Recent Advances in the Chemistry of Phthalocyanines as Functional Chromophores

Phthalocyanine (Pc), a conventional dyestuff exhibiting vivid blue or green color, has been utilized as a functional molecule for application in a variety of fields due to its excellent optical and electrochemical properties. Creation of novel π-conjugated systems based on the structure of Pc with the aim of further developing unique properties has, therefore, been of a prime importance. Despite the over a hundred-year history of phthalocyanine chemistry, progress in this regard has been fairly limited mainly due to the problems inherent in the synthesis of Pc. The authors have pioneered this research area by focusing on the control of the optical properties in the visible and near-infrared regions by (1) creation of the novel π-conjugated systems and (2) introduction of perturbation that is as simple as possible to the electronic structures and have reported a variety of unprecedented Pc analogues. Considerable attention has also been focused on the structure-optical property relationships of these novel Pc compounds. This chapter summarizes the contribution of the authors to the recent advances in the chemistry of phthalocyanine as functional chromophore systems.