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Three new compounds, apocimycin A-C, were identified from a saltern-derived Micromonospora sp. strain FXY415, isolated from Dongshi saltern, Fujian, China. Their planar structures and relative configuration were confirmed mainly by analysis of 1D- and 2D- NMR spectra. Three compounds belong to 4,6,8-trimythyl nona-2,7-dienoic acid derivatives, apocimycin A also has a phenoxazine nucleus. Apocimycin A-C exhibited weak cytotoxic and antimicrobial activities. Our research showed again that microbial communities in extreme environments are a potential resource in looking for new and bioactive led compounds. [ABSTRACT FROM AUTHOR]

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]

Phenoxazines have sparked a lot of interest owing to their numerous applications in material science, organic light-emitting diodes, photoredox catalyst, dye-sensitized solar cells and chemotherapy. Among other things, they have antioxidant, antidiabetic, antimalarial, anti-alzheimer, antiviral, anti-inflammatory and antibiotic properties. Actinomycin D, which contains a phenoxazine moiety, functions both as an antibiotic and anticancer agent. Several research groups have worked on various structural modifications over the years in order to develop new phenoxazines with improved properties. Both phenothiazines and phenoxazines have gained prominence in medicine as pharmacological lead structures from their traditional uses as dyes and pigments. Organoelectronics and material sciences have recently found these compounds and their derivatives to be quite useful. Due to this, organic synthesis has been used in an unprecedented amount of exploratory alteration of the parent structures in an effort to create novel derivatives with enhanced biological and material capabilities. As a result, it is critical to conduct more frequent reviews of the work done in this area. Various stages of the synthetic transformation of phenoxazine scaffolds have been depicted in this article. This article aims to provide a state of the art review for the better understanding of the phenoxazine derivatives highlighting the progress and prospects of the same in medicinal and material applications. [ABSTRACT FROM AUTHOR]

Third-generation organic light-emitting diodes (OLEDs) based on metal-free thermally activated delayed fluorescent (TADF) materials have sparked tremendous interest in the last decade due to their nearly 100% exciton utilization efficiency, which can address the low-efficiency issue of the first-generation fluorescent emitters and the high-cost issue of the second-generation organometallic phosphorescent emitters. Construction of efficient and stable TADF-OLEDs requires utilizing TADF materials with a narrow singlet–triplet energy gap (ΔEST), high photoluminescence quantum yield (PLQY) and short TADF lifetime. A small ΔEST is necessary for an efficient reverse intersystem crossing (RISC) process, which can be achieved through the effective spatial separation of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). TADF emitters have been generally designed as intramolecular charge transfer (ICT) molecules with highly twisted donor–acceptor (D–A) molecular architectures. A wide variety of combinations of electron donors and acceptors have been explored. In this review, we shall focus on recent progress in organic TADF molecules incorporating strong electron-donor phenoxazine moiety and their application as emitting layer (EML) in OLEDs. [ABSTRACT FROM AUTHOR]

Abstract Microbes well-adapted to the Arctic Ocean are promising for producing novel compounds, due to their fancy strategies for adaptation and being under-investigated. Two new phenazine alkaloids (1 and 2) and one new phenoxazine (3) were isolated from Nocardiopsis dassonvillei 502F, a strain originally isolated from Arctic deep-sea sediments. AntiSMASH analysis of the genome of Nocardiopsis dassonvillei 502F revealed the presence of 16 putative biosynthetic gene clusters (BGCs), including a phenazine BGC. Most of the isolated compounds were evaluated for their antibacterial, antiallergic, and cytotoxic activities. Among them, compounds 4 and 5 exhibited potent in vitro cytotoxic activities against osteosarcoma cell line 143B with IC50 values 0.16 and 20.0 μM, respectively. Besides, the results of antiallergic activities of compounds 6–8 exhibited inhibitory activities with IC50 values of 10.88 ± 3.05, 38.88 ± 3.29, and 2.44 ± 0.17 μg/mL, respectively (IC50 91.6 μM for the positive control loratadine). Graphical Abstract

Class II histone deacetylases (HDACs) are considered as potential targets to treat Alzheimer's disease (AD). Previously, C-3 substituted phenothiazine-containing compounds with class II HDAC-inhibiting activities was found to promote neurite outgrowth. This study replaced phenothiazine moiety with phenoxazine that contains many C-3 and C-4 substituents. Some resulting compounds bearing the C-4 substituent on a phenoxazine ring displayed potent class II HDAC inhibitory activities. Structure-activity relationship (SAR) of these compounds that inhibited HDAC isoenzymes was disclosed. Molecular modelling analysis demonstrates that the potent activities of C-4 substituted compounds probably arise from π-π stacked interactions between these compounds and class IIa HDAC enzymes. One of these, compound 7d exhibited the most potent class II HDAC inhibition (IC50= 3–870 nM). Notably, it protected neuron cells from H2O2-induced neuron damage at sub-μM concentrations, but with no significant cytotoxicity. These findings show that compound 7d is a lead compound for further development of anti-neurodegenerative agents. [ABSTRACT FROM AUTHOR]

Ribosomal frameshifting (RFS) at the slippery site of SARS-CoV-2 RNA is essential for the biosynthesis of the viral replication machinery. It requires the formation of a pseudoknot (PK) structure near the slippery site and can be inhibited by PK-disrupting oligonucleotide-based antivirals. We obtained and compared three types of such antiviral candidates, namely locked nucleic acids (LNA), LNA–DNA gapmers, and G-clamp-containing phosphorothioates (CPSs) complementary to PK stems. Using optical and electrophoretic methods, we showed that stem 2-targeting oligonucleotide analogs induced PK unfolding at nanomolar concentrations, and this effect was particularly pronounced in the case of LNA. For the leading PK-unfolding LNA and CPS oligonucleotide analogs, we also demonstrated dose-dependent RSF inhibition in dual luciferase assays (DLAs). Finally, we showed that the leading oligonucleotide analogs reduced SARS-CoV-2 replication at subtoxic concentrations in the nanomolar range in two human cell lines. Our findings highlight the promise of PK targeting, illustrate the advantages and limitations of various types of DNA modifications and may promote the future development of oligonucleotide-based antivirals. [ABSTRACT FROM AUTHOR]

