Electron-deficient Moiety Research Articles

Construction of Donor-Acceptor-Type Conjugated Microporous Polymers by Oxidative Coupling of Boranil-Carbazole Mixed Monomers for Enhanced Photocatalytic Oxidation.

Conjugated microporous polymers (CMPs), featuring photoactive structures, a high surface area, robust thermal stability, and facile modulation, provide a versatile platform for fabricating diverse heterogeneous photocatalysts. The incorporation of donor-acceptor (D-A) structures into CMPs to increase their charge separation potential and enhance the photocatalytic efficacy is a viable strategy. In this work, we designed and synthesized a unique set of D-A monomers, incorporating boranil dyes as electron-deficient moieties and carbazoles as electron-rich subunits. Subsequently, D-A CMPs were prepared via an economical and environmentally friendly oxidation coupling reaction, and their potential in photocatalytic oxidation reactions was investigated. Modulation of the polymer's photoelectronic properties and photocatalytic performance can be achieved by adjusting the boranil content in the monomer. The polymer pCZFB-3, with the highest content of boranil units, exhibited an optimal photocatalytic activity. This finding confirms that strengthening the D-A effect can significantly enhance a catalyst's photoelectronic properties and catalytic efficacy. This study presents insights into designing innovative heterogeneous photocatalysts based on boron-containing dyes.

Suppressing the hydrogen bonding interaction with *OOH toward efficient H2O2 electrosynthesis via remote electronic tuning of Co-N4

The non-covalent interaction that appears along with electronic tuning is often overlooked in interpreting the oxygen reduction reaction (ORR) dynamics, resulting in a limited understanding of the governing principles. Herein, through intricately engineering pedant substituents on porphyrins backbones, Co-N4 moieties featuring varied electronic configurations served as an exemplary model to elucidate the role of hydrogen bonding interaction appears along with electronic tuning in determining 2e- ORR performance. Co-TEPP with an electron-deficient Co-N4 moiety emerges as a standout performer for O2-to-H2O2 conversion. Upon covalently linking the Co-TEPP monomer on rGO to form robust organic polymer structures (Co-TEPP-COP/rGO), superior H2O2 selectivity (> 95 %), remarkable H2O2 production rate (∼18.8 mol gcat−1 h−1), and excellent performance durability are identified. Such optimized H2O2 electrosynthesis could be attributed to the suppressed hydrogen bonding interaction between *OOH and electron-deficient Co-N4 moiety, which consequently weakens *OOH binding strength to favor H2O2 electrosynthesis.

Thermally activated delayed fluorescence dyes featuring an intramolecular-locked azaryl ketone acceptor for electroluminescence application

We have developed two novel thermally activated delayed fluorescence (TADF) emitters, IQLO-PXZ and IQLO-DMAC, featuring an intramolecularly locked indeno[1,2-b]quinolin-11-one (IQLO) acceptor. Our comprehensive investigation, including structural analysis, theoretical calculations, and photophysical studies, aims to assess the viability of IQLO-PXZ and IQLO-DMAC as light emitters in electroluminescent devices. Unlike existing aryl ketone-based emitters, IQLO-PXZ and IQLO-DMAC exhibit red-shifted emission due to their structurally rigid and electron-deficient IQLO moiety. The stronger intramolecular charge transfer effect in IQLO-PXZ results in longer-wavelength emission compared to IQLO-DMAC. Both emitters demonstrate significant TADF properties, facilitating efficient triplet-to-singlet spin conversion. When utilized as the emissive core in electroluminescent devices, IQLO-PXZ and IQLO-DMAC achieved long-wavelength electroluminescence peaking at 612 nm and 578 nm, with commendable external quantum efficiencies of 10.3 % and 11.7 %, respectively. These findings underscore the potential of IQLO as an effective acceptor for constructing high-performance TADF electroluminescent materials.

