Functionalized Naphthalenediimide Based Supramolecular Charge-Transfer Complexes Via Self-Assembly And Their Photophysical Properties

We report here the design and syntheses of a naphthalenediimide (NDI)-N functionalized organic fluorophore, 1, and its supramolecular CT complexes [(1 center dot 2H)(2+)center dot(PA(-))(2)] (2) and [(1 center dot 2H)(2+)center dot(3,5-DNSA(-))(2)] (3), self-assembled from 1 as an electron acceptor (A) and picric acid (PA) or 3,5-dinitrosalicylic acid (3,5-DNSA) as a donor (D), with a very large Stokes shift (>170 nm) and significant fluorescence lifetime (similar to 1.55 ns). NDI is functionalized with phenylpyridyl units (chromophore) to extend the pi-conjugation and thus provide a suitable platform for strong C-H---pi and pi MIDLINE HORIZONTAL ELLIPSIS pi stacking interactions, which are the prime requirements for any compound to be used as a fluorescent probe. The organic fluorophore, 1, and its supramolecular CT complexes 2 and 3 exhibit decent electronic properties as suggested by DFT, cyclic voltammetry, and fluorescence studies. Moreover, compounds 1-3 were also exploited as fluorescent probes for cell imaging under normal cell isolation and with time-bound exposure.