title: Excited state intramolecular proton transfer in electron-rich and electron-poor derivatives of 10-hydroxybenzo[h]quinoline.
abstract: Eight previously inaccessible derivatives of 10-hydroxybenzo[h]quinoline were prepared via a straightforward strategy comprising formation of the benzo[h]quinoline skeleton followed by C-H acetoxylation at position 10. The occurrence of excited state intramolecular proton transfer (ESIPT) was detected in all cases since emission was observed only from the excited keto-tautomer. Studies on derivatives bearing both electron-donating and electron-withdrawing groups adjacent to the pyridine ring allowed us to identify some design patterns giving rise to NIR emission and large Stokes shifts. For a derivative of 10-hydroxybenzo[c]acridine, emission at 745 nm was observed, one of the lowest energy fluorescence ever reported for ESIPT system. On the basis of time-resolved measurements, proton transfer was found to be extremely fast with time constants in the range (0.08-0.45 ps).
authors.affiliation: Institute of Chemistry of the Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Piechowska
authors.forename: Kirsi
authors.initials: K
authors.lastname: Huttunen
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Wróbel
authors.forename: Helge
authors.initials: H
authors.lastname: Lemmetyinen
authors.forename: Nikolai V
authors.initials: NV
authors.lastname: Tkachenko
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Gryko