Pyridyl substituted 4-(1,3-Dioxo-1H,3H-benzo[de]isoquinolin-2-ylmethyl)-benzamides with aggregation enhanced emission and multi-stimuli-responsive properties.

1,8-Naphthalimide connected to benzoic acid chloride via methylene group was condensed separately with 3-aminopyridine and 4-aminopyridine and provided compounds 4-(1,3-Dioxo-2,3-dihydro-1H- phenalen-2-ylmethyl)-N-pyridin-3-yl-benzamide 1 and 4-(1,3-Dioxo-2,3-dihydro-1H-phenalen-2-yl- methyl)-N-pyridin-4-yl-benzamide 2. The compounds are characterized by spectral(IR,UV–Visible, 1H and 13C NMR)measurements and supported by their X-ray crystallography. Their photoelectrons pec- troscopy, SEM and TEM measurements are also made. They are found luminescent in DMF solution as well as in the solid state and form nano-aggregates with enhanced emission (AEE)in aqueous-DMF solution. Their AEE behavior depends on the polarity of the solvents. On grinding, crystalline solids 1 and 2 turn to amorphous and the process is reversible on annealing as supported by their powder X-ray diffraction (PXRD)measurements. Both compounds show mechanochromic properties and display multi-stimuli response. Density Functional Theory calculations rationalize their optical data.