Sensitive and selective PET-based π-expanded phenanthrimidazole luminophore for Zn2+ ion

Area of Science:

• Materials Chemistry
• Supramolecular Chemistry
• Photochemistry

Background:

• Development of selective fluorescent chemosensors for metal ion detection is crucial in various scientific fields.
• Photoinduced electron transfer (PET) mechanisms offer a pathway for designing sensitive and selective molecular probes.
• Understanding the photophysical properties and electronic structure of chemosensors is key to optimizing their performance.

Purpose of the Study:

• To synthesize and characterize a novel PET chemosensor, 1-(1-(4-methoxyphenyl)-1H-phenanthro[9,10-d]imidazol-2-yl)naphthalen-2-ol (MPPN), and its zinc complex.
• To investigate the sensing capabilities of MPPN, particularly its selectivity and sensitivity towards Zn(2+) ions.
• To elucidate the photophysical mechanisms underlying the luminescence enhancement upon metal ion binding using theoretical calculations.

Main Methods:

• Synthesis and characterization of MPPN and its zinc complex using electronic spectral analysis.
• Investigation of metal ion binding properties and selectivity using fluorescence spectroscopy.
• Density Functional Theory (DFT) calculations to analyze Frontier molecular orbital energies and luminescence mechanisms.

Main Results:

• MPPN acts as an efficient fluorescent chemosensor with a strong preference for Zn(2+) ions.
• Upon binding with Zn(2+), MPPN exhibits significantly enhanced luminescence at λemi = 421 nm.
• DFT calculations reveal that Zn(2+) binding stabilizes key π-orbitals, suppressing non-radiative decay pathways and enhancing luminescence.

Conclusions:

• The synthesized MPPN chemosensor demonstrates high selectivity and sensitivity for Zn(2+) detection.
• The observed luminescence enhancement is attributed to the specific electronic interactions between MPPN and Zn(2+) ions.
• MPPN shows a high affinity for zinc ions (K = 6 × 10(6) M(-1)) and possesses favorable nonlinear absorption properties.