Tuning Solid-State Fluorescence
of a Twisted π‑Conjugated
Molecule by Regulating the Arrangement of Anthracene Fluorophores
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Abstract
1-(5-(Anthracen-9-yl)-3-(4-methoxyphenyl)-4,5-dihydropyrazol-1-yl)ethanone
was synthesized and crystallized to provide three types of crystals
with different fluorescent colors and host–guest structures.
Crystal structure analysis reveals that this compound possesses twisted
π-conjugated structure and different degrees of distortion depending
on guest molecules in the three crystal structures. The anthracene
fluorophore stacking modes are regulated from monomer arrangement
to face-to-face π-stacked arrangement by means of the entrapment
of organic acid molecules in the lattice. The vibrational spectroscopy,
thermal behaviors, diffuse reflectance absorption spectroscopy, solid-state
fluorescence properties, and fluorescence quantum yields and lifetimes
of the three types of crystals were investigated. Such properties
are closely related to the fluorophore stacking modes and intermolecular
electronic interactions in crystals. The π-stacked geometries
of anthracene fluorophores are responsible for the red-shifted emissions
and longer fluorescence lifetimes. It indicates that the optical properties
of organic materials could be modulated by entrapping different guest
molecules in lattice
