Carbazole Core Research Articles

Total Synthesis of Dictyodendrins by the Gold‐Catalyzed Cascade Cyclization of Conjugated Diynes with Pyrroles

AbstractIn total and formal syntheses of dictyodendrins B, C, E, and F, the key step involved the direct construction of the pyrrolo[2,3‐c]carbazole core by the gold‐catalyzed annulation of a conjugated diyne with a pyrrole to form three bonds and two aromatic rings. The subsequent introduction of substituents at the C1 (Suzuki–Miyaura coupling), C2 (addition to an aldehyde), N3 (alkylation), and C5 positions (Ullman coupling) provided divergent access to dictyodendrins.

Total Synthesis of Dictyodendrins by the Gold-Catalyzed Cascade Cyclization of Conjugated Diynes with Pyrroles.

In total and formal syntheses of dictyodendrins B, C, E, and F, the key step involved the direct construction of the pyrrolo[2,3-c]carbazole core by the gold-catalyzed annulation of a conjugated diyne with a pyrrole to form three bonds and two aromatic rings. The subsequent introduction of substituents at the C1 (Suzuki-Miyaura coupling), C2 (addition to an aldehyde), N3 (alkylation), and C5 positions (Ullman coupling) provided divergent access to dictyodendrins.

Molecular design and theoretical investigation of new metal-free heteroaromatic dyes with D-π-A architecture as photosensitizers for DSSC application

Abstract Herein, we report design, synthesis and photovoltaic performance of four new metal-free heteroaromatic dyes ( P 1-4 ) with D-π-A architecture carrying electron donating carbazole core connected to four different electron withdrawing/anchoring groups, viz. cyanoacetic acid, rhodanine-3-acetic acid, barbituric acid and thiobarbituric acid and phenylene ring as a π-spacer. The newly designed P 1-4 were synthesized from carbazole derivative using Suzuki cross coupling approach followed by Knoevenagel condensation reaction. Their structures were confirmed by FTIR, NMR, Mass spectral and elemental analyses. The dyes were subjected to optical and electrochemical studies in order to investigate their absorption/emission behavior as well as HOMO/LUMO energies. The UV–vis spectral studies reveal that the P 1-4 showed λ max at 412, 439, 458 and 489 nm, respectively. Their optical band-gap is in the range of 2.17 to 2.61 eV and fluorescence quantum yield is in the order of 44–70%. From energy level diagram, it is clear that all the dyes possess good thermodynamic feasibility for electron injection into CB edge of TiO 2 as well as their regeneration from electrolyte system. The photovoltaic performance studies indicate that among the tested dyes, P 1 anchored with cyanoacetic acid displayed the highest IPCE (32%), resulting in improved PCE (1.94%), J SC (4.68 mA cm −2 ), V OC (0.588 V) and FF (70.3%) values, when compared to other dyes. Finally, DFT studies were performed using Turbomole 7.1 V software to investigate their electron cloud delocalization in HOMO/LUMO levels and theoretical absorption spectral data. The results reveal that the dye P 1 showed effective charge separation in its FMO levels, which has reflected in its ICT behavior and hence P 1 displayed the improved photovoltaic performance.

Redox-modulated near-infrared electrochromism, electroluminochromism, and aggregation-induced fluorescence change in an indolo[3,2-b]carbazole-bridged diamine system

A new indolo[3,2-b]carbazole-based compound (1) has been developed by linking two redox-active diphenylamine moieties to the rigid π-conjugated indolo[3,2-b]carbazole core. Its first two completely reversible oxidation steps are mainly related to the two terminal amine centers, and a moderate electron coupling between these amine centers has been determined. The associated oxidized species 1+ and 12+ both exhibited strong NIR absorptions, and a completely reversible conversion among three different colors (light-yellow, red, and blue, corresponding to neutral, monocationic and dicationic states, respectively) could be realized. In addition, reversible switching between turn-off and turn-on of its fluorescence could be accomplished by electrochemical oxidation and reduction, respectively. Compound 1 also exhibited obvious fluorescence color changes during its aggregate-forming process, and its solid showed bright-yellow fluorescence with a high emission quantum yield of 30%.

