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S. Matsumoto and J. Hwang
illustrated with a focus on the characteristic low-dimensional molecular arrangement
and their further alignment, except for copper Pc (CuPc) and quinacridone (QA). In
the case of CuPc and QA, the reported figures provided the best illustrations for
outlining the molecular arrangement of the polymorphs of these dyes.
6.2 Examples of Organic Dyes
6.2.1 CuPc (CUPOCY) and Oxotitanyl Pc (BITSAY)
Pcs are one of the most significant classes of organic dyes from both industrial and
scientific perspectives. This compound was accidentally discovered in the beginning
of twentieth century, after which many derivatives were studied for pigment applications (Zollinger 2003; Hunger and Schmidt 2018; Erk and Hengelsberg 2003; Erk
et al. 2004). Among the numerous Pc compounds, organic pigments based on CuPc
have significant market importance. In addition to their applications as colouring
materials, Pcs have also been investigated for their applicability as functional dyes.
Much research has been devoted to fundamental and application-based investigations on Pcs, particularly for optoelectronics. The most successful example of Pcs for
functional dye applications is their use as organic photoconductors (OPCs). Pcs have
been investigated as potential charge generation materials for electrophotography
(Zollinger 2003; Law 1993). In parallel with research on OPCs, their application to
solar cells (Kim et al. 2009; Ameri et al. 2009) and semiconductors (Gsänger et al.
2016; Chung and Diao 2016) has also been pursued. An important characteristic of
Pc compounds in these applications is that they can be prepared in polymorphic solid
phases such as powders and films with NIR absorption or semiconducting properties. Oxotitanyl Pc (TiOPc), a representative OPC compound, has been reported to
exhibit several polymorphs (Engel 2003; Xerox 1994). Among them, the Y-form has
excellent OPC properties.
Numerous structural reports have been published on Pc compounds. Engle
summarised them in both a study report (Engel 1996) and in part of the handbook of
Pcs (Engel 2003). The polymorph occurrence of Pc compounds was also reviewed
in these articles. This section was written by referencing several books (Hunger and
Schmidt 2018; Erk and Hengelsberg 2003; Engel 2003) and from a review by Erk
et al. (2004). The polymorphic crystal structures of Pcs, particularly Pcs related to
pigment applications, are summarised in these references. The analysed crystal structures of four polymorphs of CuPc and five polymorphs of TiOPc are described in
this section.
S. Matsumoto and J. Hwang
illustrated with a focus on the characteristic low-dimensional molecular arrangement
and their further alignment, except for copper Pc (CuPc) and quinacridone (QA). In
the case of CuPc and QA, the reported figures provided the best illustrations for
outlining the molecular arrangement of the polymorphs of these dyes.
6.2 Examples of Organic Dyes
6.2.1 CuPc (CUPOCY) and Oxotitanyl Pc (BITSAY)
Pcs are one of the most significant classes of organic dyes from both industrial and
scientific perspectives. This compound was accidentally discovered in the beginning
of twentieth century, after which many derivatives were studied for pigment applications (Zollinger 2003; Hunger and Schmidt 2018; Erk and Hengelsberg 2003; Erk
et al. 2004). Among the numerous Pc compounds, organic pigments based on CuPc
have significant market importance. In addition to their applications as colouring
materials, Pcs have also been investigated for their applicability as functional dyes.
Much research has been devoted to fundamental and application-based investigations on Pcs, particularly for optoelectronics. The most successful example of Pcs for
functional dye applications is their use as organic photoconductors (OPCs). Pcs have
been investigated as potential charge generation materials for electrophotography
(Zollinger 2003; Law 1993). In parallel with research on OPCs, their application to
solar cells (Kim et al. 2009; Ameri et al. 2009) and semiconductors (Gsänger et al.
2016; Chung and Diao 2016) has also been pursued. An important characteristic of
Pc compounds in these applications is that they can be prepared in polymorphic solid
phases such as powders and films with NIR absorption or semiconducting properties. Oxotitanyl Pc (TiOPc), a representative OPC compound, has been reported to
exhibit several polymorphs (Engel 2003; Xerox 1994). Among them, the Y-form has
excellent OPC properties.
Numerous structural reports have been published on Pc compounds. Engle
summarised them in both a study report (Engel 1996) and in part of the handbook of
Pcs (Engel 2003). The polymorph occurrence of Pc compounds was also reviewed
in these articles. This section was written by referencing several books (Hunger and
Schmidt 2018; Erk and Hengelsberg 2003; Engel 2003) and from a review by Erk
et al. (2004). The polymorphic crystal structures of Pcs, particularly Pcs related to
pigment applications, are summarised in these references. The analysed crystal structures of four polymorphs of CuPc and five polymorphs of TiOPc are described in
this section.