Abstract

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⁾(d₁₂ = 38 and d₁₁ = 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 MNA² from organic solutions. Large prismatic orange-red colored crystals of an equimolar complex crystallized in the monoclinic space group P2₁ 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

© 1994 IEEE