Pressure-Induced Solvate Crystallization of 1,4-Diazabicyclo[2.2.2]octane Perchlorate with Methanol

1,4-Diazabicyclo[2.2.2]octane perchlorate, [C6H13N2]+ClO4-, dabcoHClO(4), the first NH+center dot center dot center dot N hydrogen-bonded ferroelectric, exhibits at least ten unsolvated polymorphs, depending on temperature and pressure. When crystallized from the methanol solution above 2 GPa, dabcoHClO(4) crystallizes with two molecules of methanol to form solvate dabcoHClO(4)center dot 2CH(3)OH. This solvate structure has been determined by single-crystal X-ray diffraction up to 3 GPa. High pressure transforms the H-bonding pattern and the hierarchy of different cohesion forces. The solvate formation is additionally favored by its molecular volume lower than the sum of the molar equivalents of unsolvated components.