Class II histone deacetylases (HDACs) are considered as potential targets to treat Alzheimer’s disease (AD). Previously, C-3 substituted phenothiazine-containing compounds with class II HDAC-inhibiting activities was found to promote neurite outgrowth. This study replaced phenothiazine moiety with phenoxazine that contains many C-3 and C-4 substituents. Some resulting compounds bearing the C-4 substituent on a phenoxazine ring displayed potent class II HDAC inhibitory activities. Structure-activity relationship (SAR) of these compounds that inhibited HDAC isoenzymes was disclosed. Molecular modelling analysis demonstrates that the potent activities of C-4 substituted compounds probably arise from π-π stacked interactions between these compounds and class IIa HDAC enzymes. One of these, compound 7d exhibited the most potent class II HDAC inhibition (IC50= 3–870 nM). Notably, it protected neuron cells from H2O2-induced neuron damage at sub-μM concentrations, but with no significant cytotoxicity. These findings show that compound 7d is a lead compound for further development of anti-neurodegenerative agents.

Microbes well-adapted to the Arctic Ocean are promising for producing novel compounds, due to their fancy strategies for adaptation and being under-investigated. Two new phenazine alkaloids (1 and 2) and one new phenoxazine (3) were isolated from Nocardiopsis dassonvillei 502F, a strain originally isolated from Arctic deep-sea sediments. AntiSMASH analysis of the genome of Nocardiopsis dassonvillei 502F revealed the presence of 16 putative biosynthetic gene clusters (BGCs), including a phenazine BGC. Most of the isolated compounds were evaluated for their antibacterial, antiallergic, and cytotoxic activities. Among them, compounds 4 and 5 exhibited potent in vitro cytotoxic activities against osteosarcoma cell line 143B with IC50 values 0.16 and 20.0 μM, respectively. Besides, the results of antiallergic activities of compounds 6–8 exhibited inhibitory activities with IC50 values of 10.88 ± 3.05, 38.88 ± 3.29, and 2.44 ± 0.17 μg/mL, respectively (IC50 91.6 μM for the positive control loratadine). [ABSTRACT FROM AUTHOR]

Abstract While numerous phenoxazine-based small molecules developed for organic electronic devices, very limited attention has been received on synthesized conjugated polymers containing this phenoxazine. Herein, we designed and synthesized two new low-bandgap donor−acceptor conjugated copolymers based on phenoxazine with different side chains and diketopyrrolopyrrole by Pd-catalyzed direct (hetero)arylation polycondensation using a Pd(OAc)2 catalyst and PCy3.HBF4 ligand. The effects of side chain branched alkyl and benzoyl of phenoxazine on the thermal, and optical properties of the polymers have been investigated. Both the polymers have a good yield 85%, high molecular weight up to 41500 g/mol, low dispersity index 1.91, excellent solubility in common organic solvents, and a broad absorption spectrum in the range of 500-900 nm with optical bandgaps as low as 1.40 eV. All these polymers possess good thermal stability with decomposition temperatures over 350 oC and no obvious thermal transitions.

Two compounds based on pyridazine as the acceptor core and 9,9-dimethyl-9,10-dihydroacridine or phenoxazine donor moieties were designed and synthesized by Buchwald–Hartwig cross-coupling reaction. The electronic, photophysical, and electrochemical properties of the compounds were studied by ultraviolet-visible spectroscopy (UV-vis), photoluminescence spectrometry, differential scanning calorimetry, thermogravimetric analysis, and cyclic voltammetry. The compounds are characterized by high thermal stabilities. Their 5% weight loss temperatures are 314 and 336 °C. Complete weight loss of both pyridazine-based compounds was detected by TGA, indicating sublimation. The derivative of pyridazine and 9,9-dimethyl-9,10-dihydroacridine is capable of glass formation. Its glass transition temperature is 80 °C. The geometries and electronic characteristics of the compounds were substantiated using density functional theory (DFT). The compounds exhibited emission from the intramolecular charge transfer state manifested by positive solvatochromism. The emission in the range of 534–609 nm of the toluene solutions of the compounds is thermally activated delayed fluorescence with lifetimes of 93 and 143 ns, respectively. [ABSTRACT FROM AUTHOR]

Mitochondria have been recognized as a significant target for cancer therapy due to their vital role in many basic cell functions. In recent years, the development of mitochondrial targeted anti-tumor drugs has become important research directions. Herein, We report three new targeted preparations (FEQ-TPP, FEQ-BDP, and FEQ-TEA), which were synthesized by conjugating triphenylphosphine (TPP), Bodipy-pyridine salt (BDP) and triethylamine salt (TEA) with phenoxazine (FEQ). It was observed that greater delocalization range of TPP cationic carriers can enhance the recognition and accumulation efficiency of FEQ-TPP in tumor cell mitochondria. As a result, FEQ-TPP exhibits excellent mitochondrial targeting and significant anti-tumor selectivity; FEQ-BDP can show the ability of real-time fluorescence imaging. This research provides valuable insights for the screening of mitochondrial targeting vectors and the subsequent exploration and development of targeted anti-tumor medications, particularly those based on phenoxazine and its derivatives. [Display omitted] • FEQ-TPP demonstrated remarkable antitumor selectivity. • FEQ-BDP showed real-time fluorescence imaging and excellent mitochondrial targeting ability. • Different lipophilic cations have different effects. [ABSTRACT FROM AUTHOR]

