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The low specific capacity determined by the limited electron transfer of p‐type cathode materials is the main obstruction to their application towards high‐performance aqueous zinc‐ion batteries (ZIBs). To overcome this challenge, boosting multi‐electron transfer is essential for improving the charge storage capacity. Here, as a typical heteroaromatic p‐type material, we unveil the unique reversible two‐electron redox properties of phenoxazine in the aqueous electrolytes for the first time. The second oxidation process is stabilized in the aqueous electrolytes, a notable contrast to its less reversibility in the non‐aqueous electrolytes. A comprehensive investigation of the redox chemistry mechanism demonstrates remarkably stable redox intermediates, including a stable cation radical PNO⋅+ characterized by effective electron delocalization and a closed‐shell state dication PNO2+. Meanwhile, the heightened aromaticity contributes to superior structural stability during the redox process, distinguishing it from phenazine, which features a non‐equivalent hybridized sp2‐N motif. Leveraging these synergistic advantages, the PNO electrodes deliver a high capacity of 215 mAh g−1 compared to other p‐type materials, and impressive long cycling stability with 100 % capacity retention over 3500 cycles. This work marks a crucial step forward in advanced organic electrodes based on multi‐electron transfer phenoxazine moieties for high‐performance aqueous ZIBs. [ABSTRACT FROM AUTHOR]

Finding new efficient p‐type sensitizers for NiO photocathodes is a great challenge for the development of promising low‐cost tandem dye‐sensitized solar cells (DSSCs). Now, the focus of researchers investigating these cells has been to create high‐performance p‐type systems. With this intention, herein, the design and synthesis of six new phenoxazine‐based donor–acceptor (D–A)‐configured organic dyes PO1–6 was reported, comprising different acceptor moieties specially designed for the sensitization of mesoporous p‐type semiconductor NiO for the construction of p‐type DSSCs (p‐DSSCs). This work includes structural, photophysical, thermal, electrochemical, theoretical, and photoelectrochemical studies of these dyes, including evaluation of their structure‐property relationships. The optical studies revealed that PO1–6 displayed adequate absorption and emission features in the range of 480–550 and 560–650 nm, respectively, with a bandgap in the order of 2.05–2.40 eV, and their thermodynamic parameters favored an efficient interfacial charge transfer involving NiO. Among the six new dyes, the device based on sensitizer PO2 carrying electron‐withdrawing 1,3‐diethyl‐2‐thiobarbituric acid achieved the highest power conversion efficiency of 0.031 % (short‐circuit current density=0.89 mA cm−2, open‐circuit voltage=101 mV, and fill factor=35 %). Conclusively, the study furnishes an understanding of the intricacies involved in the structural modification of phenoxazine‐based sensitizers to further ameliorate the performance of the p‐type DSSCs. [ABSTRACT FROM AUTHOR]

We have evaluated six phenoxazine derivatives as visible light photosensitizers for the photochemical reduction of CO2 to CO with an iron porphyrin catalyst in organic media. The phenoxazine core was functionalized with electron‐donating or ‐withdrawing groups to modify the photophysical properties. Both singlet and triplet excited state potentials of the sensitizers spanned several hundred mV range and the ground state oxidation potentials spanned 250 mV. We observed that no correlation can be established between the production of CO and the excited state potential of the phenoxazine, which determines the driving force for electron transfer to the catalyst. On the contrary, a clear correlation can be made between the oxidation potentials of the phenoxazine and the production of CO. This observation indicates that the process was limited by photosensitizer regeneration and highlights the fact that electron transfers not directly related to the catalyst activation could play a key role in homogeneous photocatalytic systems. [ABSTRACT FROM AUTHOR]

Delicately designed dopant‐free hole‐transporting materials (HTMs) with ordered structure have become one of the major strategies to achieve high‐performance perovskite solar cells (PSCs). In this work, we report two donor‐π linker‐donor (D‐π‐D) HTMs, N01 and N02, which consist of facilely synthesized 4,8‐di(n‐hexyloxy)‐benzo[1,2‐b:4,5‐b′]dithiophene as a π linker, with 10‐bromohexyl‐10H‐phenoxazine and 10‐hexyl‐10H‐phenoxazine as donors, respectively. The N01 molecules form a two‐dimensional conjugated network governed by C−H⋅⋅⋅O and C−H⋅⋅⋅Br interaction between phenoxazine donors, and synchronously construct a three‐dimension lamellar structure with the aid of interlaminar π–π interaction. Consequently, N01 as a dopant‐free small‐molecule HTM exhibits a higher intrinsic hole mobility and more favorable interfacial properties for hole transport, hole extraction and perovskite growth, enabling an inverted PSC to achieve a very impressive power conversion efficiency of 21.85 %. [ABSTRACT FROM AUTHOR]

