Scientific article
English

Ultrafast Energy Transfer in Orthogonal Heptamethine Cyanine–Naphthalimide Systems: A Pathway toward High-Energy Excitation

Published inThe journal of physical chemistry. A, acs.jpca.6c01137
First online date2026-05-14
Abstract

We report the synthesis and photophysical characterization of a family of bichromophoric systems, in which substituted naphthalimides (NMI) are covalently attached at the meso position of heptamethine cyanines (Cy7). Single crystal X-ray diffraction and DFT calculations reveal a near-perpendicular arrangement of the NMI and Cy7 moieties, resulting in minimal electronic communication. Complementary variable-temperature NMR measurements reveal potential fluctuations in the dihedral angle between the two moieties. Steady-state spectroscopy and femtosecond transient absorption measurements reveal a non-negligible excited state coupling, linked to ultrafast internal conversion/energy transfer from an NMI localized high-lying excited state to the cyanine S1 state. This process occurs on a subpicosecond time scale for all dyads, regardless of NMI substitution, leading to a large excitation-emission wavelength difference and an effective monochromophoric fluorescence behavior. Comparative studies with the NMI-pyridine precursors further highlight the role of intramolecular charge transfer in shaping the ultrafast dynamics in these systems, prior to cyanine attachment. Altogether, our results establish clear structure-property relationships for cyanine-based antenna constructs, thus providing design principles for multichromophoric systems that broaden cyanine absorption while preserving the integrity of the polymethine core.

Citation (ISO format)
JAMJAH, Ali et al. Ultrafast Energy Transfer in Orthogonal Heptamethine Cyanine–Naphthalimide Systems: A Pathway toward High-Energy Excitation. In: The journal of physical chemistry. A, 2026, p. acs.jpca.6c01137. doi: 10.1021/acs.jpca.6c01137
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Article (Accepted version)
accessLevelRestrictedaccessLevelPublic 15/05/2027
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Identifiers
Additional URL for this publicationhttps://pubs.acs.org/doi/10.1021/acs.jpca.6c01137
Journal ISSN1089-5639
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