Organic fluorophores are extensively utilized in the second near-infrared window (NIR-II) for bioimaging applications, owing to their superior biocompatibility and favorable metabolic properties. This study focused on the shielding unit-donor-acceptor-donor-shielding unit (S-D-A-D-S) architecture of organic π-conjugated molecules, which mitigates aggregation-induced quenching by the modification of terminal shielding units. The introduction of thiophene groups as donor units serves to augment conjugation length, thereby inducing a redshift in the fluorescence wavelength with an increasing number of donor units. Density functional theory (DFT) and time-dependent DFT (TD-DFT) methods were employed to investigate the frontier molecular orbitals, electronic absorption, and fluorescence spectra of the designed compounds. An in-depth analysis elucidates the fluorescence mechanisms and the impact of shielding units on the fluorescence properties of the compounds. The results indicate that the phenoxazine group (POZ) linked at position 'a' provides the most pronounced shielding effect. Extending the conjugation in the POZ-a compound results in an extend fluorescence wavelength within the NIR-II spectrum, with the POZ-5 compound achieving a fluorescence wavelength of up to 1308 nm in aqueous environment. Furthermore, modulating the π-conjugated bridge's length enables precise control over the compound's fluorescence wavelength, luminescence intensity and color purity, with negligible impact from the shielding units on the compound's fluorescence performance. [Display omitted] • Novel NIR-II fluorescent probes with S-D-A-D-S architecture. • Thiophene donor induces significant fluorescence redshift. • POZ-a linkage maximizes shielding and fluorescence extension. • Tuning π-conjugation achieves high-performance bioimaging agents. • DFT/TD-DFT validates molecular and electronic properties. [ABSTRACT FROM AUTHOR]

Redox-active organic molecules that store positive charge in aqueous redox flow cells (catholyte redoxmers) frequently exhibit poor chemical stability for reasons that are not entirely understood. While for some catholyte molecules, deprotonation in their charged state is resposible for shortening the lifetime, for well designed molecules that avoid this common fate, it is seldom known what causes their eventual decomposition as it appears to be energetically prohibitive. Here, a highly soluble (1.6 M) phenoxazine molecule with a redox potential of 0.48 V vs. Ag/AgCl has been examined in flow cells. While this molecule has highly reversible redox chemistry, during cycling the capacity fades in a matter of hours. Our analyses suggest a cooperative decomposition pathway involving disproportionation of two charged molecules followed by anion substitution and deprotonation. This example suggests that cooperative reactions can be responsible for unexpectedly low chemical instability in the catholyte redoxmers and that researchers need to be keenly aware of such reactions and methods for their mitigation.

Donor-acceptor dyads and triads comprising core-substituted naphthalene diimide (NDI) chromophores and either phenothiazine or phenoxazine donors are described. Synthesis combined with electrochemical and spectroelectrochemical investigations facilitates characterisation of the various redox states of these molecules, confirming the ability to combine arrays of electron donating and accepting moieties into single species that retain the redox properties of these individual moieties. [ABSTRACT FROM AUTHOR]

Two new organic electron-donors derived from carbazole and phenothiazine, 9-Octyl-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) carbazole-3-carbaldehyde and 10-octyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenoxazine-3-carbaldehyde, have been synthesized successfully. The process was initiated with multistep reactions, alkylation, formylation, bromination and finally borylation, to give the final products. The successful formation of each structure was confirmed by IR, 1H NMR, 13C NMR, and HRMS. The newly synthesized key electron donors could have promising roles as key intermediates in different synthetic approaches. [ABSTRACT FROM AUTHOR]

G4-stabilizing ligands are now being considered as anticancer, antiviral and antibacterial agents. Phenoxazine is a promising scaffold for the development of G4 ligands. Here, we profiled two known phenoxazine-based nucleoside analogs and five new nucleoside and non-nucleoside derivatives against G4 targets from telomere repeats and the KIT promoter region. Leading new derivatives exhibited remarkably high G4-stabilizing effects (comparable or superior to the effects of the commonly used selective G4 ligands PDS and NMM) and selectivity toward G4s over duplex (superior to BRACO-19). All phenoxazine-based ligands inhibited cellular metabolic activity. The phenoxazine derivatives were particularly toxic for lung adenocarcinoma cells A549' and human liver cancer cells HepG2 (CC 50 of the nucleoside analogues in the nanomolar range), but also affected breast cancer cells MCF7, as well as immortalized fibroblasts VA13 and embryonic kidney cells HEK293t (CC 50 in the micromolar range). Importantly, the CC 50 values varied mostly in accordance with G4-binding affinities and G4-stabilizing effects, and the phenoxazine derivatives localized in the cell nuclei, which corroborates G4-mediated mechanisms of action. • Phenoxazine-based derivatives were probed as G4 ligands. • Some derivatives exhibited remarkably high G4-stabilizing effects and selectivity. • All phenoxazine-based ligands inhibited cellular metabolic activity. • The ligands were particularly toxic for lung adenocarcinoma cells. • Localization in the cell nuclei corroborated G4-mediated mechanisms of action. [ABSTRACT FROM AUTHOR]

