Search for molecular crystals with NLO properties: 5-Sulfosalicylic acid with nicotinamide and isonicotinamide

Two proton transfer hydrogen-bonded complexes of 5-sulfosalicylic acid (3-carboxy-4-hydroxybenzenesulfonic acid, 5-SSA) with the aromatic amides: nicotinamide (NA) and isonicotinamide (INA), are characterized by X-ray diffraction and spectroscopic studies. In the crystal structures of nicotinamidium 3-carboxy-4-hydroxybenzenesulfonate, 1, and isonicotinamidium 3-carboxy-4-hydroxybenzenesulfonate monohydrate, 2, the ions are linked into three dimensional frameworks by a combination of O–H⋯O, N–H⋯O and C–H⋯O hydrogen bonds and cation–anion π–π stacking interactions. The hydrogen-bonding behavior of the pyridine N atom is different in the two crystals, bonding to a sulfonate O atom of anion in 2 but to a carbonyl O atom of cation in 1. The complex 1 shows relatively efficient second harmonic frequency generation.