Modeling of the hydrophobic microenvironment of water-soluble molybdoenzymes in an aqueous micellar solution

Abstract

A toluene-soluble molybdenum(vi) complex containing a bulky hydrophobic substituent, (Et4N)2[Mo(VI)O2{1,2-S2-3,6-(RCONH)2C6H2}2] (R = (4-(t)BuC6H4)3C), was dissolved in the hydrophobic core of a micelle in an aqueous medium and catalyzed the biomimetic reduction of an amine N-oxide by an NADH analog. The kinetic isotope effect of solvent water clearly indicates that water molecules are essential for catalysis and are involved in the rate-determining step.

Unexpected Reaction Promoted by NH+···O=Mo Hydrogen Bonds in Nonpolar Solvents

“…[35] In dichloromethane, a solvent with intermediate polarity between that of toluene and DMF, similar (Et 3 NH) 2 [2] formation was observed, but the absorption did not change rapidly. As mentioned above, (Et 4 N) 2 [2] is stable in DMF.…”

“…We have reported a biomimetic catalytic reduction of an amine N ‐oxide by a nicotinamide adenine dinucleotide (NADH) analogue in aqueous media. In the proposed mechanism, protonated Mo VI O 2 species, [Mo VI O(OH)( L ) 2 ] – , is converted into [Mo V O( L ) 2 ] – accompanying the generation of H 2 O by one‐electron reduction …”