Phenothiazine Moiety Research Articles

Efficient organic deep-red to near-infrared light emitters based on boron difluoride curcuminoid derivatives

Organic light-emitting materials in the near-infrared (NIR) region are important for lightweight and wearable medical and military device applications. However, there has been little development of highly efficient NIR light-emitting materials made of purely organic small molecules. This paper introduces tBuPZ and PZ, two novel deep-red to NIR light-emitting curcuminoid boron difluoride derivatives with phenothiazine moiety, to demonstrate organic light-emitting diodes with a maximum external quantum efficiency of 4.11% and 3.92%, respectively, and electroluminescence at 618 nm, with a shoulder peak at 673 nm. By analyzing the donor characteristics of di-tert-butyl substitution, the correlations between electron-donating strength, the emission mechanism, and quantum efficiency were investigated. This study presents a methodology for the design of low toxicity, dye-derived, purely organic NIR light-emitting molecules.

Phenothiazine functionalized fulleropyrrolidines: synthesis, charge transport and applications to organic solar cells.

A series of phenothiazine-C60/70 dyads containing fulleropyrrolidine tethered to C-3 position (C60-PTZ and C70-PTZ) or to the heteroatom N-position via either phenyl (C60-Ph-PTZ and C70-Ph-PTZ) or phenoxyethyl linkers (C60-PhOEt-PTZ and C70-PhOEt-PTZ) of the phenothiazine were synthesized and light-induced electron transfer events were explored. Optimized studies suggested that the highest molecular orbital (HOMO) resides on donor phenothiazine moiety while lowest molecular orbital (LUMO) on the acceptor fulleropyrrolidine moiety of the dyads. Optical and electrochemical properties suggested no electronic communication between the donor and acceptor moieties in the ground state. However, steady-state emission studies in solvents of varied polarity, involving selective excitation of C60/C70, disclosed that the emission intensity of C60/C70 was quenched in the dyads in the increasing order, C60/70-PTZ > C60/70-Ph-PTZ > C60/70-PhOEt-PTZ as a consequence of the donor-acceptor distance resulted due to spacer lengths. Also, the emission quenching is more pronounced in polar solvents such as DMF compared to a non-polar solvent, toluene. With the support of parallel electrochemical studies, the emission quenching is attributed to intramolecular photo-induced electron transfer occurring from PTZ to (C60/C70)* generating a radical ion pair, PTZ+⋅-C60-⋅/PTZ+⋅-C70-⋅. Finally, bulk heterojunction (BHJ) solar cells devices inverted fashion prepared by employing the dyads as acceptors, and PTB7 as donor, suggested that the devices prepared from C70 derivatives i.e., PTB7:C70-PTZ and PTB7:C70-PhOEt-PTZ exhibited better power conversion efficiency of 2.66% and 2.15%, respectively over C60 derivatives i.e., PTB7:C60-PTZ and PTB7:C60-PhOEt-PTZ with the efficiencies of 1.80 and 1.72%, respectively. AFM studies revealed that the poor performance of PTB7:C60-PTZ- and PTB7:C60-PhOEt-PTZ-based devices can be ascribed to the lower solubility of the dyads in 1,2-DCB solvent leading to rough morphology.

Naphthalimide-phenothiazine dyads: effect of conformational flexibility and matching of the energy of the charge-transfer state and the localized triplet excited state on the thermally activated delayed fluorescence.

In order to investigate the joint influence of the conformation flexibility and the matching of the energies of the charge-transfer (CT) and the localized triplet excited (3LE) states on the thermally activated delayed fluorescence (TADF) in electron donor–acceptor molecules, a series of compact electron donor–acceptor dyads and a triad were prepared, with naphthalimide (NI) as electron acceptor and phenothiazine (PTZ) as electron donor. The NI and PTZ moieties are either directly connected at the 3-position of NI and the N-position of the PTZ moiety via a C–N single bond, or they are linked through a phenyl group. The tuning of the energy order of the CT and LE states is achieved by oxidation of the PTZ unit into the corresponding sulfoxide, whereas conformation restriction is imposed by introducing ortho-methyl substituents on the phenyl linker, so that the coupling magnitude between the CT and the 3LE states can be controlled. The singlet oxygen quantum yield (ΦΔ) of NI-PTZ is moderate in n-hexane (HEX, ΦΔ = 19%). TADF was observed for the dyads, the biexponential luminescence lifetime are 16.0 ns (99.9%)/14.4 μs (0.1%) for the dyad and 7.2 ns (99.6%)/2.0 μs (0.4%) for the triad. Triplet state was observed in the nanosecond transient absorption spectra with lifetimes in the 4–48 μs range. Computational investigations show that the orthogonal electron donor–acceptor molecular structure is beneficial for TADF. These calculations indicate small energetic difference between the 3LE and 3CT states, which are helpful for interpreting the ns-TA spectra and the origins of TADF in NI-PTZ, which is ultimately due to the small energetic difference between the 3LE and 3CT states. Conversely, NI-PTZ-O, which has a higher CT state and bears a much more stabilized 3LE state, does not show TADF.