Cationic manganese(II)-based metal-organic framework constructed from viologen derivative with multifunctional properties

Utilizing the rigid and linear viologen carboxylic ligand as an organic linker, we have successfully synthesized and structurally characterized a multifunctional Mn-based cationic metal-organic framework (1). Compound 1 features a three-dimensional framework structure with a positively charged skeleton, wherein triangular pores accommodate [MnCl4]2− anions to preserve charge neutrality. Notably, compound 1 demonstrates a chemical chromism phenomenon, transitioning from yellow-brown to deep green upon exposure to ammonia. This color change is attributed to the nucleophilic attack of electron-rich ammonia molecules on the electron-deficient viologen moiety of viologen carboxylic ligand, leading to the formation of viologen radicals and charge transfer complexes. Moreover, compound 1 exhibits rapid and selective detection of antibiotics like metronidazole (MDZ) and dimetridazole (DTZ) via a competitive absorption-induced luminescence quenching process, featuring high quenching coefficients and low detection limits. Additionally, magnetic property investigations reveal predominant antiferromagnetic coupling between Mn(II) ions within compound 1.

Tailored fluorophore design: Enhancing selectivity for cyanide ion sensing in water and food samples, and innovative device development

A rigid fluorophore unit of Julolidine/coumarin fused with an indolium-conjugated system was built for the immediate and effective recognition of cyanide ions in a 90 % aq. DMSO solution. The probes are capable of displaying better sensitivity/selectivity for the cyanide ion over a wide range of other interfering ions. The probe JI showed an instant colorimetric variation, whereas the modified probe JCI showed both colorimetric and fluorimetric variation with cyanide ion. The observed detection limit values indicated excellent sensitivity of the probe to the cyanide ion. HRMS and 1H NMR studies confirmed that the mechanism of detection of CN− is via the nucleophilic attack on the electron-deficient indolium moiety of the molecule. Moreover, the probes are well proficient in selective recognition of cyanide in various real time applications (test strips, electronic sensor kit, food and water sample analysis).

Novel Re(I) Complexes as Potential Selective Theranostic Agents in Cancer Cells and In Vivo in Caenorhabditis elegans Tumoral Strains.

A series of rhenium(I) complexes of the type fac-[Re(CO)3(N^N)L]0/+, Re1-Re9, was synthesized, where N^N = benzimidazole-derived bidentate ligand with an ester functionality and L = chloride or pyridine-type ligand. The new compounds demonstrated potent activity toward ovarian A2780 cancer cells. The most active complexes, Re7-Re9, incorporating 4-NMe2py, exhibited remarkable activity in 3D HeLa spheroids. The emission in the red region of Re9, which contains an electron-deficient benzothiazole moiety, allowed its operability as a bioimaging tool for in vitro and in vivo visualization. Re9 effectivity was tested in two different C. elegans tumoral strains, JK1466 and MT2124, to broaden the oncogenic pathways studied. The results showed that Re9 was able to reduce the tumor growth in both strains by increasing the ROS production inside the cells. Moreover, the selectivity of the compound toward cancerous cells was remarkable as it did not affect neither the development nor the progeny of the nematodes.

A reaction based carbazole-indolium conjugate probe for the selective detection of environmentally toxic ions.

A nucleophilic addition based chemodosimeter was designed and synthesized with a carbazole donor and an indole acceptor. The addition of a cyanide ion to an electron-deficient indole moiety disrupts the acceptor-donor relationship, resulting in noticeable color shifts and spectrum differences in both the absorption and emission profiles. The design has a D-π-A molecular arrangement. Selectivity was investigated in 90% aqueous DMSO solution of probe CI with various anions such as SCN-, PF6-, NO3-, N3-, I-, HSO4-, CN-, H2PO4-, F-, HS-, ClO4-, Cl-, Br-, and AcO-. An intermolecular charge transfer (ICT) band at 506 nm in the UV-visible spectra vanished and the intensity of emission was quenched at 624 nm upon the addition of CN- ions. These outcomes demonstrate the effective nucleophilic addition of cyanide ions to the electron-deficient indole moiety of the probe, resulting in the formation of a new adduct in which the ICT transition is interrupted when π conjugation is blocked. The Job plot, 1H NMR spectroscopy, and HRMS analysis confirmed the formation of a new product. An outstanding response was shown by paper test strips made using probe molecules for the easy detection of cyanide ions in aqueous solutions. Besides, the probe selectively senses cyanide ions in different water samples.

