remarkably similar to that of manganese(iii) porphyrins. [16] Most relevant are the split Soret band and the Cytotoxicity: HL-60 (human promyelocytic leukemia) cells were cultured in a 24-well culture plate (5 Â 10 4 mL À1 ). The cells were exposed to various amounts of LDH (1 ± 1000 mg mL À1 ).…”