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Updated: Feb 17, 2026

Author Spotlight: Experimental Approaches for the Synthesis of Low-Valent Metal-Organic Frameworks from Multitopic Phosphine Linkers
Published on: May 12, 2023
Pillar[4]pyridinium: a square-shaped molecular box
Sandra Kosiorek1, Bartłomiej Rosa1, Tomasz Boinski2
1Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-248 Warsaw, Poland. vsashuk@ichf.edu.pl.
Abstract:
Numerous applications of Stoddart's 'blue-box', a pyridinium containing macrocycle of rectangular shape, encouraged us to seek successors of this amazing molecule. Using a one-step cyclization reaction we synthesized a square-shaped cyclic tetramer consisting of 4-methylenepyridinium units - pillar[4]pyridinium (P[4]P). Pillar[4]pyridinium is a quadruply positively charged water-soluble macrocycle with a highly symmetric, strained structure and an electron-deficient cavity. These features impel the macrocycle to assemble into channel networks in the solid state and render it an effective fluoride receptor in water.
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