Dicyanovinyl Group Research Articles

Hexaphenylbenzene based push-pull fluorophores displaying intriguing polarity-dependent fluorescence behavior, AIE(E) characteristics and mega-large Stokes shifts

In general, most donor-acceptor type fluorophores are known to exhibit solvatochromic behavior and obey the energy gap law simultaneously, showing decreased emission with increasing solvent polarity. In this work, four push-pull hexaphenylbenzene (HPB) derivatives 1–4 have been designed and synthesized by introducing methoxy and dicyanovinyl groups at the tip of aromatic blades, which behave exceptionally polarity-dependent emission properties. In the low to medium solvent polarity region, the four dipole fluorophores display gradually enhanced fluorescence, whereas a reverse trend is observed with the further increase of solvent polarity. Meanwhile, 1–4 are found to exhibit the strongest emission at the same wavelength remarkably, which appears to be somewhat relevant to the intrinsic characteristics of dicyanovinyl-phenyl acceptor. A mechanistic scheme containing a conical intersection (CI) has been proposed to explain the up-down emission of 1–4 with increasing solvent polarity. Large Stokes shifts (up to 254 nm) and AIE(E) characteristics have also been achieved in these four HPB fluorophores. Besides, fluorophores 1–4 exhibit obvious freezing-solution induced chromism (FSIC), demonstrating an enhancement of the local matrix polarity upon freezing solutions.

Novel styrylbenzimidazolium-based fluorescent probe for reactive sulfur species: Selectively distinguishing between bisulfite and thiol amino acids

In this study, a new fluorescent probe containing dicyanovinyl moiety has been designed and synthesized. Fluorescent probe based on styrylbenzimidazolium derivative was reported for the effective detection of bisulfite and distinguish it from biothiols by exploiting dicyanovinyl group as the recognition site. The photophysical properties of the novel styrylbenzimidazolium derivative were assessed by determination of absorption and fluorescence spectra, fluorescence quantum yield, and fluorescence lifetime. Its spectroscopic behavior towards various analytes has been evaluated in aqueous media at a pH of 7.4. The highest increase in fluorescence intensity of compound 5 in the presence of different analytes was observed for sodium bisulfite and the limit of detection was estimated to be 0.25 μM. The styrylbenzimidazolium dye was applied to detect bisulfite in various wine sample using fluorimetry. Finally, the ability of this novel probe to detect HSO3− in red wine samples was evaluated.

Effects of electron-withdrawing group and π-conjugation length in donor-acceptor oligothiophenes on their properties and performance in non-fullerene organic solar cells

The development of small-molecule donor materials for highly efficient non-fullerene (NF) organic solar cells (OSC) remains an urgent research task. In this work, the synthesis of donor-acceptor molecules containing either five (5T) or seven (7T) thiophene units end-capped with methyl dicyanovinyl (DCV) or ethyl cyanoacetate (CNA) electron-withdrawing groups was reported. Their thermal stability, phase behaviour, optical and electrochemical properties as well as photovoltaic performance in blends with IDIC or Y6 as acceptor materials were comprehensively investigated and compared. All of the obtained donor molecules are characterized by high thermal stability, efficient sunlight absorption and excellent solubility in combination with a good crystallinity. The results obtained allowed us to reveal the impact of the oligothiophene conjugation length and type of electron-withdrawing group on the properties and performance of the D-A oligothiophenes in NF OSC. The results clearly demonstrate that the devices based on donor molecules with 7T or CNA fragments significantly outperform those based on 5T or DCV groups.

Water-soluble AIE-active Fluorescent Organic Nanoparticles: Design, Preparation and Application for Specific Detection of Cyanide in Water and Food Samples.

A dilactosyl-dicyanovinyl-functionalized tetraphenylethene (TPELC) was designed, synthesized and used for ratiometric sensing of cyanide. TPELC was comprised of three moieties (tetraphenylethylene, dicyanovinyl group and lactose unit) in one molecule, making TPELC water-soluble and aggregation-induced emission (AIE)-active and selectively reactive to cyanide. Compared with other reported fluorescent probes containing dicyanovinyl group, TPELC is the first AIE luminogen to be assembled as fluorescent organic nanoparticles (FONs) for sensing of cyanide in water without the use of surfactant or the help of organic solvents based on the nucleophilic addition reaction. The detection mechanism was verified by liquid chromatograph mass spectrometry experiments and by protonation of cyanide to reduce the nucleophilicity of cyanide. In addition, TPELC was used for detection of the cyanide content of food samples and test strips were developed to simplify the detection procedure.

