Papers by Keyword: Carbazole

Abstract: The development of drug lead compounds has been a focus in organic synthesis methods due to their emerging potential in biomedical applications. However, most synthesis methods involve the use of hazardous solvents, which contribute negatively to the environment with continued use, leading to regulations that limit the use of these solvents. Hence, this study was done to assess the feasibility of Cyrene^TM, a neoteric bio-based green solvent, as an alternative to industrial, dipolar aprotic organic solvents such as DMF and DMSO. The methodology for this study consists of several steps, including preparation of materials, microwave synthesis, thin-layer chromatography, extraction of the products formed, purification and isolation of the target compound, and finally, data analysis. The reaction of interest is the carbazole intermediate formation through Suzuki-Miyaura cross-coupling between 2-iodoaniline and 2-bromophenylboronic acid in Cyrene^TM in the presence of Pd (OAc)₂ and PPh₃ as the catalyst and ligand under microwave-assisted conditions. Through NMR spectroscopy, the isolated product was identified to be 2’-bromobiphenyl-2-amine, with functional groups verified through FTIR spectroscopy. Optimal conditions in Cyrene^TM involve using Cs₂CO₃ as the base at 90 °C for 2 hrs. However, side reactions in Cyrene^TM resulted in lower yields in comparison to DMSO at 130 °C. It is recommended to identify new methods to minimize the Cyrene^TM side reactions that adversely affect product yield and to test the possibility of completing the carbazole formation via cascade C-C/C-N bond formation under microwave irradiation with Cyrene^TM as a solvent.

Abstract: Generally, it is difficult to generate a high-performance pure blue emission organic light-emitting diode (OLED). That is because the intrinsically wide band-gap makes it hard to inject charges into the emitting layer in such devices. To solve the problem, carbazole derivatives have been widely used because they have more thermal stability, a good hole transporting property, more electron rich (p-type) material, and higher photoconductivity. In the present work, novel copolymers containing donor-acceptor-acceptor-donor (D-A-A-D) blue compounds used for OLEDs were investigated. The theory of the geometrical and electronic properties of N-ethylcarbazole (ECz) as donor molecule (D) coupled to a series of 6 acceptor molecules (A) for advanced OLEDs were investigated. The acceptors were thiazole (TZ), thiadiazole (TD), thienopyrazine (TPZ), thienothiadiazole (TTD), benzothiadiazole (BTD), and thiadiazolothienopyrazine (TDTP). The ground state structure of the copolymers were studied using Density Functional Theory (DFT) at B3LYP/6-31G(d) level. Molecular orbital analysis study indicated 3 investigated copolymers (ECz-diTZ-ECz, ECz-diTD-ECz, ECz-diBTD-ECz) have efficient bipolar charge transport properties for both electron and hole injection to the TiO₂ conduction band (4.8 eV). In addition, the excited states electronic properties were calculated using Time-Dependent Density Functional Theory (TD-DFT) at the same level. Among these investigated copolymer ECz-diTZ-ECz and ECz-diTD-ECz showed the maximum absorption wavelengths (λ_abs) with blue emitting at 429 and 431 nm, respectively. The results suggested that selected D-A-A-D copolymers can improve the electron- and hole- transporting abilities of the devices. Therefore, the designed copolymers would be a promising material for future development of light-emitting diodes, electrochromic windows, photovoltaic cells, and photorefractive materials.

Abstract: A modular approach was used in the synthesis of the 3-(diphenylamino)carbazolyl- functionalized 2-(4-(dimethylamino)benzylidene)-1H-indene-1,3(2H)-dione (DMABI) derivatives. For this purpose, carboxyl functional group was introduced into the framework of DMABI molecule. Additionally, a regioselective method for substitution of carbonyl group of DMABI with dicyanomethylene group was investigated and verified using the heteronuclear multiple bond correlation NMR spectra. Steglich esterification method was used to connect the 3‑(diphenylamino)carbazolyl moiety via an unconjugated spacer. The UV-Vis absorption spectra and molecular energy level data were obtained for the evaluation of the synthesized compounds as donor materials in bulk-heterojunction solar cells.

Abstract: A novel zinc metal organic frameworks, named ZnL(2,2′-bpy), has been successfully synthesized, serving 3,6-dicarboxylic-9-ethylcarbazole acid (H₂L) as ligand. This kind of ZnMOFs was characterized by FI-IR, elemental analysis, SEM, powder X-ray diffraction and single crystal X-ray diffraction to illustrate the structures. TG analysis was applied to investigate the thermostability. Structural analysis demonstrates that ZnMOFs possess triclinic crystal structure which is a 1D chain that occurs distorted-octahedral coordination geometry. Furthermore, the luminescent performance of ZnMOFs is performed and discussed in detail. The results show that ZnMOFs can emit blue luminescence originating, which is assigned to the ligand-to-metal charge transfer (LMCT).

