A non-radical mechanism for methane hydroxylation at the diiron active site of soluble methane monooxygenase.

We propose a non-radical mechanism for the conversion of methane into methanol by soluble methane monooxygenase (sMMO), the active site of which involves a diiron active center. We assume the active site of the MMOH(Q) intermediate, exhibiting direct reactivity with the methane substrate, to be a bis(mu-oxo)diiron(IV) complex in which one of the iron atoms is coordinatively unsaturated (five-coordinate). Is it reasonable for such a diiron complex to be formed in the catalytic reaction of sMMO? The answer to this important question is positive from the viewpoint of energetics in density functional theory (DFT) calculations.

Iron twin-coronet porphyrins as models of myoglobin and hemoglobin: amphibious electrostatic effects of overhanging hydroxyl groups for successful CO/O2 discrimination.

Inspired by the observation of polar interactions between CO and O(2) ligands and the peptide residues at the active site of hemoglobin and myoglobin, we synthesized two kinds of superstructured porphyrins: TCP-IM, which contains a linked imidazole ligand, and TCP-PY, which contains a linked pyridine ligand, and examined the thermodynamic, kinetic, and spectroscopic (UV/Vis, IR, NMR, and resonance Raman) properties of their CO and O(2) complexes. On both sides of each porphyrin plane, bulky binaphthyl bridges form hydrophobic cavities that are suitable for the binding of small molecules. In the proximal site, an imidazole or pyridine residue is covalently fixed and coordinates axially to the central iron atom.

Effects of a Side Chain Aromatic Ring on the Reactivity of Copper(I) Complexes with Dioxygen.

Stabilization of the bis(μ-oxo)dicopper(III) intermediate is achieved by using a bidentate N-donor ligand with pendent indole rings: N,N-bis[(3-indolyl)methyl]-N-[(2'-pyridyl)methyl]amine (BIP). The intermediate decomposes to give products arising from N-dealkylation and a product with a spiro ring composed of two indole rings. This latter product probably results from a radical-coupling reaction.

A Potassium Complex of a Fluorine-Containing Macrocyclic Cage Compound: Interactions between Fluorine Atoms and Metal Ions.

A new donor, the C-F unit, can be added to the field of host-guest chemistry. The interaction between fluorine atoms and a potassium ion was proven with the fluorine-containing cage compound 1 as a host. The six fluorine atoms of K ⊂1 are coordinated to K in a distorted octahedral fashion.