Carbazole Substituents Research Articles

Open and Closed Cage Silsesquioxane Dimers.

Polyhedral oligomeric silsesquioxane (POSS) is an organic-inorganic hybrid molecule with two structural variations, closed- and open-cage configurations, referred to as completely condensed POSS (CC-POSS) and corner-opened POSS (CO-POSS), respectively. In this study, we synthesized 12 dimers by combining CC- and CO-POSS variants decorated with isobutyl or phenyl substituents to explore their structure-property relationships. The choice of substituents, both at the cage vertices and open sites, significantly affected the thermal and optical properties of the materials. Modifying the substituents on CO- and CC-POSS, which are isomers, led to significant alterations in the material properties. Notably, isomer-bearing carbazole substituents exhibited a substantially higher quantum yield (0.32) than its counterpart isomer (0.13), underscoring the crucial role of structural nuances in determining material performance. These results offer valuable insights for the design of novel silsesquioxane-based materials.

Synthesis and optical properties of tris(2,4,6-trichlorophenyl)methyl-type luminescent radicals bearing multiple carbazole substituents

Abstract Two tris(2,4,6-trichlorophenyl)methyl (TTM)-type luminescent radicals, TTM-(3PCz)2 and TTM-(3PCz)3, bearing 2 and 3 9-phenylcarbazol-3-yl (3PCz) substituents, respectively, were synthesized and characterized. The photobleaching of these radicals was suppressed compared with that of previously reported TTM-type luminescent radicals, suggesting a favorable effect of the multiple electron-donating 3PCz groups on the photostability of the TTM-type radicals.

Enhancing Triplet–Triplet Annihilation Upconversion Performance Through Anthracene–Carbazole Interactions for Organic Optoelectronic Applications

Three carbazole‐substituted anthracene 2CbzAn, 26CbzAn, and 246CbzAn have been developed. The introduction of these carbazole substituents could generate more triplet states with energy levels close to 2× E(T1) that could successfully facilitate the triplet‐triplet annihilation upconversion (TTA‐UC) process to achieve high upconversion quantum yield (UCQY). This observation aligns with the Adachi theory about TTA‐UC mechanisms. In organic light‐emitting diode (OLED) device investigation, in a non‐doped state show an external quantum efficiency (EQEmax) of 5.82% with exceptional pure‐blue emission (CIEy of 0.101), and the DPaNIF doped DMPPP/26CbzAn bilayer structure reaches an impressive EQEmax of 11.12%.

Synthetic Strategies for 3,6-Substituted Carbazole-based Polymers and Their Opto-Electronic Applications-A Review.

The use of conducting polymers in devices makes them desirable due to their allowance for the fabrication of flexible, lightweight, and potentially inexpensive devices. This review explores the synthetic strategies and characterizations of 3,6-substituted carbazole-based polymers, emphasizing the influence of these modifications on their electronic structure and absorption properties. Polymers containing carbazole substituents are widely studied due to their unique optical and electronic properties, high electron-donating ability, and photoconductivity. The structural adaptability of the carbazole with the 3,6-substitution makes it as an outstanding candidate for their integration into polymers and also possesses improved stability and triplet energy. The role of intramolecular charge transfer (ICT) was highlighted by donor-acceptor architectures with tailoring energy levels to extract their advantageous physicochemical characteristics and optimized performances. Collectively, this comprehensive review delves into the burgeoning field of 3,6-substituted carbazole-based polymers and their crucial role in advancing optoelectronic applications. By amalgamating materials design, synthetic strategies, and application-driven insights, the review serves as a valuable resource for researchers to understand the structure-property relationships and foster innovative solutions for next-generation opto-electronic applications.

