4-N-Methylstilbazolium toluene-p-sulfonate salts with large second-order optical non-linearities

Donor-substituted 4-N-methylstilbazolium toluene-p-sulfonate salts and related salts containing cations with extended conjugation exhibit an unusually high propensity to crystallize in non-centrosymmetric space groups. The new compound 3′,4′-dihydroxy-4-N-methylstilbazolium toluene-p-sulfonate crystallizes in the space group P1 and exhibits a powder second-harmonic generation efficiency 106 times that of urea measured at 1.907 µm.