Very sensitive probes for quantitative and organoleptic detection of oxygen based on conformer-induced room-temperature phosphorescence enhancement of the derivative of triazatruxene and phenothiazine

Organic materials which show room-temperature phosphorescence (RTP) are of interest for many applications including chemical qubits which are the core units of a quantum information systems, organic light emitting diodes, chemical sensors. In contrast to triplet emitters based on noble metals (e.g. Ir, Rh), quantum yields of RTP of noble-atom-free organic emitters are much lower than unity. In this work, we report on a new approach to conformer-induced RTP enhancement of organic triplet emitters. The synthesis, thermal, photophysical, charge-transporting and oxygen sensing properties of the derivative of phenothiazine and triazatriazatruxene in which phenothiazine moieties are linked to nitrogen atoms of triazatriazatruxene via C-2 positions are presented. This compound exhibit stable RTP with a quantum yield of 54% which is more than six times higher than that of a reference material. For 1% solid solution of the compound in Zeonex, the ratio of intensity of RTP observed under vacuum and fluorescence intensity recorded in air reached the value of 19 which allows quantitative detection of oxygen with the high Stern-Volmer quenching constant of 7.83 × 10−3 ppm−1. The observed change of emission colour depending on the oxygen concentration can be used for the simple detection of oxygen by human eye.

Design, Regioselective Synthesis, and Photophysical Properties of Perfluoronaphthalene-Based Donor-Acceptor-Donor Fluorescent Dyes.

A one-step route to a series of perfluoronaphthalene-based donor (D)-acceptor (A)-D fluorescent dyes with various electron-donating groups was developed. The perfluoronaphthalene moiety in the D-A-D dyes served as a good electron-accepting aromatic ring with excellent intramolecular charge transfer properties, as determined by density functional theory calculations and measurements of the fluorescence properties in solution, in poly(methyl methacrylate) (PMMA) films, and in crystal form. Notably, replacing the naphthalene ring with perfluoronaphthalene in the D-A-D dyes carrying the phenothiazine moiety not only stabilized the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels but also reduced the energy band gap to change the emission color from blue to yellow. Among the four synthesized perfluoronaphthalene D-A-D dyes, those bearing diphenylamino groups afforded the best fluorescence quantum yields in Et2O solution (0.60) and in PMMA film (0.65) because the propeller structure of the diphenylamino group that acts as a donor substituent effectively suppresses radiation-free deactivation. In contrast, in the crystalline state, the carbazoyl-bearing D-A-D dye provided the best fluorescence quantum yield (0.35) because the radiation-free inactivation was suppressed by π-πF stacking at the donor site, which was confirmed by single-crystal X-ray analysis.

Novel Phenothiazine/Donepezil-like Hybrids Endowed with Antioxidant Activity for a Multi-Target Approach to the Therapy of Alzheimer's Disease.

Alzheimer’s disease (AD) is a complex multi-factorial neurodegenerative disorder for which only few drugs (including donepezil, DPZ) are available as symptomatic treatments; thus, researchers are focusing on the development of innovative multi-target directed ligands (MTDLs), which could also alter the course of the disease. Among other pathological factors, oxidative stress has emerged as an important factor in AD that could affect several pathways involved in the onset and progression of the pathology. Herein, we propose a new series of hybrid molecules obtained by linking a phenothiazine moiety, known for its antioxidant properties, with N-benzylpiperidine or N-benzylpiperazine fragments, mimicking the core substructure of DPZ. The investigation of the resulting hybrids showed, in addition to their antioxidant properties, their activity against some AD-related targets, such as the inhibition of cholinesterases (both AChE and BChE) and in vitro Aβ1-40 aggregation, as well as the inhibition of the innovative target fatty acid amide hydrolase (FAAH). Furthermore, the drug-likeness properties of these compounds were assessed using cheminformatic tools. Compounds 11d and 12d showed the most interesting multi-target profiles, with all the assayed activities in the low micromolar range. In silico docking calculations supported the obtained results. Compound 13, on the other hand, while inactive in the DPPH assay, showed the best results in the in vitro antioxidant cell assays conducted on both HepG2 and SHSY-5Y cell lines. These results, paired with the low or absent cytotoxicity of these compounds at tested concentrations, allow us to aim our future research at the study of novel and effective drugs and pro-drugs with similar structural characteristics.

