Indolo[3,2-b]carbazole-based poly(arylene ethynylene)s

Abstract

A novel family of indolo[3,2-b]carbazole (ICZ)-based polymers was designed and synthesized using Sonogashira cross-coupling reaction between three bisbromine indolo[3,2-b]carbazoles and 1,4-diethynylbenzene. The new polymers have an arylene ethynylene structure with ICZ moiety interconnected in the main chain by 2,8-, 3,9- or 6,12- positions. The polymers were obtained as partially soluble materials, in chlorinated, aromatic and aprotic polar solvents. The structure of the polymers was studied by spectroscopic methods such as Fourier transform infrared, proton and carbon-13 nuclear magnetic resonance, ultraviolet–visible and photoluminescence spectroscopies, thermogravimetry and molecular weights determined by gel permeation chromatography. Electrochemical properties were investigated by cyclic voltammetry using films cast on platinum disc working electrode. Optical and electronic properties were discussed from the viewpoint of the connection positions of ICZ units in the polymer chain.

Indolo[3,2‐b]carbazole‐based poly(arylene vinylene)s. The influence of substitution position on spectroscopic and electrochemical properties

“…). The first two absorptions correspond to the S 2 ← S 0 electronic excitation or HOMO − 1 → LUMO + 2 and HOMO − 1 → LUMO vertical transitions, respectively . The third absorption band is assigned from theoretical calculations to the S 1 ← S 0 electronic transition (HOMO → LUMO) …”

“…Similar behaviour is observed for thermal, UV and fluorescence spectra of poly(arylene ethynylene)s containing ICZ nuclei connected in the main chain at 2,8‐, 3,9‐ and 6,12‐positions. The UV and electrochemical measurements show the poly(arylene ethynylene)s containing ICZ linked at 3,9‐positions have higher effective conjugation length, the order being 3,9 > 2,8 > 6,12 …”

“…trans ‐1,2‐Bis(tributylstannyl)ethane, N , N ‐dimethylformamide (DMF), tetrahydrofuran (THF), acetonitrile, dimethylsulfoxide (DMSO), toluene and triethylamine were purchased from Sigma Aldrich and used as received or purified by usual methods. The bis‐bromine ICZ monomers ( M1 , M2 and M3 ; Scheme ) were synthesized by acid‐catalysed condensation of 4‐bromindole or 5‐bromindole with benzaldehyde or indole with p ‐brombenzaldehyde, followed by aromatization and alkylation in a three‐step route and previously presented …”

“…To the best of our knowledge, all known ICZ polymers synthesized until now have a polyarylene structure of the main chain and contain the heteroaromatic skeleton connected only at 3,9‐ or 2,8‐positions. In a previous paper we presented the synthesis of three poly(arylene ethynylene)s by varying the connection positions of ICZ moieties, starting from three ICZs monomers. It was observed that the polymer containing ICZ linked at 3,9‐positions had higher effective conjugation length than the other two isomeric structures, being similar to 2,7‐carbazole‐substituted polymers in behaviour.…”

Indolo[3,2‐b]carbazole‐based poly(arylene ethynylene)s through Sonogashira coupling for optoelectronic and sensing applications

“…In a simple experimental procedure equimolar amounts of 5‐bromoindole (1.25 g) and benzaldehyde (0.65 g) were added into a round‐bottomed flask containing acetonitrile (5 mL). HCl (0.055 g,) was added into it, while stirring.…”