Salts containing different amino acids: Salts with β-alaninium L-proline dimeric cation

Abstract

Recently we have discovered a new class of amino acids salts containing different amino acids. In the present paper we report crystal structures of salts with the β-alaninium L-proline dimeric cation: β-alaninium L-proline chloride, (β-AlaH⋅⋅⋅l-Pro)Cl (I), β-alaninium L-proline bromide, (β-AlaH⋅⋅⋅l-Pro)Br (II), β-alaninium L-proline iodide, (β-AlaH⋅⋅⋅l-Pro)I (III), β-alaninium L-proline tetrafluoroborate, (β-AlaH⋅⋅⋅l-Pro)BF4 (IV), β-alaninium L-proline perchlorate, (β-AlaH⋅⋅⋅l-Pro)ClO4 (V) and β-alaninium L-proline nitrate, (β-AlaH⋅⋅⋅l-Pro)NO3 (VI). The salts (I–III) are isostructural and crystallize in the polar space group P21 with one formula unit in the asymmetric unit. The salts (IV-VI) crystallize in space group P212121 with two (isotypic compounds (IV) and (V)) resp. one (VI) formula units in the asymmetric unit. The O⋅⋅⋅O distances in the dimeric cations are 2.490(5) Å (I), 2.5001(19) Å (II), 2.529(3) Å (III) and 2.556(4), 2.581(4) Å (IV), 2.566(5), 2.570(5) Å (V) and 2.561(2) Å (VI). These values are compared with those in salts with dimeric cations (β-AlaH⋅⋅⋅β-Ala) and (l-ProH⋅⋅⋅l-Pro) with respective anions. Infrared spectra of obtained salts were registered and are discussed.