31 Cooperative and Hierarchal Photoresponses of Molecular …
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widely applicable to not only the crystallization of proteins but also that of other
organic and inorganic materials and colloids.
Against this background, we conduct real-time measurements of the molecular
assembly process using the cooperative and hierarchical fluorescence changes of
organic molecules to optimize the fluorescence color modulation properties in the
organic solid and understand the relationship between fluorescence color and molecular arrangement including the assembling process. Fluorescence spectroscopy can
provide information about the state of molecular aggregates ranging in size from
several molecules to the bulk scale because excited molecules show spectral changes
that strongly depend on the electronic state, aggregated state or size, and surrounding
environment. We have been investigating changes in electronic states associated with
cooperative interactions between molecules in organic molecular aggregates. In this
chapter, we introduce research based on the concept of monitoring the fluorescence
color while crystallization occurs as the solvent evaporates under ultraviolet (UV)
light irradiation (evaporative crystallization).
In this chapter, studies of the direct visualization of crystal formation and growth
probed by organic fluorescent molecules using fluorescence microscopy and spectroscopy are introduced. We focus on the fluorescence spectral changes of a Dibenzoylmethanatoboron difluoride complex exhibiting mechanofluorochromism [8] and
a dipyrrolyldiketone difluoroboron complex derivative displaying polymorphismdependent fluorescence [9].
31.2 Fluorescence Detection of the Molecular Assembly
Process by a Mechanofluorochromic Compound
Dibenzoylmethanatoboron difluoride (BF 2 DBM) derivatives possess excellent
optical properties such as high fluorescence quantum yield in the solid-state [10],
multiple fluorescence colors [11–15], reversible mechanofluorochromic properties [16, 17], and two-photon absorption cross-sections. In particular, BF 2 DBM
based on the 4-tert-butyl-4
-methoxydibenzoylmethane (avobenzone) boron difluoride complex (BF 2 AVB) exhibits different emission behavior depending on the
crystal phase (polymorph) [18]. BF 2 AVB shows not only excellent durability to light
irradiation but also high fluorescence quantum yield in the solid-state (~0.5), which is
advantageous for photonic applications. In this section, real-time visualization of the
two-step nucleation model is investigated by evaluating the fluorescence properties
of BF 2 DBM solution during solvent evaporation-induced crystallization.
In this work, 4,4
-di-tert-butyldibenzoylmethane boron difluoride (BF 2 DBMb,
Fig. 31.1a) was used as a probe to investigate evaporative crystallization. First, we
examined the fluorescence of BF 2 DBMb in dilute solution, crystals, and the amorphous state, fluorescence images of which are shown in Fig. 31.1b–d, respectively.
These images indicate that the molecular forms of BF 2 DBMb such as monomer
539
widely applicable to not only the crystallization of proteins but also that of other
organic and inorganic materials and colloids.
Against this background, we conduct real-time measurements of the molecular
assembly process using the cooperative and hierarchical fluorescence changes of
organic molecules to optimize the fluorescence color modulation properties in the
organic solid and understand the relationship between fluorescence color and molecular arrangement including the assembling process. Fluorescence spectroscopy can
provide information about the state of molecular aggregates ranging in size from
several molecules to the bulk scale because excited molecules show spectral changes
that strongly depend on the electronic state, aggregated state or size, and surrounding
environment. We have been investigating changes in electronic states associated with
cooperative interactions between molecules in organic molecular aggregates. In this
chapter, we introduce research based on the concept of monitoring the fluorescence
color while crystallization occurs as the solvent evaporates under ultraviolet (UV)
light irradiation (evaporative crystallization).
In this chapter, studies of the direct visualization of crystal formation and growth
probed by organic fluorescent molecules using fluorescence microscopy and spectroscopy are introduced. We focus on the fluorescence spectral changes of a Dibenzoylmethanatoboron difluoride complex exhibiting mechanofluorochromism [8] and
a dipyrrolyldiketone difluoroboron complex derivative displaying polymorphismdependent fluorescence [9].
31.2 Fluorescence Detection of the Molecular Assembly
Process by a Mechanofluorochromic Compound
Dibenzoylmethanatoboron difluoride (BF 2 DBM) derivatives possess excellent
optical properties such as high fluorescence quantum yield in the solid-state [10],
multiple fluorescence colors [11–15], reversible mechanofluorochromic properties [16, 17], and two-photon absorption cross-sections. In particular, BF 2 DBM
based on the 4-tert-butyl-4
-methoxydibenzoylmethane (avobenzone) boron difluoride complex (BF 2 AVB) exhibits different emission behavior depending on the
crystal phase (polymorph) [18]. BF 2 AVB shows not only excellent durability to light
irradiation but also high fluorescence quantum yield in the solid-state (~0.5), which is
advantageous for photonic applications. In this section, real-time visualization of the
two-step nucleation model is investigated by evaluating the fluorescence properties
of BF 2 DBM solution during solvent evaporation-induced crystallization.
In this work, 4,4
-di-tert-butyldibenzoylmethane boron difluoride (BF 2 DBMb,
Fig. 31.1a) was used as a probe to investigate evaporative crystallization. First, we
examined the fluorescence of BF 2 DBMb in dilute solution, crystals, and the amorphous state, fluorescence images of which are shown in Fig. 31.1b–d, respectively.
These images indicate that the molecular forms of BF 2 DBMb such as monomer