Catenated and Non-Catenated Inclusion Complexes of Trimesic Acid

Abstract

Trimesic acid (benzene-1,3,5-tri-carboxylic acid; TMA) can in principle form two-dimensional hydrogen-bonded hexagonal networks in which central holes of the network have net diameters of 14 Å Although such holes would be expected to be natural locations for guest molecules, non-catenated single networks have not been found in any of the crystals containing TMA studied in the last sixteen years. Instead, anhydrous α-TMA, TMA pentaiodide (TMA.I₅) and (so-called) γ- TMA have mutually triply-catenated structures in which triplets of networks are interlaced [3,4,5], while the hydrated complexes are based on non-catenated nets of composition TMA.H₂O [6]. We have now found conditions under which single networks are preserved without catenation, the cavities being occupied by guests such as n-tetradecane, n-heptanol, n-octanol, n-decanol, octene, cyclooctane and isooctane. The structures of 2TMA.n-tetradecane and 2TMA.isooctane have been solved and refined to R=13.0% and R=11.3%, respectively, disorder of the guest molecules having prevented further refinement of the room- temperature data. Determination of the crystal structures of the other complexes, which are isostructural with 2TMA.n-tetradecane, is now in progress. We are also investigating other potential guests.