Abstract: It is well known that copper ions play a critical role in various physiological processes. However, a variety of human diseases are tightly correlated with copper overload. Although there are numerous fluorescent probes capable of detecting copper ions, most of them are "turn‐off" probes owing to copper (II) ions fluorescence quenching effect, resulting in poor sensitivity. Herein, a novel "turn‐on" near‐infrared (NIR) fluorescent probe PZ‐N based on phenoxazine was designed and synthesized for the selective detection of copper (II) ions (Cu2+). Upon the addition of Cu2+, the probe could quickly react with Cu2+ and emit strong fluorescence, along with colour change from colourless to obvious blue. Moreover, the probe PZ‐N showed good water solubility, high selectivity, and excellent sensitivity with low limit of detection (1.93 nM) towards copper (II) ions. More importantly, PZ‐N was capable of effectively detecting Cu2+ in living cells. [ABSTRACT FROM AUTHOR]

Luminogens featuring aggregation‐induced emission characteristics (AIEgens) have been widely applied in high‐performance non‐doped blue organic light‐emitting diodes (OLEDs). However, AIEgens with high exciton utilization are rare. Herein, a tetraphenylbenzene (TPB)‐based AIEgen of PXZ‐TPB‐CN, in which phenoxazine (PXZ) and cyano (CN) serve as strong electron‐donating and withdrawing group, respectively, was rationally designed and facilely synthesized. PXZ‐TPB‐CN exhibits a unique mechanochromic luminescence. The lifetime of its ground powders and films exhibits a new decay component compared with the pristine powders, which attributes to the reverse intersystem crossing from the high‐lying triplet state process according to the theoretical calculation. To further verify this process, a non‐doped OLED using PXZ‐TPB‐CN as emitting layer was fabricated, and a much higher maximum external quantum efficiency (EQE) of the device than that of theoretical one was obtained, suggesting that triplet excitons are involved in a radiative process. In addition, the high horizontally oriented dipoles also contribute to this high EQE. This work provides a new strategy to realize blue AIEgen‐based OLEDs with high exciton utilization by attaching strong donors and acceptors on twisted AIE cores. [ABSTRACT FROM AUTHOR]

Phenoxazines have gained enormous interest because of their diverse applications in both material science and chemotherapy. They exhibit numerous biological activities, ranging from anti‐malarial, anticancer, antiviral, antidiabetic, anti‐Alzheimer, antioxidant, anti‐inflammatory, to antibiotic and many more. Actinomycin D, for instance, which embodies a phenoxazine scaffold, displays both antibiotic and anticancer property. Phenoxaxines have also found usefulness in organic light‐emitting diodes, fluorescent probes and dye‐sensitized solar cells. Over the years, various research groups have strived for several structural modifications targeting new derivatives of phenoxazines with improved properties. This present review highlights the progress, challenges and prospects in medicinal and material applications of phenoxazine moiety to provide greater insight into the development of future derivatives with improved properties. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HOCl), one of the reactive oxygen species (ROS), is a key microbicidal agent which is used for natural defense. However, it is also linked to varieties of human diseases owing to the overproduction of HOCl. Much effort has been made to exploit selective fluorescent sensors for the detection of HOCl, but most of them have some disadvantages such as short excitation wavelength, low selectivity, and slow response and so on. These restrict the biological application of the probes. In this work, BR‐O was designed and synthesized on the base of phenoxazine for the detection of HOCl. BR‐O exhibited a violent fluorescence enhancement in the presence of HOCl, showing excellent selectivity and high sensitivity. More importantly, the probe BR‐O was capable of detecting exogenous and endogenous HOCl in living cells. [ABSTRACT FROM AUTHOR]

Metal‐mediated base pairs (MMBPs) formed by natural or artificial nucleobases have recently been developed. The metal ions can be aligned linearly in a duplex by MMBP formation. The development of a three‐ or more‐metal‐coordinated MMBPs has the potential to improve the conductivity and enable the design of metal ion architectures in a duplex. This study aimed to develop artificial self‐bases coordinated by three linearly aligned AgI ions within an MMBP. Thus, artificial nucleic acids with a 1,3,9‐triaza‐2‐oxophenoxazine (9‐TAP) nucleobase were designed and synthesized. In a DNA/DNA duplex, self‐base pairs of 9‐TAP could form highly stable MMBPs with three AgI ions. Nine equivalents of AgI led to the formation of three consecutive 9‐TAP self‐base pairs with extremely high stability. The complex structures of 9‐TAP MMBPs were determined by using electrospray ionization mass spectrometry and UV titration experiments. Highly stable self‐9‐TAP MMBPs with three AgI ions are expected to be applicable to new DNA nanotechnologies. [ABSTRACT FROM AUTHOR]