Modular Synthesis of Benzoylpyridines Exploiting a Reductive Arylation Strategy.

Herein we disclose a telescoped flow strategy to access electronically differentiated bisaryl ketones as potentially new and tunable photosensitizers containing both electron-rich benzene systems and electron-deficient pyridyl moieties. Our approach merges a light-driven (365 nm) and catalyst-free reductive arylation between aromatic aldehydes and cyanopyridines with a subsequent oxidation process. The addition of electron-donating and withdrawing substituents on the scaffold allowed effective modification of the absorbance of these compounds in the UV-vis region, while the continuous flow process affords high yields, short residence time, and high throughput.

Facile Synthesis of Nitrogen Cation-Doped Polycyclic Aromatic Hydrocarbons by Anodic Intramolecular Pyridination

The bottom-up synthesis of heteroatom-doped polycyclic aromatic hydrocarbons (PAHs) has attracted attention in the development of models of doped graphene. Among PAHs, nitrogen-cation (N +)-doped PAHs are known to exhibit superior optoelectronic functionalities; however, practical methods for synthesizing N +-doped PAHs are limited and challenging [1]. In our previous study, the SNAr reaction was used for the intramolecular cyclization of phenylpyridine derivatives possessing an electron-deficient perfluoroaryl moiety to give the corresponding N +-doped triphenylene in high yields under moderate conditions without the use of a transition-metal catalyst [2,3]. However, one of the challenges in the synthesis of N +-doped PAHs via the SNAr reaction is poor functional-group tolerance.Here, a facile and selective synthesis method for N +-doped PAHs has been established via anodic intramolecular cyclization, inspired by the Yoshida’s protocol for C–H amination without a transition-metal catalyst or an oxidant [4]. The reaction mechanism, in particular the reaction selectivity, was elucidated using density functional theory (DFT) calculations. The N +-doped PAH products were found to have a donor–acceptor structure composed of an arene moiety and a pyridinium moiety, as evidenced by DFT calculations, UV–vis analysis, and electrochemical measurements. The proposed intramolecular anodic pyridination is a practical strategy for the late-stage introduction of N+ into π-electron systems and broadens the scope of molecular design of N +-doped PAHs.

An electron-deficient viologen metal-organic material for colorimetric and luminescence sensing of organic amines

Organic amines are ubiquitous and essential in the dye, polymer, and pharmaceutical industries, but can also be highly corrosive and toxic. Developing a quick and efficient method to detect organic amines is an important challenge. In this paper, we demonstrate the detection of organic amines by colorimetric and luminescence sensing of an electron-deficient viologen metal organic material. The material, comprising 1-(3,5-dicarboxyphenyl)-4,4′-bipyridinium and Cd(II), possesses a two-dimensional framework with viologen-lined chromophores and accessible electron-deficient viologen moieties constituting Lewis acidic sites. It exhibits reversible photochromic behavior under UV–Vis light irradiation and a visual color change and fluorescence quenching upon contact with amine vapors and solutions. Due to the defined pore size of the framework, the fluorescence sensing efficiency showed organic amine size dependence. The vapochromism and fluorescence quenching is attributable to electron transfer from the organic amine to the electron-deficient viologen moiety, generating colored viologen radicals.

