Bis(Naphthalimide-Piperazine)-Based Off-On Fluorescent Probe for Acids

Area of Science:

• Chemical Sensing
• Fluorescent Probes
• Molecular Design

Background:

• Photo-induced electron transfer (PET) is a key mechanism in designing fluorescent sensors.
• Developing selective and reversible probes for pH monitoring is crucial in various scientific fields.
• Naphthalimide derivatives offer versatile platforms for creating advanced optical sensors.

Purpose of the Study:

• To synthesize and characterize a novel bis(naphthalimide-piperazine) derivative as a pH-sensitive fluorescent probe.
• To elucidate the operating mechanism of the probe, focusing on pH-dependent photo-induced electron transfer (PET).
• To evaluate the probe's selectivity, reversibility, and performance across a wide pH range.

Main Methods:

• Synthesis of a bis(naphthalimide-piperazine) derivative (compound 1).
• Absorption and fluorescence spectroscopy were employed to investigate optical properties.
• Evaluation of pH-dependent fluorescence changes and selectivity studies.

Main Results:

• Compound 1 functions as an Off-On fluorescent probe, exhibiting pH-sensitive behavior.
• A PET process from piperazine to naphthalimide quenches fluorescence at pH 11-4.5.
• Inhibition of PET at pH 4.5-1 leads to fluorescence enhancement, demonstrating a 'turn-on' response.
• The probe shows high selectivity for protons (H+) over other species and good reversibility.

Conclusions:

• The synthesized bis(naphthalimide-piperazine) derivative is an effective pH-sensitive fluorescent probe.
• The probe's operation relies on a pH-modulated PET mechanism.
• Its high selectivity and reversibility make it a promising tool for monitoring proton concentrations.