Aggregation-controlled excimer emission in an axial anthracene–Sn(iv)porphyrin–anthracene triad in the solid and solution phases

Abstract

The synthesis and structure of a multichromophore triad consisting of two anthracene units axially bound to a Sn(IV)porphyrin centre via the carboxylate functionality has been reported, in which two anthracene moieties of two neighboring molecules generate a 1D polymeric chain. The fluorescence intensity of the axially coordinated 9-anthracenecarboxylic acid (9-ACA) in triad (excited at 330 nm) is significantly quenched due to the efficient singlet-to-singlet energy transfer from the excited state of 9-ACA to Sn(IV)porphyrin. The effective energy transfer from axial anthracene to equatorial porphyrin makes the triad a rare example amongst anthracene–porphyrin donor–acceptor systems. The triad shows excimer-type structureless emission band at around the 470 nm region in the concentration >10⁻⁵ M because of the strong π–π interaction between the two anthracene moieties of neighboring molecules, which is also evident from the solid-state structure of the complex.