Synthesis, Photophysics, Live Cell Imaging, and Aggregation Behavior of Some Structurally Similar Alkyl Chain Containing Bromonaphthalimide Systems: Influence of Alkyl Chain Length on the Aggregation Behavior

A series of 4-bromonaphthalimide systems (BNI-C-n; n = 4, 10, 12, and 16) comprising different alkyl side chains have been synthesized and used as the building blocks to fabricate organic fluorescent micro materials. The systems have been developed basically to investigate the effect of alkyl side chains on the aggregation behavior of the systems. The aggregation behavior of these systems has been studied by spectroscopic and microscopic techniques. Microscopic investigation reveals that there is a decrease in the size of the aggregates with an increase in the linear alkyl side chain length. A change in the shape from rod-like to spherical with an increase in the length of alkyl group has also been observed during microscopic investigation. The photophysical properties of these well-characterized aggregates have been studied and compared with those in molecular form. A bathochromic shift both in absorption and in emission spectrum of the aggregates has indicated the formation of J aggregates. A confocal fluorescence microscopic investigation also reveals that the long chain systems (12 and 16 member) are cell permeable and can be used as the imaging probe in live cells.