1,8-diphenyl-carbazole-based boron, sulfur-containing multi-resonance emitters with suppressed aggregation emission for narrowband OLEDs

Multi-resonance emitters are attractive for organic light-emitting diode (OLED) applications because of their narrowband emissions and high photoluminescent efficiencies. Nevertheless, their tendency to aggregation by intermolecular interactions could cause doping sensitivity and reduce color purity at high concentrations. Here, we report a novel boron, sulfur (B, S)-containing multi-resonance emitter (BSS-Ph-TBCz) consisting of 1,8-diphenyl-carbazole substituent at para-position of boron atom of B, S-doped polycyclic aromatic skeleton. Different from control compound (BSS-TBCz) containing conventional carbazole substituents showing aggregation-caused spectral broadening, BSS-Ph-TBCz with 1,8-diphenyl-carbazole group exhibits weak intermolecular aggregation behavior owing to the large twist angle between polycyclic skeleton and carbazole plane caused by two steric phenyl groups on carbazole group, leading to nearly unchanged emissions with small full width at half-maximum of 30–31 nm at doping concentration ranging from 1 to 100 wt%. OLEDs employing BSS-Ph-TBCz as emitter reveal blue electroluminescence at 468 nm and maximum external quantum efficiency of 21.4% at 5 wt% doping concentration, which remains at 20.1% at high doping concentration of 25 wt%.

Rational Multidimensional Shielded Multiple Resonance Emitter Suppresses Concentration Quenching and Spectral Broadening for Solution-Processed Organic Light-Emitting Diodes.

Thermally activated delayed fluorescence (TADF) emitters based on multiple resonance (MR) effects are promising for high-definition organic light-emitting diodes (OLEDs) with narrowband emission and high efficiency. However, they still face the challenges of aggregation-caused quenching (ACQ) and spectral broadening. Solution-processable MR-TADF emitters with an external quantum efficiency (EQE) of >20% and a full width at half-maximum (fwhm) of <30 nm have rarely been reported. To construct ACQ-resistant emitters without sacrificing color purity, the aggregation-induced MR-TADF material 6TBN with a rigid B,N-containing polycyclic aromatic hydrocarbon core and four carbazole substituents as well as 12 tert-butyl groups on the periphery is designed. The multidimensional shielded effect largely limits the ACQ, intermolecular interactions, and spectral broadening. Consequently, solution-processed OLEDs based on 6TBN exhibit a maximum EQE of 23.0% and high color purity with a fwhm of 25 nm. Furthermore, the nondoped device achieves a high efficiency (12.3%) and merely a slight widening of the fwhm to 27 nm. This work provides a feasible strategy to achieve MR-TADF materials with resistance to concentration quenching and high color purity.

Photophysical and electrochemical properties of 9-naphthyl-3,6-diaminocarbazole derivatives and their application as photosensitizers

A series of 3,6-diamino-9-naphthylcarbazole derivatives were synthesized and characterized experimentally and computationally. As the lowest unoccupied molecular orbital of the naphthyl group has lower energy than that of the phenyl group, a charge transfer from carbazole to naphthyl in the excited states occurred causing solvatofluorochromism and solvent-dependency in fluorescence quantum yields. A molecule having two carbazole substituents sandwiching the central naphthyl ring had absorption reaching 470 nm and a high reducing capability in the excited state. This molecule could successfully photosensitize the hydrodehalogenation of haloarenes under visible light irradiation.

Synthesis, photophysical properties and two-photon absorption of benzothiazole/benzoxazole π-expanded carbazole dyes

We report the synthesis and spectroscopic characterization (NMR, HRMS) of a series of benzazole derivatives with different carbazole substituents. The photophysical properties of these molecules were investigated in several solvents of different polarity by UV–vis absorption and fluorescence spectroscopy. These dyes show strong absorption bands in the near ultraviolet region, fluorescence emission with high quantum yields in the blue-green as well as large Stokes' shifts. Two-photon absorption properties were recorded and all of the dyes show moderate TPA cross sections in the 700–800 nm zone. Molecular modeling was also used to explain spectroscopic behavior of these dyes. Interestingly, they possess high thermal stability.

Isomeric thermally activated delayed fluorescence emitters based on a quinolino[3,2,1-de]acridine-5,9-dione multiple resonance core and carbazole substituent

The color purity of the pixels is an essential indicator in organic light-emitting diode (OLED) commercial displays.

Synthesis and Thermal, Photophysical, Electrochemical Properties of 3,3-di[3-Arylcarbazol-9-ylmethyl]oxetane Derivatives.

