Chapter 4
Phthalocyanine and Related Analogues
Soji Shimizu
Abstract Phthalocyanine (Pc) has been one of the most important industrial dyes
exhibiting lasting blue or green color and used in various research fields including
not only organic electronics but also biomedical field. The aim of this chapter is to
overview the chemistry of Pc and its ring contracted analogue, subphthalocyanine
(SubPc), with an emphasis on their syntheses and optical properties from a viewpoint
of molecular symmetry–property relationships. A basic theoretical description of
the absorption properties of Pc and SubPc, which is referred to as Gouterman’s
four orbital theory, is introduced. In addition, magnetic circular dichroism (MCD)
spectroscopy, a powerful spectroscopic tool to analyze the absorption spectra of Pc,
SubPc, and related analogues, is briefly described. Finally, recent advances in the
synthesis of new Pc-based NIR chromophores will also be covered.
Keywords Phthalocyanine · Subphthalocyanine · Functional dyes · Near-infrared
absorption · Magnetic circular dichroism (MCD)
4.1 Introduction
The first synthesis of phthalocyanine (Pc, Fig. 4.1) traces back to 1907 when Braun
and Tcherniac obtained an insoluble blue pigment in a reaction of o-cyanobenzamide
at high temperature (Braun and Tcherniac 1907). A quarter-century after this accidental discovery, Linstead et al. characterized the structure of the free base of unsubstituted Pc (H 2 Pc) and investigated its optical properties in their pioneering research
(Ficken et al. 1934). Meanwhile, Robertson determined the crystal structure of Pc by
X-ray diffraction analysis (Robertson and Woodward 1935). Owing to the robust blue
and green color, Pc was found its initial use as a coloring staff known as “Phthalocyanine Blue BN” and “Phthalocyanine Green G”. From the late twentieth century,
S. Shimizu (B)
Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University,
Fukuoka 819-0395, Japan
e-mail: ssoji@cstf.kyushu-u.ac.jp
Center for Molecular Systems (CMS), Kyushu University, Fukuoka 819-0395, Japan
© Springer Nature Singapore Pte Ltd. 2021
Y. Ooyama and S. Yagi (eds.), Progress in the Science of Functional Dyes,
https://doi.org/10.1007/978-981-33-4392-4_4
85
Phthalocyanine and Related Analogues
Soji Shimizu
Abstract Phthalocyanine (Pc) has been one of the most important industrial dyes
exhibiting lasting blue or green color and used in various research fields including
not only organic electronics but also biomedical field. The aim of this chapter is to
overview the chemistry of Pc and its ring contracted analogue, subphthalocyanine
(SubPc), with an emphasis on their syntheses and optical properties from a viewpoint
of molecular symmetry–property relationships. A basic theoretical description of
the absorption properties of Pc and SubPc, which is referred to as Gouterman’s
four orbital theory, is introduced. In addition, magnetic circular dichroism (MCD)
spectroscopy, a powerful spectroscopic tool to analyze the absorption spectra of Pc,
SubPc, and related analogues, is briefly described. Finally, recent advances in the
synthesis of new Pc-based NIR chromophores will also be covered.
Keywords Phthalocyanine · Subphthalocyanine · Functional dyes · Near-infrared
absorption · Magnetic circular dichroism (MCD)
4.1 Introduction
The first synthesis of phthalocyanine (Pc, Fig. 4.1) traces back to 1907 when Braun
and Tcherniac obtained an insoluble blue pigment in a reaction of o-cyanobenzamide
at high temperature (Braun and Tcherniac 1907). A quarter-century after this accidental discovery, Linstead et al. characterized the structure of the free base of unsubstituted Pc (H 2 Pc) and investigated its optical properties in their pioneering research
(Ficken et al. 1934). Meanwhile, Robertson determined the crystal structure of Pc by
X-ray diffraction analysis (Robertson and Woodward 1935). Owing to the robust blue
and green color, Pc was found its initial use as a coloring staff known as “Phthalocyanine Blue BN” and “Phthalocyanine Green G”. From the late twentieth century,
S. Shimizu (B)
Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University,
Fukuoka 819-0395, Japan
e-mail: ssoji@cstf.kyushu-u.ac.jp
Center for Molecular Systems (CMS), Kyushu University, Fukuoka 819-0395, Japan
© Springer Nature Singapore Pte Ltd. 2021
Y. Ooyama and S. Yagi (eds.), Progress in the Science of Functional Dyes,
https://doi.org/10.1007/978-981-33-4392-4_4
85