Electrochromic and Photochromic Properties

This chapter introduces transition metal complexes and organometallics that display photochromic and electrochromic phenomena. First, electrochromic materials are enumerated, which feature linkage isomerization, intramolecular ligand exchange, and changes in the oxidation state of metal centers without significant structural changes. Several applications relating to electrochromism are also described. Second, those exhibiting photochromism inherently are inducted. They are also divided into three categories: linkage isomerization, intramolecular ligand exchange, and metastable state trapping at low temperatures upon photoinduced electron transfers or photoexcitation. Third, a convenient methodology for introducing photochromism into transition metal complexes and organometallics - conjugation with organic photochromics - is accounted for. Electronic and structural interactions between the two components result in synergetic effects, including regulation of the physical properties of metal-containing parts, control over the isomerization behavior of organic photochromics, and mutual control of the two properties. Also introduced are multiphotochromic systems where two or more organic photochromics are conjugated to one metal center.