Abstract: Novel D-A type conjugated organic molecules composed of central carbazole and phenothiazine units and aldehyde terminal groups have been designed and constructed. Optical properties of the resulting compounds were examined by the mean of UV-vis and fluorescence spectroscopies. The fluorescence spectra of the molecule C2 based on central carbazole unit show strong emission peaks in the blue light regions, which are expected to be promising light-emitting materials for organic light-emitting diodes applications.

Abstract: A series of bipolar materials for thermally activated delayed fluorescence (TADF) based on carbazole and diphenylsulfone, is synthesized by Ulmann and Suzuki coupling reactions. In these materials, the 3,6-di-tert-butylcarbazole and N-phenylcarbazole group as donors are linked at the 3-, 4-position of diphenyl sulfone. The electronic, photophysical and electrochemical properties of these materials are studied by extensive UV-vis, fluorescence spectroscopic measurements, cyclic voltammetry as well as theoretical calculations. The energy gap between singlet and triplet (△E_ST) in these materials is tuned from 0.99 eV to 0.24 eV by changing the donor units and the positions of substitution.

Abstract: Four novel charged Ir (III) cyclometallates based on 9-phenylcarbazole unit have been developed. By attaching isoquinoline or 5-trifluoromethylpyridine group, the light-emitting properties of the resulting Ir (III) cyclometallates have been improved. Meanwhile, 1,10-phenanthroline or 4,4′-dimethyl-2,2′-bipyridine has been utilized to modify the thermal stability. The four Ir (III) cyclometallates emit yellow light with the highest photoluminescence quantum yields (Φ_P) of 0.32 (C4), which is only less than that of the state-of-art complex fac-tris (2-phenylpyridine) iridium (III) [fac-Ir (ppy)₃], which shows Φ_P of 0.40 under the same condition. This inspiring result reveals that the bulky character of CF₃ group enhances the performance of reported charged Ir (III) cyclometallates and makes them to be potential phosphors in OLED applications.

Abstract: A water-soluble fluorescent probe was described for detecting hydrogen peroxide with the carbazole-derived as fluorophore and boronate moiety as recognition unit. The probe was developed as a turn-off fluorescent chemosensor with fast, high selectivity and sensitivity toward H₂O₂ over other biological reactive oxygen species. What is more, the probe was quenched linear response to H₂O₂ concentration in the range of 1.0×10⁻⁸ - 2.0×10⁻⁵ M and lower detection limit down to 6 nM (S / N = 3) was obtained.

Abstract: In order to understand the effect of β-diketone ligands containing carbazole group on luminescent europium (III) complexes, a series of europium (III) complexes (Phen)Eu (DBM)_3-nL_n with 1-(9-Ethyl-9H-carbazol-3-yl)-4,4,4-trifluorobutane-1,3-dione (L) were synthesized and investigated contrastively (n = 0, 1, 2, 3; DBM: dibenzoylmethane; Phen: 1,10-phenanthroline). The results show amorphous nature, glass transition temperatures and luminescent intensity can be improved obviously by 1-(9-ethyl-9H-carbazol-3-yl)-4,4,4-trifluorobutane-1,3-dione, at the same time, their thermal decomposition temperatures have seldom effected by it. The results verify the performance of europium (III) complexes used as luminescent materials can be effectively improved by the β-diketone ligands of this type.

Abstract: This paper report the synthesis of a crosslink network of Carbazole substituted Poly (dimethylsiloxane). Vinyl Carbazole and Vinyl Trimethoxysilane were introduced into polydimethylsiloxane chain backbone through hydrosilylation reaction. 4-hydroxybutyl acrylate was then grafted into vinyl trimethoxysilane by condensation followed by UV curing to afford an elastomeric crosslink network. FTIR and ¹H NMR spectroscopy were used to confirm the structure of the product as well as monitoring the progress of the reactions. The visual observation shows the changing appearance of the samples with increasing curing time and distance from UV exposure. The materials displayed refractive index between 1.407 1.452 which is within an acceptable range of application as electronic encapsulant. The crosslink network improved material hardness compared to that without. These properties were examined and thoroughly discussed within the scope of Lorentz-Lorenz model.