Enantioselectivity of resolved Δ and Λ orthoruthenated 2-phenylpyridine complexes [Ru(o-C6H4-2-py)(LL)2]PF6 (LL = bpy and phen) toward glucose oxidase

Cyclometalated 2-phenylpyridine complexes [RuII(o-C6H4-2-py)(LL)2]PF6, LL = 2,2′-bipyridine (1) and 1,10-phenanthroline (2) were resolved into Δ and Λ enantiomers using column chromatography on SP Sephadex C-25 in the presence of (+)-2,3-dibenzoyl-D-tartrate. The absolute configuration of enantiomers was established using circular dichroism spectroscopy. The rate constants ket for the electron transfer from reduced glucose oxidase (GO from Aspergillus niger) and PQQ-dependent glucose dehydrogenase (GDH) at the generated RuIII species were measured by cyclic voltammetry and UV–vis spectroscopy. The electron transfer shows enantioselectivity. In the case of GO, the bell-shaped pH profile for the ratio kΛ/kΔ has a maximum at pH 7 (kΛ/kΔ equals 3.4 and 3.9 for 1 and 2, respectively), but its inversion is observed at pH around 5 and 9. The kΛ/kΔ ratio equals 2.0 for 2 and GDH at pH 7. The results of theoretical modeling of biological electron transfer for GO using functional docking Monte-Carlo simulations are presented and analyzed together with the experimental observations.