Synthesis, Photophysical Characterization, and Sensor Activity of New 1,8-Naphthalimide Derivatives

Abstract

Three new 1,8-naphthalimide derivatives M1–M3 with different substituents at the C-4 position have been synthesized and characterized. Their photophysical properties have been investigated in organic solvents of different polarity, and their fluorescence intensity was found to depend strongly on both the polarity of the solvents and the type of substituent at C-4. For compounds M1 and M2 having a tertiary amino group linked via an ethylene bridge to the chromophore system, high quantum yield was observed only in non-polar media, whereas for compound M3, the quantum efficiency did not depend on the medium polarity. The effect of different metal ions (Ag+, Ba2+, Cu2+, Co2+, Mg2+, Pb2+, Sr2+, Fe3+, and Sn2+) on the fluorescence emission of compounds M1 and M2 was investigated. A significant enhancement has been observed in the presence of Ag+, Pb2+, Sn2+, Co2+, Fe3+, as this effect is expressed more preferably in the case of M2. Both compounds have shown significant pH dependence, as the fluorescence intensity was low in alkaline medium and has been enhanced more than 20-fold in acidic medium. The metal ions and pH do not affect the fluorescence intensity of M3. Density-functional theory (DFT) and Time-dependent density-functional theory (TDDFT) quantum chemical calculations are employed in deciphering the intimate mechanism of sensor mechanism. The functional properties of M1 and M2 were compared with polyamidoamine (PAMAM) dendrimers of different generations modified with 1,8-naphthalimide.

Dioxepine-Peri-Annulated PMIs—Synthesis and Spectral and Sensing Properties

“…The S 1 -excited state of the complex was optimized at the same level of theory, and the energies and shape representation of the frontier molecular orbitals are given in Figure 9 . The S 1 -excited state geometry optimization is necessary as the consideration of the MO in the ground state only is not sufficient to reliably predict the photoinduced electron transfer [ 14 , 48 ].…”

“…Various classes of light-active organic compounds were successfully used as fluorophores in the design of PET sensors—1,8-naphthalimides, benzanthrone, benzofurazan and xanthene derivatives, etc. [ 13 , 14 , 15 , 16 , 17 , 18 ]. One of the emerging classes of fluorophores used as signal fragments are perylene monoimides (PMIs) and diimides (PDIs) [ 19 , 20 , 21 ].…”

Naphthalimide-Piperazine Derivatives as Multifunctional “On” and “Off” Fluorescent Switches for pH, Hg2+ and Cu2+ Ions

“…In PET systems, a fluorophore is covalently linked with a receptor through a short aliphatic spacer, while both segments maintain their individual properties. Upon interaction with the target analyte, the PET process is inhibited thereby causing changes in the quantum yield or fluorescence intensity [ 17 , 18 , 19 ].…”