Supramolecular aggregation in new crystals with nonlinear optical properties: 2-aminophenol-HClO4, 3-aminophenol-HClO4 and 4-aminophenol-HClO4

Three new hybrid crystals of 2-aminophenol-HClO₄ (2-AP-HClO₄, 1), 3-aminophenol-HClO₄ (3-AP-HClO₄, 2) and 4-aminophenol-HClO₄ (4-AP-HClO₄, 3) were obtained and their crystal structures determined. The 1 crystallises in centrosymmetric space group C2/c of monoclinic system while the other two (2 and 3) crystallise in the non-centro symmetric space group P2₁ and P2₁2₁2₁, respectively. The oppositely charged units of the crystals, i.e. positively charged 2-APH⁺, 3-APH⁺ and 4-APH⁺ and ClO₄⁻, interact via weak N⁺–HO and O–HO hydrogen bonds forming 3D-supramolecular network. Relative to KDP the SHG efficiencies are 0.62 for 2 and 0.33 for 3, measured at 1064 nm using the Kurtz–Perry method.