Novel oxetane-functionalized derivatives were synthesized to find the impact of carbazole substituents, such as 1-naphtyl, 9-ethylcarbazole and 4-(diphenylamino)phenyl, on their thermal, photophysical and electrochemical properties. Additionally, to obtain the optimized ground-state geometry and distribution of the frontier molecular orbital energy levels, density functional theory (DFT) calculations were used. Thermal investigations showed that the obtained compounds are highly thermally stable up to 360 °C, as molecular glasses with glass transition temperatures in the range of 142–165 °C. UV–Vis and photoluminescence studies were performed in solvents of differing in polarity, in the solid state as a thin film on glass substrate, and in powders, and were supported by DFT calculations. They emitted radiation both in solution and in film with photoluminescence quantum yield from 4% to 87%. Cyclic voltammetry measurements revealed that the materials undergo an oxidation process. Next, the synthesized molecules were tested as hole transporting materials (HTM) in perovskite solar cells with the structure FTO/b-TiO2/m-TiO2/perovskite/HTM/Au, and photovoltaic parameters were compared with the reference device without the oxetane derivatives.

Manganese phthalocyanine and its graphene quantum dot conjugate: Synthesis, characterization electrochemistry, spectroelectrochemistry, electropolymerization, and electrochromism

Manganese phthalocyanine (MnPc) bearing peripherally substituted octacarbazole moieties was synthesized and characterized by matrix-assisted laser desorption/ionization spectrometry (MALDI), FT-IR, and UV–Vis spectroscopy. The complex was then conjugated to graphene quantum dots (GQDs) via π-π stacking and characterized by energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), energy dispersive spectroscopy, and X-ray diffraction. Electrochemical performances of MnPc and its nanoconjugate were investigated using cyclic voltammetry (CV), square wave voltammetry (SWV) and spectroelectrochemistry (SEC) to determine the influence of the carbazole substituents and graphene quantum dots on the redox mechanism of MnPc. Although the carbazole substituents did not significantly influence the reduction processes of MnPc, they induced MnPc coating onto the electrode surface due to cationic electropolymerization of the carbazole substituents. The composite comprising graphene quantum dots and MnPc exhibited redox responses that were comparable to those of MnPc.

Multicolor ultralong room-temperature phosphorescence from pure organic emitters by structural isomerism

The current research of ultralong room-temperature phosphorescence (RTP) materials is mainly focused on the lifetimes and efficiencies. The tuning of emission colors is in high demand for various potential applications in optoelectronics, however the corresponding research lags behind. Herein, we report three ultralong RTP molecules based on the carbazole and chromone units through isomerization engineering. By adjusting the linking positions of the carbazole substituents, the ultralong RTP emission can be tuned from blue to red band along with lifetime variation. Detailed experimental and theoretical investigations reveal that the changeable emission color emerges from the mixing of multiple phosphorescence bands and have great relation to the stacking of carbazole and chromone chromophores. These materials were used to construct anti-counterfeiting patterns with diverse afterglow emission colors, presenting a promising application potential in the field of information security.

Maximizing Chiral Perturbation on Thermally Activated Delayed Fluorescence Emitters and Elaboration of the First Top-Emission Circularly Polarized OLED.

Molecular designs merging circularly polarized luminescence (CPL) and thermally activated delayed fluorescence (CP-TADF) using the concept of chiral perturbation appeared recently as a cornerstone for the development of efficient CP-organic light emitting diodes (CP-OLED). Such devices could strongly increase the energy efficiency and performances of conventional OLED displays, in which 50% of the emitted light is often lost due to the use of antiglare filters. In this context, herein, ten couples of enantiomers derived from novel chiral emitter designs are reported, exhibiting CPL, TADF, and aggregation induced enhancement emission properties (AIEE). Representing the first structure properties relationship investigation for CP-TADF materials, this thorough experimental and theoretical work highlights crucial findings on the key structural and electronic parameters (isomerism, nature of the carbazole substituents) governing the synergy between CPL and TADF properties. To conclude this study, the first top emission CP-OLED is elaborated as a new approach of generating CP light in comparison with classical bottom-emission CP-OLED architecture. Indeed, the top-emission configuration represents the only relevant device architecture for future microdisplay applications. Thereby, in addition to offer molecular guidelines to combine efficiently TADF and CPL properties, this study opens new avenues toward practical applications for CP-OLEDs.

