Ru(II) polypyridine complexes: photophysics, photochemistry, eletrochemistry, and chemiluminescence

High-resolution crystal structure of cytochrome P450cam.

Reactivity of Dioxygen−Copper Systems

1,1‘-Binaphthyl Dimers, Oligomers, and Polymers: Molecular Recognition, Asymmetric Catalysis, and New Materials†

On the function and mechanism of action of peroxidases

"Picket fence porphyrins." Synthetic models for oxygen binding hemoproteins.

The synthesis, redox properties, and ligand binding of heterobinuclear transition-metal macrocyclic ligand complexes. Measurement of an apparent delocalization energy in a mixed-valent copper(I)copper(II) complex

Reversible oxygen adduct formation in ferrous complexes derived from a picket fence porphyrin. Model for oxymyoglobin

Electrochemical techniques were employed to study electron transfer properties of a binuclear copper--macrocyclic ligand complex and to prepare several reduced derivatives. The complex, Cu/sup II/Cu/sup II/L(ClO/sub 4/)/sub 2/.2H/sub 2/O, was prepared by condensing 1,3-diaminopropane with 5-methyl-2-hydroxyisophthalaldehyde and Cu(ClO/sub 4/)/sub 2/.6H/sub 2/O. The Cu/sup II/Cu/sup II/ complex was reduced in successive, quasi-reversible, one-electron steps at - 0.52 and - 0.91 V vs. NHE. Constant-potential electrolysis was employed to prepare the reduced species, Cu/sup II/Cu/sup I/L(ClO/sub 4/) and Cu/sup I/Cu/sup I/L, both of which were isolated and fully characterized. The mixed-valence species, Cu/sup II/Cu/sup I/L/sup +/, is stable in oxygen-free solutions (conproportionation constant: 3.97 x 10/sup 6/) and reacts with carbon monoxide to form an adduct, Cu/sup II/Cu/sup I/L(CO)ClO/sub 4/. The diamagnetic Cu/sup I/Cu/sup I/L species was obtained as essentially insoluble black needles which, however, formed a soluble dicarbonyl adduct, Cu/sup I/Cu/sup I/L(CO)/sub 2/, on exposure to CO. The latter complex was not isolated. At the ambient temperature Cu/sup II/Cu/sup I/L/sup +/ exhibits an isotropic seven-line solution EPR spectrum while an anisotropic pattern was observed in frozen solutions (77/sup 0/K), with four lines for g parallel to and unresolved g perpendicular to. Variable-temperature experiments indicated coalescence at about 200/sup 0/K suggesting anmore » intramolecular electron transfer rate of about 1.7 x 10/sup 10/ s/sup -1/ at 298/sup 0/K. Electronic absorption spectral measurements revealed at least two absorptions for Cu/sup II/Cu/sup I/L(ClO/sub 4/)/sub 2/ at 1700 and 1200 nm (CH/sub 2/Cl/sub 2/), which are not present in Cu/sup II/Cu/sup II/L(ClO/sub 4/)/sub 2/.2H/sub 2/O, Cu/sup I/Cu/sup I/L, or the carbonyl derivatives. The new spectral bands may be attributable to intramolecular electron transfer processes. 11 figures, 5 tables.« less

Binuclear complexes of macrocyclic ligands: electrochemical and spectral properties of homobinuclear Cu/sup II/Cu/sup II/, Cu/sup II/Cu/sup I/, and Cu/sup I/Cu/sup I/ species including an estimated intramolecular electron transfer rate

The preliminary structural characterization of a reversible ferrous dioxygen complex is reported. Mono(N-methyl imidazole) (dioxygen) meso-tetra (α,α,α,α-o-pivalamidephenyl) porphinatorino(II), [Fe(O2)-(N-Me imid) (α,α,α,α-TpivPP)], 1, isolated from toluene solution, crystallizes in the monoclinic system with four molecules in a unit cell of dimensions a = 18.690 (3), b = 19.514 (3), c = 18.638 (3) A, and β = 91.00 (1)°. R = 0.15 for 841 reflections having F2 > 3σ (F2). 

The complex 1 has four pivalamido groups on one side of the porphyrin forming a hydrophobic pocket of 5.4-A depth which encloses coordinated dioxygen. The dioxygen is coordinated “end-on,” with a bent Fe-O-O bond. The Fe-O-O plane bisects an N-Fe-N right angle of the equatorial iron porphyrin plane and is four way statistically disordered. In addition there is a crystallographic 2-fold axis through iron, coordinated oxygen, and nitrogen of the axially bound N-methyl imidazole. Thus there are two types of coordinated dioxygen with the Fe-O-O plane either parallel or perpendicular to the trans axial imidazole plane. Corresponding values for the Fe-O-O bond angles are 135-(4)° and 137(4)° and for the O-O bond lengths are 1.23 (0.08) and 1.26 (0.08) A, with a dihedral angle of 90° between alternative orientations of the Fe-O-O plane. The Fe-O distance is 1.75 (0.02) A and Fe-N (imidazole) is 2.07 (0.02) A, suggesting multiple bond character in the Fe-O moiety. The similarity of the Mossbauer spectrum of the model complex, 1, with oxyhemoglobin indicates that 1 may be a good model for oxygen binding in the oxygen transport hemeproteins.

https://www.pnas.org/content/pnas/71/4/1326.full.pdf

Robert R. Gagne

Papers

"Picket fence porphyrins." Synthetic models for oxygen binding hemoproteins.

The synthesis, redox properties, and ligand binding of heterobinuclear transition-metal macrocyclic ligand complexes. Measurement of an apparent delocalization energy in a mixed-valent copper(I)copper(II) complex

Reversible oxygen adduct formation in ferrous complexes derived from a picket fence porphyrin. Model for oxymyoglobin

Binuclear complexes of macrocyclic ligands: electrochemical and spectral properties of homobinuclear Cu/sup II/Cu/sup II/, Cu/sup II/Cu/sup I/, and Cu/sup I/Cu/sup I/ species including an estimated intramolecular electron transfer rate

Structure of an Iron(II) Dioxygen Complex; A Model for Oxygen Carrying Hemeproteins