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Three carbazole derivatives, AcPTC, PxPTC and PtPTC, consisting of two 9,9-dimethyl-9,10-dihydroacridine, phenoxazine or phenothiazine donor groups and one diphenyltriazine acceptor group fixed at 1,8,9-positions of a single carbazole ring via phenylene, are designed and synthesized. X-ray diffraction analysis of AcPTC reveals that there exist multiple π-π interactions between the donor and acceptor groups to form a sandwich-like structural unit with edge-to-face interaction model. The compounds thus show obvious thermally activated delayed fluorescence with through-space charge transfer character and possess considerable photoluminescence quantum yields of up to 73% in doped films with sky-blue to yellow emissions. The solution-processed electroluminescent devices achieve the highest maximum external quantum efficiencies of 10.0%, 11% and 5.6% for AcPTC, PxPTC and PtPTC, respectively, with small efficiency roll-offs.

Radical cations of photoredox catalysts used in organocatalyzed atom transfer radical polymerization (O-ATRP) have been synthesized and investigated to gain insight into deactivation in O-ATRP. The stability and reactivity of these compounds were studied in two solvents, N,N-dimethylacetamide and ethyl acetate, to identify possible side reactions in O-ATRP and to investigate the ability of these radical cations to deactivate alkyl radicals. A number of other factors that could influence deactivation in O-ATRP were also probed, such as ion pairing with the radical cations, radical cation oxidation potential, and halide oxidation potential. Ultimately, these studies enabled radical cations to be employed as reagents during O-ATRP to demonstrate improvements in polymerization control with increasing radical cation concentrations. In the polymerization of acrylates, this approach enabled superior molecular weight control, a decrease in polymer dispersity from 1.90 to 1.44, and an increase in initiator efficiency from 78 to 102%. This work highlights the importance of understanding the mechanism and side reactions of O-ATRP, as well as the importance of catalyst radical cations for successful O-ATRP.

AKG is grateful to the Royal Society for Newton International Fellowship NF171163. We acknowledge support from the Engineering and Physical Sciences Research Council of the UK (grants EP/P010482/1 and EP/L017008/1). We thank the EPSRC UK National Mass Spectrometry Facility at Swansea University for analytical services. We thank Umicore for providing palladium (II) acetate. We report an organic emitter containing a β-triketone electron acceptor core and phenoxazine as the electron donors ( TPXZBM ) for solution-processed organic light-emitting diodes (OLEDs). The resulting molecule is very unusual because it shows both thermally activated delayed fluorescence (TADF) and intramolecular proton transfer. We compare its performance with the previously reported diketone analogue PXZPDO . Solution-processed OLEDs of PXZPDO and TPXZBM show maximum external quantum efficiencies of 20.1% and 12.7%, respectively. The results obtained for the solution-processed PXZPDO -based device are as good as the previously reported evaporated device. At a very high luminance of 10,000 cd/m2 the efficiency of the OLEDs was 10.6% for PXZPDO and 4.7% for TPXZBM , demonstrating relatively low efficiency roll-off for TADF materials. The low efficiency roll-off was rationalized on the basis of the short delayed lifetimes of 1.35 μs for PXZPDO and 1.44 μs for TPXZBM . Our results suggest that intramolecular proton transfer may be useful for the design of OLED materials with low efficiency roll-off. Postprint

Benzopyrylium-coumarin fluorescent probes for sensing hypochlorous acid (HClO) or sulfur dioxide (SO2) are unable to distinguish between HClO and SO2 because the two compounds can react with the 4-position of benzopyrylium-coumarin dyes through the nucleophilic attack. In the current work, we introduced a phenoxazine moiety to the benzopyrylium-coumarin dye to synthesize a new fluorescent probe PBC1, which can dually sense HClO and SO2 and generate distinct fluorescence signals with rapid response time and high sensitivity and selectivity. Moreover, probe PBC1 was also successfully utilized to detect intracellular HClO and SO2 in HeLa cells and zebrafish.

The design and synthesis of a phenoxazine-based metal-organic tetrahedron (Zn4L4) as biomimetic lectin for selectively recognition of glucosamine (GlcN) was reported. Different from the free phenoxazine-based ligand (L), Zn4L4 displayed the highest fluorescent intensity enhancement efficiency toward GlcN over other related natural mono- and disaccharides. Fluorescence titration demonstrated a 1:1 stoichiometric host-guest complex was formed with an association constant about 4.03 × 104 L/mol. 1H NMR spectroscopic studies confirmed this selectivity resulted from the multiple hydrogen bonding interactions formed between GlcN and Zn4L4. The present results suggested that rational arrangement of recognition sites in the confined space of metal-organic cage is crucial for the selectivity toward target guests.