Donor-Acceptor Type Pendant Conjugated Molecules Based on a Triazine Center with Depressed Intramolecular Charge Transfer Characteristics as Gain Media for Organic Semiconductor Lasers.

A set of fluorene-capped pendant conjugated molecules (T-m and T-p), which consist of a triazine center with three carbazole substituents as the donor-acceptor (D-A) type pendant structure, were designed, synthesized, and investigated as gain media for organic semiconductor lasers (OSLs). In particular, varying the capping positions of the fluorene units on the pendant core structures results in significantly different intramolecular charge transfer (ICT) properties, where T-m manifested depressed ICT characteristic and high fluorescence quantum yield. The lowest amplified spontaneous emission (ASE) threshold in neat films was recorded as 1.9 μJ cm-2 for T-m and 83.8 μJ cm-2 for T-p, which indicated that the depressed ICT characteristics in the case of T-m help to enhance the ASE properties. Remarkably, the ASE threshold remained almost unchanged and the ASE spectra showed very small shifts (within 1 nm) for T-m with film samples annealed up to 180 °C in open air. In contrast, its linear counterpart 2FEtCz-m showed a clearly increased ASE threshold upon annealing above 100 °C. The results suggest that the selective construction of conjugated pendant molecules with depressed ICT characteristics is beneficial for finely modulating the optical and electrical properties as well as improving the thermostability and photostability, which manifests the great potential as a robust gain media for OSLs.

Stereoregularity effect on hole mobility in poly(N-vinylcarbazole) thin film evaluated by MIS-CELIV method

The stereoregularity effect on carrier mobility of stereoregular poly(N-vinylcarbazole) (PVK) was studied using metal–insulator–semiconductor charge extraction by the linearly increasing voltage technique. The hole mobility of stereoregular PVK thin film was dependent upon the stereoregularity (mm) and was enhanced to be 4.02 × 10−6 cm2 V−1 s−1 at mm = 94%, which was 4.8 times higher than that at mm = 50%. Furthermore, the activation energy depending on the stereoregularity of PVK was evaluated to be from 118 meV (mm = 50%) to 111 meV (mm = 94%) in faint variation. The enhanced carrier transport in the stereoregular PVK thin film was discussed by taking the stereoregularity involved with the intramolecular interaction through the carbazole substituents into consideration.

Fluorene vs carbazole substituent at quinoline core toward organic electronics

Two novel 2,4-difluorenylquinoline derivatives with different length of alkyl chain at fluorene unit (Q-F1 with methyl and Q-F2 with octyl chain) of donor-acceptor (D-A) type were synthesized and comprehensively characterized. The compounds exhibited bright emission in the blue spectral region at 400 nm and high fluorescence efficiency of 63–97% in solution. The EL measurements of OLEDs with Q-F1, and for comparison 2,4-dicarbazolylquinoline (Q-C1) were performed to determine any correlations between the device performance and the different D units at quinoline core. These fluorenyl and carbazolyl substituted quinolines (Q-F1 and Q-C1) were found to display good thermal stability with a decomposition temperature of 301 and 416 °C, respectively. A molecule with carbazole units (Q-C1) dispersed in a host matrix exhibited higher PL quantum yield (15%) compared to Q-F1 (11%). The devices with structure ITO/PDOT:PSS/PVK:PBD:compound/Al with 15 (Q-F1) and 2 (Q-C1) wt. % of compound content in a blend were constructed. The diode based on Q-C1 emitted green light with EL maximum at 550 nm under an applied external voltage. Furthermore, by incorporation of a layer of plasmonically active silver nanowires into the device based on Q-C1 (ITO/PEDOT:PSS + AgNWs/PVK:PBD:Q-C1 (2 wt%)/Al) the noticeably more intense EL signal was detected. These results show that these compounds are promising candidates and may be used in organic light emitting devices.

