Synthesis, Physical Properties, and Light-Emitting Diode Performance of Phenazine-Based Derivatives with Three, Five, and Nine Fused Six-Membered Rings

Synthesis and luminescent properties of a linear difluorene pyrazine (D-A-D) derivative as a selective indicator for a reversible acid-base vapour sensor

We have synthesized a structure in which pyrazine is the core structure and fluorene derivatives are attached to both sides. Photo physical investigations such as aprotic solvents (Hexane to DMF) were carried out. A redshift was revealed from non-polar aprotic solvents to polar aprotic solvents. The luminescence intensity was gradually decreased, which is incredibly more complex towards changes in the solvent polarization than their UV/Vis absorption spectra. The compound showed a redshift from 445 nm to 473 nm when slowly increasing the water fraction (fw) from 0 to 30 %. Also, rising water fraction (fw > 40-90 %) effectively attenuated the instantaneous emission intensity was observed. At the same time, the intensity of the emission peak was reduced due to the TICT effect on fluorene and pyrazine rings due to enhanced solvent polarity. In addition, optically reversible acidofluorochromic properties were performed experimentally in both solvent and solid phases. For the acidic substances TFA and HF, which contain fluorine, new redshift peaks from 425 nm and 503 nm were observed upon reaction with the PDF solution, and the emission intensity was extinguished by more than 90 % and 60 %, respectively. Upon addition of TFA up to 1500 equal, the PDF mixture suffered from 50 % lower energy absorption intensity. The 1H NMR spectrum confirmed the proposed mechanism (TFA/TEA, ON-OFF-ON). Therefore, the present work presents a novel approach to fabricating ON-OFF-ON active-pull pyrazine scaffolds that can be used in DSEgens, referred to as "ON-OFF-ON" fluorescent sensors, for multifunctional applications.

Covalent Organic Frameworks for Photocatalytic Reduction of Carbon Dioxide: A Review

Covalent organic frameworks (COFs) are crystalline networks with extended backbones cross-linked by covalent bonds. Due to the semiconductive properties and variable metal coordinating sites, along with the rapid development in linkage chemistry, the utilization of COFs in photocatalytic CO2RR has attracted many scientists' interests. In this Review, we summarize the latest research progress on variable COFs for photocatalytic CO2 reduction. In the first part, we present the development of COF linkages that have been used in CO2RR, and we discuss four mechanisms including COFs as intrinsic photocatalysts, COFs with photosensitive motifs as photocatalysts, metalated COF photocatalysts, and COFs with semiconductors as heterojunction photocatalysts. Then, we summarize the principles of structural designs including functional building units and stacking mode exchange. Finally, the outlook and challenges have been provided. This Review is intended to give some guidance on the design and synthesis of diverse COFs with different linkages, various structures, and divergent stacking modes for the efficient photoreduction of CO2.

Recent synthetic strategies of small heterocyclic organic molecules with optoelectronic applications: a review

Over the past few years, there have been tremendous developments in the design and synthesis of organic optoelectronic materials with appealing applications in device fabrication of organic light-emitting diodes, superconductors, organic lasers, organic field-effect transistors, clean energy-producing organic solar cells, etc. There is an increasing demand for the synthesis of green, highly efficient organic optoelectronic materials to cope with the issue of efficiency roll-off in organic semiconductor-based devices. This review systematically summarized the recent progress in the design and synthesis of small organic molecules having promising optoelectronic properties for their potential applications in optoelectronic devices during the last 10-year range (2010-early 2021).

Management of triplet excitons transition: fine regulation of Förster and dexter energy transfer simultaneously

Understanding and management of triplet excitons transition in the same molecule remain a great challenge. Hence, for the first time, by host engineering, manageable transitions of triplet excitons in a naphthalimide derivative NDOH were achieved, and monitored through the intensity ratio (ITADF/IRTP) between thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP). Energy differences between lowest triplet excited states of host and guest were changed from 0.03 to 0.17 eV, and ITADF/IRTP of NDOH decreased by 200 times, thus red shifting the afterglow color. It was proposed that shorter conjugation length led to larger band gaps of host materials, thus contributing to efficient Dexter and inefficient Förster energy transfer. Interestingly, no transition to singlet state and only strongest RTP with quantum yield of 13.9% could be observed, when PBNC with loosest stacking and largest band gap acted as host. This work provides novel insight for the management and prediction of triplet exciton transitions and the development of smart afterglow materials.

