Peroxynitrite (ONOO(-)), the product of a radical combination reaction of nitric oxide and superoxide, is a potent biological oxidant involved in a broad spectrum of physiological and pathological processes. Herein we report the development, characterization, and biological applications of a new fluorescent probe, HKGreen-4, for peroxynitrite detection and imaging. HKGreen-4 utilizes a peroxynitrite-triggered oxidative N-dearylation reaction to achieve an exceptionally sensitive and selective fluorescence turn-on response toward peroxynitrite in chemical systems and biological samples. We have thoroughly evaluated the utility of HKGreen-4 for intracellular peroxynitrite imaging and, more importantly, demonstrated that HKGreen-4 can be efficiently employed to visualize endogenous peroxynitrite generated in Escherichia coli-challenged macrophages and in live tissues from a mouse model of atherosclerosis. This probe should serve as a powerful molecular imaging tool to explore peroxynitrite biology under a variety of physiological and pathological contexts.

Highly efficient lepidine‐based phosphorescent iridium(III) complexes with pentane‐2,4‐dione or triazolpyridine as ancillary ligands have been designed and prepared by a newly developed facile synthetic route. Fluorine atoms and trifluoromethyl groups have been introduced into the different positions of ligand, and their influence on the photophysical properties of complexes has been investigated in detail. All the triazolpyridine‐based complexes display the blueshifted dual‐peak emission compared to the pentane‐2,4‐dione‐based ones with a broad single‐peak emission. The complexes show emission with broad full width at half maximum (FWHM) over 100 nm, and the emissions are ranges from greenish–yellow to orange region with the absolute quantum efficiency (ΦPL) of 0.21–0.92 in solution, i.e., ΦPL = 0.92 (18), which is the highest value among the reported neutral yellow iridium(III) complexes. Furthermore, high‐performance yellow and complementary‐color‐based white organic light‐emitting diodes (OLEDs) have been fabricated. The FWHMs of the yellow, greenish–yellow OLEDs are in the range of 94–102 nm, which are among the highest values of the reported yellow or greenish–yellow‐emitting devices without excimer emission. The maximum external quantum efficiency of monochrome OLEDs can reach 24.1%, which is also the highest value among the reported yellow or greenish–yellow devices. The color rendering indexes of blue and complementary yellow‐based white OLED is as high as 78.

A novel fluorescent probe, HKGreen-3, for sensing peroxynitrite is designed on the basis of the rhodol scaffold and a peroxynitrite-specific oxidation reaction. The probe turns out to be highly sensitive and selective for detecting peroxynitrite in both chemical and biological systems.

By incorporating ultrathin (<0.1 nm) green, yellow, and red phosphorescence layers with different sequence arrangements in a blue fluorescence layer, four unique and simplified fluorescence/phosphorescence (F/P) hybrid, white organic light-emitting diodes (WOLEDs) were obtained. All four devices realize good warm white light emission, with high color rending index (CRI) of >80, low correlated color temperature of <3600 K, and high color stability at a wide voltage range of 5 V-9 V. These hybrid WOLEDs also reveal high forward-viewing external quantum efficiencies (EQE) of 17.82%-19.34%, which are close to the theoretical value of 20%, indicating an almost complete exciton harvesting. In addition, the electroluminescence spectra of the hybrid WOLEDs can be easily improved by only changing the incorporating sequence of the ultrathin phosphorescence layers without device efficiency loss. For example, the hybrid WOLED with an incorporation sequence of ultrathin red/yellow/ green phosphorescence layers exhibits an ultra-high CRI of 96 and a high EQE of 19.34%. To the best of our knowledge, this is the first WOLED with good tradeoff among device efficiency, CRI, and color stability. The introduction of ultrathin (<0.1 nm) phosphorescence layers can also greatly reduce the consumption of phosphorescent emitters as well as simplify device structures and fabrication process, thus leading to low cost. Such a finding is very meaningful for the potential commercialization of hybrid WOLEDs.

