title: Complexes of a naphthalimide photoacid with organic bases, and their excited-state dynamics in polar aprotic organic solvents.
abstract: Complex formation and intermolecular excited-state proton transfer (ESPT) between a dihydroxy-1,8-naphthalimide photoacid and organic bases are investigated in polar aprotic solvents. First, quantum chemical calculations are used to explore the acid-base and spectroscopic properties and to identify energetically favorable complexes. The two hydroxyl groups of the photoacid enable stepwise formation of 1 : 1 and 1 : 2 complexes. Weak bases exhibit only hydrogen-bonding interactions whereas strong bases are able to deprotonate one of the hydroxyl groups resulting in strong negative cooperativity (K1≫ 4K2) in the formation of the 1 : 2 complex. Time-resolved fluorescence studies of the complexes provide strong indications of a three-step dissociation process. The species involved in the model are: a hydrogen-bonded complex, a hydrogen-bonded ion pair, a solvent separated ion pair, and a free ion pair.
authors.affiliation: Van't Hoff Institute for Molecular Sciences, Faculty of Science, University of Amsterdam, P. O. Box 94157, 1090 GD Amsterdam, The Netherlands. tatu.kumpulainen@gmail.com a.m.brouwer@uva.nl.
authors.forename: Tatu
authors.initials: T
authors.lastname: Kumpulainen
authors.forename: Bert H
authors.initials: BH
authors.lastname: Bakker
authors.forename: Albert M
authors.initials: AM
authors.lastname: Brouwer