Total synthesis of the dictyodendrins as an arena to highlight emerging synthetic technologies.

Covering: 1993-2017This review discusses the isolation, biological activity, and syntheses of the dictyodendrin class of natural products, covering the years 1993-2017. The dictyodendrins are a family of alkaloids isolated from marine sponges, Dictyodendrilla verongiformis and Ianthella sp., which possess a highly substituted pyrrolo[2,3-c]carbazole core at the phenol or quinone oxidation states. Dictyodendrins exhibit a wide range of biological activities, such as telomerase inhibition, BACE1 enzyme inhibition, and cytotoxicity against several cancer cell lines. The unique structure and interesting biological activities of dictyodendrins provided a platform for the application of novel synthetic methods including C-H insertion, C-H arylation, and electrocyclization cascades.

Correction: Solution-processable naphthalene and phenyl substituted carbazole core based hole transporting materials for efficient organic light-emitting diodes

Correction for ‘Solution-processable naphthalene and phenyl substituted carbazole core based hole transporting materials for efficient organic light-emitting diodes’ by Sudhir Kumar et al., J. Mater. Chem. C, 2017, 5, 9854–9864.

Solution-processable naphthalene and phenyl substituted carbazole core based hole transporting materials for efficient organic light-emitting diodes

Solution-processable molecular hole transporting materials (HTMs) are crucial to realize inexpensive fabrication of energy-efficient and large area organic light emitting diodes (OLEDs) for next-generation displays and lighting.

Highly Site‐Selective and Direct Ortho‐C−H Nitration, Trifluoromethylation and Cyanation at the C1‐Position of Carbazole Frameworks

AbstractWe report a concise, versatile, and practical method for ortho‐C−H mononitration, monotrifluoromethylation and monocyanation of carbazole cores via a transition‐metal‐catalyzed reaction using an appropriate functional group source. The significant advantage of this transformation is the generation of highly site‐selective direct C1–heteroatom bonds that are geometrically difficult to access, in good to excellent yields.

Nanocage containing metal-organic framework constructed from a newly designed low symmetry tetra-pyrazole ligand

1368-Tetra(1H-pyrazol-4-yl)-9H-carbazole (H4CTP), a tetra-pyrazole ligand with Cs symmetry, has been synthesized based on a carbazole core. A solvothermal reaction of this ligand with NiCl2·6H2O gave a three-dimensional (3-D) metal-organic framework (MOF), [Ni(H4CTP)Cl2]·nS (BUT-41), which crystallized in the cubic space group Pm-3 in spite of H4CPT with a central carbazole core and four peripheral pyrazole rings has low symmetry. The framework of BUT-41 can be regarded as a four-connected 3-D net with the rhr topology when both the organic ligand and the metal center are considered as four-connected nodes. Nanocages with internal diameter of 2 nm are present in the framework of BUT-41, which are formed by interconnecting 12 H4CTP ligands and 20 Ni(II) ions. Each nanocage connects with six adjacent cages through sharing hexagonal windows with diameter over 7 Å, resulting in 3-D intersecting channels of the MOF. Although the tetra-pyrazole ligand is not deprotonated after coordination with the metal ions, powder X-ray diffraction and N2 adsorption experiments reveal that the framework of BUT-41 is rigid and permanently porous with the Brunauer-Emmett-Teller surface area up to 1551 m2 g−1. Furthermore, gas adsorption experiments show that this MOF selectively adsorbs CO2 over N2 and CH4.

