Mechanistic Investigations of Photoinduced Oxygenation of Ru(II) Bis-bipyridyl Flavonolate Complexes

Abstract

We previously reported that a Ru-bound flavonolate model of flavonol dioxygenases, [Ru(bpy)(3-hydroxyfla)][PF], photochemically reacts with dioxygen in two different manners. Broad-band excitation generates mixtures of products characteristic of 1,3-addition of dioxygen across the central pyrone ring, as is observed in enzymatic reactions. However, low temperature excitation at wavelengths longer than 400 nm generates a unique Ru-bound 2-benzoatophenylglyoxylate product resulting from a 1,2-dioxetane intermediate. Herein, we investigate this reactivity in a series of Ru(II)bis-bipyridyl flavonolate complexes [Ru(bpy)(3-hydroxyfla)][PF] (bpy = 2,2'-bipyridine; fla = flavonolate; R = p-OMe (1), p-Me (2), p-H (3), p-Cl (4)), and [Ru(bpy)(5-hydroxyfla)][PF] (5). The complexes' structures, photophysical and electrochemical properties, and photochemical reactivity with oxygen were investigated in detail. Two different reaction product mixtures, from 1,2- and 1,3-additions of dioxygen, are observed by illumination into distinct excitation/emission manifolds. By analogy to previous reports of excited state intramolecular proton transfer, the two manifolds are attributed to tautomeric diradicals that predict the observed reactivity patterns.

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

“…In addition, the Ru II cymene complex 203 released CO upon irradiation at either 300 or 419 nm. 1106 Additionally, Farmer and co-workers synthesized and characterized a series of Ru II bipyridinesubstituted flavonolato complexes 204, 1107,1108 and studied the mechanism of their photooxygenation by 1 O 2 at low temperatures. Their results suggest that this process occurs via 1,2-or 1,3-addition to the flavonol core.…”

CO Sense and Release Flavonols: Progress toward the Development of an Analyte Replacement PhotoCORM for Use in Living Cells

“…It is important to note that a recently reported series of Pd­(II) complexes of 3-hydroxyflavone, [Pd­(bpy)­(3-HFl-X)]­BF 4 , are nonemissive species at room temperature. , Emission spectra of solutions of Flav-1 in the presence of CORM-2 show some fluorescence emission quenching but less than that produced in the presence of PdCl 2 (Figure a). In this regard, we note that Ru­(II) flavonolato species are emissive when excited in the flavonol-related absorption bands. − The absorption spectrum of Flav-1 in the presence of CORM-2 contains a new band >500 nm. The appearance of this band suggests the formation of a Ru­(II) flavonolato complex.…”

3-Hydroxyflavone derivatives: promising scaffolds for fluorescent imaging in cells

“…In addition to interaction with solvent molecules, coordination with metal ions (such as Cu 2+ , Zn 2+ , Ru 2+ , Al 3+ and so on) can also modulate the ESIPT process of various organic molecules (such as avones, aminosalicylimines, quinolines, azoles and so on). [57][58][59][60][61][62][63][64][65] For the hydroxyavones, metal chelation usually occurs at the 3-hydroxyl, 5-hydroxyl, and 2-carbonyl groups, which can be used for Cu 2+ , Zn 2+ , Al 3+ , Hg 2+ , Pb 2+ and Fe 3+ Sening. [66][67][68][69][70][71][72][73][74][75] The complexation of metal ions with 3HF derivatives at the a-hydroxy-carbonyl site can interrupt the ESIPT process, and then change the uorescence emission.…”