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Discovery of a size-record breaking green-emissive fluorophore: small, smaller, HINA
Rui Kang1, Laura Talamini2, Elisa D'Este3
1Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT) Hermann-von-Helmholtz Platz 1 76344 Eggenstein-Leopoldshafen Germany frank.biedermann@kit.edu willem.klopper@kit.edu.
Abstract:
Astonishingly, 3-hydroxyisonicotinealdehyde (HINA) is despite its small size a green-emitting push-pull fluorophore in water (QY of 15%) and shows ratiometric emission response to biological relevant pH differences (pK a2 ∼ 7.1). Moreover, HINA is the first small-molecule fluorophore reported that possesses three distinctly emissive protonation states. This fluorophore can be used in combination with metal complexes for fluorescent-based cysteine detection in aqueous media, and is readily taken up by cells. The theoretical description of HINA's photophysics remains challenging, even when computing Franck-Condon profiles via coupled-cluster calculations, making HINA an interesting model for future method development.