4-{[3-(4-Hydroxy­benzyl­ideneamino)-2,2-dimethyl­propyl]iminiomethyl}phenolate dihydrate

The asymmetric unit of the title compound, C(19)H(22)N(2)O(2)·2H(2)O, comprises a zwitterionic form of the Schiff base compound and two water mol­ecules of crystallization. Inter­molecular N—H⋯O, C—H⋯O and O—H⋯N hydrogen bonds involving one of the water mol­ecules in the asymmetric unit generate seven- and eight-membered rings, with R (2) (1)(7) and R (2) (2)(8) ring motifs, respectively. The dihedral angle beween the two aromatic rings is 86.5 (2)°. The imino and iminium groups are coplanar with the benzene rings to which they are attached, making dihedral angles (N—C—C—C) of −179.3 (5) and −179.2 (4)°, respectively. Validation software indicates the higher symmetry space group Pnma for this structure. However, this process ignores H atoms and the zwitterionic configuration of the main mol­ecule breaks the higher symmetry. Solution in Pna2(1) provides a chemically sensible zwitterionic compound with improved residuals. In the crystal structure, mol­ecules are linked together through inter­molecular O—H⋯O, O—H⋯N, N—H⋯O and C—H⋯O inter­actions, forming a three-dimensional network. The crystal structure is further stabilized by inter­molecular C—H⋯π inter­actions.