Cooperative assistance in a very short O-H···O, hydrogen bond. Low-temperature X-ray crystal structures of 2,3,5,6-pyrazinetetracarboxylic and related acids

Abstract

In contrast to the well documented role of charge- and resonance-assistance in very short hydrogen bonds, a very short O-Hacid···Owater hydrogen bond [O···O 2.4791(13) Å] in the title acid is ascribed to the cumulative stabilisation from σ- and π-bond cooperativity.