Systematic Structure–Property Investigations on a Series of Alternating Carbazole–Thiophene Oligomers

Abstract

A series of alternating carbazole-thiophene oligomers, namely 2,7-linked carbazole-thiophene oligomers 1, 3, 5, 7, and 9 and 3,6-linked ones 2, 4, 6, 8, and 10, in which the molecular length was systematically elongated, were synthesized by Suzuki-Miyaura coupling reactions. The effects of the conjugation connectivity between the carbazole and thiophene moieties and the molecular length on the electronic, photophysical, and electrochemical properties of 1-10 were comprehensively investigated. In the present oligomer architectures, the connection with thiophene at the 2,7-positions of carbazole ensures π-conjugation to a high extent and high fluorescence quantum yields, while that at the 3,6-positions enhances the donor ability. The increase in the molecular length of the 2,7-linked oligomers effectively extends π-conjugation. The relationship between structural variations and photophysical properties was examined by fluorescence lifetime measurements in detail. The X-ray crystal structure of 6 was also disclosed.

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

“…Polymer P2 with 3,9‐substitued ICZ rings has a more extended conjugation along the backbone occurring by virtue of the three para ‐linked phenyl rings of ICZ and vinylene spacer. The optical behaviour of P1 and P2 is similar to that of poly(3,6‐carbazole)s and poly(2,7‐carbazole)s, respectively . The conjugation pathway in both P2 and P3 occurs by virtue of the three para ‐linked phenylene rings spaced by vinylene spacers, but of P2 is red‐shifted compared with P3 .…”

“…A feature of the ICZ polymers is that photophysical and spectral properties can be readily tuned by the introduction of ICZ nuclei at different substitution positions in the polymer chain, similar to carbazole oligomers and polymers . Thus, the structure of ICZ moiety allows the introduction of functional groups in many possible positions and to obtain polymers having ICZ skeleton covalently linked at different sites.…”

Novel liquid crystalline organic semiconducting oligomers incorporating N-heterocyclic carbazole moieties for fluorescent OLEDs

“…properties, e.g. relatively intense luminescence and reversible oxidation processes, π-stacking capability and ease of further derivation [44][45][46][47][48][49][50][51]. Therefore, a series of carbazole-functionalised derivatives containing different cores were synthesised and are discussed below.…”

“…The presence of the hetero-atoms in aromatic heterocyclic moieties in some highly conjugated organic semiconductors contributes to the improved optoelectronic properties of such materials. For example, the carbazole moiety has long been recognized as an excellent construction of photoconductive organic semiconductors due to strong fluorescence, good hole-transporting ability, low redox potential and chemical/environmental stability [44][45][46][47][48][49][50][51]. Compared with the corresponding 2,7-disubstituted fluorene moiety, the electron-donating nature of the nitrogen hetero-atoms present in the carbazole moieties can increase the electron density of the delocalized π-electronic cloud and thereby affect the magnitude of the physical properties of interest for OLEDs.…”

Polymer network hole transport layers based on photochemically cross-linkable N′N′-diallyl amide tri-N-substituted triazatruxene monomers

“…Triazatruxenes 1 and 2, Scheme 1, were synthesised by alkylation of the carbazole moieties present in triazatruxene using modied literature procedures. 42,43 The reactions were carried out under a nitrogen atmosphere at 50 C using a dispersion of sodium hydride as the base, N,N-dimethylformamide as the solvent and a 5.0 molar equivalent of N,N-diallyl-5-bromopentanamide or N,N-diallyl-2-bromoacetamide, respectively. The experimental procedures and NMR spectra are recorded in the ESI.…”