Unexpected Synthesis, Properties, and Nonvolatile Memory Device Application of Imidazole-Fused Azaacenes

Solvation controlled excited-state dynamics in a donor-acceptor phenazine-imidazole derivative

In the past few decades, significant efforts have been devoted to developing phenazine derivatives in various fields such as medicine, pesticides, dyes, and conductive materials owing to their highly Stokes-shifted fluorescence and distinctive photophysical properties. The modulation of the surrounding environment can effectively influence the luminescent behavior of phenazine derivatives, prompting us to investigate the solvent effect on the excited state dynamics. Herein, we present the solvent controlled excited state dynamics of a novel triphenylamine-based phenazine-imidazole molecule (TPAIP) through steady-state spectra and femtosecond transient absorption spectra. The fluorescence emission spectrum exhibited a redshift with increasing solvent polarity, indicating the existence of a charge transfer state. Furthermore, by tracking the femtosecond transient absorption spectra of TPAIP, we found that the nature of the relaxed S1 state was strongly influenced by the solvent polarity: intersystem crossing character appears in apolar solvent, whereas intramolecular charge transfer character occurs in polar solvent because of solvation. These findings provide significant theoretical insights into the impact of solvents on the excited state dynamics within phenazine derivatives. This understanding supports diverse applications ranging from advanced biological probe design to photocatalysis and pharmaceutical research.

Tuning the Electronic and Charge Transport Properties of Schiff Base Compounds by Electron Donor and/or Acceptor Groups

Organic semiconductors have gained substantial interest as active materials in electronic devices due to their advantages over conventional semiconductors. We first designed four Schiff base compounds, then the effect of electron donor/acceptor groups (methyl/nitro) was studied on the compounds' electronic and transport nature. The absorption spectra (λ_abs) were computed by time-dependent DFT at TD-B3LYP/6-31+G** level. The effect of different solvents (ethanol, DMF, DMSO, and acetone) was investigated on the λ_abs. The substitution of the -NO₂ group to the furan moiety at the 5th position in Compound 3 leads to a red-shift in the absorption spectrum. A smaller hole reorganization energy value in Compound 3 would be beneficial to get the hole's intrinsic mobility. In contrast, a reduced-electron reorganization energy value of Compound 4 than hole may result in enhanced electron charge transfer capabilities. The reorganization energies of compounds 1 and 2 exposed balanced hole/electron transport probability. The optical, electronic, and charge transport properties at the molecular level indicate that Compound 3 is suitable for organic electronic device applications.

MNP-cellulose-OSO3H as an efficient and biodegradable heterogeneous catalyst for green synthesis of trisubstituted imidazoles

Cellulose is an eco-friendly, efficient, and suitable substrate for use as a coating material and support in the preparation of catalysts. Herein, MNP–cellulose–OSO₃H was prepared as an efficient heterogeneous catalyst composed of Fe₃O₄ nanoparticles covered with cellulose–OSO₃H and used for the synthesis of trisubstituted imidazoles. The catalyst was characterized by FT-IR, CHNS, ICP, PXRD, EDAX, elemental mapping, SEM, TEM, zeta potential, TGA, and VSM techniques. The catalytic activity was evaluated in the one-pot three-component synthesis of trisubstituted imidazole derivatives using benzil or 9,10-phenanthrenequinone, different aldehydes, and ammonium acetate in EtOH solvent at 80 °C over 30 min. The yields of products were excellent, in the range 83–97%. The catalyst showed outstanding catalytic performance toward heating conditions and good reusability. Also, this methodology had several advantages, such as simple procedures, short reaction time, excellent yield, simple workup, and mild reaction conditions.

Cellulose is an eco-friendly, efficient, and suitable substrate for use as a coating material and support in the preparation of catalysts.

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.

Cata-Annulated Azaacene Bisimides

Ultra‐electron‐deficient azaacenes were synthesized via Buchwald‐Hartwig coupling of ortho‐diaminoarenes with chlorinated mellophanic diimide followed by oxidation of the intermediate N,N’‐dihydro compounds with MnO₂ or PbO₂. The resulting cata‐annulated bisimide azaacenes have ultrahigh electron affinities with first reduction potentials as low as −0.35 V recorded for a tetraazapentacene. Attempts to prepare a tetrakis(dicarboximide)tetraazaheptacene resulted in the formation of a symmetric butterfly dimer.

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.

Diazapentacenes from Quinacridones

Bis(silylethynylated) 5,7‐ and 5,12‐diazapentacenes were synthesized from cis‐ and trans‐quinacridone using protection, alkynylation and deoxygenation. The solid‐state packing of the targets is determined by choice and position of the silylethynyl substituents. The position of the substituents and nitrogen atoms influence the optical properties of the targets.

Controllable Site-Selective Construction of 4- and 5-Hydroxyalkyl-Substituted Imidazoles from Amidines, Ynals, and Water

The first example of controllable site-selective pathways to construct 4- and 5-hydroxyalkyl-substituted imidazoles through a three-component reaction of amidines, ynals, and water has been documented. Particularly, the high regioselectivity of the reaction was simply switched by changing the additives. In addition, further ¹⁸O-labeled experiments to probe a plausible mechanism and the gram-scale synthesis were studied.

Resistive Switching Memory Performance of Two-Dimensional Polyimide Covalent Organic Framework Films

Two-dimensional polyimide covalent organic framework (2D PI-NT COF) films were constructed on indium tin oxide-coated glass substrates to fabricate two-terminal sandwiched resistive memory devices. The 2D PI-NT COF films condensated from the reaction between 4,4',4″-triaminotriphenylamine and naphthalene-1,4,5,8-tetracarboxylic dianhydride under solvothermal conditions demonstrated high crystallinity, good orientation preference, tunable thickness, and low surface roughness. The well-aligned electron-donor (triphenylamine unit) and -acceptor (naphthalene diimide unit) arrays rendered the 2D PI-NT COF films a promising candidate for electronic applications. The memory devices based on 2D PI-NT COF films exhibited a typical write-once-read-many-time resistive switching behavior under an operating voltage of +2.30 V on the positive scan and -2.64 V on the negative scan. A high ON/OFF current ratio (>10⁶ for the positive scan and 10⁴-10⁶ for the negative scan) and long-term retention time indicated the high fidelity, low error, and high stability of the resistive memory devices. The memory behavior was attributed to an electric field-induced intramolecular charge transfer in an ordered donor-acceptor system, which provided the effective charge-transfer channels for injected charge carriers. This work represents the first example that explores the resistive memory properties of 2D PI-COF films, shedding light on the potential application of 2D COFs as information storage media.

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.