Chapter 17
Azulene-Based Materials for Organic
Field-Effect Transistors
Hiroshi Katagiri
Abstract Azulene is a non-alternant non-benzenoid hydrocarbon that has attracted
much attention because of its large dipole moment and long-wavelength absorption
properties that are derived from its unique molecular orbital geometry; its highest
occupied and lowest unoccupied molecular orbitals are not mirror images. In this
chapter, we describe the synthesis, structures, properties, and organic field-effect transistor (OFET) characteristics of 2-azulenyl end-capped oligomers and 2, 6-connected
terazulene isomers, in which the azulene moieties deliver molecules that are flat and
linear. These compounds show high-order orientations with herringbone packing in
their crystalline states and typical OFET characteristics with high carrier mobilities.
In particular, terazulene isomers are unique π-conjugated systems with asymmetrically distributed molecular orbitals, which leads to an unconventional concept:
polarity control of OFET by molecular orbital distribution control. These findings
provide a key approach for constructing various OFET materials and a basis for the
accelerated development of the solid-state chemistry of azulene.
Keywords Azulene · π-Conjugation · Herringbone structure · Organic field-effect
transistors · Dipole moment · Structure–property relationship
17.1 Introduction
Azulene consists of a five-membered ring and a seven-membered ring fused to form
a stable bicyclic 10-π-electron system (Fig. 17.1). Since it has a dipole moment of
1.0 D, which is rare among hydrocarbons, and is blue in color, extending the πelectron system of azulene has been of interest. In particular, the polarized structure
and small excitation energy of azulene are attractive in a π-conjugated system, and
H. Katagiri (B)
Graduate School of Science and Engineering, Yamagata University,
Jonan Yonezawa 992-8510, Japan
e-mail: kgri7078@yz.yamagata-u.ac.jp
© Springer Nature Singapore Pte Ltd. 2020
M. Sakamoto and H. Uekusa (eds.), Advances in Organic Crystal Chemistry,
https://doi.org/10.1007/978-981-15-5085-0_17
341
Azulene-Based Materials for Organic
Field-Effect Transistors
Hiroshi Katagiri
Abstract Azulene is a non-alternant non-benzenoid hydrocarbon that has attracted
much attention because of its large dipole moment and long-wavelength absorption
properties that are derived from its unique molecular orbital geometry; its highest
occupied and lowest unoccupied molecular orbitals are not mirror images. In this
chapter, we describe the synthesis, structures, properties, and organic field-effect transistor (OFET) characteristics of 2-azulenyl end-capped oligomers and 2, 6-connected
terazulene isomers, in which the azulene moieties deliver molecules that are flat and
linear. These compounds show high-order orientations with herringbone packing in
their crystalline states and typical OFET characteristics with high carrier mobilities.
In particular, terazulene isomers are unique π-conjugated systems with asymmetrically distributed molecular orbitals, which leads to an unconventional concept:
polarity control of OFET by molecular orbital distribution control. These findings
provide a key approach for constructing various OFET materials and a basis for the
accelerated development of the solid-state chemistry of azulene.
Keywords Azulene · π-Conjugation · Herringbone structure · Organic field-effect
transistors · Dipole moment · Structure–property relationship
17.1 Introduction
Azulene consists of a five-membered ring and a seven-membered ring fused to form
a stable bicyclic 10-π-electron system (Fig. 17.1). Since it has a dipole moment of
1.0 D, which is rare among hydrocarbons, and is blue in color, extending the πelectron system of azulene has been of interest. In particular, the polarized structure
and small excitation energy of azulene are attractive in a π-conjugated system, and
H. Katagiri (B)
Graduate School of Science and Engineering, Yamagata University,
Jonan Yonezawa 992-8510, Japan
e-mail: kgri7078@yz.yamagata-u.ac.jp
© Springer Nature Singapore Pte Ltd. 2020
M. Sakamoto and H. Uekusa (eds.), Advances in Organic Crystal Chemistry,
https://doi.org/10.1007/978-981-15-5085-0_17
341