The prediction and/or rationalization of diarylamine radical-trapping antioxidant (RTA) activity at the elevated temperatures where they are most useful presents a significant challenge, precluding the development of new technology. Whilst structure–activity relationships at ambient temperatures are well established, their predictive capacity at elevated temperatures is poor due to competing reactions. A striking example involves phenoxazine, which is a superior RTA relative to its sulfur analog phenothiazine at ambient temperature (e.g. k = 3.9 × 107vs. 7.6 × 106 M−1 s−1 at 37 °C, respectively), but is demonstrably inferior at elevated temperatures. Despite being inherently less oxidizable in electrochemical experiments and high-accuracy computations, phenoxazine is more rapidly consumed than phenothiazine in autoxidations at 160 °C – a result which we attribute to a lower reorganization energy barrier to oxidation. Given these observations, we surmised that incorporation of an electronegative N-atom into the phenoxazine ring system would decrease the driving force for oxidation and ‘rescue’ its activity. Indeed, this was found to be the case for nitrogen incorporation at any position, regardless of the impact on the inherent RTA activity. Analogous experiments were carried out on phenothiazines into which nitrogen atoms were incorporated, revealing little benefit at 160 °C. These results suggest that for highly reactive diarylamines (i.e. those with k > 106 M−1 s−1), further enhancements in reactivity do not materially improve their ability to inhibit hydrocarbon autoxidation at elevated temperatures. Instead, their stability to one-electron oxidation determines their efficacy., Studies of potent diarylamine antioxidants illustrate how their high-temperature activity can be limited by direct reaction with O2, and how driving force and barrier to oxidation can be modulated for future antioxidant development.

The lack of high throughput screening (HTS) techniques for small molecules that stabilize DNA iMs limits their development as perspective drug candidates. Here we showed that fluorescence monitoring for probing the effects of ligands on the iM stability using the FAM-BHQ1 pair provides incorrect results due to additional dye-related interactions. We developed an alternative system with fluorescent phenoxazine pseudonucleotides in loops that do not alter iM unfolding. At the same time, the fluorescence of phenoxazine residues is sensitive to iM unfolding that enables accurate evaluation of ligand-induced changes of iM stability. Our results provide the basis for new approaches for HTS of iM ligands.

Redox-active covalent organic frameworks (COFs) with dense redox sites are promising electrical energy storage materials with robust architectures, high surface areas, insolubility in electrolytes, and open pores for electrolyte transportation. However, low redox potentials and poor electrical conductivity of pristine COFs often result in low accessibilities of redox-active sites and slow redox kinetics, greatly limiting their practical applications. Herein, we report the design and synthesis of two novel p-type phenoxazine-based COFs (DAPO-COFs) with high redox potentials (∼3.6 V vs. Li/Li+) and excellent electrical conductivities. Simply blended with conductive additives (CAs) and binders, pristine bulk DAPO-COFs without pre-composition with CAs or extra exfoliation are readily useable as cathode materials for lithium-ion batteries. Both as-synthesized DAPO-COF powders displayed superior active-site accessibility, ultrafast redox kinetics, and remarkable cycling stability. This work provides new perspectives on the development of readily useable COF-based cathode materials, and contributes to the advancement of eco-friendly and sustainable organic-based energy storage devices.

An organic reaction in water using visible light as the only energy source is one of the goals of modern synthetic organic chemistry, and the encapsulation of a photoredox catalyst by a water-solub...

A condensed phenoxazine dimer was synthesized and characterized. X-ray crystallographic analysis of the dimer shows a double-butterfly structure, in which the nitrogen atoms are located above and below the molecular plane. A radical cation salt of the dimer was obtained using tris(4-bromophenyl)aminium hexafluoroantimonate as the oxidant. The salt is air-stable in solid and solution states. The cation structure was evaluated by X-ray crystallographic analysis, showing that the phenoxazine units were converted to a planar structure upon oxidation.

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.

Organic photocatalytic atom transfer radical polymerization (ATRP) has recently become a research highlight. Organic photocatalysts based on phenothiazine, phenoxazine, and phenazine have been reported and exhibited remarkable performance. All of those structures contain two heteroatoms, which makes the oxidative state (i.e., the radical cation) of the photocatalysts stable enough to complete the catalytic cycle. However, despite the similar structure, 9,9-dimethyl dihydroacridine (DHA) was rarely used for constructing photocatalyst due to its unstable oxidative state. DHA is a weak electron donor that was widely applied in blue-emitting thermally activated delayed fluorescence (TADF) molecules. Its weaker electron-donating ability will contribute to a higher energy level of the excited state. Also, the higher oxidation potential of its radical cation will contribute to better controllability due to fast reversible dormancy. In this study, we found that substitution on the active sites of DHA could make it stable enough to be the donor part of a donor–acceptor (D–A)-type photocatalyst for ATRP. Moreover, chemical modification is necessary for both stabilizing the radical cation and improving the controllability in the polymerization process. Further modification was made to construct a rapid equilibrium between initiation and reversible dormancy, and polymerization with quantitative initiator efficiencies was achieved with a polydispersity of 1.14. It is notable that such modification can probably apply to different kinds of electron donors, and various organic chromophores could thus be applied to construct organic photocatalyst with superior performance.

Nitroxides were recently shown to catalyze the cross-dismutation of alkylperoxyl and hydroperoxyl radicals, making them uniquely effective radical-trapping antioxidants (RTAs) in unsaturated hydrocarbons where both species are formed. Given the abundance of unsaturated lipids in biological membranes, the continuous generation of hydroperoxyl (superoxide) as a byproduct of aerobic respiration, and the demonstrated cytoprotective properties of some nitroxides, we probed if cross-dismutation operates in phospholipid bilayers and cell culture. Interestingly, only nitroxides that were efficiently converted to amines in situ were effective, with their activity paralleling the stability of the incipient aminyl radicals. The ether-linked diarylamine phenoxazine, one of the most potent RTAs known, was particularly effective as a cross-dismutation catalyst. In contrast, phenolic RTAs such as α-tocopherol (α-TOH), the most potent form of vitamin E, were found to be inefficient due to the preference for the combination of hydroperoxyl and phenoxyl radicals over H-atom transfer between them. Experiments carried out in mouse embryonic fibroblasts corroborated these findings. Cells cotreated with phenoxazine (or its nitroxide) and a superoxide source were better protected from ferroptosis than those treated with phenoxazine (or its nitroxide) alone. No such synergy was observed for cells treated with α-TOH. Live cell imaging established that cytoprotection was associated with suppression of (phospho)lipid peroxidation. These results highlight the remarkable capacity for select amines to act as effective phase-transfer catalysts for a reducing equivalent (an H atom), such that a water-soluble "reactive oxygen species" can be used to quench a lipid-soluble one.

