Fluorescent 4-amino-1,8-naphthalimide Troger's bases possessing conjugated 4-amino-1,8-naphthalimide moieties and their potential fullerenes Host-Guest complexes

The synthesis and characterisation of two new 1,8-naphthalimide Troger's bases (TBNaps) 1 and 2 is described from the commercially available 4-chloro-1,8-naphthalic anhydride. These structures possess two additional 4-amino-1,8-naphthalimide (Naps) units, each of these 'terminal' Naps units have either 1-(2-aminoethyl)-pyrrolidine or 1-(2-aminoethyl)-piperidine moieties, that are conjugated to the TBNaps units via a short propyl spacer. The ground and the excited state properties of 1 and 2, as well as the bis-Nap precursor 10, were evaluated in a range of solvents that varied by polarity and hydrogen bonding ability. The UV-Vis absorption and the fluorescence emission spectra, demonstrated that all three compounds possess Internal Charge Transfer (ICT) excited state properties. Both 1 and 2 were designed as potential receptor molecules for the detection of C-60 (buckminsterfullerene) where it was anticipated that C-60 could possibly bind within the orthogonal cavity of the Troger's base's, through additional interactions with the terminal Naps. While the titrations of 1 and 2 with C-60 in a chlorobenzene:DMF (86:14) solvent mixture showed only minor changes in the absorption spectra, significant fluorescence quenching was observed for both 1 and 2. Analysis of the fluorescence data in terms of a Stern-Volmer plot, showed that the quenching involves a combination of both static and dynamic mechanisms.