Hemicyanine Dye Research Articles

Hemicyanines-potential heavy metal ion sensors

The synthesis of four hemicyanine dyes are reported. Varying the donor-acceptor properties of hemicyanine dyes has a drastic influence on the aggregation properties and photophysical properties. 4-(N, N-dimethyl)amino benzaldehyde, 4-nitro benzaldehyde and 4-hydroxy benzaldehyde are used as donors. Quarternary salts of 2-methyl benzothiazole with bromoacetic acid and methyl iodide are used as acceptors. Synthesis and characterization of the dyes were carried out. Preliminary studies shows that these compounds possess pH sensing as well as heavy metal ion sensing properties.

Ionic Aggregation‐Induced Emission: Bulky Hydrophobic Counterions Light Up Dyes in Polymeric Nanoparticles

AbstractDye‐loaded polymeric nanoparticles emerge as powerful bioimaging tools, but their assembly is challenged by aggregation‐caused quenching (ACQ) of flat fluorophores. Aggregation‐induced emission (AIE) proposes an effective solution against ACQ by exploiting propeller‐shaped neutral fluorophores without polymeric blending. Fighting ACQ of ionic dyes in polymeric nanoparticles can be achieved by bulky hydrophobic counterions. Here, it is aimed to generate an AIE phenomenon in poorly emissive ionic dyes using bulky counterions. Three cationic hemicyanine dyes of styryl pyridinium family are synthesized: two planar fluorophores featuring ACQ and one propeller‐shaped AIE fluorophore. It is found that, in water, bulky fluorinated tetraphenylborates can light up all three dyes, including planar non‐AIE fluorophores. The described “ionic” AIE (iAIE) with bulky counterions enables preparation of 50‐nm dye‐loaded polymeric nanoparticles showing 40% quantum yield at 500 mm dye loading, whereas small anions favor poorly emissive large aggregates. Single‐particle microscopy reveals that these nanoparticles emit without blinking 50‐fold brighter than commercial quantum dots “Qdot 605” (at 470‐nm excitation). iAIE opens the route to assembling charged intrinsically non‐AIE fluorophores into bright fluorescent (nano)materials.

Aggregation-Dependent Photoreactive Hemicyanine Assembly as a Photobactericide.

Organic materials that show substantial reactivity under visible light have received considerable attention due to their wide applications in chemical and biological systems. Hemicyanine pigments possess a strong intramolecular donor-acceptor structure and thereby display intense absorption in the visible spectral region. However, most excitons are consumed via the twisted intramolecular charge-transfer (TICT) process, making hemicyanines generally inert to light. Herein, we describe the development of an amphiphilic hemicyanine dye whose aggregation could be easily regulated using salt or counterions. More importantly, its intrinsic photoreactivity was successfully induced by steric restriction and cofacial arrangement within the H-aggregate, thus creating an effective photobactericide. This strategy could be extended to the development of photocatalysts for photosynthesis and a photosensitizer for photodynamic therapy.

Improved photocurrent generation of three hybrid films made of [BW11Co(H2O)O39]7- and hemicyanines with alkyl linkers of varying length

