Chapter 3
Porphyrins: Syntheses and Properties
Jun-ichiro Setsune
Abstract It is well known that meso-tetraarylporphyrins are obtained readily by
condensation reactions between pyrroles and aromatic aldehydes. The 2+2 type
condensation of aryldipyrrylmethanes and the second aromatic aldehyde is useful for
synthesizing porphyrins with mixed meso-aryl groups, and further transformations of
the porphyrin periphery are performed conveniently by using organometallic methodology. Some meso-aryl substituted porphyrins are designed for supramolecular application and photosensitizing effect. Porphyrins substituted at pyrrole β-positions
are obtainable by using Barton–Zard synthesis, and these compounds are further
converted into benzoporphyrins that are structurally similar to phthalocyanines and
play an important role in the development of a variety of photo-functional materials.
Porphyrins more heavily π-extended than benzoporphyrin are focused in the last part
of this chapter. Multiple porphyrin cores are directly bridged by π-units or aromatic
substituents at the porphyrin periphery are forced to come into π-conjugation with
the porphyrin π-system by Scholl reactions, leading to strong infrared absorption
bands at longer wavelength beyond 1000 nm, very small HOMO–LUMO gap, and
very high two-photon absorption efficiency.
3.1 Introduction
Porphyrins are fully π-conjugated macrocycles where four pyrrole rings are
connected by sp
2 -hybridized carbon atoms. The macrocyclic π-conjugation and the
dianionic tetradentate coordination site provide basis for a wide variety of applications. Photophysical, electrochemical, and coordination properties of porphyrins
have been drawing great interest in a variety of scientific fields and these properties
are tunable by the abundant methodology for structure modification. Comprehensive reviews on the current porphyrin studies have been published as multi-volume
reference books (Kadish et al. 2000, 2010; Dolphin 1978). This chapter describes
functionalized porphyrins with focusing on their synthetic methodology and their
J. Setsune (B)
Department of Chemistry, Graduate School of Science, Kobe University, Kobe, Japan
e-mail: setsunej@kobe-u.ac.jp
© 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_3
49
Porphyrins: Syntheses and Properties
Jun-ichiro Setsune
Abstract It is well known that meso-tetraarylporphyrins are obtained readily by
condensation reactions between pyrroles and aromatic aldehydes. The 2+2 type
condensation of aryldipyrrylmethanes and the second aromatic aldehyde is useful for
synthesizing porphyrins with mixed meso-aryl groups, and further transformations of
the porphyrin periphery are performed conveniently by using organometallic methodology. Some meso-aryl substituted porphyrins are designed for supramolecular application and photosensitizing effect. Porphyrins substituted at pyrrole β-positions
are obtainable by using Barton–Zard synthesis, and these compounds are further
converted into benzoporphyrins that are structurally similar to phthalocyanines and
play an important role in the development of a variety of photo-functional materials.
Porphyrins more heavily π-extended than benzoporphyrin are focused in the last part
of this chapter. Multiple porphyrin cores are directly bridged by π-units or aromatic
substituents at the porphyrin periphery are forced to come into π-conjugation with
the porphyrin π-system by Scholl reactions, leading to strong infrared absorption
bands at longer wavelength beyond 1000 nm, very small HOMO–LUMO gap, and
very high two-photon absorption efficiency.
3.1 Introduction
Porphyrins are fully π-conjugated macrocycles where four pyrrole rings are
connected by sp
2 -hybridized carbon atoms. The macrocyclic π-conjugation and the
dianionic tetradentate coordination site provide basis for a wide variety of applications. Photophysical, electrochemical, and coordination properties of porphyrins
have been drawing great interest in a variety of scientific fields and these properties
are tunable by the abundant methodology for structure modification. Comprehensive reviews on the current porphyrin studies have been published as multi-volume
reference books (Kadish et al. 2000, 2010; Dolphin 1978). This chapter describes
functionalized porphyrins with focusing on their synthetic methodology and their
J. Setsune (B)
Department of Chemistry, Graduate School of Science, Kobe University, Kobe, Japan
e-mail: setsunej@kobe-u.ac.jp
© 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_3
49