Novel group 14 element-bridged bithiophene dimers appended with terminal electron-withdrawing groups: Red-to-near infrared fluorescence and efficient photosensitized singlet oxygen generation

A series of group 14 element bridged bithiophene dimers bearing dicyanovinyl (DC) or thiobarbiturylmethylene (TB) electron-withdrawing groups at the molecular termini (series E-1a and series E-1b; E = C, Si, and Ge) were developed as red absorbing singlet oxygen (1O2) photosensitizing dyes. These dyes exhibited broad and strong absorption in the red-to-deep red regions and efficient red-to-NIR fluorescence (photoluminescence quantum yield ΦPL; 0.32–0.45 in dichloromethane). The terminal TB groups led to more red-shifted electronic absorption and fluorescence emission than the DC groups, owing to more intense intramolecular charge transfer. The 1O2 generation photosensitization abilities of series E-1a and series E-1b were evaluated by the 1,3-diphenylisobenzofuran method, and large 1O2 generation quantum yields (ΦΔ) were obtained upon irradiation of 630 nm light, ranging from 0.35 to 0.68 in dichloromethane. Therefore, these dyes show fluorescence properties as well as 1O2 generation photosensitization ability. Introduction of bromo groups at the 3,3′-positions in Si-1a and Si-1b afforded the new potential photosensitizers Si-2a and Si-2b that accompanied blue-shifted electronic absorption as well as blue-shifted fluorescence emission with the low ΦPL. Unfortunately, as Si-2a exhibited quite low absorptivity in the red region, 1O2 generation photosensitization with 630 nm light was not evaluated for Si-2a. On the other hand, Si-2b showed significantly efficient 1O2 generation photosensitization upon irradiation of 630 nm light (ΦΔ; 0.88). Considering the result of theoretical calculations showing that the bromo groups effectively contribute to the frontier orbitals, these bromo substituents should facilitate the intersystem crossing from the excited singlet state to the triplet excited state through the strong spin‒orbit coupling.

A chromene based fluorescence probe: Accurate detection of peroxynitrite in mitochondria, not elsewhere

• A novel fluorescent probe was synthesized for the detection of ONOO − by conjugating dicyano-vinyl with benzopyran-chromone. • The probe shows specifically selectivity over other biologically relevant ROS/RNS/RSS. • The sensing mechanism is the cleavage of the carbon-carbon double bond by the nucleophilicity and oxidation of peroxynitrite. • The probe has a certain mitochondrial targeting and localization effect. • BC-PN-2 can accurately identify ONOO − in mitochondria by imaging of exogenous ONOO − in HepG2 cells. A novel fluorescent probe (BC-PN-2) for the detection of ONOO − was synthesized by conjugating dicyano-vinyl with benzopyran-chromone. The dicyano-vinyl group can be destructed by ONOO − to generate an aldehyde group resulting in strong fluorescence. Compared with the general fluorescence probes, a novel reactive site to detect ONOO − in mitochondria is used in this probe and the results show short response time, high sensitivity and excellent selectivity toward ONOO − among reactive oxygen species (ROS) and reactive nitrogen species (RNS) in PBS. Subsequent fluorescence imaging shows the high membrane permeability, a certain mitochondrial targeting and localization effect of the probe. In addition, the product BC-aldehyde cannot permeate through the membrane. Meanwhile, BC-PN-2 can accurately identify ONOO − in mitochondria by imaging of exogenous ONOO − in HepG2 cells and prove detected ONOO − are from mitochondria.

Near-infrared fluorescent probe for tracing diquat in aqueous solutions and bioimaging in vivo

In this work, we rationally design a new type of squaraine dye SQ, modified with the dicyanovinyl motif that can specifically detect DQ (Diquat) by virtue of aggregation-disaggregation mechanism and electrostatic interaction between DQ and SQ. It undergoes H-aggregation in aqueous solution, resulting in fluorescence quenching. After the addition of DQ, the dicyanovinyl group on the probe reacts with DQ to deagglomerate so that the fluorescence is enhanced, tracing DQ in the environment with high sensitivity (LOD = 4.9 × 10−7 M), selectivity and good stability. In addition, the actual sample spike recovery experiment and the confocal fluorescence imaging experiment of DQ in zebrafish also confirmed the detection method. At present, the “turn-on” type fluorescence probe for detecting DQ by using near-infrared squaraine dye has not been reported. The application of SQ provides a new strategy for the quantification of DQ.

