A photochromic, electrochromic, therrhochromic Ru complexed benzannulene: an organometallic example of the dimethyldihydropyrene-metacyclophanediene valence isomerization

The preparation of the first photochromic, organometallic derivative of the diarylethene class, the CpRu-complexed benzodimethyidihydropyrene 3, in which the organometallic is directly attached to the photochromic core, is described. The negative dark purple photochrome 3 readily bleaches to form the almost colorless cyclophanediene 3' on irradiation with visible light. The latter switches back to 3 either photochromically with UV light, electrochromically on reduction, or thermochromically on heating. Essentially quantitative conversion between the two states is possible. The open complex 3' thermally closes 2.6 times faster than the uncomplexed parent 2', but the closed form 3 opens with visible light at about 30% of the rate of uncomplexed 2. Both open forms, complexed 3' and uncomplexed 2' close equally fast with UV light.