We study the effect of molecular conformation on the electronic coupling between the donor amines and acceptor 1,8-naphthalimide (NPI) in a series of D-A systems 1-4 (A = NPI; D = phenothiazine, phenoxazine, carbazole, diphenylamine, respectively, for 1, 2, 3, and 4). Weakly coupled systems show dual emission in the solution state, while strongly coupled systems show single emission bands. The energy of transitions and photoluminescence (PL) quantum yield are sensitive to the molecular conformation and donor strength. These compounds show delayed emission in the solutions and aggregated state and phosphorescence in the solid state. Compounds 3 and 4 with weak donors exhibit intermolecular slipped π···π interactions in the solid state and consequently exhibit dual (intra- and inter-) phosphorescence at low temperature. Steady state and time-resolved PL studies at variable temperature together with computational and crystal structure analysis were used to rationalize the optical properties of these compounds. The delayed emission of these compounds is sensitive to molecular oxygen; accordingly, these molecules are utilized for differential imaging of normoxia and hypoxia cancer cells.

Structurally robust tetradentate gold(III)-emitters have potent material applications but are rare and unprecedented for those displaying thermally activated delayed fluorescence (TADF). Herein, a novel synthetic route leading to the preparation of highly emissive, charge-neutral tetradentate [C^C^N^C] gold(III) complexes with 5-5-6-membered chelate rings has been developed through microwave-assisted C-H bond activation. These complexes show high thermal stability and with emission origin (3 IL, 3 ILCT, and TADF) tuned by varying the substituents of the C^C^N^C ligand. With phenoxazine/diphenylamine substituent, we prepared the first tetradentate gold(III) complexes that are TADF emitters with emission quantum yields of up to 94 % and emission lifetimes of down to 0.62 μs in deoxygenated toluene. These tetradentate AuIII TADF emitters showed good performance in vacuum-deposited OLEDs with maximum EQEs of up to 25 % and LT95 of up to 5280 h at 100 cd m-2 .

Thermally activated delayed fluorescence (TADF) materials, combining high fluorescence quantum efficiency and short delayed emission lifetime, are highly desirable for application in organic light-emitting diodes (OLEDs) with negligible external quantum efficiency (EQE) roll-off. Here, we present the pathway for shortening the TADF lifetime of highly emissive 4,6-bis[4-(10-phenoxazinyl)phenyl]pyrimidine derivatives. Tiny manipulation of the molecular structure with methyl groups was applied to tune the singlet–triplet energy-level scheme and the corresponding coupling strengths, enabling the boost of the reverse intersystem crossing (rISC) rate (from 0.7 to 6.5) × 106 s–1 and shorten the TADF lifetime down to only 800 ns in toluene solutions. An almost identical TADF lifetime of roughly 860 ns was attained also in solid films for the compound with the most rapid TADF decay in toluene despite the presence of inevitable conformational disorder. Concomitantly, the boost of fluorescence quantum efficiency to near unity was achieved in solid films due to the weakened nonradiative decay. Exceptional EQE peak values of 26.3–29.1% together with adjustable emission wavelength in the range of 502–536 nm were achieved in TADF OLEDs. Reduction of EQE roll-off was demonstrated by lowering the TADF lifetime.

C28H23N3O3, orthorhombic, Pna21 (no. 33), a = 29.0466(11) Å, b = 5.2448(3) Å, c = 14.4825(7) Å, V = 2206.32(19) Å3, Z = 4, R gt (F) = 0.0511, wR ref (F 2) = 0.1341, T = 100.00(10) K.

The host in phosphrescent organic light emitting devices (PhOLEDs), showing the thermally activated delayed fluorescence (TADF) charateristic, can effectively overcome the efficiency roll-off. Herein, six bipolar compounds with donor-π-acceptor (D-π-A) and D-π-A-π-D structures have been synthesized using 1,2,4-triazole derivative (TAZ) as an acceptor and phenothiazine (PTZ), phenoxazine (PXZ), and 9, 9-dimethylacridane (DMAC) as donors. The molecular structures were confirmed by 1H NMR, 13C NMR and X-ray single-crystal diffractions. The large steric hindrance endows these molecules with typical TADF features, including the small singlet-triplet energy splitting ( Δ E S T ) of 0.08–0.30 eV and completely spatially separate highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO) electron densities. The PhOLEDs hosted by these novel TADF materials display excellent performances with low efficiency roll-off.

Understanding and control of weak intermolecular interactions, including π-interactions, is an element toward the strategic design of supramolecular materials. In this work, we describe an approach...

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.

