NLO crystals of bis[1-(diaminomethylene)thiouron-1-ium] tartate(2−) hemihydrate and deuterated [1-(diaminomethylene)thiouron-1-ium] tartate(−)

► Protiated and deuterated crystals of 1-(diaminomethylene)thiouron-1-ium tartate were obtained. ► Hydrogen bonding motifs R21(6) and R22(8) in protiated and R12(5) and R21(6) in deuterated crystals are present. ► Both compounds crystallise in the non-centrosymmetric space groups and exhibit NLO properties.