Pt(II) Tetrafacial Barrel with Aggregation-Induced Emission for Sensing

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Analytical Chemistry

Background:

• Tetraphenylpyrazine-based tetraimidazole ligand (L) exhibits aggregation-induced emission (AIE).
• Subcomponent self-assembly is a powerful method for constructing complex supramolecular architectures.
• Picric acid (PA) is an explosive and environmental contaminant requiring sensitive detection methods.

Purpose of the Study:

• To synthesize and characterize novel tetrafacial supramolecular barrels using a new ligand.
• To investigate the photophysical properties, specifically AIE, of the synthesized metal-organic assemblies.
• To evaluate the potential of the AIE-active assembly for the selective detection of hazardous nitroaromatic compounds like picric acid.

Main Methods:

• Synthesis of a novel tetraphenylpyrazine-based tetraimidazole ligand (L).
• Subcomponent self-assembly of ligand L with cis-(tmeda)Pd(NO3)2 and cis-Pt(PEt3)2(OTf)2 to form Pd(II) and Pt(II) barrels.
• Characterization of the assemblies using spectroscopic techniques and evaluation of their AIE properties and sensing capabilities for picric acid.

Main Results:

• Formation of two tetrafacial barrels: [Pd8L4(tmeda)8](NO3)16 (1) and [Pt8L4(PEt3)16](OTf)16 (2).
• Ligand L is AIE active, but only the Pt(II) barrel (2) shows significantly enhanced AIE activity.
• Pd(II) barrel (1) exhibits aggregation-caused quenching (ACQ), while Pt(II) barrel (2) selectively detects picric acid with high sensitivity due to ground-state complex formation and energy transfer.

Conclusions:

• The Pt(II) supramolecular barrel (2) demonstrates significantly enhanced AIE properties compared to the free ligand.
• The AIE-active Pt(II) barrel (2) serves as a selective and sensitive sensor for the detection of explosive picric acid.
• This work highlights the potential of rationally designed supramolecular assemblies for advanced photophysical applications and environmental sensing.