Postfunctionalization of a Perfluoroarene-Containing π-Conjugated Polymer via Nucleophilic Aromatic Substitution Reaction

Abstract

Postfunctionalization is a useful strategy to tune the properties of conjugated polymers, while polymer reactions in the main chain of a conjugated backbone are still underexplored. Here we report the postfunctionalization of the main chain of a conjugated polymer via nucleophilic aromatic substitution reaction. Poly­(9,9-dioctylfluorene-alt-tetrafluoro-p-phenylene) is used as a precursor to react with thiophenol derivatives in the presence of a base to enable multiple introduction of arylthio groups into the polymer main chain in high yield with preserving the backbone and the dispersity of the precursor polymer. The main chain structure and optoelectronic properties of the resulting polymers were significantly changed, evidenced by spectroscopic analysis of both model compounds and polymers as well as a computational simulation.

Diversification of Conjugated Polymers via Postpolymerization Nucleophilic Aromatic Substitution Reactions with Sulfur-, Oxygen-, and Nitrogen-Based Nucleophiles

“…When four arylthio groups are introduced onto one arene ring, the rotation of the C fluorene –C arene bonds is restricted because of the steric hindrance, which results in orthogonality with the neighboring π-systems to induce a TICT transition in the absorption spectrum. In previous work, M3a–c were all obtained as a mixture of atropisomers, which was most easily confirmed by two distinct singlets for the methyl groups of the fluorene moiety in the 1 H NMR spectra at room temperature . At elevated temperatures, the methyl signals in M3b and M3c merged into one singlet, indicating free rotation of the C fluorene –C arene bond, whereas the two peaks remained distinct until 150 °C in the case of M3a .…”

“… a Data from ref . b Obtained as a mixture of octa- and hexa-substituted units in the ratio of 6:4. c Obtained as a mixture of non-, mono-, di-substituted units in the ratio of 14:8:5. d Unknown peaks, presumably derived from 1,2- or 1,3-substituted arene rings, were observed in the 19 F NMR spectrum. …”

“…Reagents and dehydrated solvents were obtained from commercial sources and used without further purification. Precursor materials P1,2 and M1,2 were synthesized according to previously reported procedures. − Reactions were performed under an inert atmosphere using Schlenk techniques.…”

“…In this context, our group previously used an S N Ar reaction with arylthiolates as nucleophiles to modify the main chain of a conjugated polymer bearing a tetrafluoro-arene unit . We found that the reaction of poly­(9,9-dioctylfluorene- alt -tetrafluoro- p -phenylene) , ( P1 , Figure ) with 4-(trifluoromethyl)­benzenethiol or benzenethiol in the presence of K 2 CO 3 at an elevated temperature resulted in quantitative substitution of the fluorine groups.…”

Peptide Cyclization Methodologies Amenable to in Vitro Display

“…Perfluoroarenes react with a reactive thiol in peptide via nucleophilic aromatic substitution reaction SNAr, which has been used extensively for polymer arylation and bioconjugation. [14][15][16][17][18] Derda et al 19 used decafluoro-diphenylsulfone (DFS) to crosslink Cys thiols yielding cyclic peptides in one of the fastest Cys conjugation reactions (Figure 2B). They improved the previously reported S N Ar reagents such as 1-chloro-2,4-dinitrobenzene, 20 perfluorobenzene 21,22 and perfluorobiphenyl 22 which show low reactivity and poor solubility in aqueous systems� The group has demonstrated this reaction to be biocompatible and faster than most Cys conjugation reactions with the reaction rates up to 180 M -1 S -1 , although the rate is largely sequence dependent; e.g.…”