Discrete CH center dot center dot center dot N Bonded Patterns Modified by Temperature and Pressure in Four Pyrazine Polymorphs

摘要

Pyrazine molecules aggregate by remarkably similar CH center dot center dot center dot N hydrogen bonds into four polymorphs. Of eight CH center dot center dot center dot N bonds to each molecule, six H-bonds are very similar for all pyrazine structures. A diagram of four crystalline phases has been outlined and their low-temperature and high-pressure structures determined. Phase I is metastable and occurs only within the ambient-pressure region of phase II.