Insights into the AIEE of 1,8-naphthalimides (NPIs): inverse effects of intermolecular interactions in solution and aggregates.
Systematic structural perturbation has been used to fine-tune and understand the luminescence properties of three new 1,8-naphthalimides (NPIs) in solution and aggregates. The NPIs show blue emission in the solution state and their fluorescence quantum yields are dependent upon their molecular rigidity. In concentrated solutions of the NPIs, intermolecular interactions were found to quench the fluorescence due to the formation of excimers. In contrast, upon aggregation (in THF/H2O mixtures), the NPIs show aggregation-induced emission enhancement (AIEE). The NPIs also show moderately high solid-state emission quantum yields (ca. 10-12.7 %). The AIEE behaviour of the NPIs depends on their molecular rigidity and the nature of their intermolecular interactions. The NPIs 1-3 show different extents of intermolecular (π-π and C-H⋅⋅⋅O) interactions in their solid-state crystal structures depending on their substituents. Detailed photophysical, computational and structural investigations suggest that an optimal balance of structural flexibility and intermolecular communication is necessary for achieving AIEE characteristics in these NPIs.
Department of Inorganic & Physical Chemistry, Indian Institute of Science, Bangalore 560 012 (India), Fax: (+91) 8023601552.
Sanjoy
S
Mukherjee
Pakkirisamy
P
Thilagar
D005453:Fluorescence; D015394:Molecular Structure; D053644:Naphthalimides / Q000138:chemical synthesis* / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*
D053644:Naphthalimides; D012997:Solvents
aggregation; density functional calculations; fluorescence; stacking interactions