Sulfone/Carbonyl-Based Donor-Acceptor Fluorescent Dyes: Synthesis, Structures, Photophysical Properties and Cell Imaging

Electron-accepting units play vital roles in constructing donor-acceptor (D-A) conjugated organic optoelectronic materials; the electronic structures and functions of the acceptors need to be carefully unveiled to controllably tailor the optoelectronic properties. We have synthesized two D-A conjugated organic fluorophores, TPA-SO and TPA-CO, with similar molecular skeletons based on sulfone- or carbonyl-containing polycyclic aromatic acceptors. Both TPA-SO and TPA-CO display obvious solvent polarity-dependent photophysical properties and large Stokes shift of over 100 nm for strong intramolecular charge transfer processes. Experimental evidence indicates that the sulfone group in TPA-SO merely serves as a strong electron-withdrawing unit. TPA-SO shows yellowish-green emission with a peak at 542 nm and an absolute photoluminescence quantum yield (PLQY) of 98 % in solution, whereas the carbonyl group in TPA-CO can act as both an electron-withdrawing unit and spin transition convertor, so TPA-CO displays red emission with a low absolute PLQY of 0.32 % in solution. Impressively, upon going from solution to aggregate state, TPA-SO nanoparticles keep a high PLQY of 9.5 % and moderate biocompatibility, thus they are good nano-agents for cellular fluorescence imaging. The results reveal that the inherent acceptor characteristic acts as a crucial effect in the photophysical properties and applications of the organic fluorophores.

Synthesis and Photophysical, Electrochemical, and DFT Studies of Piperidyl and Pyrrolidinyl Chalcones

Small organic molecules with interesting optical and electrochemical properties find applications as organic luminescent materials. In this work, we report the synthesis of novel chalcones with D-A-D and D-A-D-A architecture, followed by their optical, electrochemical, and computational studies. The absorption band of these compounds occurs at 360-480 nm with emission maxima appearing around 513-552 nm. The large Stokes shifts (Δλ) for all compounds (90-132 nm) suggest intramolecular charge transfer (ICT) in the excited states. The molar absorptivity and fluorescence quantum yields were found to be in the range of 1.7-4.26 × 104 M-1 cm-1 and 0.29-0.39, respectively. The electrochemical parameters were determined by using cyclic voltammetry (CV). Density functional theory (DFT) calculations of all compounds were made by using B3LYP/G (d,p) functionals in chloroform and were found to have a good correlation with experimental results. Preliminary studies of absorption, photoluminescence, CV, and their theoretical correlation suggest that these compounds may be optimized for their applications in optoelectronics, sensing, and bioimaging.

Highly emissions of TPA-linear based pyrazine derivatives with different mechanochromic luminosity

We designed the TPA-based linear pyrazine derivatives of PP-1 and PP-2, synthesized using the conventional Suzuki cross-linking reaction. It was followed by photophysical studies such as aprotic solvent (Haxene to DMF). A red-shift was observed from the non-polar aprotic solvent to the polar aprotic solvent, and the emission intensity was gradually decreased. In addition, the Aggregation-induced emission (AIE) effect has been studied against the DMF/water addition of linear pyrazine compounds. It showed a classic aggregation-caused quenching effect (ACQ) and red-shifted at an increase of (f_w) 0 to 40%. After this case, when the water fraction in these studies was increased by (fw) 50 to 90%, a blue shift and a mild AIE effect has occurred. And also, was investigated acidochromic effect of compounds PP-1 and PP-2 using TFA acid. Absorption and emission intensity were gradually reduced as the acid concentration increased for these studies, while the new peaks appeared red-shifted in the absorption spectrum. They were examined before and after exposure to UV light irradiation in the synthesized dye compounds.

