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 rigid...

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Bibliographic Details
Published in:Chemistry : a European journal 2014-06, Vol.20 (26), p.8012-8023
Main Authors: Mukherjee, Sanjoy, Thilagar, Pakkirisamy
Format: Article
Language:English
Subjects:
Agglomeration
Aggregates
aggregation
Chemistry
density functional calculations
Emission
Emission analysis
Flexibility
Fluorescence
Hydrogen bonds
Mathematical models
Molecular Structure
Naphthalimides - chemical synthesis
Naphthalimides - chemistry
Rigidity
Solvents - chemistry
stacking interactions
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Summary: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. Aggregate emission: The types of emission behaviour of a series of 1,8‐naphthalimides with differing degrees of intermolecular association in solution and upon aggregation have been studied, providing insights into the mechanism of aggregation‐induced emission enhancement (see figure).
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201304694