Host–guest complexes in the crystal land: a plethora of crystal forms and crystallization peculiarities

Abstract

This review focuses on the pathway-dependent crystallization of the host–guest complexes based on the macrocyclic host molecules in aqueous media. The high degree of structural diversity from the same host and guest molecular building blocks can be achieved through simple manipulation of the crystallization conditions, such as pH, presence of additives, or cosolvents. The kinetic factors can also be crucial to determine the crystallization pathway and structure of the host–guest assemblies, especially in the case of macrocyclic hosts with constrictive binding. All these significantly broaden the host–guest crystal engineering landscape and accessibility of different crystal forms. The exciting perspectives encompass the on-demand obtaining of various crystal complexes with programmed structure and lifetime from the same host and guest components.