Rational design of dibenzo[a,c]phenazine-derived isomeric thermally activated delayed fluorescence luminophores for efficient orange-red organic light-emitting diodes

It is an immense challenge to develop efficient long-wavelength (orange-to-red) thermally activated delayed fluorescence (TADF) materials due to the increasing nonradiative decay rates following the energy-gap law. Herein, two pairs of asymmetric isomers; DPyPzTPA and TPAPzDPy, and PyPzDTPA and DTPAPzPy based on electron-deficient moieties dibenzo[a,c]phenazine (Pz) and pyridine (Py) combined with electron-donor units of triphenylamine (TPA) were designed and synthesized. Their photophysical properties could be finely modulated by changing the position and number of Py groups as well as TPA fragments onto Pz cores. DPyPzTPA and DTPAPzPy possess much more rigidity and thus less geometry relaxation and non-radiative decay between ground states and excited states than those of PyPzDTPA and TPAPzDPy. Intriguingly, DPyPzTPA exhibits the highest relative photoluminescence quantum yield (ΦPL) and the fastest reverse intersystem crossing (rISC) rate among them owing to relatively stronger rigidity and spin-orbit coupling (SOC) interactions between the lowest singlet (S1) and energetically close-lying excited triplet state and therefore, the device showed the highest maximum external quantum efficiency (EQEmax) of 16.6% (60.9 lm/W, 53.3 cd/A) with Commission Internationale de I'Eclairage (CIE) coordinates of (0.43, 0.55), peak wavelength 556 nm. In stark contrast, due to its lower rigidity and extremely weak delayed fluorescence (DF) characteristic and thus the much lower ΦPL, TPAPzDPy-based devices are only half as efficient (30.8 lm/W, 27.5 cd/A, 8.3% EQE) despite the isomers possessing equal singlet-triplet energy gaps (ΔEST) of 0.43 eV. On the other hand, the device based on DTPAPzPy also demonstrated a strongly enhanced performance (59.1 lm/W, 52.7 cd/A, 16.1% EQE) than its isomer PyPzDTPA-based device (39.5 lm/W, 35.2 cd/A, 10.3% EQE). This work explicitly implicates that the asymmetric and isomeric molecular design is a potential strategy for promoting the development of highly efficient long-wavelength TADF materials.

Recent Advances in the Gold-Catalyzed Reactions of Propargyl Esters.

ConspectusLate-transition-metal-based complexes represent an indispensable catalytic tool in chemical synthesis due to their ability to increase molecular complexity rapidly and efficiently from readily accessible substrates in a single operation. Added to this is the exquisite control of product chemo-, diastereo-, enantio-, and site-selectivities achieved by catalytic systems of the transition-metal salts that have been developed to mediate a wide range of functional group transformations. Within this venerable synthetic toolbox, complexes and salts of Au(I) and Au(III) have emerged in recent years as an invaluable addition as a result of their potent σ- and π-Lewis acidities and ability to stabilize cationic reaction intermediates. The insights provided by mechanistic studies examining the various electronic, steric, and stereoelectronic factors at play in the organogold species that are expected to be formed in the catalytic chemistry of the transition-metal complex have also been pivotal in understanding and exploring their potential synthetic utility. Illustrative of this, for example, is the contribution made by the gold-catalyzed cycloisomerization chemistry of propargyl esters in synthetic strategies to a variety of bioactive natural products and compounds of current pharmaceutical and materials interest. This Account summarizes our efforts over the past decade toward realizing new single-step strategies for carbocyclic and heterocyclic synthesis that relied on the gold-catalyzed reactions of propargyl esters. It outlines synthetic methods developed by the group that exploited the unique reactivities of the gold-carbene species typically generated from the [2,3]-sigmatropic rearrangement of the compound class containing a terminal or electron-deficient alkyne moiety on exposure to the transition-metal salt. This Account also describes the realization of synthetic methods initiated by the gold-catalyzed 1,3-acyloxy migration of propargyl esters with an electronically unbiased disubstituted C≡C bond that delivers the corresponding allenyl ester that is primed for further reactivity on activation by the group 11 metal complex. The studies formed a part of an ongoing overarching program within our group that was focused on determining reactivities in gold catalysis that would enable their application as readily recognizable disconnections in retrosynthetic analysis. They were additionally a part of efforts aimed at evaluating the opportunities offered by the relativistic effects possessed by a Au(I) and Au(III) complex, the most pronounced among the d-block elements and thus the catalyst of choice in alkyne activation chemistry, to generate new chemical space. For instance, we demonstrated in several studies the cycloisomerization of 1,3- and 1,4-enyne esters to be a reliable strategy for the in situ formation of a wide range of 1,4-cyclopentadienyl derivatives. Their further reaction with an appropriately placed functional group or a second starting material was then shown to afford a variety of synthetic targets containing the five-membered ring structure. An example of this was the assembly of a new member of the 1H-isoindole compound family that was found to exhibit potent TNF-α (tumor necrosis factor-α) inhibitor activity.