Synthetic Approach to Dictyodendrins: A Facile Synthesis of Pyrrolo[2,3‐c]carbazole, Pyrrolodibenzothiophene, and Benzo[e]indole

The FeCl3/DDQ‐PTSA/NBS‐mediated cyclization (DDQ = 2,3‐dichoro‐5,6‐dicyano‐1,4‐benzoquinone, PTSA = p‐toluenesulfonic acid, NBS = N‐bromosuccinimide) of 2‐arylvinyl‐3‐indolylpyrrole led to the formation of the pyrrolo[2,3‐c]carbazole core unit of dictyodendrins in yields of 75–90 %. The cyclization method was also successfully applied to the syntheses of pyrrolodibenzothiophene and benzo[e]indole derivatives.

Photophysical properties and computational investigation on substituent effects on the structural and electronic properties of 3,6-di(thiophene-2-yl)-carbazole-based derivatives

A series of 3,6-carbazole-based derivatives, 3,6-CzTh-(1), 3,6-CzTh-(2), 3,6-CzTh-(3) and 3,6-CzTh-(4), were synthesized to investigate the influence of structural distortion on intramolecular charge transfer (ICT) complexation between the conjugation components and carbazole core unit of the 3,6-carbazole-based derivatives. The 3,6-carbazole-based derivatives were synthesized and analysed using UV-Visible, photoluminescence spectroscopy and DFT calculations. The electron-donating substituents on the carbazole core unit, which was linked by formyl and acetyl at the 3,6-positions of the carbazole core so as to directly involve the electron-donating edge substituents in backbone, exhibited conjugation breaks in the middle of the carbazole core units. The break lead to a planar structure with an extraordinary ability to stabilize on the excited state resulting in a strong fluorescence quantum yield (Фfluo≈0.6–0.7). The results of the Time-dependent density functional theory (TD-DFT) calculations were in agreement with the experimental results, and indicated that the low fluorescence of 3,6-CzTh-(1) and 3,6-CzTh-(2) is derived not only from intersystem crossing but also from internal conversion due to the proximity effect; this inference was also supported by the measurements of the photoluminescence spectra at low temperatures. In addition, factors leading efficiently to non-radiative processes were shown to be absent in 3,6-CzTh-(3) and 3,6-CzTh-(4). This work deepens our understanding of 3,6-di(thiophen-2-yl)-carbazole-based derivatives and provides insight into the future design of novel materials for improved fluorescence efficiencies and optoelectronic devices.

Divergent Syntheses of Carbazole Alkaloids Clausenapin, Indizoline, Claulansine M, and Clausenaline D.

We described the first total syntheses of clausenapin, indizoline, claulansine M, and a novel synthetic route to clausenaline D via divergent method. Key steps involved TFAA-mediated intramolecular acylation to construct the carbazole core and subsequent Claisen rearrangement to generate key intermediates for further elaboration to target molecules.

Indolo[3,2-b]carbazole-based multi-donor–π–acceptor type organic dyes for highly efficient dye-sensitized solar cells

Four novel indolo[3,2-b]carbazole-based multi-donor–π–acceptor type organic dyes QX01–04 have been designed, synthesized, and applied for dye-sensitized solar cells. These dyes consist of an indolo[3,2-b]carbazole core acting as the main donor group, a couple of groups such as ethylbenzene, N,N-diethylaniline, ethyloxylbenzene, and octyloxylbenzene acting as the secondary donors. The photophysical, electrochemical, and theoretical studies indicate that the four dyes are all capable as the photosensitizers. When introducing N,N-diethylaniline as the secondary donor, QX02 exhibits a broader absorption region and significantly improved IPCE values, which ensured a good light-harvesting ability and a high Jsc of 15.2 mA cm−2. Finally, QX02-based cell achieved a high efficiency of 8.09% which is very close to that of the commercial N719-based cell (8.26%) under 100 mW cm−2 irradiation.