The fundamentals of Pd-catalyzed Csp2−Csp2 Miyaura borylation, Suzuki cross-coupling, and Stille cross-coupling reactions for a variety of borylated precursors based on phenothiazine (PTZ), phenoxazine (POZ), carbazole (Cz), and quinoxaline (QX) units have been explored. Three palladium-based catalysts were chosen for this study: Pd(PPh3)4, Pd(PPh3)2Cl2, and Pd(dppf)Cl2, applying different reaction conditions. Around 16 desired chromophores were successfully designed and synthesized using C-C cross-coupling reactions in moderate to excellent yields, including PTZ, POZ, and Cz units coupled with QX, indolinium iodide, thienyl, phenyl, or triphenylamine moieties. Additionally, PTZ, POZ, and Cz have been employed in synthesizing various pinacol boronate ester derivatives in good to moderate yields. Interestingly, Pd(dppf)Cl2 was found to be the best catalyst for borylation, and C-C cross-coupling reactions occurred in as little as 30 min, with an excellent yield exceeding 98%. Pd(PPh3)4 and Pd(PPh3)2Cl2 catalyzed the reaction to obtain the desired products in moderate to good yields after a long time (20–24 h). On the other hand, the Suzuki-Miyaura cross-coupling between N-(2-methyl)hexyl carbazole pinacol boronate ester derivative 10c and three halogenated quinoxaline derivatives—4-(3-(5-bromothiophen-2-yl)quinoxalin-2-yl)benzaldehyde (27), 4-(5-(3-(5-bromothiophen-2-yl)quinoxalin-2-yl)thiophen-2-yl)benzaldehyde (30), and 4-(3-chloroquinoxalin-2-yl)benzaldehyde (25) catalyzed by Pd(PPh3)4—afforded three carbazole-quinoxaline chromophores (28, 30, and 31, respectively) in 2–3 h, with good to excellent yields reaching 86%. The electron-deficient QX couplers proved to be coupled efficiently using the Stille coupling reaction, which involves the coupling between electron-rich orgaostannane and electron-deficient halide. The synthesized precursors and desired chromophores were characterized by FTIR, 1H-NMR, 13C-NMR, and HRMS. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HOCl) derived from hydrogen peroxide and chloride anion by myeloperoxidase (MPO) plays a significant role in physiological and pathological processes. Herein we report a phenoxazine-based fluorescent probe Celestine Blue B (CB) that is applicable for HOCl detection in living cells and for assaying the chlorinating activity of MPO. A remarkable selectivity and sensitivity (limit of detection is 32 nM), along with a rapid "turn-on" response of CB to HOCl was demonstrated. Furthermore, the probe was able to detect endogenous HOCl and reactive halogenated species by fluorescence spectroscopy, confocal microscopy, and flow cytometry techniques. Hence, CB is a promising tool for investigating the role of HOCl in health and disease and for screening the drugs capable of regulating MPO activity. [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]

In this study, we use cationic imidazole as the targeting group and phenoxazine as the electron donor, attaching phenoxazine to porphyrin via two different linking methods to synthesize two phenoxazine-porphyrin photosensitizers (PSs), P1 and P2 , intended for photodynamic therapy (PDT) applications. Additionally, we synthesized a molecule, P3 , that does not contain the cationic imidazole group, to serve as a control PS. We comprehensively evaluate the performance of P1 and P2 through steady-state and transient spectroscopy analysis, theoretical calculations, photooxidation experiments, and in vitro cell experiments. The results showed that P1 and P2 exhibit excellent water solubility, longer triplet state lifetimes (P1 at 200 μs, P2 at 170 μs), outstanding photostability, higher photooxidation rates and quantum yields of singlet oxygen (1O 2). Notably, in the photooxidation experiment, P1 's photooxidation rate is 1.1 times that of P2 , and 1.5 times that of tetraphenyl zinc porphyrin (ZnTPP) without phenothiazine. This may be due to the larger Gibbs free energy difference between the singlet and triplet excited states in P1 (Δ G S-T of P1 is 0.87 eV, compared to 0.83 eV for P2), which results in a greater driving force for intersystem crossing (ISC) in P1 than in P2. The introduction of the cationic imidazole group in P1 and P2 significantly enhances water solubility and tumor cell uptake compared to P3 , particularly showing higher intracellular accumulation and 1O 2 generation capabilities in HepG2 tumor cells. Flow cytometry test results further confirmed the significant photocytotoxicity of P1 and P2 , with a marked decrease in survival rates after light exposure, where the survival rate of P1 nanoparticles (NPs) dropped to 41.7 %, P2 NPs to 35.1 %, and P3 NPs to 75.0 %. The findings of this study provide crucial theoretical support for the design of new PSs. By utilizing phenothiazine as the electron donor and cationic imidazole moieties as the mitochondrial-targeting groups, we have successfully synthesized two novel phenothiazine-porphyrin photosensitizers. The two compounds exhibit outstanding water solubility, prolonged triplet state lifetimes, remarkable mitochondrial targeting capability, high singlet oxygen quantum yields, as well as excellent cellular uptake and phototoxicity. [Display omitted] [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]

Meeting the requirements and developments of modern society will be unachievable without a sustainable source of energy. However, dye sensitized solar cell (DSSC) has been found worthy to produce reliable energy source. Recently, researchers have inputted great effort toward the modulation of organic dyes to achieve highly efficient dye sensitizers for solar cell purposes. Herein, D-π-A architectural design was employed to generate ten phenoxazine-based dye engineered with five different thiophene π-linkers and two acceptor units. Density functional theory (DFT) and time-dependent DFT were used to optimize the molecules in order to cognize their intramolecular charge transport, optoelectronic properties, light-harvesting efficiency (LHE) and open-circuit voltage (Voc). DFT conceptual was engaged to elucidate the chemical reactivity parameters of the photosensitizers. Among the π-linkers employed, 2,6-diethenylbisthieno[3,2-b:2′,3′-d]thiophene (D3) remarkably improved the intramolecular charge transfer, thus generated an exceptional HOMO/LUMO energy gap (Eg), strong bathochromic shift, suitable LHE and notable Voc. The qualities of the dyes were further enhanced by replacing 2-cyano-2-pyran-4-ylidene-acetic acid with cyanoacrylic acid acceptor moiety. Comparison of these systems with other reported molecules reveals that majority of the simulated poses improved properties that are recommendable for solar cells applications. [ABSTRACT FROM AUTHOR]

