Structure and Photochemistry of Manganese Porphyrin Sulfate Complexes

New sulfate and hydrogen sulfate complexes of metalloporphyrins have been synthesized and crystallographically characterized and their photochemistry examined. Irradiation of [Mn(TPP)]₂(SO₄) and Mn(TPP)(OSO₃H) (where TPP = 5,10,15,20-tetraphenylporphyrinate(2-)) produces Mn^II(TPP) quantitatively, with quantum yields of 7.1 × 10^-4 and 9.8 × 10^-4, respectively. In contrast to other manganese oxoanion complexes, metal-oxo species are not formed and oxidation of hydrocarbons does not occur. The X-ray crystal structures of [Mn(TPP)]₂(SO₄)·2C₆H₆·½C₅H₁₂·½H₂O and Mn(TPP)(OSO₃H)·CH₂Cl₂ show stereochemistry similar to that of the analogous iron complexes. In the sulfate complex [Mn(TPP)]₂(SO₄), the average Mn-pyrrole N distance is 2.008 Å in both rings, with the metal displaced above the mean plane of the nitrogen atoms by 0.19 and 0.22 Å for Mn(1) and Mn(2), respectively. The sulfate ion is coordinated in an unidentate fashion. In Mn(TPP)(OSO₃H) the average Mn-pyrrole nitrogen distance is 1.991 Å with the metal 0.23 Å above the mean plane of the nitrogen atoms. The hydrogen sulfate ion is coordinated through one of the oxygens, with Mn-O = 2.078 Å. Crystal data for Mn(TPP)(OSO₃H)·CH₂Cl₂: space group [formula omited], a= 13.782 (8) Å, b = 13.861 (6) Å, c = 13.504 (8) Å, a = 108.57 (4)°, β = 118.77 (4)°, γ = 60.43 (4)°, V = 1956 (3) ų, and Z = 2. Crystal data for [Mn(TPP)]₂(SO₄)·2C₆H₆·½C₅H₁₂·½H₂O at -25 °C: space group [formula omited], a = 14.585 (16) Å, b = 21.949 (10) Å, c = 13.142 (6) Å, a = 90.11 (4)°, β = 104.65 (6)°, γ = 96.47 (5)°, V = 4042 (9) ų, and Z = 2.