Solvent-induced multicolour fluorescence of amino-substituted 2,3-naphthalimides studied by fluorescence and transient absorption measurements

Abstract

A series of amino-2,3-naphthalimide derivatives having the amino functionality at 1-, 5- and 6-positions (, and , respectively) were prepared, and their photophysical properties were systematically investigated based on the measurements of steady-state absorption and fluorescence spectra, fluorescence lifetimes as well as transient absorption spectra. The s efficiently fluoresced in solution, and the emission spectra appreciably shifted depending on the solvent polarity. displayed only a slight fluorescence red-shift upon increasing the solvent polarity. In contrast, and showed marked positive solvatofluorochromism with large Stokes shifts displaying multicolour fluorescence; the fluorescence colours of and varied from violet-blue in hexane to orange-red in methanol. and , thus, serve as micro-environment responding fluorophores. In methanol, the intensity of the fluorescence emission band of and significantly reduced. Based on the fluorescence quantum yields and lifetimes, and transient absorption measurements, it has been revealed that internal conversion from the S1 state of s to the ground state was accelerated by the protic medium, resulting in a reduction in their fluorescence efficiency, while intersystem crossing from the S1 state to a triplet state was not responsible for the decrease of fluorescence intensity.

Synthesis and Characterization of White-Light Luminescent End-Capped Polyimides Based on FRET and Excited State Intramolecular Proton Transfer

“…ESIPT is a process in which the excited state is relaxed by the structural relaxation (tautomerization) from the normal (N*) form to the tautomer (T*) form, through proton transfer in the excited state, resulting in a large energy gap between the absorption and emission, leading to a very large ν. In particular, the ESIPT occurring at amino (-NH 2 ) or substituted amino (-NHR) groups undergo more efficient proton transfer than that of the hydroxy (-OH) group, and its ESIPT reaction can be controlled by the electronegativity of the substituents [37][38][39][40]. To achieve white light with ESIPT, it is necessary to design molecules which emit yellow fluorescence via ESIPT (the emission wavelength should be around 550-580 nm) [41].…”

pH and thermo responsive aliphatic tertiary amine chromophore hyperbranched poly(amino ether ester)s from oxa‐Michael addition polymerization

“…These results indicated that the microenvironment solvent polarity significantly influenced the fluorescence position, which may attribute to hydrogen bonding interactions between the tertiary amine chromophore and polar protic solvent. [ 46 ]…”

Electronic Properties and Electroluminescent OLED Performance of Panchromatic Emissive N-Aryl-2,3-naphthalimides

“…With our two communications among the first reported N -aryl-2,3-napthalimides panchromatic fluorescent dyes, the considerable number of citations prompted us to expand these photoluminescent solvent studies to electroluminescent WOLEDs. , Since those early entries, relatively few small-molecule dyes have been reported to display white light emission. − The widely used approach for a single chromophore to achieve white electroluminescence is taken via short-wavelength fluorescence from the electron–hole recombination in an individual molecule and the broad longer-wavelength fluorescence from the intermolecular interactions. The intermolecular interactions usually originate from the formation of excimers, electromers, and aggregates .…”