In this research, a novel organic photocatalyst of 10-(perylene-3-yl-10H-phenoxazine (PHP) has been successfully synthesized from perylene and phenoxazine via Buchwald-Hartwig C-N coupling. The chemical structure of catalyst was determined via FT-IR, proton nuclear magnetic resonance (1H-NMR) spectrum and optical properties were investigated through UV-Vis spectroscopy. The PHP has been used as the reducing photoredox catalyst for organocatalyzed atom transfer radical polymerrization (O-ATRP) under UV irradiation. The well controlled molecular weight of the methyl methacrylate polymers have been obtained nearly 80% with a low polydispersity index under 1.5.

Donor-acceptor dyads and triads comprising core-substituted naphthalene diimide (NDI) chromophores and either phenothiazine or phenoxazine donors are described. Synthesis combined with electrochemical and spectroelectrochemical investigations facilitates characterisation of the various redox states of these molecules, confirming the ability to combine arrays of electron donating and accepting moieties into single species that retain the redox properties of these individual moieties.

ABSTRACT The therapeutic repertoire for tuberculosis (TB) remains limited despite the existence of many TB drugs that are highly active in in vitro models and possess clinical utility. Underlying the lack of efficacy in vivo is the inability of TB drugs to penetrate microenvironments inhabited by the causative agent, Mycobacterium tuberculosis, including host alveolar macrophages. Here, we determined the ability of the phenoxazine PhX1 previously shown to be active against M. tuberculosis in vitro to differentially penetrate murine compartments, including plasma, epithelial lining fluid, and isolated epithelial lining fluid cells. We also investigated the extent of permeation into uninfected and M. tuberculosis-infected human macrophage-like Tamm-Horsfall protein 1 (THP-1) cells directly and by comparing to results obtained in vitro in synergy assays. Our data indicate that PhX1 (4,750 ± 127.2 ng/ml) penetrates more effectively into THP-1 cells than do the clinically used anti-TB agents, rifampin (3,050 ± 62.9 ng/ml), moxifloxacin (3,374 ± 48.7 ng/ml), bedaquiline (4,410 ± 190.9 ng/ml), and linezolid (770 ± 14.1 ng/ml). Compound efficacy in infected cells correlated with intracellular accumulation, reinforcing the perceived importance of intracellular penetration as a key drug property. Moreover, we detected synergies deriving from redox-stimulatory combinations of PhX1 or clofazimine with the novel prenylated amino-artemisinin WHN296. Finally, we used compound synergies to elucidate the relationship between compound intracellular accumulation and efficacy, with PhX1/WHN296 synergy levels shown to predict drug efficacy. Collectively, our data support the utility of the applied assays in identifying in vitro active compounds with the potential for clinical development. IMPORTANCE This study addresses the development of novel therapeutic compounds for the eventual treatment of drug-resistant tuberculosis. Tuberculosis continues to progress, with cases of Mycobacterium tuberculosis (M. tuberculosis) resistance to first-line medications increasing. We assess new combinations of drugs with both oxidant and redox properties coupled with a third partner drug, with the focus here being on the potentiation of M. tuberculosis-active combinations of compounds in the intracellular macrophage environment. Thus, we determined the ability of the phenoxazine PhX1, previously shown to be active against M. tuberculosis in vitro, to differentially penetrate murine compartments, including plasma, epithelial lining fluid, and isolated epithelial lining fluid cells. In addition, the extent of permeation into human macrophage-like THP-1 cells and H37Rv-infected THP-1 cells was measured via mass spectrometry and compared to in vitro two-dimensional synergy and subsequent intracellular efficacy. Collectively, our data indicate that development of new drugs will be facilitated using the methods described herein.

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]

As sensitizers, a series of organic dyes containing phenoxazine is synthesized for use in dye-sensitized solar cells (DSSCs). The dyes were characterized using FT-IR, NMR and UV experiments. Quantum chemical calculations were used to gain insight into the structural, electronic and photophysical properties including its as-synthesized sensitizers, as well as to allocate experimental spectroscopic results. It has been observed that increasing the electron-donor potential and the π -conjugated bridge of the dyes would increase the photovoltaic performance. The obtained two dyes have substantially higher efficiency of 6.6 and 6.4%, respectively, under the modeled AM1.5G conditions. Efficient electron injection from the excited sensitizer to the conduction band of TiO2 film occurs due to further delocalizing electrons in the π -conjugated bridge and donor areas of the dyes. Using cyclic voltammetry, the electrochemical efficiency of BPA and BPCA was evaluated, and reversible oxidation signals were reported. The structural properties of phenoxazine derivative dyes ((E)-3-(7-bromo-10H-phenoxazin-3-yl) acrylic acid (BPA) and (E)-3-(7-bromo-10H-phenoxazin-3-yl)-2-cyanoacrylic acid (BPCA)) were synthesized and characterized by using FT-IR, NMR, and UV-Vis approaches. The DFT and TD-DFT techniques were used to calculate the geometrical and molecular electronic properties. The electrochemical properties of these dye compounds were evaluated using cyclic voltammetry. [ABSTRACT FROM AUTHOR]

