Novel fluorescent quater‐ and quinquifurans: Syntheses and photophysical properties

Abstract

In the quest for fast fluors for use in waveshifting polystyrene fibers, symmetrical oligofurans were investigated. Furan moieties were coupled by means of the Ullmann Reaction or by palladium-catalyzed unsymmetrical coupling; the latter gave higher yields. While the benzoxazole-terminated quater-and quinquifurans we prepared were both stable and fast, exhibiting a green fluorescence and decay times of about 2.4 nsec, they were inferior to other types of fluors in solubility and emission intensity when incorporated into polystyrene.

α‐Oligofurans: An Emerging Class of Conjugated Oligomers for Organic Electronics

“…The group of Kaufmann was the first to describe the synthesis of 2 F and 4 F using the Ullmann reaction (Scheme 2), [17] and later used a Negishi coupling to yield the substituted 5 F. [18] Ishida et al, used a Stille coupling to synthesize 3 F. [25] Attempts to obtain longer oligofurans resulted in unstable and inseparable mixtures. [26] In 2010, we found that the Stille coupling of a,w-dibromooligofurans with monostannyloligofurans gives long oligofurans (5 F-8 F) in good yields (Scheme 3).…”

“…Short oligofurans up to 4 F were reported about 30 years ago, [17] and only one example of a substituted a-oligofuran consisting of five rings [18] was known prior to the 2010 synthesis of long a-oligofurans (nF). [19][20][21][22] As can be seen in Figure 1, oligofurans have a 0.3-0.4 eV higher HOMO-LUMO gap than oligothiophenes.…”

α‐Oligofurane: eine aufstrebende Klasse konjugierter Oligomere für die organische Elektronik

“…Die Gruppe von Kaufmann beschrieb als erste die Synthese von 2 F und 4 F mithilfe der Ullmann‐Reaktion (Schema )17 und setzte später eine Negishi‐Kuppling zur Herstellung des substituierten 5 F ein 18. Ishida et al.…”

“…Kurze Oligofurane bis zu 4 F wurden bereits vor etwa 30 Jahren beschrieben,17 und es war nur ein Beispiel eines substituierten, aus fünf Ringen bestehenden α‐Oligofurans bekannt,18 bevor 2010 die Synthese eines langen α‐Oligofurans n F gelang 19–22. Wie aus Abbildung 1 ersichtlich, weisen Oligofurane einen um 0.3–0.4 eV größeren Energieunterschied zwischen dem HOMO und dem LUMO auf als Oligothiophene.…”

Bottom-up modular synthesis of well-defined oligo(arylfuran)s

“…In addition, oligofurans were regarded as "green" materials, as furan can be directly obtained from renewable bioresources 12 and are easily biodegradable 13 . However, compared to the thio-analog, oligothiophenes (nTs), which were considered among the workhorses in the field of organic electronic materials 14 , nF have been overlooked for a long time [15][16][17][18][19][20][21] . A decade ago, researchers have already demonstrated that oligofurans exhibited higher fluorescence, better solubility, greater rigidity, and tighter solid-state packing than the corresponding nTs.…”