The oxidative polymerization of 3,6-phenylenediamino-2,5-dichlorobenzoquinone is studied for the first time, and the monomer is shown to exhibit a high reactivity in this process. The rate of its polymerization is much higher than that of aniline and 3,6-dianiline-2,5-dichlorobenzoquinone, and the induction period of oxidation is absent. The kinetic features of the oxidative polymerization of 3,6-phenylenediamino-2,5-dichlorobenzoquinone are investigated by measuring variation in the redox potential of the reaction mixture in the course of time. It is found that the kinetic curves of 3,6-phenylenediamino-2,5-dichlorobenzoquinone polymerization do not follow the S-shaped pattern typical of aniline polymerization. The mechanism of polymerization proceeding through a number of successive tautomeric rearrangements is advanced. The structure of the polymers is studied by FTIR and X-ray photoelectron spectroscopy. During the reaction of oxidative polymerization, cyclization processes occur to form phenazine and phenoxazine rings which give rise to a ladder polyconjugated polymer. The effect of reaction conditions, such as the concentration of reagents, their ratio, and the pH of the reaction medium, on the process is investigated.

The spin–orbit charge-transfer-induced intersystem crossing (SOCT-ISC) in Bodipy-phenoxazine (BDP-PXZ) compact electron-donor/-acceptor dyads was studied. PXZ is the electron donor, and BDP is the ...

Synthesis of angular polycyclic phenoxazine derivatives incorporating different phenols is reported in 30-99% yields. O-arylation of 6-chlorodibenzo[a,j] phenoxazin-5-one with a variety of electron-deficient, electron-neutral and electron-rich phenols under the catalytic palladium (II) acetate/t-BuXphos system furnished the compounds of interest. The highest yields were obtained when the intermediate was coupled with electron-rich phenols. IR, 1H-NMR, 13C-NMR and Mass spectra data, confirmed the structures of all the synthesized compounds. Study on the in vitro biological evaluation of the compounds against microorganisms revealed that they are potent antibacterial and antifungal agents, as they showed significant biological activity against Staphylococcus aureus, Streptococcus pneumonia, Escherichia coli, Salmonella typhi, klebsiella pneumonia, Pseudomonas aeruginasa, Basillus substilis, Candida albicans and Aspergillus niger.

The metal-free atom transfer radical polymerization (ATRP) process mediated by visible light and catalyzed by new organic photocatalysts (PCs) is investigated. The new PCs, designed by diversifying N-trifluoromethylphenyl phenoxazine, are analyzed and evaluated for organocatalyzed ATRP (O-ATRP) experimentally and theoretically. Especially, 3,7-di(4-biphenyl) 4-trifluoromethylphenyl-10-phenoxazine (4) enables successful O-ATRP with good catalytic performance, to produce well-defined polymers with low dispersity (Đ) under irradiation with a CFL bulb, white LEDs, or sunlight. The structure–property–performance relationships of PCs are investigated to determine the key parameters required for a good PC for use in O-ATRP. The scope of this process is explored in terms of monomer substrates and initiators using our new PC 4. Finally, a well-defined amphiphilic block copolymer is prepared using this method to form micelles, providing a basis for future biomedical applications.

Two new coumarin derivatives containing phenothiazine or phenoxazine moiety, 3-(benzo[d]oxazol-2-yl)-7-(10H-phenoxazin-10-yl)coumarin (PXZ-C) and 3-(benzo[d]oxazol-2-yl)-7-(10H-phenothiazin-10-yl)coumarin (PTZ-C), were synthesized and characterized by elemental analysis, NMR spectroscopy, and MS. Their photophysical and electrochemical properties and thermal stabilities were investigated systematically. The results showed that these compounds have good thermal stability. The compound PTZ-C exhibits weak blue–green emission upon ultraviolet light excitation, whereas the compound PXZ-C displays weak blue emission.

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.

A phenoxazine-based fluorescence chemosensor 4PB [(4-(tert-butyl)-N-(4-((4-((5-oxo-5H-benzo[a]phenoxazin-6-yl)amino)phenyl)sulfonyl)phenyl)benzamide)] was designed and synthesized by a simple synthetic methods. The 4PB fluorescence chemosensor selectively detects Ba2+ in the existence of other alkaline metal ions. In addition, 4PB showed high selectivity and sensitivity for Ba2+ detection. The detection limit of 4PB was 0.282 μM and the binding constant was 1.0 × 106 M-1 in CH3CN/H2O (97.5:2.5 v/v, HEPES = 1.25 mM, pH 7.3) medium. This chemosensor functioned through the intramolecular charge transfer (ICT) mechanism, which was further confirmed by DFT studies. Live cell imaging in MCF-7 cells confirmed the cell permeability of 4PB and its capability for specific detection of Ba2+ in living cells.

A novel chromophore based on the phenoxazine and tricyanofuran acceptor linked together via thiophene as the bridges have been synthesized by the conventional technique and systematically investigated. Structure analysis and photophysical properties were carried out to investigate the new structure chromophore. Density functional theory was used to calculate the hyperpolarizability (β) and the result shows that chromophore A showed a lower energy gap. In addition, chromophore A displayed good thermal stability with the onset decomposition temperature over 240 °C. These results showed that chromophore A, which had good thermal stability and nonlinear optical properties was a promising candidate for practical use.