Functionalization at Nonperipheral Positions of Triazatruxene: Modular Construction of 1,6,11-Triarylated-Triazatruxenes for Potentially Organic Electronics and Optoelectronics

Functionalization from nonperipheral positions of triazatruxene is representing a challenge. Triarylation of the nonperipheral positions (1, 6, and 11) in triazatruxene scaffold has been achieved for the first time via two approaches. The transformations involve arylation/cyclotrimerization and cyclotrimerization/arylation sequences. POCl₃-mediated direct cyclotrimerization of oxindoles containing electron-deficient substituents on the aryl group at the C7-position resulted in the formation of 2-chloroindoles, whereas oxindoles containing electron-donating substituents gave the triazatruxenes. Furthermore, desired triazatruxenes were achieved through cyclotrimerization of 7-bromooxindole followed by coupling with arylboronic acids. NMR structural analysis exhibited that two of the suitably substituted oxindole and triazatuxene may have atropisomerism at room temperature. As a representative triazatruxene scaffold, the optoelectronic properties of 9a have also been studied via ultraviolet-visible (UV-vis) absorption spectra and fluorescence spectra of 9a thin films. Also, density functional theory calculation was realized to get knowledge about frontier molecular orbitals. In the light of the information obtained, an organic light-emitting diode (OLED) device utilizing 9a as an emissive layer was applied to obtain white emission. In brief, this study provides the first examples of the synthesis of triazatruxenes bearing aryl substituents at the nonperipheral positions as candidate compounds for organic electronics, optoelectronics, and material chemistry.

Advances in Phenazines over the Past Decade: Review of Their Pharmacological Activities, Mechanisms of Action, Biosynthetic Pathways and Synthetic Strategies

Phenazines are a large group of nitrogen-containing heterocycles, providing diverse chemical structures and various biological activities. Natural phenazines are mainly isolated from marine and terrestrial microorganisms. So far, more than 100 different natural compounds and over 6000 synthetic derivatives have been found and investigated. Many phenazines show great pharmacological activity in various fields, such as antimicrobial, antiparasitic, neuroprotective, insecticidal, anti-inflammatory and anticancer activity. Researchers continued to investigate these compounds and hope to develop them as medicines. Cimmino et al. published a significant review about anticancer activity of phenazines, containing articles from 2000 to 2011. Here, we mainly summarize articles from 2012 to 2021. According to sources of compounds, phenazines were categorized into natural phenazines and synthetic phenazine derivatives in this review. Their pharmacological activities, mechanisms of action, biosynthetic pathways and synthetic strategies were summarized. These may provide guidance for the investigation on phenazines in the future.

Azaacenes Based Electroactive Materials: Preparation, Structure, Electrochemistry, Spectroscopy and Applications-A Critical Review

This short critical review is devoted to the synthesis and functionalization of various types of azaacenes, organic semiconducting compounds which can be considered as promising materials for the fabrication of n-channel or ambipolar field effect transistors (FETs), components of active layers in light emitting diodes (LEDs), components of organic memory devices and others. Emphasis is put on the diversity of azaacenes preparation methods and the possibility of tuning their redox and spectroscopic properties by changing the C/N ratio, modifying the nitrogen atoms distribution mode, functionalization with electroaccepting or electrodonating groups and changing their molecular shape. Processability, structural features and degradation pathways of these compounds are also discussed. A unique feature of this review concerns the listed redox potentials of all discussed compounds which were normalized vs. Fc/Fc⁺. This required, in frequent cases, recalculation of the originally reported data in which these potentials were determined against different types of reference electrodes. The same applied to all reported electron affinities (EAs). EA values calculated using different methods were recalculated by applying the method of Sworakowski and co-workers (Org. Electron. 2016, 33, 300-310) to yield, for the first time, a set of normalized data, which could be directly compared.

