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Han X, Kumar MR, Hoogerbrugge A, Klausmeyer KK, Ghimire MM, Harris LM, Omary MA, Farmer PJ. Mechanistic Investigations of Photoinduced Oxygenation of Ru(II) Bis-bipyridyl Flavonolate Complexes. Inorg Chem 2018; 57:2416-2424. [PMID: 29461051 DOI: 10.1021/acs.inorgchem.7b01384] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We previously reported that a Ru-bound flavonolate model of flavonol dioxygenases, [RuII(bpy)2(3-hydroxyfla)][PF6], 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 [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)), and [RuII(bpy)2(5-hydroxyfla)][PF6] (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.
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Affiliation(s)
- Xiaozhen Han
- Department of Chemistry and Biochemistry , Baylor University , Waco , Texas 76798 , United States.,Department of Chemistry and Biochemistry , Stephen F. Austin State University , Nacogdoches , Texas 75962 , United States
| | - Murugaeson R Kumar
- Department of Chemistry and Biochemistry , Baylor University , Waco , Texas 76798 , United States
| | - Amanda Hoogerbrugge
- Department of Chemistry and Biochemistry , Baylor University , Waco , Texas 76798 , United States
| | - Kevin K Klausmeyer
- Department of Chemistry and Biochemistry , Baylor University , Waco , Texas 76798 , United States
| | - Mukunda M Ghimire
- Department of Chemistry , University of North Texas , Denton , Texas 76203 , United States.,Department of Chemistry , Lebanon Valley College , Annville , Pennsylvania 17003 , United States
| | - Lauren M Harris
- Department of Chemistry , University of North Texas , Denton , Texas 76203 , United States
| | - Mohammad A Omary
- Department of Chemistry , University of North Texas , Denton , Texas 76203 , United States
| | - Patrick J Farmer
- Department of Chemistry and Biochemistry , Baylor University , Waco , Texas 76798 , United States
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Characterization of the Initial Intermediate Formed during Photoinduced Oxygenation of the Ruthenium(II) Bis(bipyridyl)flavonolate Complex. Inorg Chem 2016; 55:7320-2. [PMID: 27437831 DOI: 10.1021/acs.inorgchem.6b00852] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A ruthenium(II) flavonolate complex, [Ru(II)(bpy)2fla][BF4], was synthesized to model the reactivity of the flavonol dioxygenases. The treatment of dry CH3CN solutions of [Ru(II)(bpy)2fla][BF4] with dioxygen under light leads to the oxidative O-heterocyclic ring opening of the coordinated substrate flavonolate, resulting in the formation of [Ru(II)(bpy)2(carboxylate)][BF4] (carboxylate = O-benzoylsalicylate or benzoate) species, as determined by electrospray ionization mass spectrometry. Moderation of the excitation and temperature allowed isolation and characterization of an intermediate, [Ru(II)(bpy)2bpg][BF4] (bpg = 2-benzoyloxyphenylglyoxylate), generated by the 1,2-addition of dioxygen to the central flavonolate ring.
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