Facile synthesis of phenothiazine-pyrazine-based donor-acceptor-donor regioisomers: Influence of molecular geometry on aggregation-induced emission

Aggregation-induced emission (AIE) fluorescent molecules are in great demand due to the wide range of applications. In this article, three regioisomers namely, o-PyPTZ, m-PyPTZ and p-PyPTZ, with pyrazine (Py) as acceptor and phenothiazine (PTZ) as donor, were rationally designed and synthesized. Phenothiazine moieties are attached to pyrazine core as peripheral groups at 2,3- 2,5- and 2,6-positions. The attachment of bulky PTZ pendants at different position of pyrazine core could influence the molecular packing modes, resulting in discrete photophysical and electronic properties. The resulting regioisomers are weakly fluorescent in dilute solutions but highly emissive upon aggregate formation, verifying their AIE activities. They are thermally and morphologically stable with degradation temperature of 372–407 °C. Single-crystal structures of three isomers indicate their twisted conformation. A detailed comparison of the photophysical, electronic and structural properties of these isomers has been made with a view to studying the outcome of the positional change.

Effects of donor position and multiple charge transfer pathways in asymmetric pyridyl-sulfonyl TADF emitters

We have designed and synthesized a pair of highly asymmetric D-aA-D′ type pyridyl-sulfonyl based isomers comprising phenothiazine (PTZ) and carbazole (Cz) donor units, which are able to emit thermally activated delayed fluorescence. PTZ-pS4-Py-2Cz and PTZ-mS4-Py-2Cz both possess spatial separation of HOMO/LUMO on the donor and acceptor moieties, resulting in small calculated singlet–triplet energy gaps (~0.25 eV). Both isomers exhibit dual emission, which is attributed to charge transfer states associated with the Cz and PTZ moieties at higher and lower energies, respectively. Photoluminescence quantum yields and time-resolved emission decays show significant differences for the two isomers, with the para- isomer exhibiting more efficient emission and stronger delayed fluorescence than the meta- isomer – in strong contrast to recently reported analogous Cz-Cz D-aA-D isomers. The findings clearly show that the interconversion of triplets via the rISC mechanism is promoted when parallel Cz and PTZ charge transfer states are allowed to interact, explaining the improved performance of the Cz-PTZ materials compared to the previous Cz-Cz ones. Finally, moderate device performance was achieved in warm-yellowish (CIE; 0.41; 0.53 & 0.49; 0.48) non-doped OLEDs, which exhibited 0.5% & 1.9% maximum external quantum efficiencies for the meta- and para- isomers, respectively.

N,N-di(4-methoxyphenyl)hydrazones of carbazole and phenothiazine carbaldehydes containing 4-methoxyphenyl groups as hole transporting materials

In a quest of exploitation of low-cost chemistry for the preparation of hole-transporting materials, we investigated the synthesis of N,N-di(4-methoxyphenyl)hydrazones and the corresponding dihydrazones of carbazole and phenothiazine carbaldehydes. The electron photoemission spectrometry measurements of the layers of the synthesized compounds revealed low ionization potentials in the range of 5.27–5.41 eV. Charge-transporting properties of the compounds were characterized by xerographic time of flight method. The measurements revealed hole mobilities reaching 10−3 cm2/Vs at high electric fields. DFT calculations of the geometry, electronic structure, absorption and photoluminescence spectra of the compounds were carried out to explain and supplement experimental data. The results of calculations show that the first maxima in absorption spectra of the compounds can be attributed to the π-π * local excitation of conjugated system including mainly lone electron pairs of the nitrogen atoms of hydrazone and carbazole or phenothiazine moieties. It is not accompanied by any significant charge transfer. The experimentally observed dramatic effect on the emissive properties of the compounds by attachment of the hydrazone moieties is explained by rotation of para-methoxyphenyl ring into the plane of carbazole moiety upon excitation, which leads to significantly larger charge transfer in the case of S1→S0 emission, compared to S0→S1 absorption.