Anthrathiadiazole Derivatives: Synthesis, Physical Properties and Two-photon Absorption

Anthrathiadiazole is a key synthon for the construction of large azaacenes, however, the attachment of different substituents onto the skeleton of anthrathiadiazole is difficult but highly desirable because it could be easy to enrich the structures of azaacenes. Here, it is demonstrated that anthrathiadiazole derivatives with -Br, -CN, and -OCH₃ groups could be easily constructed through a simple [4+2] cycloaddition reaction between a,a,a',a'-tetrabromo-o-xylenes derivatives and benzo[c][1,2,5]thiadiazole-4,7-dione. The structures of the as-prepared compounds with different substituents were carefully characterized. Moreover, the basic physical properties of the as-prepared anthrathiadiazole derivatives were fully investigated, where the cyano-substituted derivative (BTH-CN) has the highest stability and the methoxy-substituted derivative (BTH-OCH₃ ) is easy to be oxidized. Moreover, the two-photon absorption (TPA) characteristics of different anthrathiadiazoles are also studied by using the femtosecond Z-scan technique. The results show that the fused anthrathiadiazole skeletons possess large TPA cross-section values δ₂ in the range of 3000-5000 GM, where the nature, position and strength of the substituted groups have strong effect on these values.

Supramolecular complex strategy for pure organic multi-color luminescent materials and stimuli-responsive luminescence switching

Pure organic multi-color luminescent materials were finely tuned from blue through green to red using a supramolecular complex strategy, exhibiting force- and solvent-sensitive luminescence switching in the stimuli-responsive field.

Recent Progress in Polycyclic Aromatic Hydrocarbon-Based Organic Co-Crystals

Recently, the development of polycyclic aromatic hydrocarbon (PAH)-based organic co-crystals has attracted increasing interest due to their unique packing modes, optic-electronic properties and various potential applications in electronic, optic-electronic and magnetic devices. In this account, we mainly discuss the definition, classification, packing patterns, preparation methods, and applications of PAH-based co-crystals. Specifically, the main categories of PAH-based organic co-crystals, the frequent methods to prepare them, three main packing patterns, their optical and electrical properties, and their potential applications will be presented. Finally, an outlook of this field is provided.

Recent Progress in High Linearly Fused Polycyclic Conjugated Hydrocarbons (PCHs, n > 6) with Well-Defined Structures

Although polycyclic conjugated hydrocarbons (PCHs) and their analogues have gained great progress in the fields of organic photoelectronic materials, the in-depth study on present PCHs is still limited to hexacene or below because longer PCHs are insoluble, unstable, and tediously synthesized. Very recently, various strategies including on-surface synthesis are developed to address these issues and many higher novel PCHs are constructed. Therefore, it is necessary to review these advances. Here, the recent synthetic approach, basic physicochemical properties, single-crystal packing behaviors, and potential applications of the linearly fused PCHs (higher than hexacene), including acenes or π-extended acenes with fused six-membered benzenoid rings and other four-membered, five-membered or even seven-membered and eight-membered fused compounds, are summarized.

Utilizing Electroplex Emission to Achieve External Quantum Efficiency up to 18.1% in Nondoped Blue OLED

For the first time, electroplex emission is utilized to enhance the performance of nondoped blue organic light-emitting diodes (OLEDs). By decorating the twisted blue-emitting platform and adjusting the electronic structure, three molecules of 3Cz-Ph-CN, 3Cz-mPh-CN, and 3Ph-Cz-CN with a donor-acceptor structure are synthesized and investigated. When external voltage is applied, electroplex emission, which contributes to the emission performance of OLED, can be realized at the interface between the emitting layer and the electron-transporting layer. Accordingly, high external quantum efficiency of 18.1% can be achieved, while the emission wavelength of the device can be controlled in the blue region. Our results provide the possibility to enhance the performance of OLED through electroplex emission, in addition to the generally investigated thermally activated delayed fluorescence (TADF). Excitedly, when 3Ph-Cz-CN is used as host material in orange-emitting phosphorous OLEDs (PO-01 as the dopant), unprecedented high external quantum efficiency of 27.4% can also be achieved.