Intercalated DNA motifs (iMs) provide a convenient scaffold for the design of biocompatible pH sensors. Among unimolecular iM-based sensors, only those labeled with conventional fluorophores or fluorophore/quencher pairs at the 3′ and 5′ termini for FRET/quenching upon pH-dependent iM folding have been tested in cells and tended to accumulate in the nuclei. Here, we used cytosine mimics as internal iM labels and synthesized a new phenoxazine-based non-fluorescent nucleoside analog, tC° Azo , which quenches the fluorescence of a known cytosine mimic, tC°. Incorporation of the tC°/tC° Azo pair into a genomic iM-forming sequence C5T resulted in a high-contrast pH sensor with an increased pH transition point and a working range compatible with physiological conditions. Importantly, unlike the known nuclei-specific C5T-based sensors with conventional labels that provide a fluorescent signal in the green/red channels, the new sensor localized mainly in the cytoplasm and allowed pH monitoring based on the tC° signal in the blue channel. As the labeling scheme was the only unique feature of the new sensor, it must account for the unique distribution pattern, i.e., the accumulation of the sensor in the cytoplasm. These findings highlight the importance of the labeling scheme of unimolecular iM-based pH sensors and open the way for multiplexed pH monitoring in different cellular compartments. [Display omitted] • An optical pH sensor was developed using an i-motif ODN with a new labeling system. • It exploits the quenching of the fluorophore tC° by the new nucleoside analog tC azo • Unlike most i-motif-based tools, the new sensor allows pH monitoring in the cytoplasm. [ABSTRACT FROM AUTHOR]

By changing the π -linker groups and the anchor unit, six new organic dyes based on phenothiazine, phenoxazine, and phenohydrazine have been created in this work. Density functional theory (DFT) was used to examine their structure, electrical, and photovoltaic properties at the B3LYP/6-31G (d,p) level. In addition, the investigated dyes' charge transfer characteristics and electronic absorption spectrum in the CH 2 Cl 2 solvent were determined using the Time-Dependent DFT at the TD - BHandH/6-31G (d,p) level approach. Frontier molecular orbitals (FMOs), optoelectronic characteristics, and geometry parameters are examples of molecular properties. Through our research, we were able to demonstrate that every dye under study possesses noteworthy intramolecular charge transfer (ICT) capabilities, high light capture efficiency (LHE), and λ max in the range of 285–515 nm, with a range-wide band gap of 1.77–2.31 eV. The developed dyes with triazine, PhON, PhSN, and PhNN, have better geometric and optoelectronic properties than phenyl and -linker dyes. According to the theoretical calculations, these compounds could be exploited as potential sensitizers for DSSC applications. [Display omitted] • Dyes incorporating triazine exhibit nearly planar structures compared with those with phenyl rings. • Notably, the phenylhydrazine-based dye (PhNN) dye exhibits red-shifted absorptions compared to the other dyes. • Examination of the dyes@(TiO 2) reveals favorable adsorption onto the TiO 2 surface (negative adsorption energy). • The energies of FMO for the dyes@TiO 2 exhibit a noticeable shift in stabilization compared to the free dyes. • The analysis indicates that dyes containing triazine (PhON, PhSN, and PhNN) exhibit the highest levels of photovoltaic efficiency. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HOCl) derived from hydrogen peroxide and chloride anion by myeloperoxidase (MPO) plays a significant role in physiological and pathological processes. Herein we report a phenoxazine-based fluorescent probe Celestine Blue B (CB) that is applicable for HOCl detection in living cells and for assaying the chlorinating activity of MPO. A remarkable selectivity and sensitivity (limit of detection is 32 nM), along with a rapid “turn-on” response of CB to HOCl was demonstrated. Furthermore, the probe was able to detect endogenous HOCl and reactive halogenated species by fluorescence spectroscopy, confocal microscopy, and flow cytometry techniques. Hence, CB is a promising tool for investigating the role of HOCl in health and disease and for screening the drugs capable of regulating MPO activity.

Modulation of molecular features of metal free organic dyes is important to present sensitizers with competing electronic and optical properties for dye sensitized solar cells (DSSCs). The D-A2-π-A1 molecular design based on phenothiazine skeleton (D) connected with benzothiadiazole (A2) linked with furan π-spacer and acceptor unit of cynoacrylic acid (A1) were fabricated and examined theoretically for possible use as DSSCs. Density functional theory (DFT) and time dependent density functional theory TDDFT were used to study the effect of additional donors on the photophysical properties of the dyes. Eight (8) different donor subunits were introduced at C7 of phenoxazine based dye skeleton to extend the π-conjugation, lower HOMO-LUMO gap (Eg) and improve photo-current efficiency of the dye sensitizer. All the dye sensitizers (except P3 and P4) exhibited capability of injecting electrons into the conduction band of the semiconductor (TiO2) and regenerated via redox potential (I−/I3-) electrode. Attachment of 2-hexylthiophene (P2) remarkably lowered the Eg, extended π-electron delocalization, hence, gives higher absorption wavelength (λmax) at 752 nm. The donor subunit containing 2-hexylthiophene (P2) presented the best chemical hardness, open circuit voltage (Voc), and other comparable electronic properties, making P2 the best DSSC candidate amongst the optimized dyes. The reported dyes would be interesting for further experimental research.

Abstract In this research, a novel organic photocatalyst of 10-(Perylene-3-yl-10H-Phenoxazine (PHP) has been synthesized successfully from perylene and phenoxazine via Buchwald-Hartwig C-N coupling. The chemical structure of catalyst was determined via proton nuclear magnetic resonance (1H-NMR) spectrum and optical properties were investigated through UV-Vis spectroscopy. The PHP has been used as the reducing photoredox catalyst for organocatalyzed atom transfer radical polymerization (ATRP) under UV irradiation. The well controlled molecular weight of polymers based on methyl methacrylate monomers have been obtained with monomer conversion up to 77.61% and low polydispersity index under 1.5.

