Dimeric Self‐Assembly of Pyridyl Guanidinium Carboxylates in Polar Solvents

Abstract

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.

Pyridin-2-yl Guanidine Derivatives: Conformational Control Induced by Intramolecular Hydrogen-Bonding Interactions

“…It is known that in pyridyl guanidinium systems, the syn conformation can be stabilized by intramolecular hydrogen-bonding interactions (IMHB) when the guanidinium carrying group is placed in the ortho position . Hence, a theoretical DFT study at the B3LYP/6-31+G** computational level of all possible geometries of the neutral 2-pyridinoguanidine series (including E / Z isomers, syn / anti rotamers, and tautomers) was initially performed to approach our systems.…”