2 research outputs found
Propeller Chirality of Boron Heptaaryldipyrromethene: Unprecedented Supramolecular Dimerization and Chiroptical Properties
Chiral
boron dipyrromethenes (BPs) enjoy high fluorescence efficiency
at visible to near-IR wavelength regions with a reasonable range of
dissymmetry factors. Here, we demonstrate that the (quasi)Âpropeller
chirality, similarly to hexagonal propeller in hexaarylbenzene, can
be effectively induced in heptaarylated BP. In addition, supramolecular
dimer was formed at low temperatures in nonpolar solvent, which exhibits
strong bisignate Cotton effects at BP transitions (the couplet amplitude <i>A</i> = 193 M<sup>–1</sup> cm<sup>–1</sup>) in
the circular dichroism (CD). Due to the bulky substituents on the
propeller blades, but with void space around boron atoms, BP chromophores
in the dimer are aligned in a head-to-tail manner with a small torsion
(φ ≈ 15°), to avoid fluorescence quenching usually
observed in H-type dimer of BPs, exhibiting strong circularly polarized
luminescence (CPL) signals (<i>g</i><sub>lum</sub> = 2.0
× 10<sup>–3</sup>, Φ<sub>lum</sub> = 0.45). Such
supramolecular dimer formation would be viewed as an alternative approach
for designing and developing novel chiroptical materials
Novel Means of Controlling the Solid-State Circular Dichroism Property in a Supramolecular Organic Fluorophore Comprising 4-[2-(Methylphenyl)ethynyl]benzoic Acid by Varying the Position of the Methyl Substituent
The solid-state circular dichroism (CD) of a 4-[2-(methylphenyl)Âethynyl]Âbenzoic
acid/amine supramolecular organic fluorophore can be controlled by
changing the position of the methyl substituent of the methylphenylethynyl
unit on the achiral 4-[2-(methylphenyl)Âethynyl]Âbenzoic acid component
molecule, instead of changing the chirality of the chiral amine component
molecule