Chapter 31
Cooperative and Hierarchal
Photoresponses of Molecular Assembling
Processes Probed by Organic Fluorescent
Molecules
Fuyuki Ito
Abstract Crystal formation in solution starts from nucleation in the saturated state.
The quality of the product and the number, size, and structure of crystals are determined in the initial stage of the nucleation process. Understanding nucleation is the
key to control crystal properties including polymorph formation. In this chapter, the
fluorescence visualization of the crystal formation process probed by organic fluorescent molecules exhibiting cooperative and hierarchal photoresponses is summarized. Fluorescence observations of evaporative crystallization revealed a two-step
nucleation model for both nuclei and polymorph formation. A Dibenzoylmethanatoboron difluoride complex exhibiting mechanofluorochromism and a dipyrrolyldiketone difluoroboron complex derivative displaying polymorphism-dependent fluorescence were studied. The fluorescence from the droplets showed dramatic changes
depending on the molecular state, such as monomer, amorphous, and crystal polymorph. This method could be easily used to detect assembly processes by measuring
the real-time fluorescence changes under ambient conditions. Furthermore, the
formation of polymorphs is most likely affected by the cluster structure prior to nucleation. Therefore, insights into the nuclei precursor clusters in polymorph formation
measured by fluorescence changes will enable us to predict the outcome of polymorph
formation.
Keywords Evaporative crystallization · Fluorescence color changes ·
Mechanofluorochromism · Polymorphism-dependent fluorescence · Two-step
nucleation model · Liquid-like cluster
F. Ito (B)
Department of Chemistry, Institute of Education, Shinshu University, 6-ro Nishinagano, Nagano
380-8544, Japan
e-mail: fito@shinshu-u.ac.jp
© Springer Nature Singapore Pte Ltd. 2020
H. Miyasaka et al. (eds.), Photosynergetic Responses in Molecules
and Molecular Aggregates, https://doi.org/10.1007/978-981-15-5451-3_31
537
Cooperative and Hierarchal
Photoresponses of Molecular Assembling
Processes Probed by Organic Fluorescent
Molecules
Fuyuki Ito
Abstract Crystal formation in solution starts from nucleation in the saturated state.
The quality of the product and the number, size, and structure of crystals are determined in the initial stage of the nucleation process. Understanding nucleation is the
key to control crystal properties including polymorph formation. In this chapter, the
fluorescence visualization of the crystal formation process probed by organic fluorescent molecules exhibiting cooperative and hierarchal photoresponses is summarized. Fluorescence observations of evaporative crystallization revealed a two-step
nucleation model for both nuclei and polymorph formation. A Dibenzoylmethanatoboron difluoride complex exhibiting mechanofluorochromism and a dipyrrolyldiketone difluoroboron complex derivative displaying polymorphism-dependent fluorescence were studied. The fluorescence from the droplets showed dramatic changes
depending on the molecular state, such as monomer, amorphous, and crystal polymorph. This method could be easily used to detect assembly processes by measuring
the real-time fluorescence changes under ambient conditions. Furthermore, the
formation of polymorphs is most likely affected by the cluster structure prior to nucleation. Therefore, insights into the nuclei precursor clusters in polymorph formation
measured by fluorescence changes will enable us to predict the outcome of polymorph
formation.
Keywords Evaporative crystallization · Fluorescence color changes ·
Mechanofluorochromism · Polymorphism-dependent fluorescence · Two-step
nucleation model · Liquid-like cluster
F. Ito (B)
Department of Chemistry, Institute of Education, Shinshu University, 6-ro Nishinagano, Nagano
380-8544, Japan
e-mail: fito@shinshu-u.ac.jp
© Springer Nature Singapore Pte Ltd. 2020
H. Miyasaka et al. (eds.), Photosynergetic Responses in Molecules
and Molecular Aggregates, https://doi.org/10.1007/978-981-15-5451-3_31
537