The synthesis end characterization of some pyridinium-N-phenoxide betaine dyes (including Reichardt's dye) for second-harmonic generation (SHG) is described. These dyes are highly solvatochromic, which indicates that they can have large second-order molecular polarizabilities. The effects of substituents on the solvatochromic and optical properties of the betaines are investigated. Also the crystal structure of the betaines is discussed and ...