Unique Electron Deficient Molecule for Thermally Activated Delayed Fluorescence Application

Utilizing purely organic materials with relatively highly emissive characteristics for designing organic light-emitting diodes (OLEDs) is fascinating since employing rare metals is unessential, hence, enormous research activities have been conducted in this field. Recently, additional efforts were devoted to designing special emitting materials demonstrating thermally activated delayed fluorescence (TADF). Molecular structures were ideally designed in a specific way using an electron-deficient molecule as an acceptor (A) and an electron-rich molecule as a donor (D) in order to minimize the overlapping between the highest occupied molecular orbital (HOMO) of the donor (D) and the lowest unoccupied molecular orbital (LUMO) of the acceptor (A). TADF requires a small band gap between the singlet excited and triplet excited states (ΔEST), usually less than (c.a 0.1 eV) of the luminescent material. This makes it possible to thermally harvest the excitons from the triplet excited state (T1) to the singlet excited state (S1) by a process known as reverse intersystem crossing (RISC) and then to harvest all the excitons for the fluorescence process. Thus, the design of the TADF molecular structure needs both an electron-rich segment as a donor and an electro-deficient segment as an acceptor. Up to the present, electron-deficient moieties (EDM) have been studied less than electron rich moieties (ERM) during the last few years. This review is highlighting the recent advances regarding the specific molecular designs of TADF emission materials for OLED applications, particularly, focusing on (dibenzothiophene-S,S-dioxide) as electron deficient molecule, which exhibits a strong electron-deficient unit and high ability of photo- and electroluminescence features. HIGHLIGHTS Purely organic materials with relatively highly emissive characteristics were used for designing organic light-emitting diodes (OLEDs) since employing rare metals is unessential, hence, enormous research activities have been conducted in this field. Recently, additional efforts were devoted to designing special emitting materials demonstrating thermally activated delayed fluorescence (TADF). GRAPHICAL ABSTRACT

New Strategies for the Functionalization of Carbonyl Derivatives via α-Umpolung: From Enolates to Enolonium Ions.

ConspectusUmpolung, a term describing the reversal of innate polarity, has become an indispensable tool to unlock new chemical space by overcoming the limitations of natural polarity. Introduced by Dieter Seebach in 1979, this principle has had a tremendous impact on synthetic organic chemistry, offering previously inaccessible retrosynthetic disconnections. In contrast to the great progress made over the past decades for the generation of effective acyl anion synthons, the umpolung at the α-position of carbonyls (converting enolates into enolonium ions) has long proved challenging and only recently regained traction. Aiming to develop synthetic approaches to α-functionalization capable of complementing enolate chemistry, our group initiated, nearly 6 years ago, a program devoted to the α-umpolung of carbonyl derivatives. In this Account, following an overview of established methods, we will summarize our findings in this rapidly developing field. We focus on two distinct, yet related, topics of two carbonyl classes: (1) amides, where umpolung is enabled by electrophilic activation, and (2) ketones, where umpolung is enabled using hypervalent iodine reagents. Our group has developed several protocols to allow amide umpolung and subsequent α-functionalization, relying on electrophilic activation. Over the course of our investigations, transformations that are particularly challenging using enolate-based approaches, such as the direct α-oxygenation, α-fluorination, and α-amination of amides as well as the synthesis of 1,4-dicarbonyls from amide substrates, have been unlocked. Based on some of our most recent studies, this method has been shown to be so general that almost any nucleophile can be added to the α-position of the amide. In this Account, special emphasis will be placed on the discussion of mechanistic aspects. It is important to note that recent progress in this area has involved a shift in focus, moving even further away from the amide carbonyl, a development that shall also be detailed in a final subsection that highlights our latest investigations of umpolung-based remote functionalization of the β- and γ-positions of amides. The second section of this Account covers our more recent work dedicated to the exploration of the enolonium chemistry of ketones, unlocked through the use of hypervalent iodine reagents. By placing our work in the context of previous pioneering achievements, which mainly focused on the α-functionalization of carbonyls, we discuss new skeletal reorganizations of enolonium ions enabled by the unique properties of incipient positive charges α to electron-deficient moieties. Transformations such as intramolecular cyclopropanations and aryl migrations are covered and supplemented by detailed insight into the unusual nature of the intermediate species, including nonclassical carbocations.

