Synthesis and Properties of Poly(p-fluoranthene vinylene):  A Novel Conjugated Polymer with Nonalternant Repeating Units

Abstract

Conjugated polymers continue to attract increasing attention as a result of their promising properties for optoelectronic applications such as light-emitting diodes, 1 solar cells, 2 sensors, 3 and field effect transistors. 4 Whereas for selected applications suitable conjugated polymers are available, the quest for materials with improved properties continues. One method to achieve this objective is the introduction of functional groups. A more radical approach focuses on the design of hitherto unknown polymer backbone architectures. We have combined both tactics and prepared the novel poly(p-fluoranthene vinylene) (PFV) (Scheme 1), with a new backbone architecture containing nonalternant polycyclic aromatic hydrocarbon repeating units, in which the base structure of poly(p-phenylene vinylene) PPV remains readily recognizable.Our search for novel materials was inspired by the field of organic solar cells. In such solar cells, which currently can already reach efficiencies as high as 5%, 5 a p-type conjugated polymer such as poly(3-hexylthiophene) (P3HT) or OC 1 C 10 -PPV is combined with a soluble derivative of C 60 , PCBM, as the electron acceptor. 2,5 However, an n-type polymeric alternative for PCBM is of interest to facilitate the formation of an optimal morphology. 6 Whereas it is possible to incorporate C 60 as the substituent in a polymer, 7 this approach is rather laborious and hence not necessarily cost-effective for future applications. Fortunately, remarkable progress has been made in the synthesis of functionalized substructures of C 60 by researchers in the field of nonalternant hydrocarbons. 8 This prompted us to incorporate one of these substructures, i.e. fluoranthene, in the backbone of a conjugated polymer. The incorporation of such substructures can have a considerable impact on the electronic properties. 9 Furthermore, the use of cyclopenta-fused nonalternant hydrocarbons is expected to result in a significantly increased electron affinity of the resulting materials, which would render them possibly indeed n-type. 10 The novel conjugated polymer PFV described in this Communication is of particular interest since it is the first PPV-type polymer with nonalternant repeating units.The synthesis of PFV starts with the straightforward onestep synthesis of dimethylfluoranthene-7,10-dicarboxylic ester (1) from acenaphtenequinone, acetone dicarboxylic ester, and norbornadiene followed by the conversion of the ester groups into the diol 2 by reduction with LiAlH 4 according to a literature procedure (Scheme 1). 8 Subsequently, 7,10-bis(chloromethyl)-fluoranthene (3) was obtained by reaction with thionyl chloride in THF solution. The rather limited solubility of 2 and 3 required the use of dilute solutions. After recrystallization from chloroform, pure 3 was obtained in 62% yield as light yellow crystals (melting point 232-234°C).For the polymerization, the dithiocarbamate (DTC) precursor route 11,12 was chosen. The DTC precursor route was previously developed in our laboratory and offers not only a st...

A structure–property study of fluoranthene-cored hole-transporting materials enables 19.3% efficiency in dopant-free perovskite solar cells

“…The uoranthene unit is selected as the main structural framework due to its several promising advantages including low price, highly planar structure, easy functionality, and good thermal/electrochemical stability. [42][43][44] Moreover, the unique central cyclopenta-fused ring endows the uoranthene with an electron-decient character, 45 which thereby can be used as an electron-withdrawing core to construct various D-A type HTMs. 46,47 Herein, we functionalize the uoranthene moiety with methoxy-substituted triphenylamine (TPA) units on the 3-, 8-positions or 3-, 8-, 9-positions to form a linear and star-shaped structure, respectively.…”

Cyclic voltammetry studies of n-type polymers with non-alternant fluoranthene units

“…The UV-vis spectroscopic characteristics of PFVs and PFTs polymers have already been studied before. [11] We have made use of the intrinsic fluorescence of these materials to gain some further insight on them. Fig.…”

“…The investigated PFTs polymers, monomodal with molecular mass M w = 5.9 × 10 4 , have been prepared as described previously [11]. Alkyl substituted PFTs materials (C 6 PFT, C 10 PFT and C 12 PFT with M w = 27.2 × 10 4 , 10.6 × 10 4 and 7.5 × 10 4 , correspondingly) studied in this communication have been synthesized by polymerization of the appropriately substituted monomeric 7,10-bis(N,N-diethyldithiocarbamate)-fluoranthenes.…”

“…Noteworthy full conversion of PFTs deposited on ITO surface into their PFVs successors takes place at relatively high temperatures, from unknown reasons higher by ca. 40-60 • C than necessary for deposits on quartz or NaBr windows applied respectively in UV-vis or IR spectroscopic investigations [11].…”

“…Both tactics have been recently [11] applied together leading to the preparation of a new backbone architecture repeatedly containing non-alternant polycyclic aromatic hydrocarbons (fluoranthene) units bonded via vinylene bridges (poly(p-fluoranthenevinylene)-PFV). This was not the first report on fluoranthene polymers (cf.…”