Exploring copper as a catalyst for cost effective synthesis of polyfluorenes: an alternative to platinum and palladium

Abstract

In the present study, we report the synthesis of a series of anthracene based polyfluorenes containing alkyl substituted 9,10-diphenylanthracene and hydrazone substituted fluorene moieties. The polymers were synthesized via copper catalysed Ullmann coupling, which comparatively is inexpensive as compared to palladium and platinum used in Suzuki coupling. The synthesized polymers were characterized by various spectroscopic techniques. All the polymers exhibited blue emission having band gap in the range of 2.7-2.83 eV. The polymers showed good thermal stability with decomposition temperature over 330 °C and glass transition temperature in the range of 125-140 °C. All the polymers were soluble in common organic solvents with weight average molecular weight in the range of 21,000-25,000. The electrochemical study reveals that the HOMO energy levels of the polymers were in the range of − 5.16 to − 5.26 eV which had elevated compared with that of polyfluorene (5.7 eV). It matched the work function of ITO and ITO/PEDOT: PSS (4.7 and 5.0 eV respectively). These results indicated that the synthesized polymers could be promising materials for applications in light emitting diode.

Ullmann coupling for low-cost synthesis of anthracene-based polyfluorenes: A photophysical approach

“…4,4′-(2,7-Dibromo-9H-fluorene-9,9-diyl) dianiline) ( I ) (FDA) was synthesized using a procedure reported. 46 –48,50 The general reaction scheme is shown in Figure 1.…”

“…51 –55 Figure 2 and Figure S1 show the reaction scheme and the experimental procedure for the synthesis of the acene monomers (II) . 46 –48…”

“…The yield of the resulting brown colored polymer was around 65–70%. 46 –48 Using a similar scheme, series of the FDA-diphenylacene polymers P1, P2, and P3 were synthesized.…”

“…23,24 We also emphasize the low-cost copper-catalyzed synthesis of polymers with relatively high molecular weight and strong thermal and optical properties. 46 –48…”

Recent Advancement of Ullmann Condensation Coupling Reaction in the Formation of Aryl-Oxygen (C-O) Bonding by Copper-Mediated Catalyst

“…In the last century, C-C bond transformation (catenation) has permitted chemists to assemble intricate molecular frameworks of diversified interests encompassing complete synthesis of natural products, pharmaceuticals, and industrial process improvement, as well as biochemistry, materials, and nanotech [2,3]. The evolution of chemicals through the transition-metal catalyzed reaction is an exciting era for the chemistry of palladium [4], ruthenium [5], platinum [6], etc., and has been significantly adopted by the industry. For example, ruthenium-catalyzed N-H insertion reaction for the formation of benzofused six/five-membered azaheterocycles [7] which have a wide range of significant biological activity, such as anti-bacterial, -fungal, -tubercular, helminthic, -plasmodial, -cancer, -inflammatory, cardiotonic, -hypertensive, -thrombotic, histaminic, -ulcer, analgesic, neuroleptic, etc.…”