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A series of eight carbazole-cyanoacrylate based donor-acceptor dyes were studied. Within the series the influence of modifying the thiophene bridge, linking donor and acceptor and a change in the nature of the acceptor, from acid to ester, was explored. In this joint experimental and computational study we have used electronic absorbance and emission spectroscopies, Raman spectroscopy and computational modeling (density functional theory). From these studies it was found that extending the bridge length allowed the lowest energy transition to be systematically red shifted by 0.12 eV, allowing for limited tuning of the absorption of dyes using this structural motif. Using the aforementioned techniques we demonstrate that this transition is charge transfer in nature. Furthermore, the extent of charge transfer between donor and acceptor decreases with increasing bridge length and the bridge plays a smaller role in electronically mixing with the acceptor as it is extended. [ABSTRACT FROM AUTHOR]

The formation of a poly(2,6-carbazole) derivative during an electrochemical polymerization process is shown. Comparison of 3,5-bis(9-octyl-9H-carbazol-2-yl)pyridine and 3,5-bis(9-octyl-9H-carbazol-3-yl)pyridine by electrochemical and UV-Vis-NIR spectroelectrochemical measurements and DFT (density functional theory) calculation prove the formation of a poly(2,6-carbazole) derivative. Both of the compounds form stable and electroactive conjugated polymers. [ABSTRACT FROM AUTHOR]

During research on cross-linked conducting polymers, double-functionalized monomers were synthesized. Two subunits potentially able to undergo oxidative coupling were used—perimidine and, respectively, carbazole, 3,6-di(hexylthiophene)carbazole or 3,6-di(decyloxythiophene)carbazole; alkyl and alkoxy chains as groups supporting molecular ordering and 14H-benzo[4,5]isoquinone[2,1-a]perimidin-14-one segment promoting CH⋯O interactions and π–π stacking. Electrochemical, spectroelectrochemical, and density functional theory (DFT) studies have shown that potential-controlled oxidation enables polarization of a specific monomer subunit, thus allowing for simultaneous coupling via perimidine and/or carbazole, but mainly leading to dimer formation. The reason for this was the considerable stability of the dicationic and tetracationic π-dimers over covalent bonding. In the case of perimidine-3,6-di(hexylthiophene)carbazole, the polymer was not obtained due to the steric hindrance of the alkyl substituents preventing the coupling of the monomer radical cations. The only linear π-conjugated polymer was obtained through di(decyloxythiophene)carbazole segment from perimidine-di(decyloxythiophene)-carbazole precursor. Due to the significant difference in potentials between subsequent oxidation states of monomer, it was impossible to polarize the entire molecule, so that both directions of coupling could be equally favored. Subsequent oxidation of this polymer to polarize the side perimidine groups did not allow further crosslinking, because rather the π–π interactions between these perimidine segments dominate in the solid product. [ABSTRACT FROM AUTHOR]

A series of cobalt (II) porphyrin complexes modified with carbazole rings at one or more meso positions of the macrocycle were synthesized and characterized as to their spectroscopic and basic electrochemical properties in non-aqueous media. The effect of the number and position ( syn and anti ) of carbazole groups on the complexes properties were investigated. The comparison was made to cobalt (II) porphyrin containing mesityl groups at the meso -positions. The relation between the site of redox processes in cobalt meso -carbazole substituted porphyrins were analysed. It was shown that the conjugated π -ring system of the porphyrin macrocycle, the cobalt central metal ion and the carbazole peripheral substituents are redox-active. [ABSTRACT FROM AUTHOR]

A set of new donor-π-acceptor organic PM dyes, bearing carbazole as electron donor and cyanoacrylic acid as electron acceptor, has been synthesized and fully characterized with particular focus on application in dye-sensitized solar cells (DSSCs). Importantly, a change in 'linker' structure resulted in the electron re-distribution in the oxidized dye, in general, and the localization of the 'electron hole', in particular, when compared with the MK2 benchmark. In addition, modifying the PM dyes with different lengths of alkoxy chains, that is, 1, 4, and 8 carbons, strongly influences the access of the oxidized cobalt ions to the surface affecting recombination, which had an appreciable effect on dye-sensitized solar cell performances. While the performance of the PM dyes was 15–20% lower than MK2 , they are considerably easier and less expensive to synthesize, offering excellent potential for future DSSC applications. Image 1 [ABSTRACT FROM AUTHOR]