Glycine hydrogen fluoride: Remarkable hydrogen bonding in the dimeric glycine glycinium cation

Crystals of glycine hydrogen fluoride (Gly center dot HF) were prepared from an aqueous solution containing stoichiometric quantities of the components. The crystal structure of was determined, IR and Raman spectra were registered and are discussed. Gly center dot HF crystallizes in the orthorhombic space group Pbca with Z = 32. The most remarkable feature of the structure is the existence of symmetric dimeric glycine-glycinium cations with short hydrogen bonds (O center dot center dot center dot O distance of 2.446 angstrom), charge-counterbalanced by hydrogen bifluoride (F-H center dot center dot center dot F)(-) anions - in addition to the expected glycinium cations and fluoride anions. These results were compared with previously published data on crystals grown in the system glycine-HF-H2O. (C) 2010 Elsevier B.V. All rights reserved.