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Relevant academic research and scientific papers

π-Conjugated Copolymers Composed of Boron Formazanate and Their Application for a Wavelength Converter to Near-Infrared Light

We report conjugated polymers consisting of boron formazanate in the main chains. By employing typical donor-type comonomers, such as fluorene and bithiophene, copolymers were prepared with the Migita-Kosugi-Stille cross-coupling polymerization. Their electronic structures were evaluated by optical and electrochemical measurements. Absorption and emission bands were obtained in the deep-red and near-infrared (NIR) regions. A conjugated polymer composed of formazanate and fluorene, especially, exhibited remarkable NIR emission at 751 nm with 0.14 of absolute quantum yield. Further, boron formazanate works as a strong electron-accepting unit in main-chain conjugation. Therefore, emission from the polymers has the intramolecular charge transfer character. Finally, we demonstrate the application for wavelength-conversion materials from visible to NIR light based on partially modified polymers. By changing complexation ratios in the polymer main chains, broad absorption bands covering the whole visible region and the single NIR emission band were obtained. As a result, the scheme for visible light absorption followed by the NIR emission has been constructed.

Near-Infrared Boron Difluoride Formazanate Dyes

Near-infrared (NIR) dyes are sought after for their utility in light harvesting, bioimaging, and light-mediated therapies. Since long-wavelength photoluminescence typically involves extensive π-conjugated systems of double bonds and aromatic rings, it is often assumed that NIR dyes have to be large molecules that require complex syntheses. We challenge this assumption by demonstrating that facile incorporation of tertiary amine groups into readily available 3-cyanoformazans affords efficient production of relatively simple NIR-active BF2 formazanate dyes (λabs=691–760 nm, λPL=834–904 nm in toluene). Cyclic voltammetry experiments on these compounds reveal multiple reversible redox waves linked to the interplay between the tertiary amine and BF2 formazanate moieties. Density-functional calculations indicate that the NIR electronic transitions in BF2 formazanates are of π→π*-type, but do not always involve strong charge transfer.

Synthesis and chemical reactivity of 3-oxo-2-arylhydrazono-propanenitriles

2-Formyl-2-arylhydrazonoethanenitriles 6b-d where prepared via reacting enaminonitrile 2b,c with aromatic diazonium salts. These reacted with phenylhydrazine to yield bis hydrazones that were converted to arylazopyrazoles via a novel Vilsmeier-Haack reaction type. Reaction of 6c with hydroxylamine afforded oxime that could be successfully cyclised into arylazoisoxazole. Reaction of 6c with hydrazine hydrate to yield arylazoaminopyrazole that proved to be excellent precursors for synthesis functional substituted pyrazolopyrimidines.