A fundamental study on the fluorescence-quenching effect of nitro groups in tetraphenylethene AIE dyes with electron-withdrawing groups

A nitro group is a common fluorescence quencher, but its quenching efficiency can be easily affected by the surrounding environment. To date, there has been no systematic study on the effects of electron-withdrawing groups on the quenching efficiency of nitro groups. Herein, by virtue of experimental validation and theoretical calculations, we found that strong electron-withdrawing groups, such as pyridinium and dicyanovinyl groups, are detrimental to the quenching effect of nitro groups. Decreasing the electron-withdrawing ability could restore the nitro group’s quenching effect.

π-Extended Tetraphenylethylene Containing a Dicyanovinyl Group as an Ideal Fluorescence Turn-On and Naked-Eye Color Change Probe for Hydrazine Detection.

A π-extended tetraphenylethylene derivative 1 was developed as a fluorescent “turn-on” and “naked-eye” color change probe for hydrazine detection. Probe 1 was composed of the representative AIE luminogen (AIEgen), tetraphenylethylene, and a dicyanovinyl group was adopted for hydrazine recognition. Upon exposure of hydrazine, probe 1 immediately gave a significant aggregation-induced emission around 575 nm and excellent photostability. A naked-eye color change was also observed from red to yellow. Moreover, probe 1 was simply coated with a glass-backed silica gel-coated thin-layer chromatography plate, showing rapid and on-site detection of hydrazine vapor.

A naphthalene-based colorimetric and fluorometric dual-channel chemodosimeter for sensing cyanide in a wide pH range

A novel α-ethoxynaphthalene-dicyanovinyl conjugate 1 with an intramolecular charge transfer (ICT) characteristic was synthesized for the highly selective and reactive detection of CN− in a wide pH range of 3–10. The colorimetric and fluorometric response of the sensor to CN− is attributable to the addition of CN− to the β-conjugated position of the dicyanovinyl group of 1, which blocks ICT. The sensing mechanism is supported by 1H NMR titration experiments and density functional theory (DFT) calculations. Moreover, chemodosimeter 1 shows strong yellow fluorescence in the solid-state, and 1-based test strips can be easily prepared at low-cost and can be used in practical and efficient test kits for CN− detection. The results provide the proof of concept that the ICT-based colorimetric and fluorometric cyanide-selective chemodosimeter can be created based on a simple alkoxy-substituted small molecule.

A colorimetric and near-infrared ratiometric fluorescent probe for hydrazine detection and bioimaging.

Hydrazine (N2H4) is extensively used in industry but highly toxic; hence, highly sensitive detection of N2H4 is extremely meaningful. Herein, a colorimetric and near-infrared (NIR) ratiometric fluorescent probe named DXM-OH was rationally designed and synthesized based on oxanthrene malononitrile derivative for the specific detection of N2H4. The dicyanovinyl group in DXM-OH was served as the recognition unit for N2H4. DXM-OH showed high sensitivity to N2H4 in the range of 1-900μM, with the limit of detection (LOD) of 0.09μM (2.87ppb), which is much lower than the U.S. Environmental Protection Agency standard (10ppb). Furthermore, the practical applications of DXM-OH in detecting N2H4 in real water samples and imaging of N2H4 in living cells were demonstrated, indicating its potential utility for N2H4 sensing in environmental and biological samples.

Structural Control of the Molecular Packing and Dynamics of Mechanofluorochromic Materials Based on Small Donor–Acceptor Systems with Turn‐On Luminescence

AbstractA series of simple donor–acceptor molecules consisting of an oligo‐oxyethylene (OOE) N‐substituted diphenylamine connected to a dicyanovinyl (DCV) acceptor group by a thienyl π‐conjugating spacer are synthesized. Amorphous deep‐red freshly cast thin films rapidly evolve towards an almost colorless pale beige poly‐crystalline stable material from which a deep‐red photoluminescent state can be switched‐on by mechanical stimulation. The effects of the length of the OOE chain on the molecular packing of the material and on the dynamics of the recovery process and aggregation in solution are analyzed. Crystallographic results show that the length of the OOE chain directly controls the molecular packing from head‐to‐tail arrangement of the dipoles for short chain to co‐facial dimers leading to a non‐centrosymmetric material with nonlinear optics (NLO) activity for the longer ones. The analysis of the dynamics of the self‐recovery process of thin films and of molecular aggregation in solution shows that the dynamics of both processes is directly controlled by the length of the OOE chain. Since, as confirmed by optical and electrochemical results, the OOE substituents have strictly no influence on the electronic properties of the π‐conjugated system, the observed effects are unambiguously related to changes in intermolecular interactions.

