Preparation, Characterization, and Electronic Structure of Asymmetric Isonaphthalimide: Mechanism of Dual Fluorescence in Solid State

The asymmetric isonaphthalene imide,
3-[(4-nitrophenyl)­imino]-1H,3H-benzo­[de]­isochromen-1-one
was obtained by condensation of 1,8-naphthoylchloride with p-nitroaniline in the presence of pyridine. The crystal
structure and vibrational and electronic absorption spectra are reported.
The emission spectrum of the crystalline phase demonstrates dual luminescence,
with short and long wavelength components, while only the short wavelength
component is present in chloroform solution. The geometrical and electronic
structures of the ground and excited states of the molecule are investigated
using density functional theory methods. Dual fluorescence is explained
in terms of the excited states of different nature. The spectroscopic
properties of newly synthesized compounds for possible biosensor applications
are discussed.