Mixed salts of amino acids: L-histidinium(+) L-histidinium(2+) nitrate-hexafluorosilicate

► We discovered a new mixed salt ((L-His+⋯L-His2+)·NO3-·SiF62-) with different anions. ► This is the first observation of dimeric L-histidinium(+) L-histidinium(2+) cation. ► The dimeric cation is characterized by an O⋯O distance equal to 2.507(2) Å. ► The dimeric cation is reflected in the infrared spectrum as a broad absorption band at ca. 1300 cm−1.