New nonlinear optical materials in the mixed (2,4-dinitrophenyl)-L-alanine (DPA) and 2-methyl-4-nitroaniline (MNA) system: crystal growth and investigation

Among innumerable organic materials investigated for their exceptional nonlinear optical (NLO) properties 2-methyl-4-nitroaniline (MNA) has one of the largest second-order nonlinear coefficients, χ (2) (d 12 = 38 and d 11 = 250 pm/V), 1 crystallizing in the monoclinic space group Cc. 1 Large crystals of MNA could not be grown from either solution or melt. Therefore, we tried crystallizing mixtures of methyl-(2,4-dinitriphenyl)-aminopro-panoate (MAP) and MNA 2 from organic solutions. Large prismatic orange-red colored crystals of an equimolar complex crystallized in the monoclinic space group P2 1 with lattice parameters different from those of either MAP or MNA. 3 The color, ascribed to a band starting at 530-nm, reduced second-harmonic generation (SHG) efficiency. 3 Therefore, MAP was substituted by the precursor in its synthesis, (2,4-dinitrophenyl)-L-alanine (DPA). 4