In the crystalline state of the title solvate, C18H13NO3·C4H8O, hydrogen-bonding interactions between hydroxyl groups on a phenoxazine backbone and the tetrahydrofuran solvent are observed that suggest the ability for this compound to act as a chelating ligand. The O...O donor–acceptor distances for this hydrogen bonding are 2.7729 (15) and 2.7447 (15) Å. The three-ring backbone of the phenoxazine bends out of planarity by 18.92 (3)°, as computed using mean planes that encompass each half of the three-ring structure, with the central N and O atoms forming the line of flexion. In the crystal, a π–π stacking arrangement exists between inversion-related molecules, with a centroid-to-centroid distance of 3.6355 (11) Å. In the disordered tetrahydrofuran solvate, all atoms except oxygen were modeled over two positions, with occupancies of 0.511 (8) and 0.489 (8).

Tuberculosis (TB), the leading cause of death due to an infectious agent, requires prolonged and costly drug treatments. With the rise in incidence of MDR and XDR TB, newer more efficacious treatments which are better able to permeate into the deeper recesses of the human lung where bacteria reside are urgently required. To this end, two new promising drug candidates, the decoquinate derivative RMB041 and the phenoxazine PhX1, were assessed for their abilities to permeate into specific murine organs. In particular, PhX1 permeation into the lungs and heart was notably efficient, as reflected in the high relative AUC values of 9669 ± 120.2 min/nmol/mg and 12450 ± 45.2 min/nmol/mg for lung and heart tissue, respectively. However, neither compound maintained a free concentration in the lung which exceeded the compound’s respective MIC90 values, indicating the importance of correcting for organ specific binding.

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]

Tuberculosis (TB), the leading cause of death due to an infectious agent, requires prolonged and costly drug treatments. With the rise in incidence of MDR and XDR TB, newer more efficacious treatments which are better able to permeate into the deeper recesses of the human lung where bacteria reside are urgently required. To this end, two new promising drug candidates, the decoquinate derivative RMB041 and the phenoxazine PhX1, were assessed for their abilities to permeate into specific murine organs. In particular, PhX1 permeation into the lungs and heart was notably efficient, as reflected in the high relative AUC values of 9669 ± 120.2 min/nmol/mg and 12450 ± 45.2 min/nmol/mg for lung and heart tissue, respectively. However, neither compound maintained a free concentration in the lung which exceeded the compound's respective MIC90 values, indicating the importance of correcting for organ specific binding. [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]

• This manuscript is a review article. • All phenoxazine-based hole-transport materials investigated in perovskite solar cells are presented. • This article is focused on perovskite solar cells. • Phenoxazine-based HTM mostly differs by the nature of the peripheral groups. • Phenoxazine is a wide bandgap material widely used in Organic Electronics. SpiroOMeTAD is a well-recognized hole-transport materials for perovskite solar cells (PSCs). Besides, due to a complex synthesis, this compound is costly and alternatives to this structure are thus actively researched. With aim at developing low-cost hole-transport materials while maintaining an excellent hole-transport ability, phenoxazine has been identified as an appealing candidate. In this review, an overview of the phenoxazine-based hole-transport materials developed to date for perovskite solar cells is provided. [ABSTRACT FROM AUTHOR]

[Display omitted] • Trifluoromethylphenyl and phenoxazinyl or phenothiazinyl compounds are presented. • The position of their 1CT emission band is polarity-dependent. • Phenoxazinyl disubstituted trifluoromethylphenyl shows efficient TADF properties. • Its' small singlet-triplet energy splitting is facilitated by spin-orbit coupling. • Phenothiazine derivative has efficient RTP that shows oxygen sensitivity. Two compounds consisting of electron-accepting trifluoromethylphenyl moiety and electron-donating phenoxazine and phenothiazine moieties were designed and synthesized via Buchwald-Hartwig coupling reaction. Thermal, photophysical, and electrochemical properties of the compounds are discussed. Only compound with phenothiazine form molecular glass, with glass transition temperatures of 90 °C. The geometry and electronic characteristics of the compounds were substantiated within density functional theory (DFT). 10,10′-(2-(Trifluoromethyl)-1,4-phenylene)bis(10 H -phenoxazine) shows efficient thermally activated delayed fluorescence with high spin-orbit coupling values. 10,10′-(2-(Trifluoromethyl)-1,4-phenylene)bis(10 H -phenothiazine) as efficient room-temperature phosphor shows high oxygen sensitivity. [ABSTRACT FROM AUTHOR]

Low color temperature candlelight organic light-emitting diodes (LEDs) are human and environmentally friendly because of the absence of blue emission that might suppress at night the secretion of melatonin and damage retina upon long exposure. Herein, we demonstrated a lighting device incorporating a phenoxazine-based host material, 3,3-bis(phenoxazin-10-ylmethyl)oxetane (BPMO), with the use of orange-red and yellow phosphorescent dyes to mimic candlelight. The resultant BPMO-based simple structured candlelight organic LED device permitted a maximum exposure limit of 57,700 s, much longer than did a candle (2750 s) or an incandescent bulb (1100 s) at 100 lx. The resulting device showed a color temperature of 1690 K, which is significantly much lower than that of oil lamps (1800 K), candles (1900 K), or incandescent bulbs (2500 K). The device showed a melatonin suppression sensitivity of 1.33%, upon exposure for 1.5 h at night, which is 66% and 88% less than the candle and incandescent bulb, respectively. Its maximum power efficacy is 23.1 lm/W, current efficacy 22.4 cd/A, and external quantum efficiency 10.2%, all much higher than the CBP-based devices. These results encourage a scalable synthesis of novel host materials to design and manufacture high-efficiency candlelight organic LEDs.

