Second-harmonic generation from single crystals of N-substituted 4-nitroanilines

Six RT-substituted derivatives of 2-methyl-4-nitroaniline (MNA) and two N-substituted derivatives of 4-nitroaniline were synthesized and their physical and optical properties were examined in the search for nonlinear optical materials with a sufficiently large second harmonic (SH) activity and applicability to practical use. Some derivatives produced single crystals and their structures were determined by X-ray crystallography. The trends of the SH intensity of these materials could be qualitatively explained based on the b tensor (the effective molecular hyperpolarizability in the crystal). Amongst the derivatives examined in this investigation, N-benzyl-MNA showed the highest SH activity (up to twice that of MNA), thermostability and phase-matching ability.