Salts containing different amino acids: Three types salts of l-arginine containing glycine, dimethylglycine or β-alanine

Abstract Recently we have discovered a new class of amino acids salts containing different amino acids. In the present paper we report synthesis, crystal structures and infrared spectra of four such salts: l -Argininium(+) dimethylglycine iodide ( l -ArgH)(DMG)I (I), di- l -argininium(+) glycinium glycine triiodide monohydrate ( l -ArgH)2(GlyH•••Gly)I3•H2O (II), di- l -argininium(+) β-alaninium β-alanine triiodide ( l -ArgH)2(β-AlaH•••β-Ala)I3 (III), and l -argininium(2+) bis-dimethylglycine diiodide ( l -ArgH2•••DMG)(DMG)I2 (IV). The salts (I-III) crystallize in P212121, P1, P21 space groups, respectively, each with one formula unit in the asymmetric unit, while the salt (IV) forms in space group P21 with two formula units in the asymmetric unit and is pseudo-centrosymmetric. The dimeric cations (GlyH•••Gly), (β-AlaH•••β-Ala) and ( l -ArgH2•••DMG) are built by O-H•••O strong hydrogen bonds with very short O⋅⋅⋅O distances. The ( l -ArgH2•••DMG) dimeric cation of the [A(1)2+•••A(2)] type was encountered for the first time. The obtained iodide salts (I, II, III, IV) containing different amino acids can be used in medicine as regulators of thyroxine synthesis in the body.