Crystalline Complexes Involving Amino Acids. II. (R)-(-)-1-Phenylglycinium Hydrogen Squarate Monohydrate

The title compound, C₈H₁₀NO₂⁺.C₄HO₄^-.H₂O, crystallizes in the orthorhombic space group P2₁2₁2₁ in a layered structure of charged phenylglycinium and squarate/water layers stacked along the c axis and held together by an extensive hydrogen-bonding network. The amino group of the phenylglycine molecule adopts a proton from the squaric acid. The C-C bond lengths within the squarate anion are consistent with a delocalized double bond around the hydroxyl-bearing C atom: 1.414 (3) and 1.431 (3) Å versus 1.481 (3) and 1.494 (3) Å for the opposite bonds in the ring.

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