Simple electron donor molecules based on triphenylamine and carbazole derivatives
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Triphenylamine
Carbazole
Quantum yield
Triphenylamine
Carbazole
Quantum yield
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Triphenylamine
Carbazole
Thermal Stability
HOMO/LUMO
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Carbazole
Triphenylamine
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New organic materials containing a cyano‐functionalized carbazole moiety at one end linked to different chromophores such as fluorene, carbazole, and triphenylamine at the other end through an acetylene spacer are synthesized and characterized by photophysical, electrochemical, thermal, and electroluminescence studies. A meta ‐like linkage at the C‐2 and C‐7 atoms of the central carbazole moiety and the choice of chromophore restricted the emission to the near‐ultraviolet region. The photophysical properties of the compounds depend on the nature of the chromophore attached to the carbazole unit. A triphenylamine‐substituted derivative exhibited the longest wavelength emission in the series, attributable to the elongated conjugation and electron richness of triphenylamine, whereas the phenyl‐ and fluorene‐functionalized molecules showed the shortest wavelength emissions with vibronic patterns. The compounds containing carbazole and triphenylamine units exhibited positive solvatochromism in their fluorescence spectra, and this behavior is characteristic of charge transfer from a donor to an acceptor. A fluorene derivative containing cyano substituents at the carbazole and fluorene moieties exhibited the best electroluminescence characteristics in the series, probably because of balanced charge transport and effective confinement of the excitons in the emissive layer.
Triphenylamine
Carbazole
Chromophore
Moiety
Solvatochromism
Acceptor
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The 2,7- and 3,6-substituted carbazole and triphenylamine chalcogenophene (Se, Te) derivatives and their electrodeposited polymers are investigated using electrochemical and UV–vis–NIR/ESR spectroelectrochemical methods. Major differences in the case of oxidation and electropolymerization behavior between monomers and related polymers are shown. Se and Te atoms do not conjugate their lone electron pairs with the π-conjugated system and therefore only increase the contribution of the quinoid form of the chalcogenophene unit. The 2,7- substituted carbazole derivatives present stronger carbazole–chalcogenophene conjugation than 3,6-substituted derivatives. One 3,6-substituted carbazole derivative and triphenylamine derived polymers were found to have promising electrochromic properties with black electrochromism.
Triphenylamine
Carbazole
Lone pair
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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.
Carbazole
Oligomer
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The electronic and photophysical properties of a series of N-thienylcarbazoles were first clarified and compared to one another.The characters of both ground and excited states of carbazole moiety are much more affected by a 2-thienyl group than a 3-thienyl group.Carbazole and thiophene are important heteroaromatic compounds from the aspects of constructing functional materials such as organic light-emitting materials, photoconductors, and so on. 1 For instance, these heterocycles have been used as building-blocks for hole-transport and light-emissive materials or host materials for triplet emitters in OLEDs. 2,3As one of the most fundamental compounds containing carbazole and thiophene, N-(2-thienyl)carbazole (2) has been prepared, 4 but its photophysical properties are unknown.2,5-Bis(N-carbazolyl)thiophene ( 3) is also known in the literature, 5 but its photophysical properties are not clarified, although those of 5,5'-bis(N-carbazolyl)-2,2'-bithiophene are disclosed. 6rprisingly, N-(3-thienyl)carbazole (1) has been unknown in the literature.Thus, we were prompted to investigate and compare the electronic and photophysical properties of 1-3 systematically.As a result, we have found that their photophysical properties remarkably depend on the substitution positions of thiophene.
Carbazole
Moiety
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The main objective of the present research is to investigate structure property
of a series of carbazole-thiophene. Electronic properties were evaluated by UV-Vis,
cyclic voltammogram and theoretical calculations. Particularly, the effects of
conjugation connectivity on photophysical and electrochemical properties, as well as
the correlation between carbazole-thiophene were linked at the N-9 position for
different core groups via biphenyl, dimethylbiphenyl and phenyl were studied.
Literature review on the carbazole-thiophene moieties and their derivatives and methods
for the synthesis of carbazole-thiophene have been described. The literature search on
the various potential application of carbazole-thiophene were also studied. A brief
introduction on the background of this study was provided which gave an insight of the
key step involved in the synthesis of carbazole-thiophenes via Suzuki Miyaura and
Ullmann coupling reaction. Results of the physical properties on the electronic
absorption spectroscopy via UV-visible and fluorescence were discussed. We noted a
maximum absorption wavelength at a higher absorbance, indicating that the attachment of thiophene groups at the 3- and 6-positions of the carbazole significantly enhances the
optical properties. The absorption bands of all of the compounds were gradually red shifted, when the thiophene group was connected to the carbazole at the 3- and 6-
positions and the extent of π-conjugation in the compounds increased, as expected. After the functionalization of the carbazole groups, the fluorescence maxima (λem)
gradually red shifted upon the addition of thiophene group, resulting a significant red
shift in the emission spectrum. Epa values for 2.38 (P1), 2.39 (P2), 2.40 (P3), 2.41 (P4),
2.42 (P5), 2.43 (P6), 2.44 (P7), 2.45 (P8), 2.46 (P9) and 2.47 (P10) are cathodically
shifted compared to those for 1.4 (CBP), 2.36 (CDBP), 2.37 (BCP) by the subsequent
addition of thiophene molecules, demonstrating that the connection with thiophene at the 3- and 6-positions on carbazole of 1.4 (CBP), 2.36 (CDBP) and 2.37 (BCP) gives
rise to high electrochemical stability and effectively enhances donor ability. Carbazole
substituted with thiophene groups at the 3- and 6-positions leads to greater stabilization
of HOMO and LUMO energy levels where the band gap (ΔE) of all the compounds is
significantly reduced and such unit can be introduced into the backbone of 1.4 (CBP),
2.36 (CDBP) and 2.37 (BCP) π-conjugated small molecules to develop new materials
with low band gap that may have potential application in optoelectronic fields. A brief
introduction of theoretical calculation was provided. A brief theoretical calculation on
the carbazole-thiophenes compounds by geometrical optimization and frontier molecular orbital calculations were also discussed. All computation were performed
using GAUSSION 09W software package employing the Density Functional Theory (DFT) method with correlation functional B3LYP and 6-31G as functional basis set.
Carbazole
Absorbance
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Triphenylamine
Carbazole
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A new family of well-defined and fully conjugated oligoelectrolyte compounds were elaborated based on one or two bis-thiophene dialkoxyphenylene units.
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