Synthesis of Anthracene Derivatives with Azaacene-Containing Iptycene Wings and the Utilization as a Dopant for Solution-Processed Organic Light-Emitting Diodes

Substituted acene derivatives are regarded as promising materials for organic electronic devices such as organic light-emitting diodes (OLEDs). In particular, anthracene derivatives are known to exhibit good fluorescence property, with the air stability and solubility in common organic solvents expected to give advantages for solution-processed device fabrication. In this study, a series of bistriisopropylsilyl(TIPS)ethynyl anthracene derivatives with azaacene-containing iptycene wings have been synthesized by using condensation reactions. Effects of size of azaacenes on optical properties and packing structures were investigated. UV/Vis absorption and fluorescence spectra indicate that the π-elongation of iptycene units has small effects on the overall π-system, which is also supported by electrochemical measurements. Secondly, single-crystal X-ray analysis implies that the molecules likely have interactions with the iptycene units of adjacent molecules, while the iptycene wings and TIPSethynyl groups can prevent the central anthracene unit from undesirable non-radiative energy loss. Finally, the most emissive derivative was used as a dopant for solution-processed OLEDs, showing obvious electroluminescence with a luminance of over 920 cd m^-2 .

Sulfur-Containing Bent N-Heteroacenes

A series of novel sulfur-containing bent N-heteroacenes were constructed and characterized by NMR and UV/Vis spectroscopy, cyclic voltammetry, and single-crystal X-ray diffraction. By introducing sulfur-containing groups (thio, sulfinyl, and sulfonyl) into bent azaacenes, their electronic delocalization was improved and frontier energy levels were modulated. The target products displayed tunable optical and electronic properties through altering the valence of sulfur and fused length of the azaacenes. For the first time, typical products were utilized as organic field effect transistor materials, affording promising results.

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

The synthesis and properties of 1,2,3,4-tetrahydro-1,4,5,8-tetraazaanthracene (THTAA) – a heterocycle involving both >N–H donating and =N– accepting moieties – have been reinvestigated. Unlike previously reported, THTAA is a thermally stable compound that can be re-sublimed at 300–310 °C without decomposition. Controlled introduction of substituents at the nitrogen atoms of THTAA led to variation of its electron donor/acceptor capability that allowed fine-tuning the absorption properties. The propensity of these compounds and a number of its derivatives to form infinite chains involving >N–H···N= and >N–H···Hal⁻···N⁺ atoms is demonstrated by X-ray structure analysis. The DFT level optimized and experimental geometry of THTAA and its derivatives show considerable loss of aromaticity within the quinoxaline moiety.

Recent Progress in Organic Electron Transport Materials in Inverted Perovskite Solar Cells

Organic n-type materials (e.g., fullerene derivatives, naphthalene diimides (NDIs), perylene diimides (PDIs), azaacene-based molecules, and n-type conjugated polymers) are demonstrated as promising electron transport layers (ETLs) in inverted perovskite solar cells (p-i-n PSCs), because these materials have several advantages such as easy synthesis and purification, tunable frontier molecular orbitals, decent electron mobility, low cost, good solubility in different organic solvents, and reasonable chemical/thermal stability. Considering these positive factors, approaches toward achieving effective p-i-n PSCs with these organic materials as ETLs are highlighted in this Review. Moreover, organic structures, electron transport properties, working function of electrodes caused by ETLs, and key relevant parameters (PCE and stability) of p-i-n PSCs are presented. Hopefully, this Review will provide fundamental guidance for future development of new organic n-type materials as ETLs for more efficient p-i-n PSCs.

Crystal structure and optical properties of fused-ring chalcone (E)-3-(anthracen-9-yl)-1-(4-nitro-phen-yl)prop-2-en-1-one

The title compound, C23H15NO3, adopts an s-cis conformation with respect to the ethyl-ene C=C and carbonyl C=O double bonds in the enone unit. The mol-ecule is significantly twisted with a dihedral angle of 48.63 (14)° between the anthracene ring system and the benzene ring. In the crystal, mol-ecules are linked into inversion dimers with an R 2 2(10) graph-set motif via pairs of C-H⋯O hydrogen bonds. The inter-molecular inter-actions were analysed and qu-anti-fied by Hirshfeld surface analysis. The mol-ecular structure was optimized and a small HOMO-LUMO energy gap of 2.55 eV was obtained using the DFT method at the B3LYP/6-311 G++(d,p) level of theory. This value is in close agreement with the experimental value of 2.52 eV obtained from the UV-vis analysis. The crystal used was a two-component merohedral twin with a refined ratio of 0.1996 (16):0.8004 (16).

