Synthesis and dioxygen-binding properties of double-sided porphyrinatoiron(II) complexes bearing covalently bound axial imidazole

Abstract

Double-sided porphyrinatoiron( 11) complexes bearing covalently bound axial imidazole, 5-[2-(5imidazolylvaleryloxy) -6-(piva1oyloxy)phenyll -1 0.1 5,20-tris[2.6-bis(pivaloyloxy)phenyl] porphyrinatoiron(//) and 5-[2-(3.3-dimethylbutyryloxy) -6-(5-imidazolylvaleryloxy)phenyl] -1 0.1 5,20-tris[2,6bis(3,3-dimethylbutyryloxy)phenyl] porphyrinatoiron (11).have been synthesized. On the basis of their absorption and 'H NMR spectra, the axial imidazole group is co-ordinated. The complexes reversibly form stable dioxygen adducts in toluene at 25 "C, and the kinetics of binding of 0, and CO has been investigated. When embedded in phospholipid unilamellar vesicles, the complexes possess the ability to transport dioxygen in an aqueous medium. The binding affinity of the pivaloyloxy derivative [P+(O,) = 27 Torr] is equal to that of a red blood cell suspension and the half-life of the dioxygen adduct formed was 1.5 d under physiological conditions (pH 7.4,37 "C).

Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function

“…941 The overall spectroscopic properties of [( 5/6 L)Fe II -(CO)] and [( 5/6 L)-Fe II –CO---Cu I (CO)] + (Figure 113) complexes were similar to those of their parent compounds, [(F 8 TPP)Fe II (CO)] and [(TMPA)Cu I (CO)] + . 415,964–967 13 C-NMR experiments suggested the presence of two distinct isomeric forms of the Fe- only carbonyl complex of 5/6 L platforms, where the CO could either be at the same or the opposite side of the tethered copper chelate (Figure 113). Furthermore, infrared spectroscopic insights revealed the presence of two isomeric forms of [( 5/6 L)Fe II –CO⋯Cu I (CO)] + complexes as well, where the Cu I –CO unit is supported by either a tri- (major isomer; IR v (CO) Cu 2070 cm −1 ) or tetradentate (minor isomer IR v (co) Cu 2091–2093 cm −1 ) fashion, with the presence of a dangling, dissociated pyridine in the case of the former (Figure 113).…”

pH-dependent redox and CO binding properties of chelated protoheme-l-histidine and protoheme-glycyl-l-histidine complexes

“…With the aim of studying these effects, several chelated iron-porphyrin model systems have been synthesized, containing an appended imidazole residue which can intramolecularly bind to the iron center [8][9][10][11][12][13][14][15][16][17][18][19]. A different approach involves the use of heme-peptide complexes (called microperoxidases) obtained from the proteolysis of horse heart cytochrome c [20,21].…”

Cross-Linked Human Serum Albumin Dimer Incorporating Sixteen (Tetraphenylporphinato)iron(II) Derivatives: Synthesis, Characterization, and O2-Binding Property

“…The O 2 -binding affinities [P 1/2 : O 2 pressure at half O 2 binding for the (porphyrinato)-iron(II)] and its thermodynamic parameters (∆H, ∆S) were determined (Table 1). 3d, [14][15][16] The P 1/2 value of (rHSA-FeP) 2 (30 Torr at 37°C) was almost identical to that of red blood cells (27 Torr), 18 and its O 2 -binding equilibrium curve showed Langmuir type absorption; the Hill coefficient was 1.0 ( Figure 6). It is known that cooperativity observed in the O 2 binding to hemoglobin has implications for physiological use.…”

“…3d, [14][15][16] It has also recently been found that the O 2 recombination of rHSA-FeP obeyed three-phase kinetics. 3d In the case of (rHSA-FeP) 2 , the assumption of multiphase rebinding of dioxygen is too complicated, so we employed the monophasic first-order reaction of O 2 association.…”