Sodium 4-nitrophenolate 4-nitrophenol dihydrate crystal: a new herringbone structure for quadratic nonlinear optics

Sodium 4-nitrophenolate 4-nitrophenol dihydrate is a new nonlinear optical crystal of C2 monoclinic symmetry composed of two distinct organic chromophores of respective calculated molecular hyperpolarisabilities β _xxx =18.2×10 ^–30 and 5.2×10 ^–30 esu. The chromophores are organised in herringbone motifs along inorganic chains of NaO6 edge shared octahedra. A short H-bond network assembles the herringbone motifs. A remarkable feature is the unique proton shared between the two chromophores respecting the twofold symmetry. The structure is isotypic with that of the magnesium bis(4-nitrophenolate) dihydrate. Structural analogies with other known metal nitrophenolates are pointed out and the nonlinear optical efficiency is discussed.