Crystallization induced room-temperature phosphorescence and chiral photoluminescence properties of phosphoramides.

We report the design and synthesis of a series of room temperature phosphorescent phosphoramides TPTZPO, TPTZPS, and TPTZPSe with a donor (phenothiazine)–acceptor (P = X, X = O, S, and Se) architecture. All the compounds show structureless fluorescence with a nanosecond lifetime in dilute solutions. However, these compounds show dual fluorescence and room temperature phosphorescence (RTP) in the solid state. Both the intensity and energy of luminescence depend on the heteroatom attached to the phosphorus center. For example, compound TPTZPO with the P Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O unit exhibits fluorescence at a higher energy region than TPTZPS and TPTZPSe with the PS and PSe groups, respectively. Crystalline samples of TPTZPO, TPTZPS, and TPTZPSe show stronger RTP than the amorphous powder of respective compounds. Detailed steady-state, time-resolved photoluminescence and computational studies established that the 3n–π* state dominated by the phenothiazine moiety is the emissive state of these compounds. Although TPTZPS and TPTZPSe crystallized in the chiral space group, only TPTZPSe showed chiroptical properties in the solid state. The luminescence dissymmetry factor (glum) value of TPTZPS is small and below the detection limit, and a CPL spectrum could not be observed for this compound.

Photophysical Properties and Electronic Structure of Symmetrical Curcumin Analogues and Their BF2 Complexes, Including a Phenothiazine Substituted Derivative

Symmetrically substituted curcumin analogue compounds possess electron donor moieties at both ends of the conjugated systems; their difluoroboron complexes were synthesized, and their structures were fully characterized. A novel compound with enhanced photophysical properties bearing phenothiazine moieties is reported. The introduction of BF2 into the molecular structures resulted in bathochromic shifts both in the absorption and emission spectra, indicating that the π-conjugation was more extended than the one in the initial compounds. The solvatochromic effects were studied, which in case of the phenothiazinyl-curcumin BF2 complex was the most notable. Theoretical study of the investigated compounds was carried out using DFT and TD-DFT methods to evaluate the ground state geometries and vertical excitation energies.

Circularly polarized luminescent 4, 4′-bicarbazole scaffold for facile construction of chiroptical probes

Small molecules with circularly polarized luminescence (CPL) are especially valuable in solution-based applications, like chiroptical probes for effective sensing. However, such application has not been well explored due in part to hard introduction of appropriate triggerable fluorophores. Herein, we report an easily post-modifiable CPL-active scaffold (4) and further propose a feasible strategy to construct chiroptical probes for sensing hypochlorous acid. Helically chiral 4 with a 4, 4′-bicarbazole scaffold exhibits a large Stokes shift up to 142 nm and glum value of 0.9 × 10−3. Through facile construction of phenothiazine moiety on 4, red-emitting compound 5 was obtained in high yield (85.3%), showing distinct optical and chiroptical responses towards hypochlorous acid with good liner relationships and CPL sign blue-shifting of 120 nm in vitro. The probe is also applied to detect endogenous hypochlorous acid in living macrophages and can serve as a CPL sensor. Taking 5 as an application example, we envision that CPL-enabling scaffold 4 could find broad use in the design of more chiroptical probes.

TADF quenching properties of phenothiazine or phenoxazine-substituted benzanthrones emitting in deep-red/near-infrared region towards oxygen sensing

Aiming to develop new deep-red/near-infrared emitters, benzanthrone as a new acceptor moiety with a rigid molecular structure was used. For the design of target compounds phenothiazine and phenoxazine moieties with strong electron-donating ability were also used. Such combination allowed new materials demonstrating thermally activated delayed fluorescence (TADF) in the long wavelength region to be obtained. The maximum intensity of fluorescence of the solid samples of the synthesized compounds was observed at 700 nm. Electroluminescence was peaked at similar wavelength when the compounds were used as emitters for the fabrication of non-doped organic light-emitting diodes. Due to the different substitutions of benzanthrone moieties, the values of TADF lifetimes at room temperature were found to be of in the range of 291–1198 μs which are directory related to their different oxygen sensing properties. Due to high sensitivity to the presence of oxygen in the atmosphere one of the obtained compounds was used for radiometric oxygen sensing. The film of molecular dispersion of phenoxazine containing compound in inert polymer ZEONEX® showed the ratio of intensity of TADF taken in vacuum and of prompt fluorescence taken under oxygen purge of 15.2. The oxygen sensitivity of the film estimated by Stern-Volmer constant was found to be of 1.6 × 10−4 ppm−1 demonstrating good reversibility. The time dependent density functional theory (DFT) calculations were used for the interpretation of the experimental results related to the structure and photophysical properties of the compounds.

