HYPERPOLARIZABILITY OF NEW NITRO-AROMATIC-N-OXIDE SPECIES - NONLINEAR OPTICAL-PROPERTIES OF A FERROMAGNETIC ORGANIC MATERIAL

N-t-butyl-(4-nitrophenyl)nitrone (BNPN) and 2-(4-nitro-phenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl-3-oxide (NPNN) are nitro-aromatic-N-oxide species, both of interest for their nonlinear optical properties, the latter being a stable radical. Their first molecular hyperpolarizabilities β were measured in solution by the electric-field-induced second-harmonic generation (EFISHG) method and their crystalline efficiency assessed by a second-harmonic generation powder test. NPNN is SHG active with a SH signal equivalent to that of urea at 1.06 and 1.34 μm. NPNN has been reported to exhibit ferromagnetic properties in the solid state, and this is the first time that magnetic and nonlinear optical properties have been determined on the same organic material. Similarities and differences in symmetry requirements underlying the design of ferromagnetic and nonlinear crystals are pointed out. © 1990.