ORCID Profile
0000-0002-7995-6894
Current Organisation
University of North Carolina at Chapel Hill
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Publisher: American Chemical Society (ACS)
Date: 23-09-2022
DOI: 10.1021/ACS.JPCLETT.2C02061
Abstract: Interchromophoric interactions such as Coulombic coupling and exchange interactions are crucial to the functional properties of numerous π-conjugated systems. Here, we use magnetic circular dichroism (MCD) spectroscopy to investigate interchromophoric interactions in singlet fission relevant pentacene dimers. Using a simple analytical model, we outline a general relationship between the geometry of pentacene dimers and their calculated MCD response. We analyze experimental MCD spectra of different covalently bridged pentacene dimers to reveal how the molecular structure of the "bridge" affects the magnitude of through-space Coulombic and through-bond exchange interactions in the system. Our results show that through-bond interactions are significant in dimers with conjugated molecules as bridging units and these interactions promote the overall electronic coupling in the system. Our generalized approach paves the way for the application of MCD in investigating interchromophoric interactions across a range of π-conjugated systems.
Publisher: Springer Science and Business Media LLC
Date: 17-10-2016
DOI: 10.1038/NPHYS3909
Publisher: American Chemical Society (ACS)
Date: 03-10-2023
DOI: 10.1021/JACS.3C07082
Publisher: American Chemical Society (ACS)
Date: 09-2017
DOI: 10.1021/JACS.7B05204
Abstract: We have designed a series of pentacene dimers separated by homoconjugated or nonconjugated bridges that exhibit fast and efficient intramolecular singlet exciton fission (iSF). These materials are distinctive among reported iSF compounds because they exist in the unexplored regime of close spatial proximity but weak electronic coupling between the singlet exciton and triplet pair states. Using transient absorption spectroscopy to investigate photophysics in these molecules, we find that homoconjugated dimers display desirable excited-state dynamics, with significantly reduced recombination rates as compared to conjugated dimers with similar singlet fission rates. In addition, unlike conjugated dimers, the time constants for singlet fission are relatively insensitive to the interplanar angle between chromophores, since rotation about σ bonds negligibly affects the orbital overlap within the π-bonding network. In the nonconjugated dimer, where the iSF occurs with a time constant >10 ns, comparable to the fluorescence lifetime, we used electron spin resonance spectroscopy to unequivocally establish the formation of triplet-triplet multiexcitons and uncoupled triplet excitons through singlet fission. Together, these studies enable us to articulate the role of the conjugation motif in iSF.
Publisher: American Chemical Society (ACS)
Date: 26-09-2018
DOI: 10.1021/JACS.8B08100
Abstract: The textbook photoreaction between two alkenes is the [2 + 2]-photocycloaddition resulting in functionalized cyclobutanes. Herein, we disclose an unusual reactivity of alkenes that favor photoene reaction over the [2 + 2]-photocycloaddition.
Publisher: American Chemical Society (ACS)
Date: 16-08-2021
Location: United States of America
No related grants have been discovered for Elango Kumarasamy.