Toward Understanding the Origin of Structural Phase Transition in Guanidinium Pyridinium 1,5-Naphthalenedisulfonate

A phase transition compound 9PY was screened from a series of organic salts (Cat)center dot G center dot NDS, where the Cat is protonated amine or N-containing heterocycle (Cat = methylammonium, 1MA; ethylammonium, 2EA; propylammonium, 3PA; dimethylammonium, 4DMA; isopropylammonium, 5iPA; tert-butylammonium, 6tBA; imidazolium, 7IM; pyrazolium, 8PZ; pyridinium, 9PY; 2-methylimidazolium, 10MIM; 2-ethylimidazolium, 11EIM; (R,S)-3-methylpiperidium, 12MP), the G is guanidinium, and the NDS is 1,5-naphthalenedisulfonate. Detailed crystal structural analysis of 9PY shows the competing hydrogen-bonding interactions among the pyridinium and sulfonates are the driving force for the structural phase transition at 211 K.