This report describes the syntheses and structural characterizations of four new cobalt(III) compounds (1–4) derived from a tetradentate Schiff base ligand and their catalytic oxidation of different o-aminophenols in aerobic condition. X-ray crystal structural studies reveal that both pseudohalide ions and solvents used for the syntheses have significant influence on the structural diversity in these systems. All these compounds show the diverse catalytic activity towards the aerial oxidation of different o-aminophenols. As expected, the substitutionally labile coordination sites available for substrate binding is responsible for significantly higher catalytic activity of 1 and 2 then others. Literature reports reveal that although significant attention has been made to the catalytic oxidation of some substituted o-aminophenols in terms of the isolations and characterizations of their oxidised products with the native enzyme and its models, but the detailed kinetic studies were not available in the literature. Herein, we have examined the detailed kinetic studies of the aerobic oxidation of two substituted o-aminophenols, namely 2-amino-5-methylphenol and 2-amino-4-methylphenol, using 1 and 2 as catalysts. ESI mass spectrometry provides significant information to get insight into the mechanistic details and further disclose that the methyl substation in aromatic ring does not inhibit formation of the complex-substrate aggregate but it resulted the phenoxazine chromophore instead of phenoxazinone chormophore.

A series of ionic and neutral alcohol soluble Cu(I) complexes were obtained by reaction of 2-(pentafluorophenyl)-1H-imidazo[4,5-f][1,10]-phenanthroline (ppipH), [Cu(MeCN)4]ClO4 and the chelating diphosphine ligands bis[(2-diphenylphosphino)phenyl]ether (POP), 4,6-bis(diphenylphosphino)phenoxazine (nixantphos), 9,9-dimethyl-4,5-bis(diphenylphosphino)-9H-xanthene (xantphos) and (±)-2,2′-bis(diphenylphosphino)-1,1′-binaphthalene (BINAP) in neutral and strong alkaline media, respectively. Most complexes display moderate to intense luminescence in the solid state and weak, negligible luminescence in EtOH solutions. The aggregation-induced emission for the Cu(I) complexes of flexible POP ligands in ethanol/water system was studied.

A phenoxazine based molecule termed SP has been synthesized and used as selective sensor for halogenated solvents. This molecule shows selective fast response towards halogenated solvent via naked-eye detectable chromism. SP shows colorless solution when dissolved in most solvents initially but changes to blue color in chloroform under UV irradiation (λ = 365 nm) within 5 s. The luminescence spectra of SP in halogenated solvent show a large bathochromic shift (> 100 nm) with 60-fold enhanced emission intensity compared to that in halogen-free solvents. It is also worth mentioning that the photoinduced reaction between SP molecule and the halogenated solvents occurred. Based on the detailed NMR, fluorescence and mass spectra, the possible radical reaction mechanism was proposed. Different from the majority of solvatochromic sensors that based on the polarity of solvents for detection of halogenated solvents, our sensor system worked in a special fashion

Three novel tripodal bipolar compounds (CNTPA-CZ, CNTPA-PXZ and CNTPA-PTZ) were designed and synthesized, where three functional groups were attached to 1,3,5-positions of the central benzene ring, respectively. In these three compounds, carbazole/phenoxazine/phenothiazine (CZ/PXZ/PTZ) and benzonitrile were applied as electron-donating and electron-withdrawing groups, respectively, to achieve bipolar transport functionality, which was confirmed by the hole-only and electron-only device results. Due to the efficient energy transfer from these compounds to the dopant (Ir(MDQ)2(acac)), the red phosphorescent OLEDs demonstrated high device performance with maximum external quantum efficiency (EQE) over 20%. Particularly, the red OLED hosted by CNTPA-PTZ achieved a maximum efficiency of 42.5 cd/A, 44.3 lm/w and 23.4% with the EQE roll-off ratio of 3.4% from the peak value to that at a brightness of 500 cd/m2.

Two novel organic dyes POZ7 and POZ8, with D35 donor functionalized phenoxazine (POZ) derivative as donor and cyanoacrylic acid as acceptor, have been developed and applied in the solid-state dye-sensitized solar cells (s-DSCs). Compared with the dye POZ7 without π-bridge (6.24%), an impressive overall conversion efficiency of 7.37% for s-DSCs device based on POZ8 containing one thiophene unit as π-bridge, was obtained under standard AM 1.5 illumination (100 mW cm−2) by using 2, 2‘, 7, 7‘-tetrakis-(N, N-di-pmethoxyphenyl-amine)9, 9‘-spiro-bifluorene (Spiro-OMeTAD) as hole-transport materials (HTMs). This can be attributed to the impressive panchromatic photocurrent response over the whole visible range (380 nm–720 nm), which is much broader than that of POZ7, resulting in a much higher Jsc for POZ8 based device. The results clearly show that POZ derivative could be a promising donor unit to construct efficient dyes for s-DSCs.

Phenoxazine dyes with a hexyloxy chain and furan moiety were synthesized and used in dye-sensitized solar cells. The dyes were designed to investigate the effects of these substituents on the photophysical and electrochemical properties of the dyes and on cell photovoltaic performance. The introduced hexyloxy moiety, as an additional donor, improved the short-circuit current and open-circuit voltage of the cell by increasing light absorption and steric hindrance, respectively. The furan moiety introduced in the phenoxazine dye as a bridge unit led to a bathochromic shift of the absorption band and a large amount of dye adsorption, increasing the short-circuit current of the cell. Among the synthesized dyes, those with the furan moiety showed the best conversion efficiency of 6.34%.