Highly Selective and Sensitive Turn-Off-On Fluorescent Probes for Sensing Al3+ Ions Designed by Regulating the Excited-State Intramolecular Proton Transfer Process in Metal-Organic Frameworks

The concept of high-performance excited-state intramolecular proton transfer (ESIPT)-based fluorescent metal-organic framework (MOF) probes for Al³⁺ is proposed in this work. By regulating the hydroxyl groups on the organic linker step by step, new fluorescent magnesium-organic framework (Mg-MOF) probes for Al³⁺ ions were established based on the ESIPT fluorescence mechanism. It is observed for the first time that the number of intramolecular hydrogen bonds between adjacent hydroxyl and carboxyl groups can effectively adjust the ESIPT process and lead to tunable fluorescence sensing performance. Together with the well-designed porous and anionic framework, the Mg-TPP-DHBDC probe decorating with a pair of intramolecular hydrogen bonds exhibits extra-high quantitative fluorescence response to Al³⁺ through an unusual turn-off (0-1.2 μM) and turn-on (4.2-15 μM) luminescence sensing mechanism. Notably, the 28 nM limit of detection value represents the lowest record among all reported MOF-based Al³⁺ fluorescent sensors up to now. Benefited from the unique turn-off-on ESIPT fluorescence detection process, the Mg-TPP-DHBDC MOF sensor exhibits single Al³⁺ detection compared with other 16 common metal ions including Ga³⁺, In³⁺, Fe³⁺, Cr³⁺, Ca²⁺, and Mg²⁺. Impressively, such an Al³⁺ selective sensing process can even be fulfilled by the reusable MOF test paper detected by naked eyes. Overall, the quantitative Al³⁺ detection, together with the extraordinary sensitivity, selectivity, fast response, and good reusability, strongly supports our concept of ESIPT-based fluorescent MOF Al³⁺ probes and makes Mg-TPP-DHBDC one of the most powerful Al³⁺ fluorescent sensors.

Polycyclic Aromatic Hydrocarbons Containing A Pyrrolopyridazine Core

Polycyclic aromatic azomethine ylides (PAMYs) are versatile building blocks for the bottom-up construction of unprecedented nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs). Here, we demonstrate the 1,3-dipolar cycloaddition between PAMY and 1,4-diphenylbut-2-yne-1,4-dione and the subsequent condensation reaction with hydrazine, which led to unique N-PAHs with a phenyl-substituted pyrrolopyridazine core (PP-1 and PP-2). The molecular structures of pristine PP-1 and tert-butyl-substituted PP-2 were verified by NMR spectroscopy and mass spectrometry. Moreover, the structure of PP-2 was unambiguously elucidated by X-ray single crystal analysis. The optoelectronic properties were investigated by solvent-dependent UV-Vis absorption and fluorescence emission spectroscopy as well as cyclic voltammetry. Additionally, density functional theory (DFT) calculations showed that PP-1 and PP-2 exhibit push-pull behavior. Furthermore, in situ EPR/UV-Vis-NIR spectroelectrochemistry allowed the detailed insight into the spectroscopic properties and spin distribution of radical cation species of PP-2.

Strongly Coupled Phenazine-Porphyrin Dyads: Light-Harvesting Molecular Assemblies with Broad Absorption Coverage

The development of light-harvesting architectures with broad absorption coverage in the visible region continues to be an important research area in the field of artificial photosynthesis. Here, we introduce a new class of ethynyl-linked panchromatic dyads composed of dibenzophenazines coupled ortho and meta to tetrapyrroles with an anchoring group that can be grafted onto metal oxide surfaces. Quantum chemical calculations and photophysical measurements of the synthesized materials reveal that both of the dibenzophenazine dyads absorb broadly from 300 to 636 nm and exhibit absorption bands different from those of the constituent chromophore units. Moreover, the different points of attachment of dibenzophenazines to tetrapyrroles give different absorption profiles which computations suggest result from differences in the planarity of the two dyads. Applicability of the dyads in artificial photosynthesis systems was assessed by their incorporation and characterization of their performance in dye-sensitized solar cells.