A series of electrostatically self-assembled films consisting of a Keggin-type cobalt-substituted tungstoborate anion [BW11Co(H2O)O39]7- (BW11Co) and three hemicyanine cations with two chromophores linked by varying lengths of alkyl chains, (E)-1,1'-(propane-1,3-diyl)bis(4-(4-(dimethylamino)styryl)pyridinium) cation (H3), (E)-1,1'-(hexane-1,6-diyl)bis(4-(4-(dimethylamino)styryl)pyridinium) cation (H6), and (E)-1,1'-(decane-1,10-diyl)bis(4-(4-(dimethylamino)styryl)pyridinium) cation (H10), were successfully prepared by layer-by-layer self-assembly technique. UV–visible spectra showed that BW11Co and Ha (a = 3, 6, 10) components were uniformly deposited in each dipping cycle. The visible absorption peaks of (BW11Co/Ha)n films are obviously red shifted as compared with those of corresponding Ha solution, which is beneficial for improving photoelectric conversion. As irradiated with white light, the (BW11Co/Ha)n films generated stable, large cathodic photocurrents that increasing with increasing negative applied bias potentials, increasing of electron acceptor concentrations and decreasing electron donor concentrations in the electrolyte solution. The photocurrents were also found to be strongly depending on layer number of the films, and alkyl chain length in the hemicyanine dyes of Ha (a = 3, 6, 10). The maximum photocurrent densities generated by (BW11Co/H3)4, (BW11Co/H6)5, and (BW11Co/H10)4 films were found to be 18.05, 16.6 and 15.8 μA/cm2, respectively. The photocurrent generation performance of (BW11Co/Ha)n films is superior to that of POM-free hemicyanine dye films. POM components can significantly improve the photocurrent generation properties of hemicyanine dyes by efficient electron transference between the ITO electrode and the hemicyanine, and retardation of recombination reaction in photoelectrochemical cells. This study would guide molecular design for more efficient photoelectrocatalytic, and energy conversion and storage devices.

Series of Mitochondria/Lysosomes Self-Targetable Near-Infrared Hemicyanine Dyes for Viscosity Detection.

Six mitochondria/lysosomes self-targetable and viscosity-sensitive dyes (1a-1f) were developed via simple structure modification on cyanine-derived dyes. They all showed remarkable OFF-ON fluorescent response to viscosity in the near-infrared region (652-690 nm) and exhibited good linear relationship with solution viscosity. The transient absorption spectra were used to evaluate the excited-state lifetime of dye 1a in different viscosity environments. Furthermore, cellular imaging assays indicated that different derivatives (1a-1f) with the same chromophore core exhibited different organelle-targeting abilities. Among them, dyes 1a-1c could sense lysosomal viscosity fluctuations while dyes 1d-1f could be applied in mitochondrial viscosity detections.

Synthesis of hemicyanine-based chitosan ligands in dye-affinity chromatography for the purification of chewing stick peroxidase

A novel built-in approach for the in situ formed hemicyanine dyes in the chitosan matrix is presented. Chitosan was reacted with salicylaldehyde to afford the corresponding Schiff base in good yield. This derivative was then converted to two heterocyclic quaternary ammonium salts, namely chitosan benzothiazolium and chitosan picolinium salts, which upon reaction with p-dimethylaminobenzaldehyde by Knoevenagel condensation, the corresponding built-in hemicyanine dyes were obtained. Characterization was made by NMR, FTIR, SEM, and UV–visible.The two dyed samples (benzothiazolium and picolinium) were used for the purification of chewing stick peroxidase by affinity chromatography method. 1.0 M ammonium sulfate was used as eluent to check whether the purification of enzyme proceeds by hydrophobic interactions and the result indicated that the purification proceeds by rather ionic interactions, and therefore 1 M NaCl was used instead. The overall result indicates that benzothiazolum column showed better affinity with a high specific activity of the separated enzymes compared with those obtained with the picolinium column. This novel dye ligand built-in approach onto a biopolymeric substrate is promising and would pave the way for more future work ahead in the field of the purification of proteins and other biological macromolecules.

A caveat to common hemicyanine dye components and their resolution.

Near-infrared-emitting hemicyanine dyes are widely used in activatable fluorescent probes for various biological analytes; however, they are chemically unstable and show photoinstability, as shown here with naphthalene-based hemicyanines containing a typical hemicyanine moiety, 2-indolium. These issues can be resolved with a 4-pyridinium derivative, which also has good two-photon imaging capability.

Regulating photothermal conversion of hemicyanine dye by light-controlling switch: A preliminary investigation

Photothermal therapy has the advantages of low toxicity, short treatment time, strong controllability, outstanding therapeutic effect. The photothermal conversion efficiency of photothermal agents by converting light energy into heat energy is of great significance for the therapeutic effect. In this work, the dithienylethene-based photochromic switch was firstly employed to regulate the photothermal conversion efficiency of a hemicyanine dye. The result showed that the dithienylethene-coating hemicyanine had an anticipated performance of photo-controlling photothermal conversion. The investigation provides a new idea for the design of novel photothermal agents.

