Guest Exchange in a Robust Hydrogen-Bonded Organic Framework: Single-Crystal to Single-Crystal Exchange and Kinetic Studies

Abstract

The salt 3,4-lutidinium pamoate crystallizes as its hemihydrate, forming a hydrogen-bonded organic framework with tetrahydrofuran (THF) as a guest in channels in the structure (1·THF). Extensive investigation has shown this framework to be highly robust: the THF in the channels can be exchanged for 20 different compounds, with 13 of these exchanges occurring in a single-crystal to single-crystal manner. The THF can also be exchanged for the volatile solids pyrazine or iodine, both via single-crystal to single-crystal transformations. Stepwise exchange of solvents is also possible, with a sequence of five exchanges occurring before the crystals begin to deteriorate. Investigation of the kinetics of exchange in 1·THF revealed that exchange occurs according to a deceleratory kinetic model for contracting volume.