Hydrogen-Bonded Networks from Poly(dimethylamidinium) Cations and Polycarboxylate Anions

Two ditopic and one tetratopic dialkylamidinium-containing compounds were synthesised and their ability to form hydrogen-bonded networks or frameworks with polycarboxylate anions was studied. A series of 11 different networks were crystallised: in all cases, the dialkylamidinium group is in the E/Z conformation, which limits the possibility of strong hydrogen bonding interactions. Nevertheless, a series of interesting networks were formed, several of which contain solvent-filled channels. It was found that many networks showed a tendency toward polymorphism with four forms of one network and three of another isolated under slightly different crystallisation conditions. Interestingly, several networks contain partially-protonated polycarboxylate anions, which form short anti-electrostatic O–HO– hydrogen bonds between anions that direct network formation.