A novel mitochondrial targeting fluorescent probe for ratiometric imaging SO2 derivatives in living cells

As an important endogenous signaling molecule, SO2 plays a key role in many physiological processes. However, excessive intake of SO2 and its derivatives lead to serious health complications of various diseases. In order to study the role of SO2 and its derivatives in the biological environment, it is of great significance to develop new and effective monitoring methods. Here, a new red emission fluorescent probe (TNPI) based on pyrazoline and hemicyanine dyes for the high selective detection of SO2 derivatives was developed. The probe TNPI showed some advantages such as long emission wavelength (640 nm), obvious color and fluorescence changes after reaction with SO2 derivatives, high selectivity and sensitivity toward SO2 derivatives (detection limit = 80 nM), and large fluorescence emission shift (160 nm) and signal ratio change (from 0.45–445, about 989 times). Intriguingly, the probe was successfully exploited for the fluorescence imaging of SO2 derivatives in the mitochondria of living cells with low cytotoxicity.

Computer-Assisted Design of Environmentally Friendly and Light-Stable Fluorescent Dyes for Textile Applications

Five potentially environmentally friendly and light-stable hemicyanine dyes were designed based on integrated consideration of photo, environmental, and computational chemistry as well as textile applications. Two of them were synthesized and applied in dyeing polyacrylonitrile (PAN), cotton, and nylon fabrics, and demonstrated the desired properties speculated by the programs. The computer-assisted analytical processes includes estimation of the maximum absorption and emission wavelengths, aquatic environmental toxicity, affinity to fibers, and photo-stability. This procedure could effectively narrow down discovery of new potential dye structures, greatly reduce and prevent complex and expensive preparation processes, and significantly improve the development efficiency of novel environmentally friendly dyes.

Photophysical properties of the hemicyanine Dy-630 and its potential as a single-molecule fluorescent probe for biophysical applications

Protein-induced fluorescence enhancement (PIFE) is an increasingly used approach to investigate DNA-protein interactions at the single molecule level. The optimal probe for this type of application is highly photostable, has a high absorption extinction coefficient, and has a moderate fluorescence quantum yield that increases significantly when the dye is in close proximity to a large macromolecule such as a protein. So far, the green-absorbing symmetric cyanine known as Cy3 has been the probe of choice in this field because the magnitude of the increase observed upon protein binding (usually 2–4 –fold) is large enough to allow for the analysis of protein dynamics on the inherently noisy single-molecule signals. Here, we report the characterization of the photophysical properties of the red-absorbing hemicyanine dye Dy-630 in the context of its potential application as a single-molecule PIFE probe. The behavior of Dy-630 in solution is similar to that of Cy3; the fluorescence quantum yield and lifetime of Dy-630 increase with increasing viscosity, and decrease with increasing temperature indicating the existence of an activated nonradiative process that depopulates the singlet state of the dye. As in the case of Cy3, the results of transient spectroscopy experiments are consistent with the formation of a photoisomer that reverts to the ground state thermally in the microsecond timescale. Unfortunately, experiments with DNA samples paint a more complex scenario. As in the case of Cy3, the fluorescence quantum yield of Dy-630 increases significantly when the dye interacts with the DNA bases, but in the case of Dy-630 attachment to DNA results in an already long fluorescence lifetime that does not provide a significant window for the protein-induced enhancement observed with Cy3. Although we show that Dy-630 may not be well-suited for PIFE, our results shed light on the optimal design principles for probes for PIFE applications.

