title: 7-Hydroxyquinoline-8-carbaldehydes. 2. Prototropic equilibria.
abstract: Prototropic equilibria were studied for a series of 7-hydroxyquinoline-8-carbaldehydes (7-HQCs) by (1)H NMR spectroscopy, photostationary and time-resolved UV-vis spectroscopic methods, and quantum chemical computations. These molecules represent trifunctional proton-donating/accepting systems that in aqueous solutions may assume four main neutral and ionic structures: 7-quinolinol (OH), 7(1H)-quinolinone (NH), deprotonated anion (A), and protonated cation (C). Electronic absorption and fluorescence of 7-HQCs are rationalized in terms of the ground and excited-state long-range tautomerization (part 1) as well as protonation and deprotonation processes. The photophysical properties of neutral and ionic forms of 7-HQCs are compared with those of 7-hydroxyquinolines (7-HQs), synthetic precursors of the former. The experimental results are corroborated by ab initio computations.
authors: Institute of Physical Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors: Volha
authors: V
authors: Vetokhina
authors: Jacek
authors: J
authors: Nowacki
authors: Mariusz
authors: M
authors: Pietrzak
authors: Michał F
authors: MF
authors: Rode
authors: Andrzej L
authors: AL
authors: Sobolewski
authors: Jacek
authors: J
authors: Waluk
authors: Jerzy
authors: J
authors: Herbich