Water‐Soluble Molecular Capsules: Self‐Assembly and Binding Properties

Abstract
The self‐assembly and characterization of water‐soluble calix[4]arene‐based molecular capsules (1⋅2) is reported. The assemblies are the result of ionic interactions between negatively charged calix[4]arenes 1 a and 1 b, functionalized at the upper rim with amino acid moieties, and a positively charged tetraamidiniumcalix[4]arene 2. The formation of the molecular capsules is studied by 1H NMR spectroscopy, ESI mass spectrometry (ESI‐MS), and isothermal titration calorimetry (ITC). A molecular docking protocol was used to identify potential guest molecules for the self‐assembled capsule 1 a⋅2. Experimental guest encapsulation studies indicate that capsule 1 a⋅2 is an effective host for both charged (N‐methylquinuclidinium cation) and neutral molecules (6‐amino‐2‐methylquinoline) in water.