Photochemical reactions of dioxygen with Ru-bound flavonolate complexes designed to model flavonol dioxygenases generate unique Ru-bound 2-benzoatophenylglyoxylate products resulting from a 1,2 dioxetane intermediate, as well as the products derived from 1,3 addition mechanism observed in the enzymatic reactions. This reactivity is investigated in a series of Ru(II) bis-bipyridyl flavonolate complexes [RuII(bpy)2(3-hydroxyflaR)] [PF6] (bpy = 2,2’-bipyridine; fla = flavonolate; R = p-OMe (1), p-Me (2) , p-H (3) , p-Cl (4)), [RuII(bpy)2(3,7-dihydroxyfla)] [PF6] (5) and [RuII(bpy)2(5-hydroxyfla)] [PF6] (6). Reaction of complexes 1 – 5 with O2 under light yield dioxygenation products as 2-benzoatophenylglyoxylate complexes, whereas complex 6 remains unreactive. The reactive complexes show two absorbance/emission states; selective photo-oxygenation at the high energy band yields mixtures of products derived from 1,3 addition, while photo-oxygenation at lower energy band produces the unique Ru adduct of 2-benzoatophenylglyoxylate from a 1,2 addition pathway.

Photo-induced oxygenations of Ru(II) bisbipyridyl flavonolate complexes

255th National Meeting (2018)

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