Predicting the Outcome of Photocyclisation Reactions: A Joint Experimental and Computational Investigation

Photochemical oxidative cyclodehydrogenation reactions are a versatile class of aromatic ring-forming reactions. They are tolerant to functional group substitution and heteroatom inclusion, so can be used to form a diverse range of extended polyaromatic systems by fusing existing ring substituents. However, despite their undoubted synthetic utility, there are no existing models-computational or heuristic-that predict the outcome of photocyclisation reactions across all possible classes of reactants. This can be traced back to the fact that "negative" results are rarely published in the synthetic literature and the lack of a general conceptual framework for understanding how photoexcitation affects reactivity. In this work, we address both of these issues. We present experimental data for a series of aromatically substituted pyrroles and indoles, and show that quantifying induced atomic forces upon photoexcitation provides a powerful predictive model for determining whether a given reactant will photoplanarise and hence proceed to photocyclised product under appropriate reaction conditions. The propensity of a molecule to photoplanarise is related to localised changes in charge distribution around the putative forming ring upon photoexcitation. This is promoted by asymmetry in molecular structures and/or charge distributions, inclusion of heteroatoms and ethylene bridging and well-separated or isolated photocyclisation sites.

Synthesis and Electronic Properties of Novel 5,7-Diazapentacene Derivatives

A route to the synthesis of novel 5,7-diazapentacenes and some preliminary studies on their properties is reported. A single crystal X-ray diffraction study of the dihexyl derivative showed it had formed a dimer during the analysis. The materials possess lower lying frontier orbitals than pentacene and may have potential applications in organic electronic devices. This synthetic method may be applicable to the synthesis of other azaacenes.

Strategic tuning of excited-state properties of electroluminescent materials with enhanced hot exciton mixing

Deep blue emitters with excellent stability, high quantum yield and multifunctionality are the major issues for full-color displays. In line with this, new multifunctional, thermally stable blue emitters viz., N-(4-(10-(1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-1H-phenanthro[9,10-d]imidazol-2-yl)anthracen-9-yl)phenyl)-N-phenylbenzenamine (DPIAPPB) and 2-(10-(9H-carbazol-9-yl)anthracen-9-yl)-1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-1H-phenanthro[9,10-d]imidazole (CADPPI) with hybridized local charge transfer state (HLCT) and hot exciton properties have been synthesized. These molecules show high photoluminescence quantum yield (Φ_s/f): (DPIAPPB – 0.82/0.70 and CADPPI – 0.91/0.83). The CADPPI based device (EL – 467 nm) shows high efficiencies [η_c – 9.85 cd A⁻¹; η_p – 10.84 lm W⁻¹; η_ex – 4.78% at 2.8 V; CIE (0.15, 0.10)] compared to the DPIAPPB device (EL − 472 nm) [η_c – 6.56 cd A⁻¹; η_p – 6.16 lm W⁻¹; η_ex – 4.15% at 2.8 V with CIE (0.15, 0.12)]. The green device with CADPPI:Ir(ppy)₃ exhibits a maximum L – 59 012 cd m⁻²; η_ex – 16.8%; η_c – 37.3 cd A⁻¹; η_p – 39.8 lm W⁻¹ with CIE (0.30, 0.60) and the red device with CADPPI:Ir(MDQ)₂(acac) shows a maximum L – 43 456 cd m⁻²; η_ex – 21.9%; η_c – 36.0 cd A⁻¹; η_p – 39.6 lm W⁻¹ with CIE (0.64, 0.35).

The CADPPI:Ir(ppy)₃ device exhibits L – 90 12 cd m⁻²; η_ex – 18.8%; η_c − 27.3 cd A⁻¹; η_p – 29.8 lm W⁻¹; CIE (0.30, 0.60).

