New near infrared-sensitive photochromic fluorescing molecules

The synthesis of new photochromic 2-indolylfulgide dicyanomethylene derivatives is described and their structures confirmed by X-ray crystallography, NMR, mass spectroscopy and elemental analysis. The molecules exhibit two thermally stable isomeric forms, which are only optically interconverted. The ring-open form absorbs between 400 and 550 nm, while the ring-closed form absorbs in the 650 to 700 nm region. The cyclized form emits fluorescence in the near infrared, with a 0.18 quantum yield. The spectroscopic characteristics described make this molecule suitable for optical switching and optical storage devices.