Three dermacozines, dermacozines N–P (1–3), were isolated from the piezotolerant Actinomycete strain Dermacoccus abyssi MT 1.1T, which was isolated from a Mariana Trench sediment in 2006. Herein, we report the elucidation of their structures using a combination of 1D/2D NMR, LC-HRESI-MSn, UV–Visible, and IR spectroscopy. Further confirmation of the structures was achieved through the analysis of data from density functional theory (DFT)–UV–Visible spectral calculations and statistical analysis such as two tailed t-test, linear regression-, and multiple linear regression analysis applied to either solely experimental or to experimental and calculated 13C-NMR chemical shift data. Dermacozine N (1) bears a novel linear pentacyclic phenoxazine framework that has never been reported as a natural product. Dermacozine O (2) is a constitutional isomer of the known dermacozine F while dermacozine P (3) is 8-benzoyl-6-carbamoylphenazine-1-carboxylic acid. Dermacozine N (1) is unique among phenoxazines due to its near infrared (NIR) absorption maxima, which would make this compound an excellent candidate for research in biosensing chemistry, photodynamic therapy (PDT), opto-electronic applications, and metabolic mapping at the cellular level. Furthermore, dermacozine N (1) possesses weak cytotoxic activity against melanoma (A2058) and hepatocellular carcinoma cells (HepG2) with IC50 values of 51 and 38 μM, respectively.

A new series of soluble, solution-processable metallopolyynes of platinum(II) functionalized with electron-rich phenoxazine–oligothiophene rings and their corresponding dinuclear model complexes were synthesized and characterized. The influence of the inclusion of thienyl rings along the polymer chain on the optical, electronic and photovoltaic properties of these metallopolymers was studied. The evolution of the singlet and triplet excited states in these metal-based materials was elucidated in detail. It is shown that addition of the thiophene rings can elevate the HOMO energy level of the polymers. The absorption edge of the oxygen analogue is more red-shifted than that of the sulfur congener, which is attributed to the stronger electron-donating ability of the phenoxazine unit than that of the phenothiazine group. The down-shifted HOMO level of the phenothiazine-based polymer is found to enhance the photovoltaic performance by increasing the open-circuit voltage of the polymer solar cell relative to the phenoxazine-based congener. At the same donor:acceptor blend ratio of 1:4, the light-harvesting capability and solar cell efficiency notably increase as the thienyl rings are added. Image 1 • Phenoxazine-based platinum polyyne polymers were synthesized. • Their photophysical, electrochemical, and photovoltaic properties were investigated. • A comparison of the polymer with the phenothiazine congener was made. [ABSTRACT FROM AUTHOR]

1,3-Diaza-2-oxophenoxazine (X) has been introduced as a ligand in silver(I)-mediated base pairing in a parallel DNA duplex. This fluorescent cytosine analog is capable of forming stabilizing X–Ag(I)–X and X–Ag(I)–C base pairs in DNA duplexes, as confirmed by temperature-dependent UV spectroscopy and luminescence spectroscopy. DFT calculations of the silver(I)-mediated base pairs suggest the presence of a synergistic hydrogen bond. Molecular dynamics (MD) simulations of entire DNA duplexes nicely underline the geometrical flexibility of these base pairs, with the synergistic hydrogen bond facing either the major or the minor groove. Upon silver(I) binding to the X:X or X:C base pairs, the luminescence emission maximum experiences a red shift from 448 to 460 nm upon excitation at 370 nm. Importantly, the luminescence of the 1,3-diaza-2-oxophenoxazine ligand is not quenched significantly upon binding a silver(I) ion. In fact, the luminescence intensity even increases upon formation of a X–Ag(I)–C base pair, which is expected to be beneficial for the development of biosensors. As a consequence, the silver(I)-mediated phenoxazinone base pairs represent the first strongly fluorescent metal-mediated base pairs. [ABSTRACT FROM AUTHOR]

Abstract Two novel "sister" organic dyes featuring a T-shape molecular pattern based on phenothiazine/phenoxazine and triphenylamine framework as electron donor core and cyanoacrylic acid as acceptor and anchoring group were designed, synthesized and thoroughly characterized. Both dyes were functionalized at the nitrogen atom of phenoxazine/phenothiazine with the triphenylamine unit containing two hexyloxy substituents to obtain a T-shape configuration. The photo-optical and electrochemical data corroborated with time-dependent density functional theory computations and photovoltaic features were discussed in correlation with the structural architecture of each dye. Their performances in dye-sensitized solar cells (DSSCs) were comparatively surveyed with a special concern on the influence of the heteroatom variation on the most important DSSCs characteristics. In spite of its more favorable optical performance, the cells realized with phenoxazine-based dye are less efficient than those fabricated with phenothiazine ones. The cause is the stronger electron interception by the electrolyte in the case of phenoxazine dye which consistently degrades the open-circuit voltage, corroborated with a better regeneration of the phenothiazine by the iodine/iodide redox couple. In fact, to the best of our knowledge, this is one of the first studies which highlights how a single heteroatom in a T-shape dye structure can affect the dye interaction with the electrolyte and its regeneration, consequently the photovoltaic performances and brings out new opportunities for developing novel dyes for efficient DSSCs. Graphical abstract Image 1 Highlights • Two novel "sister" organic dyes featuring a T-shape molecular pattern were developed. • TD-DFT evidenced different localization of HOMO for phenothiazine/phenoxazine dyes. • Stronger electron interception by electrolyte mediated by the phenoxazine dye was found. • A better dye regeneration was proved when phenothiazine was used in the donor core. • The best power conversion efficiency of a cell sensitized with these dyes was 4.21%. [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]