Eu3+ ternary and tetrakis complexes with carbazole and methyl group substituted dibenzoylmethane derivatives: Induction of aggregation enhanced emission

Two dibenzoylmethane (DBM) derivatives with methyl (Me-DBM) or carbazole (CBZ-DBM) substituents at the para-position of the phenyl ring and their four novel ternary and tetrakis Eu3+ complexes with 1,10-phenanthroline (PHEN) as a secondary ligand or tetraethylamonium ion (N+(Et)4) as the counter-cation were synthesized and characterized. The investigation of the optical properties of the complexes revealed that Me-DBM based compounds exhibit aggregation enhanced emission (AEE), while in the case of CBZ-DBM this effect is not observed. At the same time, the introduction of a carbazole substituent reduces the emission quantum yield of the complexes. The decrease in luminescence efficiency for CBZ-DBM based Eu3+ complexes is mainly attributed to the closely situated S1 and T1 energy levels of the ligand that obstruct the intersystem crossing process.

Heteroleptic copper(I) photosensitizers with carbazole-substituted phenanthroline ligands: Synthesis, photophysical properties and application to photocatalytic H2 generation

A series of novel 4,7-dicarbazol-1,10-phenanthroline bidentate N-ligands have been designed and synthesized, and applied in heteroleptic copper complexes [Cu(PˆP)(NˆN)]+ as photosensitizers (PS) for light-driven water reduction. In combination with a water reduction catalyst (WRC), Fe3CO12, photocatalytic performances up to 1036 turnover numbers (TON) were reached. This excellent performance can be attributed to the introduction of carbazole groups to the phenanthroline backbone, which can increase the fluorescence quantum yield, decrease the reduction potential of the copper complexes and switch the excited state quenching mechanism from reductive to oxidative. By means of DFT calculations, it has been established that the carbazole substituent contributes most significantly to the HOMO of these complexes.

Novel low color poly(ester imides) with triphenylamine and carbazole substituents for electrochromic applications

A series of novel poly(ester imides) (PEIs, individually denoted as VIIa–VIIe) with triphenylamine and carbazole substituents were prepared herein by direct polymerization of 4, 4′-bis(trimellitimido)-4″-N-carbazolytriphenylamine (V) with various bisphenols (VIa–VIe). All of the PEIs exhibit good solubility in various organic solvents, high glass transition temperatures (Tgs, 245–276 °C) and excellent thermal stability (with only 5% weight loss observed at 478–504 °C under nitrogen protection). The PEI-based films have excellent optical transparency 71–83%, 91–95%, and 94–97% at 450, 550, and 800 nm, and they are paler in color than poly(amine-imide) (PAI) films in the neutral state while also exhibiting better optical transparency. Cyclic voltammetry measurements reveal that the films exhibit two reversible oxidation redox couples at 1.06–1.12 and 1.44–1.79 V under an anodic sweep. Oxidation of the PEI-VIIa film results in the formation of radical cations with outstanding stability, and yields excellent electrochromic properties. In particular, the color of this film changes from pale yellow in the neutral form to green and then to dark blue in the oxidized form. In addition, the anodic coloring of PEI-VIIa displays a high coloration efficiency (CE = 191 cm2/C), dramatic change in optical transmittance (△T = 82% at 760 nm) and long-term redox reversibility.

New push–pull system based on 4,5,6-tri(het)arylpyrimidine containing carbazole substituents: synthesis and sensitivity toward nitroaromatic compounds

A sequence of microwave-assisted Suzuki cross-coupling reaction and bromination with N-bromosuccinimide was used for the synthesis of 3,3'-(5,5'-{5-[5-(9-ethyl-9H-carbazol-3-yl)-3-hexylthiophen-2-yl]pyrimidine-4,6-diyl}bis(thiophene-5,2-diyl))bis(9-ethyl-9H-carbazole). The obtained compound was characterized with regard to its optical properties, as well as possible applications in sensors for nitroaromatic compounds in acetonitrile solutions and in vapor phase.