Supramolecular materials rely often on macrocycles consisting of aromatic rings and aliphatic carbons to achieve host-guest chemistry. We present a carefully designed strategy for the design and construction of ternary assemblies based on weak supramolecular interactions: aromatic interactions between resorcinarene receptors (A) and nitrogen-based aromatics (B), and hydrogen bonding between the nitrogen-based aromatics (B) and different carboxylic acids of varying pka’s (C). The ternary assemblies are analyzed in the solid state through single crystal X-ray diffraction and in solution via 1D and 2D NMR spectroscopy. The binding processes were quantified through 1H NMR titration experiments. These observed findings were further supported by DFT-based computational calculations which underscore how binding of carboxylic acid (C) on the receptor (A) backbone regulate the bound nitrogen-based aromatic guests (B) in the cavity of the resorcinarene receptor. The observed binding constant for AB system shows a relatively strong affinity of pyridine to sit in the hydrophobic cavity of the resorcinarene receptor. Stronger acids gave high binding affinities upon complexation in the ternary system (ABC), aided by strong hydrogen bonding interactions compared to weaker acids with relatively lower binding affinities. This observation establishes a scenario for allosteric-like regulation of host-guest binding. As computationally predicted, multiple intra-host and host-guest, guest-guest stabilizing interactions and the cooperativity between them play a key role in the formation of the energetically favorable ternary systems compared to their binary analogues (Figure 1).

Systematic construction of ternary assemblies through weak interactions

2019 Fall National Meeting

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