Some derivatives of phenothiazine and phenoxazine compounds were synthesized via Hiyama‐cross coupling reaction protocol. The intermediates were prepared by reacting 2‐aminothiophenol, 2‐aminopyridin‐3‐ol and 4,5‐diamino‐6‐hydroxylpyrimidin‐2‐thiol with 2,3‐dibromonaphthalene‐1,4‐dione in alkaline medium of anhydrous sodium carbonate. These intermediates were subjected to the fluoride‐free Hiyama cross‐coupling reaction with 2‐(dimethylsilyl)pyridine and dimethyl(2‐thienyl)silanol using magnetically separable Pd/Fe3O4 as the catalyst under aqueous conditions to yield the derivatives. Molecular descriptors of these compounds were evaluated for their drug‐likeness. Pharmacokinetic parameters were also evaluated. Molecular docking studies were performed. The synthesized compounds showed drug‐likeness. Pharmacokinetic evaluation reveals a strong plasma protein binding and potentials to cross blood‐brain barrier. 6‐(Thiophen‐2‐yl)‐5H‐11‐azabenzo[a]phenoxazin‐5‐one (8 b) and 11‐Amino‐9‐thio‐6‐(thiophen‐2‐yl)‐5H‐8,11‐diazabenzo[a]phenoxazin‐5‐one (9 b) showed highest binding energies of −5.74 and −7.25 kcal/mol with the protein targets glucosamine‐6‐phosphate synthase (2VF5) and lanosterol‐14α‐demethylase (3JUV) respectively. The phenoxazines synthesized were found to be potential inhibitors of glucosamine‐6‐phosphate synthase and lanosterol‐14α‐demethylase. [ABSTRACT FROM AUTHOR]

Abstract: Phenoxazine and quinone are typical electron mediators in natural and engineered systems. Although the electron shuttling process of quinone has been well studied, phenoxazine is poorly characterized. Here, a model phenoxazine (resazurin) was examined as an electron mediator in a bioelectrochemical system with Shewanella oneidensis MR‐1. Results showed that the current generation was substantially enhanced by the presence of phenoxazine, and was almost unaffected even after replacing the original medium with a fresh medium without phenoxazine. This is completely different to the well‐known quinones used as electron mediators. Further study suggested that, resorufin (RR), as an intermediate product, was deposited in situ onto the electrode. The RR deposition was suggested to be a dominant mechanism for stabilizing the electron shuttling efficiency by phenoxazine. This study proposed a novel electron shuttling mechanism of phenoxazine and may provide a new insight into the extracellular electron transfer. [ABSTRACT FROM AUTHOR]

In 1982, Buckley et al. reported on the hydroxy-functionalized derivative of 6,13-diazapentacene (DAP), namely 5,12-dihydroxo-6,13-diazapentacene. In an attempt to reproduce the synthetic procedure, 1H NMR and 13C{1H} NMR spectroscopic data revealed the formation of a constitutional isomer of the supposed compound. A single-crystal X-ray structure determination revealed that the actual structure of the dark-violet product was 6-amino-5H-dibenzo[a,h]phenoxazin-5-one (2), a benzo[a]phenoxazine derivative. These kinds of compounds are, along with a wide range of pharmacological applications, known for their specific fluorescent properties, which were analyzed for compound 2. Furthermore, it was shown that 2 can be utilized as reagent for the synthesis of other benzo[a]phenoxazine derivatives, herein 6-(dimethylamino)-5H-dibenzo[a,h]phenoxazin-5-one (3). [ABSTRACT FROM AUTHOR]

Considering different solar dyes configuration, four novel metal-free organic dyes based on phenoxazine as electron donor, thiophene and cyanovinylene linkers as the [ABSTRACT FROM AUTHOR]

Antioxidant effects of phenothiazine (PtzNH), phenoxazine (PozNH), and iminostilbene (IsbNH) on the oxidation of linoleic acid (LH) and DNA induced by 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) were investigated in this work. LH was suspended in the liposome of dipalmitoyl phosphatidylcholine (DPPC) to mimic a biomembrane. In the course of AAPH-induced oxidation of LH, the inhibition period (tinh) generated by PtzNH, PozNH, and IsbNH was proportional to the concentrations of PtzNH, PozNH, and IsbNH employed. The abilities of PtzNH, PozNH, and IsbNH to protect LH were similar to that of trolox (6-hydroxyl-2,5,7,8-tetramethylchroman-2-carboxylic acid). Quantum chemical calculations elucidated that the nonplanar configurations of PtzNH, PozNH, and IsbNH transformed to planar ones when they were converted into radicals. In addition, spin-densities (SDs) on the N atom in the radicals derived from PtzNH, PozNH, and IsbNH were calculated. The N atom in the radical of PtzNH possessed the lowest SD, indicating that the radical of PtzNH was the most stable one. Moreover, PtzNH, PozNH, and IsbNH were applied to protect the DNA against AAPH-induced oxidation, in which PozNH and IsbNH were able to generate tinh. The tinh generated from PozNH and IsbNH was also proportional to their concentrations. The antioxidant effect of PozNH on the oxidation of DNA was higher than that of IsbNH. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]