This research was funded by the European Social Fund according to the activity ‘Improvement of researchers’ qualification by implementing world-class R&D projects’ of Measure No. 09.3.3-LMT-K-712. DG acknowledges to the ERDF PostDoc project No. 1.1.1.2/VIAA/1/16/177, Diphenylsulfones substituted by acridan, carbazole, phenothiazine and phenoxazine moieties were synthesized and characterized by thermal analysis, UV-, steady-state and time-resolved luminescent spectrometries, cyclic voltametry. Quantum chemical calculations on the molecular level were performed to interpret photophysical properties of the derivatives. Structural parameters, electronic properties, HOMO-LUMO gaps, molecular orbital densities, ionization potentials, reorganization energies were determined. The lowest excitation energies and the wavelengths of absorption maxima were also estimated using the time-dependent density functional theory. All the compounds were found to be capabale to form glasses with glass transition temperatures ranging from 82° to 91°C. They exhibited high thermal stabilities, with 5% weight loss temperatures exceeding 385 °C. Strong solvatochromism arising from the intramolecular charge transfer in the excited state was evidenced by bathochromic shifts of emission maxima with increasing solvent polarity. The compounds containing acridan and phenoxazine moieties showed relatively high photoluminescence quantum yield (up to 35%) in the non-doped solid state, long delayed fluorescence lifetime (in µs range) and small singlet-triplet energy splitting (ΔEST) that is attributed to thermally activated delayed fluorescence. These compounds were tested as emissive species for the fabrication of OLEDs. The sky-blue and green devices showed maximum brightness of 3200 and 12300 cd/m2 and maximum external quantum efficiency of 6.3% and 6.9%, respectively., European Social Fund 09.3.3-LMT-K-712; European Regional Development Fund 1.1.1.2/VIAA/1/16/177; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

Two phenoxazine derivatives 1 and 2 were synthesized and their photoluminescent properties were systematically investigated. These two compounds presented crystallization-induced emission (CIE) with polymorphism-dependent emission (PDE). Compound 1 presented two single crystal structures with maximum emission wavelengths of 540 nm and 560 nm, while compound 2 possessed three single crystal structures with maximum emission wavelengths of 516 nm, 547 nm, and 556 nm, respectively. Moreover, compound 1 showed reversible mechanochromic luminescence by grinding/heating or solvent fuming processes.

The photochemical dynamics of three classes of organic photoredox catalysts employed in organocatalyzed atom-transfer radical polymerization (O-ATRP) are studied using time-resolved optical transient absorption and fluorescence spectroscopies. The nine catalysts selected for study are examples of N-aryl and core-substituted dihydrophenazine, phenoxazine and phenothiazine compounds with varying propensities for control of polymerization outcomes. Excited singlet state lifetimes extracted from the spectroscopic measurements are reported in N,N-dimethylformamide (DMF), dichloromethane (DCM) and toluene. Ultrafast (< 200 fs to 3 ps) electronic relaxation of the photocatalysts after photoexcitation at near-UV wavelengths (318-390 nm) populates the first singlet excited state (S1). The S1-state lifetimes range from 130 ps to 40 ns with considerable dependence on the photocatalyst structure and the solvent. Competition between ground-electronic state recovery and intersystem crossing controls triplet state populations and is a minor pathway in the dihydrophenazine derivatives, but is of greater importance for phenoxazine and phenothiazine catalysts. Comparison of our results with previously reported O-ATRP performances of the various photoredox catalysis shows that high triplet-state quantum yields are not a pre-requisite for controlling polymer dispersity. For example, the 5,10-di(4-cyanophenyl)-5,10-dihydrophenazine photocatalyst, shown previously to exert good polymerization control, possesses the shortest S1-state lifetime (135 ps in DMF and 180 ps in N,N-dimethylacetamide) among the nine examples reported here, and a negligible triplet state quantum yield. The results call for a re-evaluation of the excited state properties of most significance in governing the photocatalytic behaviour of organic photoredox catalysts in O-ATRP reactions.

In the colorful world of pigments and dyes, the chemical reduction of chromophores usually leads to bleaching because of π-conjugation interruption. Yet, the natural phenoxazinone-based ommochrome pigment called xanthommatin displays a bathochromic (i.e. red) shift upon two-electron reduction to its corresponding phenoxazine, whose electronic origins are not completely disclosed. In this study, we investigated, at quantum chemical level, a series of phenoxazinone/phenoxazine pairs that was previously explored by UV–Vis spectroscopy (Schafer and Geyer, 1972), and which displays different hypsochromic and bathochromic shifts upon reduction. Density Functional Theory (DFT) and Time Dependent DFT (TDDFT) have been applied to compute their optical properties in order to find a rational explanation of the observed photophysical behavior. Based on our results, we propose that the electro-accepting power of auxochromes and their conjugation facilitate intramolecular charge-transfers across the phenoxazine bridge by lowering unoccupied molecular orbitals via electronic and geometric couplings, leading ultimately to bathochromy. Our findings therefore suggest new potential ways to adjust the color-changing ability of phenoxazinones in technological contexts. Overall, this model extends our mechanistic understanding of the many biological functions of ommochromes in invertebrates, from tunable color changes to antiradical behaviors.

Organic thermally activated delayed fluorescence (TADF) materials are emerging as potential candidates for time-resolved fluorescence imaging in biological systems. However, the development of purely organic TADF materials with bright aggregated-state emissions in the red/near-infrared (NIR) region remains challenging. Here, we report three donor-acceptor-type TADF molecules as promising candidates for time-resolved fluorescence imaging, which are engineered by direct connection of electron-donating moieties (phenoxazine or phenothiazine) and an electron-acceptor 1,8-naphthalimide (NI). Theoretically and experimentally, we elucidate that three TADF materials possessed remarkably small ΔEST to promote the occurrence of reverse intersystem crossing (RISC). Moreover, they all exhibit aggregation-induced red emissions and long delayed fluorescence lifetimes without the influence of molecular oxygen. More importantly, these long-lived and biocompatible TADF materials, especially the phenoxazine-substituted NI fluorophores, show great potential for high-contrast fluorescence lifetime imaging in living cells. This study provides further a molecular design strategy for purely organic TADF materials and expands the versatile biological application of long-lived fluorescence research in time-resolved luminescence imaging.

