The photophysics of pyridine-derivatized ortho-, meta-, and para-dibutylamino cruciforms

Abstract

The photophysical properties of a series of para-substituted donor-acceptor cruciform fluorophores (p1-4) were investigated and compared with their meta and ortho isomers (m1-4 and o1-4). The structural variations were found to have a significant effect on the solvatochromism, fluorescence quantum yields (Φfl), fluorescence lifetimes (τfl), and response upon addition of trifluoroacetic acid. The observed spectral shifts in absorption and emission caused by protonation of the cruciforms make them promising candidates as chemosensors. Additional computational studies provided more insight into the electronic structure of the systems. Position is everything: The position of the nitrogen atoms and groups of cruciforms containing both pyridine and N,N-dimethylaniline moieties has a profound effect on the photophysical properties (solvatochromism, fluorescence quantum yields, fluorescence lifetimes, and their response to a change in the pH of the environment) of these compounds. This effect is in part due to the meta-positioned nitrogen atoms and groups of the excited states having surprisingly large orbital coefficients in the HOMO (see picture). Additionally, these compounds show promise as pH sensors. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.