Spectroelectrochemical characterization of isomeric conjugated polymers containing 2,7- and 3,6-carbazole linked by vinylene and ethynylene segments

Abstract

The ability to form multi-colored oxidation states upon applied positive potentials, and the narrow band gap of 2,7-substituted carbazole derivatives, had encouraged the development of new carbazole containing polymers with interesting optoelectronic properties. Four conjugated polymers containing substituted carbazole units spaced in the main chain by vinylene and 1,4-phenyleneethynylene segments were synthesized via Stille and Sonogashira coupling reactions. Two different substitution positions of carbazole, such as 2,7- and 3,6-carbazole were used to tune the conjugation length and the charge transfer properties of the resulting polymers. The structures of the obtained polymers were characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy while the electronic and optical properties were investigated as function of carbazole substitution positions or spacer nature by ultraviolet-visible spectroscopy and cyclic voltammetry. The redox behaviour of polymers as films deposited on working electrode was investigated using cyclic voltammetry technique, and the lowest unoccupied molecular orbital and highest unoccupied molecular orbital energy levels values were also determined. Spectroelectrochemical measurements suggested the existence of polaronic and bipolaronic structures of polymers backbones accompanied by multi-electrochromic behavior.

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

“…The connection of ICZ at the 3,9-positions extendsconjugation relative to that at the 2,8-and 6,12-positions, being similarly with 2,7-positions of carbazole polymers. [30][31][32] The introduction of 2,8-disubstituted conjugated system comparatively with 3,9-disubstituted one linked by 1.4-phenylene ethynylene segments lead to a breakage of the electron delocalization pathway and explains the blue shift wavelength absorption. Polymers containing 3,9substituted ICZ moiety have a more extended conjugation along the backbone which occurs by the three para-linked phenyl rings of planar ICZ moiety, leading thus to a higher degree of conjugation.…”

Effect of Aluminum Nanostructured Electrode on the Properties of Bulk Heterojunction Based Heterostructures for Electronics

“…The proposed p-type conduction donors are poly(arylenevinylene)s, such as poly(N-(2-ethylhexyl)-2,7-carbazolylene-vinylene)/AMC31 and poly(N-(2-ethylhexyl)-3,6-carbazolylene-vinylene)/AMC30 containing carbazole units substituted at 2,7- and 3,6-positions, respectively. These polymers are characterized by good absorption of the radiation from the UV region and blue-green region of the Vis spectrum (wavelength < 450 nm for AMC30 and <540 nm for AMC31) [ 19 ]. The band gap estimated from the fundamental absorption edge indicated higher value for the polymer containing carbazole-substituted units in position 3,6 (E g,AMC30 = 2.74 eV) compared to the polymer containing carbazole-substituted units in position 2,7 (E g,AMC31 = 2.10 eV) [ 19 , 20 ].…”

“…These polymers are characterized by good absorption of the radiation from the UV region and blue-green region of the Vis spectrum (wavelength < 450 nm for AMC30 and <540 nm for AMC31) [ 19 ]. The band gap estimated from the fundamental absorption edge indicated higher value for the polymer containing carbazole-substituted units in position 3,6 (E g,AMC30 = 2.74 eV) compared to the polymer containing carbazole-substituted units in position 2,7 (E g,AMC31 = 2.10 eV) [ 19 , 20 ]. Thus, the phenyl group rings linked in para position lead to an extended conjugation along the backbone, without the participation of nitrogen atoms [ 19 ].…”

“…The band gap estimated from the fundamental absorption edge indicated higher value for the polymer containing carbazole-substituted units in position 3,6 (E g,AMC30 = 2.74 eV) compared to the polymer containing carbazole-substituted units in position 2,7 (E g,AMC31 = 2.10 eV) [ 19 , 20 ]. Thus, the phenyl group rings linked in para position lead to an extended conjugation along the backbone, without the participation of nitrogen atoms [ 19 ]. Additionally, the vinylene segments determine a good delocalization of the π-electrons in solid state.…”

New electroactive asymmetrical chalcones and therefrom derived 2-amino- / 2-(1H-pyrrol-1-yl)pyrimidines, containing an N-[ω-(4-methoxyphenoxy)alkyl]carbazole fragment: synthesis, optical and electrochemical properties

“…Carbazole undergoes electrophilic substitution mainly at C3 or C6 positions to give 3(6)-substituted derivatives. Nevertheless, nowadays some new synthetic procedures [ 3 , 5 – 7 ] have given the opportunity to prepare conjugated systems which include 1,8-, 2,7- or 9(3)-carbazolylene units. The incorporation of such moieties changes the optical and electrochemical properties of the resulted conjugated systems [ 5 ].…”