Structure-forming units of amino acid maleates. Case study of l-valinium hydrogen maleate

A new salt of l-valinium hydrogen maleate was used as an example to study structure-forming units in amino acid maleates. This compound was crystallized, its structure solved from single-crystal X-ray diffraction data, and the phase purity of the bulk powder sample confirmed by X-ray powder diffraction and FT-IR spectra. The stability of the new salt was analyzed using density functional theory and PIXEL calculations with focus on the C²₂(12) structure-forming crystallographic motif. This motif was of particular interest as it is common for almost all maleates. The exceptionally high ability of maleic acid to form salts with various amino acids was rationalized.A new salt of l-valinium hydrogen maleate was used as an example to study structure-forming units in amino acid maleates. Model calculations have shown the C²₂(12) motif (common for most maleates) to be crucial for the thermodynamic stability of the structure.