Structures, electronic properties, and oxidation-reduction reactivity of halogenated iron porphyrins
- Arthur Amos Noyes Lab., Pasadena, CA (United States); and others
Molecular structures of both Fe{sup III}(TFPPBr{sub 8}) Cl and Fe{sup II} (TFPPBr{sub 8})(py){sub 2} porphyrins reveal saddle distortions: Fe{sup III-} (TFPPBr{sub 8})Cl in triclinic space group P1, a = 13.649(4) {Angstrom}, c = 14.537 {Angstrom}, {alpha} = 89.26(2){degrees}, {beta} = 67.13(1){degrees}, {gamma} = 71.82(2){degrees}, V = 2494.3(13) {Angstrom}{sup 3}, Z = 2 ; Fe{sup III}(TFPPBr{sub 8})(py){sub 2} in triclinic space group P1, a = 12.459- (7) {Angstrom}, b = 13.125(8) {Angstrom}, c = 20.989(11) {Angstrom}, {alpha} = 84.72(5){degrees}, {beta} = 72.87(4){degrees}, {gamma} = 69.04(5){degrees}, V = 3063(3) {Angstrom}{sup 3}, Z = 2. Similar to other chloro-iron(III) porphyrins. {mu}{sub eff} at room temperature (5.96 {mu}{sub B}) is that of a {sup 6}A{sub 1} state; {mu}{sub eff} at 2 K (4.2{mu}{sub B}) indicates a large zero-field splitting. The Soret bands of both Fe{sup III}(TFPPBr{sub 8})Cl and Fe{sup II}(TFPPBr{sub 8})- (py){sub 2} are red-shifted by approximately 23 nm relative to those of corresponding planar Fe{sup III} porphyrins. The metal and porphyrin reduction potentials of Fe{sup III} (TFPPBr{sub 8})Cl and Fe{sup II}(TFPPBr{sub 8})(py){sub 2} are anodically shifted more than 400 mV from those of Fe{sup III}(TPP)Cl. Although [Fe{sup II}(TFPPBr{sub 8})Cl]- reacts very slowly with dioxygen, it is oxidized rapidly by tert-butyl hydroperoxide (TBHP); these Fe{sup III} reactivity properties taken together with the finding that the corresponding Fe{sup III} complex is reduced rapidly by TBHP provide strong support for the proposal that Fe{sup III}(TFPPBr{sub 8})Cl/O{sub 2}-catalyzed alkane oxygenations occur by a radical chain mechanism in which alkyl hydroperoxide intermediates are decomposed efficiently by both Fe{sup III} and Fe{sup III} species.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 210103
- Journal Information:
- Inorganic Chemistry, Journal Name: Inorganic Chemistry Journal Issue: 19 Vol. 34; ISSN 0020-1669; ISSN INOCAJ
- Country of Publication:
- United States
- Language:
- English
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