Covalent S-Adenosylhomocysteine-Based DNA Methyltransferase 2 Inhibitors with a New Type of Aryl Warhead.

The DNA methyltransferase 2 (DNMT2) is an RNA modifying enzyme associated with pathophysiological processes, such as mental and metabolic disorders or cancer. Although the development of methyltransferase inhibitors remains challenging, DNMT2 is not only a promising target for drug discovery, but also for the development of activity-based probes. Here, we present covalent SAH-based DNMT2 inhibitors decorated with a new type of aryl warhead. Based on a noncovalent DNMT2 inhibitor with N-benzyl substituent, the Topliss scheme was followed for optimization. The results showed that electron-deficient benzyl moieties highly increased affinity. By decorating the structures with strong electron-withdrawing moieties and leaving groups, we adjusted the electrophilicity to create covalent DNMT2 inhibitors. A 4-bromo-3-nitrophenylsulfonamide-decorated SAH derivative (80) turned out to be the most potent (IC50 = 1.2 ± 0.1 μM) and selective inhibitor. Protein mass spectrometry confirmed the covalent reaction with the catalytically active cysteine-79.

Exploring Zr-based Metal-Organic Frameworks as Smart Electrochromic Sensors by Coordination-Driven Surface Engineering.

As emerging stimuli-responsive materials, electrochromic metal-organic frameworks (MOFs) are still not utilized in sensing applications due to difficulties in water stability, facile synthesis and functionalization, and efficient translation of specific recognition events. Here, we firstly find that a Zr-based MOF furnished with postsynthetically created viologen-like electron-deficient moiety was electrochromic active. With a coordination-driven surface engineering strategy where phosphate-containing biomolecules are tethered to Zr nodes of the MOF, fine tuning the interface electron transfer was readily achieved, thus benefitting for constructing smart electrochromic sensors through the combination of the sensitivity of electrochemistry with the visuality of colorimetry. Particularly, MOF-coated conductive films enabled label-free detection of phosphoproteins, and aptamer-functionalized ones responded specifically to the target. In two cases distinct color changes allow for visual quantification. This study represents the first example of MOF-based electrochromic sensors developed by an efficient strategy, indicating the generality to electrochromic counterparts for various sensing applications.

Selective recognition of cyanide ion by colorimetric hydrazide based Cr(III) chemosensor

A novel chemosensor based on Nifuroxazide Cr(III) complex was developed for recognizing CN– over other tested anions e.g., F–, Cl–, Br–, I–, CH3COO–, NO2–, PO43–, and SCN– in DMSO–H2O (9:1, v/v) and THF. Without any interference from the tested anions, UV–vis spectroscopy was used to investigate the recognition of CN–. The deprotonated species that resulted from the ionization of the phenolic group may be the cause of the color shift that occurred after adding CN– to the solution of the Cr(III) complex. The charge transfer interaction between the electron-donor unit and the electron-deficient nitro-furan moiety was improved as a result of the ionization of the phenolic group. The fact that the developed color vanishes in protic polar solvents e.g., H2O, CH3OH, and C2H5OH may lend credence to this assumption. The Lambert–Beer's law was obeyed in the concentration ranges of 3.4 × 10−3–3.4 × 10−5 M and 1.0 × 10−4–5.0 × 10−6 M in DMSO–H2O (9:1, v/v) and THF, respectively, reflecting the significant role of the solvent in controlling the sensitivity of the developed probe. The electronic transitions were investigated by executing time-dependent density functional theory calculations.