An acceptor plane expansion approach is demonstrated to selectively improve horizontal dipole orientation of TADF emitters., Manipulating orientation of organic emitters remains a formidable challenge in organic light-emitting diodes (OLEDs). Here, expansion of the acceptor plane of thermally activated delayed fluorescence (TADF) emitters was demonstrated to selectively modulate emitting dipole orientation. Two proof-of-the-concept molecules, PXZPyPM and PXZTAZPM, were prepared by introducing a planar 2-phenylpyridine or 2,4,6-triphenyl-1,3,5-triazine substituent into a prototypical molecule (PXZPM) bearing a pyrimidine core and two phenoxazine donors. This design approach suppressed the influence of substituents on electronic structures and associated optoelectronic properties. Accordingly, PXZPyPM and PXZTAZPM preserved almost the same excited states and similar emission characteristics as PXZPM. The expanded acceptor plane of PXZPyPM and PXZTAZPM resulted in a 15 to 18% increase in horizontal ratios of emitting dipole orientation. PXZPyPM supported its green device exhibiting an external quantum efficiency of 33.9% and a power efficiency of 118.9 lumen per watt, competitive with the most efficient green TADF OLEDs reported so far.

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).

Aggregation-induced emission (AIE) fluorophores with second near-infrared window (NIR-II) fluorescence are very promising for in vivo imaging because they emit fluorescence in an aggregated state and provide desirable imaging resolution and depth. Up to now, only a limited number of NIR-II AIE fluorophores have been developed. Therefore, synthesizing novel NIR-II AIE fluorophores and investigating structural effects on their photophysical properties are very important for the development of AIE probes. In this work, we synthesized two donor-acceptor-donor-type NIR fluorophores with emissions extending into the NIR-II window named DPTQ-PhPTZ and DPTQ-PhPXZ with phenothiazine (PTZ) and phenoxazine (PXZ) derivatives as the electron donors, respectively, and studied their photophysical properties via theoretical and experimental approaches as well as the properties in NIR-II in vivo imaging. The PTZ and PXZ moieties provided typical AIE characteristics. Despite the very similar chemical structures of PTZ and PXZ, DPTQ-PhPTZ and DPTQ-PhPXZ exhibited rather different photophysical properties, for example, compared to DPTQ-PhPTZ, DPTQ-PhPXZ had higher quantum yield (QY) both in solution and in the aggregated state and its QY was less sensitive to solvent polarity. After being coated with an amphiphilic copolymer F-127, the fluorophores maintained fluorescence, and the formed fluorescent polymer nanoparticles (NPs) had satisfactory tumor accumulation and biocompatibility, implying that they are applicable for in vivo tumor detection.

New carboxyl-containing o-aminophenols and phenoxazines were synthesized by condensation of 3,5-di-(tert.-butyl)-quinone with p-aminobenzoic and anthranilic acids. Oxidative transformations of the o-aminophenols and intermediate o-iminoquinones occur with the formation of the ESR detected phenoxazinyl radicals, which furthermore transform to phenoxazines or the dimeric products emerged through the radical attack at the C1 carbon of a formed phenoxazine. Molecular structure of the dimer obtained by oxidation of methyl ester of 4-[3,5-di-(tert.-butyl)-1-(2′-hydroxyphenyl)amino]benzoic acid was X-ray determined. Reaction of 4-[3,5-di-(tert.-butyl)-1-(2′-hydroxyphenyl)amino]benzoic acid with thionyl chloride gives rise to the formation of a derivative of 2-oxido-3H-benzo[d,j][1,2,3]oxathiazol system, the structure of which was established using X-ray crystallography. Solutions of methyl-6,8-di-(tert.-butyl)-10H-phenoxazine-3-carboxylate solvents display intense fluorescence covering a broad spectral region in the range of 400–600 nm.

From their traditional applications as dyes and pigments, phenothiazines and phenoxazines have gained prominent place in medicine as pharmacological lead structures. Recently these compounds and their derivatives have found robust application in organo-electronics and material sciences. This has prompted unprecedented exploratory modification of the parent structures via organic synthesis with a view of synthesizing novel derivatives with improved biological and material properties. This review underscored various synthetic transformative stages of phenothiazine and phenoxazine scaffolds.

Cyano groups were introduced into the triarylboron/phenoxazine hybrids, and the resulting emitters not only exhibited distinct thermally activated delayed fluorescence (TADF) characteristics but also achieved a remarkable improvement in the photoluminescence quantum yields (PLQYs). The PLQYs of TB-1PXZ2CN and TB-2PXZ1CN are 0.67 and 0.75, which are 5.6 and 1.6 times higher than those of the respective non-cyano counterparts. Employing the two TADF emitters in solution-processed organic light-emitting diodes external quantum efficiencies (EQEs) of 9.7% and 11.4%, respectively, were achieved. Notably, the EQEs remained as high as 8.9% and 10.2% at a luminance of 2000 cd m−2 with slight efficiency roll-offs of 8% and 11%, respectively.

