A Model System for Flavoenzyme Activity − Binding of Flavin and Modulation of Its Redox Potentials through Coordination to a Lewis-Acidic Azamacrocyclic Zinc(II) Complex

König, Burkhard; Pelka, Mario; Reichenbach-Klinke, Roland; Schelter, Jürgen; Daub, Jörg

doi:10.1002/1099-0690(200106)2001:12<2297::aid-ejoc2297>3.0.co;2-r

Cited by 25 publications

(21 citation statements)

References 73 publications

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“…The redox properties of flavin were modulated by hydrogen bonding and transition metal complexation. [13][14][15][16] Scandium complexes of flavin without a detailed described structure were used by Fukuzumi to investigate photophysical parameters and propose a mechanistic scheme of the process. Some of us have used zinc-cyclen appended flavins for the photooxidation of benzyl alcohols 17 and recently extended the synthetic scope to photocatalytic cleavage of benzyl protection groups and photooxidation of activated hydrocarbons by flavin tetraacetate and blue light.…”

Section: Introductionmentioning

confidence: 99%

Unraveling the flavin-catalyzed photooxidation of benzylic alcohol with transient absorption spectroscopy from sub-pico- to microseconds

Megerle

Wenninger

Kutta

et al. 2011

Phys. Chem. Chem. Phys.

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101

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Flavin-mediated photooxidations have been described for applications in synthetic organic chemistry for some time and are claimed to be a route to the use of solar energy. We present a detailed investigation of the involved photophysical and photochemical steps in methoxybenzyl alcohol oxidation on a timescale ranging from sub-picoseconds to tens of microseconds. The results establish the flavin triplet state as the key intermediate for the photooxidation. The initial step is an electron transfer from the alcohol to the triplet state of the flavin catalyst with, followed by a proton transfer in B6 ms. In contrast, the electron transfer involving the singlet state of flavin is a loss channel. It is followed by rapid charge recombination (t = 50 ps) without significant product formation as seen when flavin is dissolved in pure benzylic alcohol. In dilute acetonitrile/water solutions of flavin and alcohol the electron transfer is mostly controlled by diffusion, though at high substrate concentrations >100 mM we also find a considerable contribution from preassociated flavin-alcohol-aggregates. The model including a productive triplet channel and a competing singlet loss channel is confirmed by the course of the photooxidation quantum yield as a function of substrate concentration: We find a maximum quantum yield of 3% at 25 mM of benzylic alcohol and significantly smaller values for both higher and lower alcohol concentrations. The observations indicate the importance to perform flavin photooxidations at optimized substrate concentrations to achieve high quantum efficiencies and provide directions for the design of flavin photocatalysts with improved performance.

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Section: Introductionmentioning

confidence: 99%

Unraveling the flavin-catalyzed photooxidation of benzylic alcohol with transient absorption spectroscopy from sub-pico- to microseconds

Megerle

Wenninger

Kutta

et al. 2011

Phys. Chem. Chem. Phys.

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101

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“…To explore the possible improvement and acceleration of the reaction at elevated temperatures, a set of experiments was performed in a laboratory microwave oven at 40-50°C (entries [8][9][10][11][12]. Every 15-30 minutes, the progress was monitored by thin layer chromatography.…”

Section: Copper-mediated Flavin 3-n-arylationmentioning

confidence: 99%

“…[3][4][5][6][7][8] Many flavoenzyme models have been developed to investigate photo-and redox properties or to utilize flavins in organocatalytic reactions. [8][9][10][11][12][13][14] The synthesis of such flavoenzyme models or catalysts requires selective modification of the parent flavin structure. [8][9][10][11] The nitrogen atom in position 3 is particularly suitable for the introduction of substituents at a late stage of the flavin synthesis.…”

mentioning

confidence: 99%

“…[8][9][10][11][12][13][14] The synthesis of such flavoenzyme models or catalysts requires selective modification of the parent flavin structure. [8][9][10][11] The nitrogen atom in position 3 is particularly suitable for the introduction of substituents at a late stage of the flavin synthesis. 15 Typically, alkylations in 3-N position give only moderate yields due to decomposition of flavins in basic solutions.…”

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confidence: 99%

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Copper-Mediated 3-N-Arylation of Flavins

Attenberger¹,

Schmaderer²,

König³

2008

Synthesis

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A generally applicable method for the direct 3-N-arylation of flavins using arylboronic acids and copper acetate was developed. The reaction conditions were optimized considering the lability of flavins in basic conditions and thermal heating. Donorand acceptor-substituted arylboronic acids were used yielding 3-Narylflavins in moderate to good yields by C(aryl)-N(imide) bond formation. UV and fluorescence measurements indicate an orthogonal orientation of the additional aromatic substituent to the flavin ring system. The arene substituent is not electronically coupled to the flavin p-system in the ground state, but electron-rich arene substituents in 3-N position significantly reduce the flavin emission intensity.

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“…The optical spectroscopic behaviour of flavins (isoalloxazine dyes) is reviewed in [9,11,17,18]. Isoalloxazine dyes covalently linked to other dyes in donor acceptor systems with bridges, antennas, and mediators are artificial model systems for their biological counterparts [19][20][21][22] and gain importance in photo-voltaic, molecular switching, and molecular logics applications [23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Absorption and emission spectroscopic characterization of 10-phenyl-isoalloxazine derivatives

et al. 2006

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A Model System for Flavoenzyme Activity − Binding of Flavin and Modulation of Its Redox Potentials through Coordination to a Lewis-Acidic Azamacrocyclic Zinc(II) Complex

Cited by 25 publications

References 73 publications

Unraveling the flavin-catalyzed photooxidation of benzylic alcohol with transient absorption spectroscopy from sub-pico- to microseconds

Unraveling the flavin-catalyzed photooxidation of benzylic alcohol with transient absorption spectroscopy from sub-pico- to microseconds

Copper-Mediated 3-N-Arylation of Flavins

Absorption and emission spectroscopic characterization of 10-phenyl-isoalloxazine derivatives

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