Red-emitting NLOphoric carbazole-coumarin hybrids - Synthesis, photophysical properties and DFT studies

The carbazole core is known to be a very efficient donor and can assist the coumarin core in achieving the red emission by pushing electrons in the chromophoric system. 9-ethyl-9H-carbazole-3-carbaldehyde and 9-ethyl-9H-carbazole-3,6-dicarbaldehyde were reacted with 3-acetyl-4-hydroxy-coumarin and 7-(N,N-diethylamino)-3-acetyl-4-hydroxy-coumarin to give the corresponding hybrids. The BF2-complexes of the 4-hydroxy-3-acetyl-coumarin derivatives were reacted to give the coumarin-carbazole hybrids. The molecules synthesized emit in the red region. Their photophysical properties were studied in various solvents of different polarity. The solvent polarity function plots were studied and show linearity. The introduction of two units of coumarin core on carbazole improves the molar extinction co-efficient of the dye. The BF2-complexation has enhanced the quantum efficiency and non-linear optical properties of the molecules.

Side-chain conjugated polymers for use in the active layers of hybrid semiconducting polymer/quantum dot light emitting diodes

Three monomers,M1–M3, with modified carbazole cores and styrene functionality were polymerized by RAFT. The polymers were then used in the active layers of hybrid polymer/quantum dot light emitting diodes.

Total synthesis and antiviral activity of indolosesquiterpenoids from the xiamycin and oridamycin families.

Indolosesquiterpenoids are a growing class of natural products that exhibit a wide range of biological activities. Here, we report the total syntheses of xiamycin A and oridamycins A and B, indolosesquiterpenoids isolated from Streptomyces. Two parallel strategies were exploited to forge the carbazole core: 6π-electrocyclization/aromatization and indole C2–H bond activation/Heck annulation. The construction of their trans-decalin motifs relied on two diastereochemically complementary radical cyclization reactions mediated by Ti(III) and Mn(III), respectively. The C23 hydroxyl of oridamycin B was introduced by an sp3 C–H bond oxidation at a late stage. On the basis of the chemistry developed, the dimeric congener dixiamycin C has been synthesized for the first time. Evaluation of the antiviral activity of these compounds revealed that xiamycin A is a potent agent against herpes simplex virus–1 (HSV-1) in vitro.

Concise syntheses of dictyodendrins A and F by a sequential C-H functionalization strategy.

Syntheses of dictyodendrins A and F have been achieved using a sequential C-H functionalization strategy. The N-alkylpyrrole core is fully functionalized by means of a rhodium(I)-catalyzed C-H arylation at the C3-position, a rhodium(II)-catalyzed double C-H insertion at the C2- and C5-positions, and a Suzuki-Miyaura cross-coupling reaction at the C4-position. The syntheses of dictyodendrins A and F were completed by formal 6π-electrocyclization to generate the pyrrolo[2,3-c]carbazole core of the natural products.

Synthesis, electrochromic, halochromic and electro-optical properties of polyazomethines with a carbazole core and triarylamine units serving as functional groups

A series of aromatic polyazomethines (PAMs) were prepared via direct polycondensation from 9-(2-ethylhexyl)-carbazole-3,6-dicarboxaldehyde and six different types of diamine containing triarylamines.

A biomimetic method to synthesise indolo[3,2-a]carbazoles

A simple and biomimetic synthetic strategy for indolo[3,2-a]carbazoles has been developed. Our approach involved the efficient conversion of 2-(3′-indolyl)tryptophan derivatives into the corresponding α-keto esters and the subsequent aromatic cyclisation of these intermediates to construct the characteristic heteroaryl-condensed carbazole core.

Efficient Synthesis of Carbazole Core Diblock Dendrimer by Double Click Chemistry

Graphical Efficient double click methods for the synthesis of carbazole core diblock codendrimers were developed. The synthetic strategy involved the sequential double click reactions between an alkyne and an azide. The chromophore building block, N-octyl-3,6-diazidocarbazole, was chosen to serve as the azide functionalities for dendrimer growth via double click reactions with the alkyne-functionalized PAMAM dendrons as hydrophilic dendron and alkyne-functionalized Fréchet-type dendrons as hydrophobic dendron. The structure of diblock codendrimers was confirmed by 1H- and 13C-NMR spectroscopy, IR spectroscopy, mass spectrometry, and GPC analysis.