Acceleration Effect of Bowl-Shaped Structure in Aerobic Oxidation Reaction: Synthesis of Homosumanene ortho-Quinone and Azaacene-Fused Homosumanenes.

An oxidation reaction of hydroxyhomosumanene on silica gel providing homosumanene ortho-quinone and its synthetic application for azaacene-fused homosumanenes is described. Hydroxyhomosumanene is photochemically oxidized by air, when it is coated on silica gel; this aerobic oxidation proceeds faster than that of planar analogues. The difference of such reactivity was attributed to the unusual keto-enol tautomerization due to structural difference between planar and curved π-system. The homosumanene ortho-quinone was used in the synthesis of several azaacene-fused homosumanenes, azaacenohomosumanenes. X-ray diffraction analysis of the single crystals revealed their columnar stacking structures due to the interactions between each bowl. Azaacenohomosumanenes exhibited high electron affinity due to the combination of buckybowl and electron-deficient azaacene moieties.

Electron-deficient moiety regulated structure: an efficient strategy for the design of a highly sensitive cyanide “turn-on” fluorescent probe

Developing fluorescent probes for the cyanide diagnosis is necessary as its extensive existence will seriously harm human health. Herein, the strategy for designing three novel probes came from our previously reported “turn-on” fluorescent probe, which was switched from a “turn-off” probe by inserting an electron-deficient benzothiadiazole (BTD) into a triphenylamine (TPA)-based dicyanovinyl (MT) compound with a phenyl group (Ph) as π-bridge (TPA-BTD-Ph-MT). To further investigate the effects of the electron-deficient group, BTD was firstly replaced by a stronger electron-deficient group of 2,3-diphenylquinoxaline (DPQ) to obtain TPA-DPQ-Ph-MT (P1). Based on P1 molecule, N-phenylcarbazole (PCZ), and thiophene (Th) were respectively used as a substitute to obtain PCZ-DPQ-Ph-MT (P2) and TPA-DPQ-Th-MT (P3) probes for investigating the effect of the electron donor and π-bridge on the fluorescent probe. P1 exhibited significant “turn-on” fluorescence response toward cyanide anion (CN−) with the best sensitivity and anti-interference performance. The sensing mechanism of P1 toward CN− was demonstrated and a good linearity was obtained in the wide concentration range of 0.025–40.0 μM with a low detection limit of 0.058 μM. Furthermore, P1 was successfully employed to determine CN– in food samples and image CN– in living cells and BALB/c mice, revealing its great practical potential for discriminative detection CN– in the fields of food and biological studies. Therefore, the strategy based on structure regulation provided good prospects for optimizing fluorescent probes.

Solvatochromic covalent organic frameworks for the low-level determination of trace water in organic solvents

Here we report a rational design and preparation of luminescent COFs via the synergetic interaction of electron-rich and electron-deficient moieties. 4,4′,4′-(1,3,5-triazine-2,4,6-triyl) trianiline (TTA) with the electron-deficient unit and 2,6-diformyl-4-methylphenol (Dp) with the electron-rich moiety and −OH group were employed to synthesize the imine-linked DpTTA-COF. The intramolecular charge transfer enables DpTTA-COF to present a strong solvent polarity-dependent color change, based on which a solvatochromic sensor was successfully established. We demonstrate an emission wavelength and intensity dual-mode photoluminescent sensor for the detection of trace water in organic solvents with good sensitivity, reversibility and stability. In addition, the dual-signal solvatochromic sensor is also capable for organic solvents decoding. This work proposes a new strategy for the design and preparation of COFs with fascinating solvatochromic effect. This strategy could extend the application field of COFs by the integration of functional groups, affinity, and structural selectivity.