title: Low-temperature spectra of the analogues of 10-hydroxybenzo[h]quinoline as an indication of barrierless ESIPT.
abstract: The absorption and fluorescence spectra of two analogues of 10-hydroxybenzo[h]quinoline (10-HBQ), namely, 1-hydroxy-7-methylbenzo[c]acridine (HMBA) and 4-hydroxybenzo[c]phenanthridine (HBPA), were studied in n-alkane matrices at 5 K. Considerable energy separation between the onsets of the spectra and broadening of the bands was an indication that intramolecular proton transfer (ESIPT) takes place at such a low temperature. DFT and ab initio methods were used to calculate the electronic transition energies and oscillator strengths and the vibronic structure of the electronic spectra. Shortcomings in our knowledge of the shape of the potential energy surface for ESIPT systems are highlighted in the context of the discussion of the shape of the electronic spectra. The π-expansion of the 10-HBQ chromophore achieved by adding a benzene moiety at various positions adjacent to the pyridine ring led to compounds possessing diverse photophysical properties, ranging from the non-ESIPT strongly fluorescent molecule of 10-hydroxy-1-azaperylene to weakly emitting (or nonemitting) molecules, where ESIPT occurs very efficiently.
authors.affiliation: Institute of Physics of the Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland.
authors.forename: Irena
authors.initials: I
authors.lastname: Deperasińska
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Gryko
authors.forename: Elena
authors.initials: E
authors.lastname: Karpiuk
authors.forename: Bolesław
authors.initials: B
authors.lastname: Kozankiewicz
authors.forename: Artur
authors.initials: A
authors.lastname: Makarewicz
authors.forename: Joanna
authors.initials: J
authors.lastname: Piechowska
mesh_terms: D011522:Protons; D011789:Quantum Theory; D011804:Quinolines / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013696:Temperature
chemical_list: C521323:10-hydroxybenzo(h)quinoline; D011522:Protons; D011804:Quinolines