A Tri-state Fluorescent Switch with "Gated" Solid-state Photochromism Induced by an External Force.

Mr. Chen Qian, Dr. Zhimin Ma, Mr. Jianwei Liu, Mrs. Xue Zhang, Prof. Shitao Wang and Prof. Zhiyong Ma. In this article, we report a newly designed molecule composed of a dihydroazulene (DHA) group and a phenothiazine (PTZ) moiety, which achieves aggregation-induced emission enhancement (AIEE), mechanochromism and "gated" solid-state photochromism upon stimulation by an external force. Grinding loosens intermolecular interactions in the crystal and causes a red-shift of fluorescence from 570 nm to 600 nm. Meanwhile, the ring-opening reaction of DHA unit is activated by grinding and a remarkable photochromism could be observed from the grinded powder. The reddish emission of the grinded powder peaked at 600 nm weakened gradually and finally became dark, and a new absorption band at 470 nm emerged in the absorption spectra. Time-dependent density functional theory (TD-DFT) calculation results reveal that the intramolecular intramolecular charge-transfer (ICT) process is replaced by a locally excited (LE) emission on the DHA group, which leads to the quenching of fluorescence. Its impressive photochromic property inspired us to a simple but effective way to develop an encryption system which can let the correct information be displayed upon external stimulation.

Phenothiazine-coumarin-pyridine hybrid as an efficient fluorescent probe for ratiometric sensing hypochlorous acid

Hypochlorous acid (HOCl) is one of the most potent reactive oxygen species and plays a vital role in many biological processes. Chemical probes for HOCl have proven to be valuable tools in understanding its contributions to healthy and disease states. Herein, a new ratiometric fluorescent probe (1), which composed of a coumarin scaffold bearing a phenothiazine moiety as the electron-donating group and a pyridine unit as the electron-accepting group, was rationally designed and synthesized for sensing HOCl. Probe 1 exhibited a distinct deep-red emission (∼630 nm), while displayed a completely different emission in the cyan region (∼500 nm) upon the addition of HOCl, thereby allowing the ratiometric detection of HOCl without spectral crosstalk interference. In addition, the presented probe has several other advantages for HOCl detection, including rapid response, high signal to noise ratio, excellent selectivity and sensitivity. Furthermore, the probe has shown the utility for visualizing HOCl in cells and organisms.

Phenothiazines as dual inhibitors of SARS-CoV-2 main protease and COVID-19 inflammation

COVID-19, caused by the severe acute respiratory coronavirus 2 (SARS-CoV-2), currently has no treatment for acute infection. The main protease (Mpro) of SARS-CoV-2 is an essential enzyme for viral replication and an attractive target for disease intervention. The phenothiazine moiety has demonstrated drug versatility for biological systems, including inhibition of butyrylcholinesterase, a property important in the cholinesterase anti-inflammatory cascade. Nineteen phenothiazine drugs were investigated using in silico modelling techniques to predict binding energies and inhibition constants (Ki values) with SARS-CoV-2 Mpro. Because most side-effects of phenothiazines are due to interactions with various neurotransmitter receptors and transporters, phenothiazines with few such interactions were also investigated. All compounds were found to bind to the active site of SARS-CoV-2 Mpro and showed Ki values ranging from 1.30 to 52.4 µM in a rigid active site. Nine phenothiazines showed inhibition constants <10 µM. The compounds with limited interactions with neurotransmitter receptors and transporters showed micromolar (µM) Ki values. Docking results were compared with remdesivir and showed similar interactions with key residues Glu-166 and Gln-189 in the active site. This work has identified several phenothiazines with limited neurotransmitter receptor and transporter interactions and that may provide the dual action of inhibiting SARS-CoV-2 Mpro to prevent viral replication and promote the release of anti-inflammatory cytokines to curb viral-induced inflammation. These compounds are promising candidates for further investigation against SARS-CoV-2.

