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Chloroform-Driven Excited-State Protonation of Pyrene-Dialkylaniline Derivatives Under Visible Light
Kumar Dineshkumar1, Muniappan Kalipriyadharshini2,3, Masiyappan Karuppusamy2,3
1Centre for Advanced Organic Materials (Sona-AROMA), Department of Chemistry, Sona College of Technology, Salem, Tamil Nadu, 636 012, India.
Chemistry, an Asian Journal
|August 13, 2025
Summary
Alkyl chain length influences organic chromophore photochemistry. The C6 chain length optimizes a novel light-induced reaction in chloroform, forming protonated N,N-dialkylaniline via electron transfer and hydrogen abstraction.
Area of Science:
- Organic Chemistry
- Photochemistry
- Spectroscopy
Background:
- Organic chromophore properties depend on aromatic cores and substituents.
- Alkyl chains typically have minor effects due to weak inductive effects.
- Investigating alkyl chain influence on photophysical and photochemical properties is crucial.
Purpose of the Study:
- Synthesize pyrene substituted with N,N-dialkylanilines with varying alkyl chain lengths (C2, C6, C10).
- Explore the impact of alkyl chain length on the photophysical and photochemical behavior of these compounds.
- Elucidate the mechanism of light-induced transformations in specific solvents.
Main Methods:
- Suzuki coupling for synthesis of pyrene-N,N-dialkylaniline derivatives.
- Solvatofluorochromic studies to analyze fluorescence shifts with solvent polarity.
- UV-Vis absorption spectroscopy and nanosecond transient absorption spectroscopy to study reaction mechanisms and intermediates.
- Photochemical irradiation experiments using blue LED.
Main Results:
- Solvatofluorochromism observed, with exceptions in protic solvents like chloroform and methanol due to hydrogen bonding.
- Blue LED irradiation in chloroform induced a light-sensitive transformation, yielding protonated N,N-dialkylaniline.
- The reaction mechanism involves photoexcitation, single-electron transfer, and hydrogen abstraction from chloroform, confirmed by transient absorption spectroscopy.
- Reaction kinetics are dependent on alkyl chain length, with C6 exhibiting optimal performance.
Conclusions:
- Alkyl chain length significantly impacts photochemical reactivity, contrary to general expectations.
- Chloroform acts as a proton source in a unique photoinduced reaction involving pyrene-N,N-dialkylaniline derivatives.
- The C6 alkyl chain length represents an optimal configuration for this specific photochemical transformation.
Keywords:
Light induced chloroform deprotonationN,N‐dialkylanilinePhoto‐protonation in chloroformPyreneSingle electron transfer (SET)More Related Videos
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