light-emitting device (OLED) in 1998, [1] phosphorescent transition-metal complexes, especially for noble metal-based ones (e.g., iridium(III), platinum(II), etc.) as triplet emitters toward highly efficient organic electroluminescence, have aroused extensive attention. [15-21] Owing to strong spin-orbit coupling effect, these complexes may use both singlet and triplet excitons to greatly enhance the efficiency of OLED, breaking the upper limit of the conventional fluorescent device efficiency. Due to their unique properties of excited states, they also have extended their applications in other fields, for instance, catalysis, organic solar cells, organic memory devices, biological sensing and imaging, photodynamic therapy, information recording, and security protection, etc. [22-27] Although extensive works have been done to the design and preparation of phosphorescent materials based on noble metals, these noble metals usually have some disadvantages (such as high cost and low abundance in nature), thereby limiting their practical applications. The relatively abundant and cheap PTMCs of low toxicity have drawn considerable interests very recently. [4,23,24,28-31] Many kinds of non-noble metal-based PTMCs such as copper(I), tungsten(VI), and manganese(II) complexes have emerged rapidly. [4,23-25,28-31] Phosphorescent manganese(II) complexes show great potentials in many applications, due to their features including highly efficient phosphorescence, flexible design in molecular structure, ease of synthesis, and rich physical properties (e.g., triboluminescence, stimuli-responsivity, etc.). [24,25a,32-36] Compared with the noble metals, manganese element with an atomic number of 25 has abundant reserves, is environmentally friendly and inexpensive. Moreover, it has richer valence and coordination mode, which has been widely used in the fields of catalysis, ferroelectric, and magnetic materials. [37-39] Among the various valence states of manganese ion, the divalent manganese ion having a 3d 5 electron configuration has a 4 T 1 − 6 A 1 radiative transition closely related to the crystal field strength. The crystal field strength in the metal complex highly depends on the chemical structure of the ligand and the coordination number. These features make the manganese(II) complexes having rich photophysical properties. By regulating the ligand structure, the organic counterion and the coordination number of the manganese(II) complex, the green, yellow, orange, red, or even near-infrared phosphorescence can be achieved. [23-25,36,40] It Phosphorescent manganese(II) complexes are emerging as a new generation of phosphorescent materials showing great potentials in many applications, owing to their unique features including highly efficient phosphorescence, diverse structural/molecular design, and ease of synthesis, structural diversity, rich physical properties (e.g., triboluminescence, stimuli-responsivity, etc.), high abundance, and low cost. The research on phosphorescent manganese(II) complexes is just in its infancy...

coupling effect induced by heavy-metal atoms. [5,6] For example, noble metal-based phosphors including iridium(III) complexes, [7][8][9][10][11][12][13][14][15][16] platinum(II) complexes, [17][18][19][20] and gold(III) complexes [21,22] have been widely used in phosphorescent OLEDs (PhOLEDs). However, these noble metals suffer from the low abundance and high cost. Hence, the relatively abundant, lowcost, and low-toxic phosphorescent metal complex have been drawing great interests for PhOLEDs.Recent explorations of phosphorescent manganese(II) complexes appear to be a new and attractive alternative toward highly efficient PhOLEDs. The manganese(II) complexes display strong photoluminescence in solid state originating from the metal-centered d-d ( 4 T 1 (G) → 6 A 1 ) radiative transition. [23][24][25] The well-known green light-emitting manganese(II) complexes are ionic compounds consisting of organic cations and inorganic tetrahalogenomanganate(II) anions. [26,27] Attributed to their excellent solid-state photophysical properties, this kind of organic-inorganic hybrid complexes have exhibited promising optoelectronic applications. For example, Chen and co-workers have realized the solution-processed PhOLEDs based on the ionic tetrabromide manganese(II) complex ((Ph 4 P) 2 (MnBr 4 )) as an emitting dopant, the external quantum efficiency (EQE) of this device can reach 9.6% for the doped OLEDs. [28] However, the ionic manganese(II) complexes often suffer from low stability and can be easily hydrolyzed Phosphorescent transition-metal complexes have played the vital role in the rapid development of organic light-emitting diodes (OLEDs) as the most promising candidates for next-generation flat-panel display and solid-state lighting techniques. In this work, novel and low-cost phosphorescent neutral tetrahedral manganese(II) complexes (DBFDPO-MnX 2 , X = Br, or Cl) based on dibenzofuran-based phosphine oxide derivative as ligand are designed and synthesized. The manganese(II) complexes exhibit intense green phosphorescence with high photoluminescence quantum yields (PLQYs) of as high as 81.4% (DBFDPO-MnBr 2 ). Using complex DBFDPO-MnBr 2 as dopant, a green OLED with current efficiency (CE max ) of 35.47 cd A −1 , power efficiency (PE max ) of 34.35 lm W −1 , and external quantum efficiency (EQE max ) of 10.49% is fabricated. Interestingly, red exciplex emission is also observed in electroluminescence, arising from the interaction between the host materials (bis(2-(2-hydroxyphenyl)-pyridine)beryllium (Bepp 2 ) or 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene (TPBi)) and the dopant (DBFDPO-MnBr 2 ).The exciplex-based red OLED in this study exhibits the maximum CE and PE reaching 18.64 cd A −1 and 17.92 lm W −1 , respectively, which are among the up-to-date highest values for exciplex-based red OLEDs. Beneficial from the exciplex, it has the great potential to broaden the electroluminescent spectra with manganese(II) complex. Phosphorescent OLEDsThe ORCID identification number(s) for the author(s) of this article can be fou...

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We have developed semiconducting polymer nanoparticle-based photosensitizers for O2mapping and enhanced the PDT effect by using fluorescence resonance energy transfer.