Dimeric Self‐Assembly of Pyridyl Guanidinium Carboxylates in Polar Solvents

A series of pyridyl guanidinium–carboxylates has been prepared and the dimeric self‐assembly of these studied in H 2 O/DMSO mixtures, principally using dilution isothermal calorimetry. Compounds 5 and 6 , incorporating an aromatic ring in the “tethering” region between the guanidinium and carboxylate groups, demonstrate the strongest dimerisation in neat DMSO. X‐ray crystal structures of 5 and 6 reveal two different dimerisation architectures in the solid‐state, but both involve carboxylate–guanidinium salt bridges as anticipated, and π–π interactions. Compounds 10 – 16 incorporating peptidic fragments between the guanidinium and carboxylate groups, showed reduced dimerisation strength with increased amino acid content, but also sustained dimerisation under increasingly aqueous conditions, up to 50 % H 2 O/DMSO in the case of 14 and 15 . The extent of our study in H 2 O/DMSO mixtures was determined by substrate solubility of 10 – 16 , and not the limit of self‐assembly.