*Article* **A Study of the Interaction between Cucurbit[7]uril and Alkyl Substituted 4-Pyrrolidinopyridinium Salts**

**Weitao Xu 1, Xinyi Zhu 1, Bing Bian 2, Xin Xiao 1,\*, Zhu Tao 1 and Carl Redshaw 3,\***


Received: 28 February 2020; Accepted: 8 April 2020; Published: 14 April 2020

**Abstract:** The interaction between cucurbit[7]uril (Q[7]) and a series of 4-pyrrolidinopyridinium salts bearing aliphatic substituents at the pyridinium nitrogen, namely 4-(C4H8N)C5H5NRBr, where R = H (C0), Et (C2), *n*-butyl (C4), *n*-hexyl (C6), has been studied in aqueous solution by 1H NMR spectroscopy, electronic absorption spectroscopy, and mass spectrometry.

**Keywords:** host–guest interaction; cucurbit[7]uril; 4-pyrrolidinopyridinium