Simulation, synthesis, characterisation and dyeing properties of a fluorescent hemicyanine dye

AbstractIn this study, a hemicyanine dye, trans‐4‐(4‐(diethylamino)styryl)‐1‐ethylpyridinium bromide (DYE‐BD), was synthesised and simulated. The maximum absorption wavelength of DYE‐BD was calculated with the same basis set by using the Gaussian 09 software based on different methods, while time‐dependent density functional theory was applied to simulate the maximum emission wavelength of the designed dye. The changes in enthalpy and Gibbs free energy were simulated at the b3lyp/6‐31G(d) level, and energy changes in the luminescence process were assessed using mathematical methods. Furthermore, DYE‐BD was used to colour acrylic fabric following the typical dyeing procedure for cationic dyes. The photostability of the synthesised dye was analysed using quantum theory and mathematical methods. The synthesised dye, analysed using the Ecological Structure Activity Relationships class program, had no toxicity to aquatic life, while the acrylic fabrics dyed with DYE‐BD met the fluorescent orange requirements for background and combined performance materials according to the EN ISO 20471:2013 standard.

Near-Infrared Hybrid Rhodol Dyes with Spiropyran Switches for Sensitive Ratiometric Sensing of pH Changes in Mitochondria and Drosophila melanogaster First-Instar Larvae.

Near-infrared hybrid rhodol dyes (probes A and B) for sensitive ratiometric visualization of pH changes were prepared by incorporating hemicyanine dyes into traditional rhodol dyes. This approach was based on π-conjugation changes involving a rhodol hydroxyl group as a spiropyran switch upon pH changes. Electronic spectra of probes A-2 and B-2 contain sharp absorption peaks at 535 nm and fluorescence peaks at 558 nm with similar π-conjugation and a closed spiropyran form at a basic pH of 10.2. However, acidic pH conditions break down the hemiaminal ether groups, leading to indolenium moieties and significantly extending the π-conjugation within the rhodol fluorophores, resulting in additional near-infrared emissions for probes A-1 and B-1. As a result, probes A and B exhibit gradual decreases of the absorption peaks at 535 nm and gradual increases in absorption peaks at 609 and 622 nm upon transition from basic to acidic pH, respectively. Both probes display ratiometric fluorescence sensing responses to pH downgrades from 10.2 to 3.6 with visible fluorescence decreases at 558 nm, as well as corresponding increases of the near-infrared fluorescence peaks at 688 and 698 nm, respectively. They exhibit fast, sensitive, and selective fluorescence responses with clearly defined ratiometric features to pH changes and show low cytotoxicity and excellent cell permeability. Our probes were successfully applied to ratiometrically detect pH changes in mitochondria, D. melanogaster first-instar larvae, and to visualize the mitophagy process caused by either cell nutrient starvation or drug treatment.

Fluorescent probes with high pKa values based on traditional, near-infrared rhodamine, and hemicyanine fluorophores for sensitive detection of lysosomal pH variations.

Sterically hindered fluorescent probes (A-C) have been developed by introducing 2-aminophenylboronic acid pinacol ester to a traditional, A, a near-infrared rhodamine dye, B, and a near-infrared hemicyanine dye, C, forming closed spirolactam ring structures. Probe A was non-fluorescent under basic pH conditions whereas probes B and C were moderately fluorescent with fluorescence quantum yields of 9% and 5% in pH 7.4 PBS buffer containing 1% ethanol, respectively. With all probes increasing acidity leads to significant increases in fluorescence at 580 nm, 644 and 744 nm for probes A, B and C with fluorescence quantum yields of 26%, 21% and 10% in pH 4.5 PBS buffer containing 1% ethanol, respectively. Probes A, B and C were calculated to have pKa values of 5.81, 5.45 and 6.97. The difference in fluorescence under basic conditions is ascribed to easier opening of the closed spirolactam ring configurations due to significant steric hindrance between the 2-aminophenylboronic acid pinacol ester residue and an adjacent H atom in the xanthene derivative moiety in probe B or C. The probes show fast, reversible, selective and sensitive fluorescence responses to pH changes, and are capable of sensing lysosomal pH variations in living cells.