Reaction-Based Electrochemiluminescent Sensors for Selective Detection of Biochemical and Environmental Targets

Electrogenerated chemiluminescence (ECL) is a luminescent process which generates light through sequential electron transfer reactons on the electrode surface. ECL-based molecular sensors have several advantages over the conventional analytical techniques such as high sensitivity and low background signal. Additionally, the ECL provides the possibility of potential point-of-care-testing and field-monitoring with the simplicity of equipment and the method. However, ECL detection of small molecules is still a great challenge because most of ECL detection methods have been developed via specific biomacromolecular recognition such as antibody-antigen and aptamer-protein interactions. Herein, we report ECL molecular sensors for qualitative and quantitative detection of biologically important and environmentally toxic molecules.In the first part, a chemodosimetric approach will be introduced for one-step analysis of Hcy levels based on the ECL. A rationally designed cyclometalated iridium(III) complex possessing a phenylisoquinoline main ligand underwent a selective ring-formation reaction with Hcy to generate a binding adduct, which produced highly luminescent excited states, and yielded strong ECL signals on the surface of an electrode. The level of Hcy was successfully monitored by the ECL increment with a linear correlation between 0–40 µM in 99.9% aqueous media. The approach required neither sample preparation nor bulky instrument, suggesting the point-of-care testing of Hcy levels, and is potentially useful for routine, cost-effective, and precautionary diagnosis of various cardiovascular diseases. ECL sensors for other biologically important analytes (pyrophosphate, hydrogen sulfide, cysteine, H2O2) and environmentally toxic molecules (thiophenol, glyphosate, Hg(II)) will also be presented.In the second part, we report a totally different approach to discriminate a target among various interferences. This is called potential-dependent electrochemiluminescence. The iridium complex having a dicyanovinyl group on the main ligand cannot perfectly distinguish cyanide from sulfide and cysteine because not only cyanide but also sulfide and cysteine can attack the beta position of the dicyanovinyl group to increase the PL intensity. However, cyanide adduct is electrochemically oxidized at much less positive potential (~ 1.0 V) than those of sulfide and cysteine adducts, and this enables the discrimination of cyanide via ECL approach. This method enables complete removal of the interfering signals from sulfide and other thiols by controlling the potential range (0 – 1.4 V).

Solvatochromic fluorophores based on thiophene derivatives for highly-precise water, alcohols and dangerous ions detection

In this paper we report on synthesis and sensing properties of novel thiophene derivatives representing typical push-pull molecules with D-π-A structure. As an electron-donating group we used benzothiophene and various positions of cyano and nitro groups as an acceptor moiety. All compounds exhibit profound solvatochromism with prominent emission varying from blue to red, which indicated high sensitivity to environment polarity. Moreover, even trace amounts of protic solvents (like water and alcohols) are able to significantly quench the luminescence, with the detection limit established to 59 ppm in THF. On the other hand, the dicyanovinyl group presented in one of the compounds made it an extremely sensitive colorimetric and fluorescent sensor for cyanide and hydroxide ions, shifting its emission towards shorter wavelengths. The detection limits for CN− and OH− were established as low as 0.0131 μM and 0.0025 μM, respectively, which is one of the lowest limit reported in literature. Highly-precise sensitivity to water, alcohols and dangerous ions put such thiophene derivatives as easy-to-use and fast detector in everyday life.

A new naphthopyran-based chemodosimeter with aggregation-induced emission: Selective dual-channel detection of cyanide ion in aqueous medium and test strips

A novel green emissive AIE active probe, a naphthopyran-malononitrile conjugate (NPM), was utilized for selective dual channel (colorimetric and fluorimetric) sensing of CN− ions in DMSO-water (2/3, v/v, pH = 7.4) solution. The nucleophilic addition of CN− ion on the dicyano-vinyl group breaks the π-electron conjugation, thereby restricting intra-molecular charge transfer(ICT) process in the probe NPM and leading to a visual color change and observable spectral changes. NPM shows good selectivity for CN− ions with the LOD of 4.27 × 10−7 M, which renders it a candidate probe for cyanide detection in aqueous environments. For the practical applicability, NPM-coated paper strips were prepared for convenient, on-site detection of cyanide in aqueous medium.

