Salts containing different amino acids: four types of salts with the sulfate anion

In the present paper, we report crystal structures of four types ([A(1)H][A(2)H]Y, [A(1)H] 3 [A(2)H]Y 2 , A(1)H[A(2)H···A(2)]Y, and A(1)H[A(1)H···A(2)]Y) of mixed salts containing the sulfate anion (Y = SO 4 2− ) and amino acids A, i.e., sarcosine (Sar), dimethylglycine (DMG), betaine (Bet), β -alanine ( β -Ala), and l -proline ( l -Pro): ( β -AlaH)(DMGH)SO 4 ·2H 2 O ( I ), ( β -AlaH)(BetH)SO 4 ( II ), ( β -AlaH)( l -ProH)SO 4 ( III ), (BetH)( l -ProH)SO 4 ( IV ), (SarH) 3 ( l -ProH)(SO 4 ) 2 ( V ), ( β -AlaH)( l -ProH··· l -Pro)SO 4 ( VI ), and ( β -AlaH)( β -AlaH···DMG)SO 4 ( VII ). The O···O distances in dimeric cations ( l -ProH··· l -Pro) and ( β -AlaH···DMG) are 2.450(3) and 2.5295(12) Å in ( VI ) and ( VII ), respectively. Crystal structure determinations of ( β -AlaH)(BetH)SO 4 ( II ) at 100 K ( P 2 1 / n ), 200 K ( Pnma ), 250 K ( Pnma ), and room temperature ( Pnma ) revealed a structural phase transition in the interval between 100 and 200 K.