825638-77-5Relevant academic research and scientific papers
Photochemical organic oxidations and dechlorinations with a μ-oxo bridged heme/non-heme diiron complex
Wasser, Ian M.,Fry, H. Christopher,Hoertz, Paul G.,Meyer, Gerald J.,Karlin, Kenneth D.
, p. 8272 - 8281 (2004)
Steady state and laser flash photolysis studies of the heme/non-heme μ-oxo diiron complex [(6L)FeIII-O-Fe III-Cl]+ (1) have been undertaken. The anaerobic photolysis of benzene solutions of 1 did not result in the buildup of any photoproduct. However, the addition of excess triphenylphosphine resulted in the quantitative photoreduction of 1 to [(6L)FeII... FeII-Cl]+ (2), with concomitant production by oxo-transfer of 1 equiv of triphenylphosphine oxide. Under aerobic conditions and excess triphenylphosphine, the reaction produces multiple turnovers (～28) before the diiron complex is degraded. The anaerobic photolysis of tetrahydrofuran (THF) or toluene solutions of 1 likewise results in the buildup of 2. The oxidation products from these reactions included γ-butyrolactone (～15%) for the reaction in THF and benzaldehyde (～23%) from the reaction in toluene. In either case, the O-atom which is incorporated into the carbonyl product is derived from dioxygen present under workup or under aerobic photolysis conditions. Transient absorption measurements of low-temperature THF solutions of 1 revealed the presence of an (P)FeII-like {P = tetraaryl porphyrinate dianion} species suggesting that the reactive species is a formal (heme)-FeII/FeIV=O(non-heme) pair. The non-heme FeIV=O is thus most likely responsible for C-H bond cleavage and subsequent radical chemistry. The photolysis of 1 in chlorobenzene or 1,2-dichlorobenzene resulted in C-Cl cleavage reactions and the formation of {[(6L)FeIII-Cl...FeIII-Cl] 2O}2+ (3), with chloride ligands that are derived from solvent dehalogenation chemistry. The resulting organic products are biphenyl trichlorides or biphenyl monochlorides, derived from dichlorobenzene and chlorobenzene, respectively. Similarly, product 3 is obtained by the photolysis of benzene-benzyl chloride solutions of 1; the organic product is benzaldehyde (～70%). A brief discussion of the dehalogenation chemistry, along with relevant environmental perspectives, is included.
Heme/non-heme diiron(II) complexes and O2, CO, and NO adducts as reduced and substrate-bound models for the active site of bacterial nitric oxide reductase
Wasser, Ian M.,Huang, Hong-Wei,Moenne-Loccoz, Pierre,Karlin, Kenneth D.
, p. 3310 - 3320 (2007/10/03)
As a first generation model for the reactive reduced active-site form of bacterial nitric oxide reductase, a heme/non-heme diiron(II) complex [( 6L)FeII-FeII-(CI)]+ (2) {where 6L = partially fluorinated tetraphenylporphyrin with a tethered tetradentate TMPA chelate; TMPA = tris(2-pyridyl)amine} was generated by reduction of the corresponding μ-oxo diferric compound [(6L) FeIII-O-FeIII-CI]+ (1). Coordination chemistry models for reactions of reduced NOR with O2, CO, and NO were also developed. With O2 and CO, adducts are formed, [(6L) FeIII(O2-)(thf)...FeII-Cl] B(C6F5)4 (2a·O2) {λmax 418 (Soret), 536 nm; νO-O = 1176 cm -1, νFe-O = 574 cm-1 and [( 6L)FeII(CO)(thf)FeII-Cl]B(C6F 5)4 (2a·CO) {νCO 1969 cm -1}, respectively. Reaction of purified nitric oxide with 2 leads to the dinitrosyl complex [(6L)Fe(NO)Fe(NO)-Cl]B(C6F 5)4 (2a·(NO)2) with νNO absorptions at 1798 cm-1 (non-heme Fe-NO) and 1689 cm-1 (heme-NO).
Efficient photodissociation of O2 from synthetic heme and heme/M (M = Fe, Cu) complexes
Fry, H. Christopher,Hoertz, Paul G.,Wasser, Ian M.,Karlin, Kenneth D.,Meyer, Gerald J.
, p. 16712 - 16713 (2007/10/03)
Single wavelength excitation (λex = 355 or 532 nm) of low-temperature stabilized (198 K) synthetic heme-dioxygen and heme-dioxygen/M complexes, where M = copper or iron in a non-heme environment, results in the dissociation of dioxygen as indicated by the generation of the ferrous heme (Soret band, 427 nm) and the bleaching of the ferric-superoxide (FeIII(O2-)) 410-nm Soret band in the transient absorption difference spectrum. Dioxygen rebinds to the four heme complexes studied with comparable rate constants (～6-9 × 105 M-1 s-1). However, the quantum yield for complete dissociation of O2 from our simplest heme-O2 complex (F8)FeIII(O2-) (φ = 0.60) is higher than the other complexes measured (φ = 0.2-0.3) as well as that for oxy-myoglobin (φ = 0.3). Copyright
