A new fluorescent sensor based on 1H-pyrazolo[3,4-b]quinoline skeleton. Part 2

Area of Science:

• Analytical Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Fluorescent dyes are crucial for chemical sensing.
• Developing selective sensors for inorganic cations remains a challenge.

Purpose of the Study:

• To synthesize and characterize a novel fluorescent dye, P1.
• To investigate P1's potential as a sensor for small inorganic cations.
• To elucidate the sensing mechanism based on fluorescence changes.

Main Methods:

• Synthesis of bis-(pyridin-2-yl-methyl)-(1,3,4-triphenyl-1H-pyrazolo[3,4-b]quinolin-6-ylmethyl)-amine (P1).
• Steady-state and time-resolved fluorescence spectroscopy.
• Quantum chemical calculations.

Main Results:

• P1 functions as a fluorescent sensor for Li+, Na+, Ba2+, Mg2+, Ca2+, and Zn2+ in acetonitrile.
• Sensing mechanism involves cation-induced retardation of intramolecular electron transfer.
• Binding constants correlate with cation charge density; strong binding observed for Zn2+ and Mg2+.
• Formation of 2/1 complexes with Zn2+ and Mg2+ leads to a bathochromic fluorescence shift, potentially due to intramolecular excimer formation.

Conclusions:

• The novel fluorescent dye P1 demonstrates effective sensing capabilities for various inorganic cations.
• The sensing mechanism is governed by cation-induced modulation of intramolecular electron transfer.
• The observed fluorescence shifts and binding affinities highlight the potential of P1 in selective cation detection.