Herein, a comparative analysis was carried out to investigate the relationship between performance and structures of PTZ-2 and POZ-2 which based on the units of phenothiazine (PTZ) and phenoxazine (POZ) respectively. The spectral analysis shows that the maximum absorption peaks of these two dyes are 438 nm (PTZ-2) and 465 nm (POZ-2). Electrochemical analysis demonstrate that the better light-harvesting performance of POZ-2 dye is due to its narrow E0–0 (zero–zero transition Energy). Further photovoltaic measurement results show that the η of POZ-2 is 6.4% (Voc=0.727 V, Jsc=12.58 mA cm−2) which is higher than that of PTZ-2 (η=4.9%, Voc=0.722 V; Jsc=9.06 mA cm−2). Finally, the theoretical calculations show that the C S C bond angle (98°) in PTZ-2 is significantly smaller than the C O C bond angle (116°) in POZ-2 which attribute to the larger atom radius of "S" than "O". Therefore, a more obvious folding deformation was created in the structure of PTZ-2. That was the main cause of the difference performance between these two dyes.

Reactions of 2,3-dichloro-1,4-naphthoquinone with o/m and p-aminophenols are studied. It was shown that reaction with 2-aminophenol results in 6-chloro-12a-methoxy-7H-benzo[c]phenozaxine-5(12aH)-one (1a) as the major product along with (6-chloro-12a-hydroxy-7H-benzo[c]phenoxazine-5(12aH)-one) (1b) in minor proportions. A major 6-chloro-12a-methoxy-9-methyl-7H-benzo[c]phenoxazin-5(12aH)-one (2a) was isolated from the 4-methyl-2-aminophenol whereas reactions with 3-aminophenol and 4-aminophenol yield products 2-(3-hydroxyphenylamino)-3-chloro-1,4-naphthoquinone (3) and 2-(4-hydroxyphenylamino)-3-chloro-1,4-naphthoquinone (4). The hydroxy phenoxazine (1b) was obtained as the minor product which is evident from the single crystal X-ray diffraction studies. Pharmacological potential of these compounds have been evaluated against pathogenic Gram positive and Gram negative bacteria. These derivatives demonstrated broad spectrum of biological activity against all bacterial isolates with the MIC bring in the range of 4–512 μg/ml. The relatively high MICs were observed compared to the reference antibiotics used. Except 1b rest of the other compounds exhibit considerably lower MICs (32–512 μg/ml), against the two Pseudomonas spp. and relatively high resistance towards reference antibiotics (with the MIC being >1024 μg/ml). It has been shown that that synergistic action of phenoxazine derivatives in mixing with conventional antibiotics can be explored for treatment of pathogens.

This is the first report on the highest efficiency NIR absorbing Aza-Bodipy small molecules. The molecular engineering of newly synthesized NIR absorbing Aza-Bodipy dyes consists of covalently linked phenothiazine (AZA-PTZ-BOD) and phenoxazine (AZA-POZ-BOD) moieties as terminal groups and Aza-Bodipy as a central core moiety. The highest efficiency for OPV devices of 8.23% is achieved for AZA-PTZ-BOD.

We report three yellow-green to yellow TADF dopants 26DAcBPy, 25DAcBPy and 26DPXZBPy containing dibenzoyl pyridine as the acceptor and dimethylacridine (Ac) and phenoxazine (PXZ) as the donors with short delayed fluorescence lifetimes of 2.3 μs, 1.9 μs, and 1.0 μs, respectively. The crystal structures show that 26DAcBPy and 26DPXZBPy have a U shape conformation and 25DAcBPy a linear chain structure. All three molecules show intramolecular hydrogen bonding between the pyridine nitrogen and the o-hydrogen of a phenyl ring. These conformations appear to be the result of hydrogen bonding, which leads to rigid structures and provides higher photoluminescence quantum yield. Lastly, these molecules show large dihedral angles between the donor group and the spacer phenyl unit leading to a well-separated HOMO and LUMO and small ΔEST values. Combined with the small ΔEST values, and good photoluminescence (PL) quantum yields, the 26DAcBPy-based devices show a maximum efficiency of 23.1% with a mild efficiency roll-off.

Purely organic luminescent materials with thermally activated delayed fluorescence have the merits of high exciton utilization and thus excellent electroluminescence (EL) efficiency in OLEDs. However, these devices, particularly solution-processed doped OLEDs, usually encounter the troublesome problem of severe efficiency roll-off at high voltages. Herein, two new organic small molecules consisting of electron-withdrawing benzoyl and electron-donating 9-hexylcarbazole and phenoxazine (or 9,9-dimethyl-9,10-dihydroacridine) moieties are designed and synthesized. The crystal and electronic structures, thermal stabilities, electrochemical behaviors and photophysical properties are thoroughly investigated. Whereas these materials are weak emitters in solution, they can fluoresce strongly in spin-coated neat films with greatly enhanced delayed fluorescence, namely they possess interesting aggregation-induced delayed fluorescence (AIDF). Solution-processed nondoped OLEDs are fabricated by using these materials as light-emitting layers, which provide high EL efficiencies of up to 9.02%. Efficient doped OLEDs with varied doping concentrations (10, 30 and 50 wt%) in a 4,4′-bis(carbazol-9-yl)biphenyl (CBP) host are also obtained by a spin-coating technique, offering higher EL efficiencies of up to 12.1%. More importantly, both solution-processed nondoped and doped OLEDs exhibit an extremely small efficiency roll-off (down to 0.08% at 1000 cd m−2 luminance), demonstrating the greatly advanced efficiency stability. These results clearly prove that luminescent materials with AIDF properties are promising candidates for the fabrication of high-performance solution-processed OLEDs.