Intercalation of Neutral Guests in Pillared Salt Cocrystals of 5-Ureidosalyclic Acid.

The salts of 5-ureidosalyclic acid (5-USA) form a range of pillared salt inclusion complexes from basic solvents, namely, triethylamine, piperidine, morpholine, and 4-ethylpyridine. The triethylamine derivative is unsolvated, while the other salts include 1-3 solvent molecules of formula XH(5-USA-H)·X (X = morpholine, = 1, 2, and 3 ( - ); X = 4-ethylpyridine, = 1 () and X = piperidine, = 2.5 ()). The morpholine salt expands the layered structure to include 1, 2, or 3 guests. The 5-USA anion can also act as a bidentate ligand for manganese(III), again forming highly solvated inclusion complex anions [Mn(5-USA-H)(Solv)]. When interacting strongly with the countercation, the 5-USA anions adopt an unusual carboxylate isomer form, whereas the morpholinium salt solvate (H-morpholine)[Mn(5-USA-H)(morpholine)]·2(morpholine) () is . The soft, plastic crystals of this complex gradually desolvate, losing channel morpholine and ultimately spontaneously recrystallizing as the 5-USA salt dimorpholine inclusion complex . The complex hydrogen-bonded, pillared 5-USA salts illustrate a design concept for intercalated materials of forming charged, planar layers that leave the charge-balancing counterion exposed, such that interlayer guest species must be incorporated to effectively solvate the charged moieties.