A novel colorimetric and fluorometric probe for the detection of CN− with high selectivity in aqueous media

A novel colorimetric and fluorometric probe L1 for detecting CN− with high selectivity was constructed and synthesized based on intramolecular charge transfer (ICT). Remarkably, L1 was found to be exclusively responsive to CN− via nucleophilic attack of dicyanovinyl group via 1H NMR titration experiment. The detection system exhibited “turn-on” fluorescence with the addition of cyanide, which was opposite to previously reported fluorescence quenching probes with the same sensing process. Moreover, the detection limit of L1 for CN− was determined to be 1.1 μM, lower than the standard (1.9 μM) regulated by the World Health Organization (WHO). This work demonstrated that L1 could serve as both a colorimetric and a fluorimetric sensor for cyanide detection in pure water, making it possible for the applications of cyanide detection in water.

Diversified AIE and mechanochromic luminescence based on carbazole derivative decorated dicyanovinyl groups: effects of substitution sites and molecular packing

Two positional isomers exhibited noticeable different luminescence properties, which were mainly attributed to their different molecular packing modes.

A novel red-emissive probe for colorimetric and ratiometric detection of hydrazine and its application in plant imaging

With the wide application in chemistry and pharmaceutical industries, the toxic effect of hydrazine on the ecological environment (e.g. inhibition on seed germination and seedling growth) as well as human health (carcinogen) arises extensive concerns. Although a lot of probes have been developed and used for fluorescence imaging of hydrazine in living cells and animals, to our best knowledge, there are rare reports on hydrazine probe successfully applied for plants imaging. In this work, we report a novel red-emissive fluorescent probe with hydrazine-sensitive dicyanovinyl group for colorimetric and ratiometric detection of hydrazine. This newly reported probe was capable of rapidly, sensitively, and selectively detecting hydrazine with a low detection limit (2.88 ppb), and more importantly, this probe achieved the ratiometric fluorescence imaging of hydrazine in plant roots.

End group tuning in small molecule donors for non-fullerene organic solar cells

Two novel small molecules, which consist of electron donating benzodithiophene core bridged through bithiophene π-spacer with terminal either dicyanovinyl (DCV-Me) or n-butyl cyanoester (CNAB) electron-withdrawing groups, were designed and used as donor materials for all-small molecule OSCs (all-SM-OSCs) with a non-fullerene acceptor (IDIC). The novel donor oligomers were firstly characterized by thermal gravimetric analysis, differential scanning calorimetry, UV–Vis spectroscopy, and cyclic voltammetry as well as studied by density functional theory calculations. The simple change of the DCV-Me to CNAB group leads to more pronounced crystallinity, higher solubility and higher energy levels in the donor BDT-2T-CNAB. The photovoltaic devices based on the BDT-2T-CNAB:IDIC blend exhibit higher short-circuit current (Jsc) and fill factor, and thus much higher power conversion efficiency (PCE) of 6.17% than those of BDT-2T-DCV-Me:IDIC devices (1.56%). Compared to the BDT-2T-DCV-Me system, the BDT-2T-CNAB based device shows smoother film surface morphology, and superior exciton dissociation, charge generation and charge carrier mobilities as well as lower non-geminate recombination losses. The results clearly demonstrate that the design of new small molecule donors for high-performance all-SM-OSCs should aim to choose suitable end acceptor units, among which the alkyl cyanoester groups are one of the most promising.

Computational study on optoelectronic and charge transport properties of diketopyrrolopyrrole-based A-D-A-D-A structure molecules for organic solar cells.

Eight novel diketopyrrolopyrrole (DPP)-based A-D-A-D-A structure molecules were designed for organic solar cells (OSCs) applications. In these molecules, the electron-deficient DPP and dicyanovinyl groups were used as the acceptor groups and different planar electron-rich groups were employed as the donor π-bridges. Applying the B3LYP/6-31G (d,p) and TD-B3LYP/6-31G (d,p) methods, the optoelectronic and charge transport properties were investigated. It turned out that the different π-bridges can tune effectively the frontier molecular orbital energy levels, band gap, and absorption spectra. Furthermore, the different π-bridges also affect the charge transport properties of the designed molecules. Our results suggest that the investigated molecules can serve as donor materials. Additionally, some investigated molecules can also be used as hole and/or electron transport materials for OSCs. Graphical abstract A series of novel A-D-A-D-A molecules are investigated systematically. The optical and electronic properties can be tuned effectively by the π-bridges. All derivatives can be used as donor materials for OSCs. Some designed molecules can be used as hole and/or electron transport materials. The different π-bridges do not significantly affect the stability of the molecules.