Helical Ullazine-Quinoxaline-Based Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic azomethine ylides (PAMYs) are powerful building blocks in the bottom-up synthesis of internally nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs) through 1,3-cycloaddition reactions. In this work, the cycloaddition reaction of PAMYs to asymmetric ortho-quinones is presented, which, in contrast to the addition to symmetric para-quinones, facilitates subsequent condensation reactions and allows the synthesis of three helical N-PAHs with ullazine-quinoxaline (UQ-1-3) backbones. UQ-1 and UQ-2 possess two helical centers; however, single-crystal X-ray analysis together with the computational modeling of UQ-3 elucidate the formation of only the thermodynamically most stable geometry with four helical centers in a (P,P,M,M) configuration. For the series UQ-1-3, the number of redox steps is directly correlated with the number of ullazine or quinoxaline units incorporated into the targeted molecular backbones. A detailed investigation of the spectroscopic and magnetic properties of the radical cation and anion as well as the dication and dianion species by in situ EPR/UV/Vis-NIR spectroelectrochemistry is provided. The excellent optical and redox properties combined with helical geometries render them possibly applicable as chiral emitter or ambipolar charge transport material in organic electronics.

UV-light intervened synthesis of imidazo fused quinazoline and its solvatochromism, antioxidant, antifungal and luminescence properties

The photochemical preparation of benzo[4,5]imidazo[2,1-b]quinazoline was assessed under the illumination of UV wavelength (>360 nm). The compound 3,4-dihydronaphthalen-1(2H)-one 1 with 1H-benzo[d]imidazol-2-amine 2 in the existence of KOH/DMF which lead to the aromatized compound 3. The notable remark of this reaction is that the UV irradiation (312 nm) plays a vital part in the formation of compound, 3 in shorter duration (2 h) which resulted in higher yield of 96%. Compound 3 was analyzed by H¹, C¹³ NMR, and HRMS. Solvatochromism impacts of the compound 3 was computed with different solvents (DCM < methanol< DMF < DMSO). The compound, 3 was presented to in-vitro free radical screening strategy. The standard ascorbic acid has less IC₅₀ value - than compound 3. Further, it was subjected to in-vitro fungicidal action against two Aspergillus species (A. flavus & niger). The anti-fungal activity of compound 3 additionally demonstrated great action, when compared antifungal specialist Fluconazole.

Synthesis, Crystal Analysis, and Optoelectronic Properties of Diazole-Functionalized Acenes and Azaacenes

Doping heteroatoms into the skeletons of parent acenes can provide more opportunities to construct novel thermally and photostable organic π-conjugated semiconductors. Herein, a family of diazole-decorated acenes (APyS and APySe) and azaacenes (PyP, PyTh, PyPy, PyPh, and PyAP) have been successfully synthesized through the classical reactions. Single-crystal X-ray analyses showed that these as-formed diazole-modified derivatives adopted a twisted topology configuration, whereas the azaacenes display reclining-chair architectures, besides a twisted structure. All these compounds displayed yellow or red light in solution. Moreover, their electrochemical behaviors were also examined. We also found that the azaacenes exhibited a positive spectroscopic response to acid.

The Effect of Random and Block Copolymerization with Pendent Carbozole Donors and Naphthalimide Acceptors on Multilevel Memory Performance

Polymeric materials have been widely used in the fabrication of data-storage devices, owing to their unique advantages and defined conduction mechanisms. To date, the most-functional polymers that have been reported for memory devices were synthesized through random copolymerization, whilst there have been no reports regarding the memory effect of block polymers. Herein, we synthesized a random copolymer (PMCz₈ -co-PMBNa₂ ) and its corresponding block copolymer (PMCz₈ -b-PMBNa₂ ) to study the effect of the method of polymerization on the memory properties of the corresponding devices. Interestingly, both devices (ITO/PMCz₈ -co-PMBNa₂ /Al and ITO/PMCz₈ -b-PMBNa₂ /Al) exhibited ternary memory performance, with threshold voltages of -1.7 V/-3.3 V and -2.7 V/-3.8 V, respectively. However, based on comprehensive measurements, the memory properties of PMCz₈ -co-PMBNa₂ and PMCz₈ -b-PMBNa₂ were found to be owing to the operation of different conduction mechanisms, which resulted from different molecular stacking in the film state. Therefore, we expect that this work will be helpful for improving our understanding of the conduction mechanisms in polymer-based data-storage devices.