L-Histidinium dipicrate dihydrate

In the title mol­ecular salt, C₆H₁₁N₃O₂²⁺·2C₆H₂N₃O₇⁻·2H₂O, the histidine mol­ecule exists as a histidinium dication, being protonated at the N atom of the imidazole ring. The charges are balanced by two picrate anions and the compound crystallizes as a dihydrate. In the crystal, the components are linked via N—H...O and O—H...O hydrogen bonds and weak C—H...O inter­actions, forming a three-dimensional supermolecular structure.

N²-(4-Meth­oxy­salicyl­idene)arginine hemihydrate

The title compound, C₁₄H₂₀N₄O₄·0.5H₂O [systematic name: (2S)-5-{[amino­(iminium­yl)meth­yl]amino}-2-{[(1Z)-4-meth­oxy-2-oxido­benzyl­idene]aza­nium­yl}penta­noate hemihydrate], has been synthesized by the reaction of L-arginine and 4-meth­oxy­salicyl­aldehyde and crystallizes with two independent substituted L-arginine mol­ecules and one water mol­ecule of solvation in the asymmetric unit. Each mol­ecule exists as a zwitterion and adopts a Z configuration about the central C=N. The mol­ecular conformation is stabilized by strong intra­molecular N—H...O hydrogen bonds that generate S(6) and S(10) ring motifs. Inter­molecular N—H...O and O—H...O hydrogen bonds involving also the water mol­ecule and weak inter­molecular C—H...O_water inter­actions link the mol­ecules into an infinite one-dimensional ribbon structure extending along the b axis. The known (2S) absolute configuration for L-arginine was invoked. Weak intermolecular C—H...π interactions are also present.