Solution-mediated and single-crystal to single-crystal transformations of cucurbit[6]uril host-guest complexes with dopamine

Host-guest complexation between cucurbit[6]uril and dopamine results in concomitant crystallization of two morphologically distinct supramolecular isomers. Form I appears as prismatic crystals and crystallizes in the P2(1)2(1)2(1) space group. Form II appears as needles and crystallizes in the R (3) over tilde space group. Form I is unstable in solution and spontaneously converts into form II. Additionally, form II undergoes single-crystal to single-crystal dehydration at room temperature mediated by an alteration of the host-guest hydrogen bonding pattern and collective reorganization of dopamine guest molecules.