Phthalocyanines (Pc) are the general term for compounds that contain the tetrabenzotetraazaporphine (H2 -Pc) ring, which is the porphyrin analog and metal phthalocyanines (M-Pc). M-Pc has attractive physical properties associated with their structures, and this has led to a broad spectrum of studies being done on synthetic methods and properties. Amongst the many synthetic methods, ones using 1,2-dicyanobenzene or 1,3-diiminoisoindoline, are the most common, since these methods produce the products in high purity.1) M-Pc possesses a large delocalized π electron system due to the tetraazaporphine ring, which leads to interesting and useful photochemical properties. The photochemical and photophysical properties of these systems have been studied extensively, and some of these compounds have been put to practical use. The weather-resistant blue and green pigments are one example, and in other examples, the photoelectric properties have been applied to optical memory disks, luminescent devices and solar batteries. M-Pc is also utilized as carrier-generation-layer of electrophotographic photoconductor.2) Furthermore, M-Pc has redox properties which ﬁnd use as an electrochromic material3), which results in a reversible discoloration phenomenon caused by changing the applied electric potential. M-Pc is also used as a deodorant and antibacterial agent by selection of the appropriate central metals and the making of pendant-type polymers.1) In other examples, M-Pc has uses in M-Pc derivative sensor4), liquid crystal5), photochemical therapy for cancer and many others. M-Pc is the functional material of the 21st-Century, and more is anticipated upon further research and development.
1)N. Kobayashi, Kagaku To Kogyo (Tokyo)1999, 52, 968; N. Kobayashi, Senryo To Yakuhin1996, 41, 312.