Oxygen sensing properties of thianthrene and phenothiazine derivatives exhibiting room temperature phosphorescence: Effect of substitution of phenothiazine moieties

Four new derivatives of thianthrene and phenothiazine are reported as emitters for oxygen sensing. They exhibit both fluorescence and phosphorescence at room temperature. Effects of the substitution pattern of phenothiazine moiety on the thermal, electrochemical, emissive and oxygen sensing properties of the compounds are discussed. No phosphorescence at room-temperature was detected for deoxygenated solutions of the compounds. Room temperature phosphorescence of the different intensity was detected for the compounds being in crystalline or amorphous phase and for their dispersions in different polymeric matrices. Fast oxygen response (ca. 0.1 s) of room temperature phosphorescence was observed for only 1 wt.% of the dispersions in polymeric host. The highest oxygen sensitivity, was demonstrated for methylphenothiazinyl-disubstituted thianthrene dispersed in poly(methyl methacrylate). Stern-Volmer constant of 21·10−4 ppm−1 was obtained compared to those of 0.97·10−4, 1.22·10−4 and 2.1·10−4 ppm−1 observed for the dispersions of other compounds. Displaying possibility of oxygen detection by different chromaticity responses of emission of the developed compounds, strong yellowish-green emission with CIE1931 coordinate of (0.294, 0.503) was observed for one sample in the absence of oxygen; while, weak deep-blue emission with CIE1931 coordinate of (0.174, 0.141) was observed for the same sample in oxygen atmosphere.

Donor-acceptor type π-conjugated diphenylsulfone derivatives showing diverse fluorescence response to mechanical force

Two donor-acceptor type π-conjugated fluorophores DPS-OCZ and DPS-OPTZ consisting of diphenylsulfone unit as the electron-accepting and carbazole or phenothiazine moiety as the electron-donating were synthesized and characterized. They showed evident ICT characters endowed both fluorophores with a prominent solvatochromic effect, with emitting color tuning by changing the solvent polarity. Spectral studies and theoretical calculations proved the presence of D-A type conjugated structures of DPS-OCZ and DPS-OPTZ. Interestingly, both fluorophores showed diverse fluorescence response to mechanical force (bathochromic shift for DPS-OPTZ or hypsochromic shift for DPS-OCZ). Based on the results of XRD patterns and X-ray single crystals analyses, the reason is as follows: the planarization of the molecular conformation and the resulting planar ICT upon grinding were responsible for the bathochromic shift in the PL spectra of DPS-OPTZ. In contrast, the highly ordered structure was destroyed, partly changed the packing mode, resulting in the hypsochromic shift in PL spectra of DPS-OCZ. The current work presented a strategy of imposing molecular feature screening for realizing diverse fluorescence response to mechanical force.

A dual-response fluoran-phenothiazine hybrid fluorescent probe for selective sensing of Fe3+ and ClO− and cell imaging application

Bifunctional fluorescent probes with dual-emission response attract extensive attention. A novel fluorescent probe FP, a hybrid of fluoran and phenothiazine, has been designed and synthesized for selective sensing of Fe3+ and ClO− with dual-emission changes, which involes mechanisms of Fe3+-promoted spirolactone ring opening and ClO−-induced oxidation of phenothiazine moiety, respectively. In addition, the detection limits for Fe3+ and ClO− were estimated to be 49.1 and 35.9 nM, respectively. Significantly, FP can be employed as an tracer for the detection of Fe3+ ions within living HeLa cells by fluorescence imaging.

Ratiometric fluorescence imaging of hypochlorous acid in living cells and zebrafish using a novel phenothiazine-fused HPQ probe

Hypochlorite (ClO−), as a typical weak acidic ROS, is mainly endogenously produced by myeloperoxidase (MPO) catalyzing hydrogen peroxide (H2O2) and chloride ion (Cl−) in leukocytes. Imbalance of hypochlorite concentration will not only cause biomolecular oxidation in organism, but also are correlated with a variety of physiological diseases. In this study, a novel ratiometric fluorescence probe PHPQ for detecting ClO- by incorporating the phenothiazine moiety into the HPQ fluorophore was designed and synthesized. The probe PHPQ was shown to be capable of selectively and sensitively monitoring ClO- in a fine ratiometric manner. It also displayed the merits of large blue-shift (98 nm), rapid response (30 s), excellent sensitivity (15 nM) and significant fluorescence ratiometric variations (253-fold). Moreover, PHPQ was successfully utilized for bioimaging exogenous/endogenous ClO- in living cells (MGC-803 and RAW264.7) and in zebrafish.