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Laser flash photolysis study of the photochemistry of 4,5-diaza-9-fluorenone

Paper ID Volume ID Publish Year Pages File Format Full-Text
26408 43950 2015 6 PDF Available
Title
Laser flash photolysis study of the photochemistry of 4,5-diaza-9-fluorenone
Abstract

•The triplet excited state of 4,5-diaza-9-fluorenone has ππ* character and its energy is located between 49.3 and 52.4 kcal/mol, with an intersystem crossing quantum yield of 0.41.•Low quenching rate constants were obtained for quenchers where the primary process corresponds to hydrogen transfer, such as 1,4-cyclohexadiene, cyclohexane, 2-propanol and toluene .•The 4,5-diaza-9-fluorenone triplet was efficiently quenched by electron donors such as triethylamine and DABCO.•A Hammett plot for the quenching by phenols containing polar substituents led to a reaction constant ρ of −1.54 ± 0.10.

The triplet excited state of 4,5-diaza-9-fluorenone (1) shows absorption maxima at 410 and 470 nm and a lifetime of 3 μs, in acetonitrile. Its intersystem crossing quantum yield was determined using 9-fluorenone as a secondary standard and a value of 0.41 ± 0.01 was obtained. The reactivity of the triplet excited state of 1 towards several quenchers, in acetonitrile, was investigated employing the laser flash photolysis technique quenching rate constants ranging from 7.9 × 104 M−1 s−1 (2-propanol) to 1.0 × 1010 M−1 s−1 (triethylamine) were obtained. From the quenching rate constants obtained one can conclude that 4,5-diaza-9-fluorenone has a ππ* triplet excited state. A Hammett plot for the quenching rate constants of triplet 1 by phenols containing polar substituents against σ+ gave a reaction constant ρ of –1.54 ± 0.10, which demonstrates the electrophilic character of the 4,5-diaza-9-fluorenone triplet excited state.

Keywords
4,5-Diaza-9-fluorenone; Triplet excited state; Laser flash photolysis; Electron transfer; Hydrogen abstraction; Hammett equation
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 299, 15 February 2015, Pages 166–171
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us