A co-crystal containing Kemp's tri-acid and acetic acid: a 0D aggregate disrupts a thermodynamically preferred 1D rod motif

A supramolecular aggregate of two Kemp's tri-acid (cis,cis-1,3,5-trimethylcyclohexane-1,3,5-tricarboxylic acid, KTA) and four acetic acid molecules is arranged in a centrosymmetric zero-dimensional (0D) motif (2). This unusual pairing of unlike carboxylic acids disrupts a 1D hydrogen-bonded rod motif that is thermodynamically preferred by KTA (1) under most conditions. The six-molecule 0D aggregate reported here behaves like a large molecule with excellent self-recognition properties. Efficient centrosymmetric packing leads to maximized van der Waals contact and multiple C–H⋯O interactions between aggregates. The synthesis and physical properties of the parent KTA rod structure (1) and the acetic acid co-crystal (2) are compared and discussed.