Dual-band simultaneous lasing in MOFs single crystals with Fabry-Perot microcavities

Multi-band microlasers based on single microcrystalline materials with Fabry-Perot (F-P) cavities are critically and technologically essential. Here, we demonstrate simultaneous dual-band lasing output (615 and 685 nm) in metal-organic frameworks (MOFs) and organic dyes hybrid single crystals, which support F-P resonances. Through a two-step assembly strategy, two different types of cationic pyridinium hemicyanine dye molecules can be encapsulated into the channel pores of anionic bio-MOF-1-2Me successfully. In addition, the employment of the host-guest system significantly increases the dye loading, enhances luminescent efficiency, and diminishes the aggregation-caused quenching (ACQ) effect in the resultant MOFs/dye composites. This finding not only combines the characteristic of MOFs materials with excellent luminescent properties of organic dyes, but also points out a simple and promising strategy to design multi-band microlasers based on F-P mechanism, opening a low-cost avenue for the rational design of miniaturized lasers in the future.

In Vivo Near-Infrared Fluorescence and Photoacoustic Dual-Modal Imaging of Endogenous Alkaline Phosphatase.

Alkaline phosphatase (ALP) is distributed widely in living organisms and is an important biomarker closely related to many physiological and pathological processes. However, in vivo real-time detection of ALP remains a significant challenge. Herein, we developed a turn-on molecular probe (denoted as LET-3) to visualize ALP activity in tumor tissues through near-infrared fluorescence (NIRF) and photoacoustic (PA) dual-modal imaging. LET-3, composed of NIR hemicyanine dye (LET-CyOH) and a phosphate moiety, showed a 23-fold NIRF enhancement at 730 nm and 27-fold PA enhancement at 710 nm upon activation by ALP. More importantly, both in vitro and in vivo diagnostic experiments indicated that LET-3 has a high sensitivity and good selectivity for ALP. These findings provide a promising strategy for in vivo ALP detection using NIRF and PA dual-channel turn-on probes.

(INVITED) Impurities in large scale produced Nd-doped phosphate laser glasses. II. Pt ion and Pt inclusion

Platinum is a special kind of impurity in Nd-doped phosphate laser glasses. Firstly, its presence in the glass depends on the production processes, rather than the purity of the raw materials used. Secondly, there coexist Pt ion and Pt inclusion in the glass, which one is the oxidized and the other is the reduced. The detection for these two kinds of Pt impurities in the large-scale produced Nd-doped phosphate laser glasses can reflect the control level and stability of the processes. To determine more accurately the content of Pt ion in the glass, a hemi-cyanine dye, instead of SnCl2 previously used, is utilized to color Pt ion solution by dissolving the glass. On the basis of such a new hemi-cyanine spectrophotometric analysis, the factor of proportionality between Pt ion content and its absorption coefficient at 400 nm is determined and discussed. To avoid the interference from other cations in the multi-cation solution by dissolving the glass, when doing ICP-MS analysis for Pt, a magnetic poly-ionic liquid is synthesized successfully by bonding an ionic liquid to nano-Fe3O4 particles covered by C. Such a new magnetic poly-ionic liquid can adsorb Pt ions with a better selection. The element distribution of Pt, O and P for differently sized Pt inclusions in the glass is analyzed by EPMA.

Recognition of Different Metal Cations by a trans‐4‐[4‐(Dimethylamino)styryl]‐1‐methylpyridinium Iodide@Tetramethylcucurbit[6]uril Probe

Based on the study of a known host–guest inclusion complex comprising cucurbit[6]uril (Q[6]) and a hemicyanine dye, trans‐4‐[4‐(dimethylamino)styryl]‐1‐pyridinium iodide (t‐DSMI), a water‐soluble symmetric tetramethylcucurbit[6]uril (TMeQ[6]), was selected to construct a t‐DSMI‐based probe to test the response to various metal cations in neutral water. The experimental results revealed that the probe responded to Cs+ cations in alkali metal systems, Ba2+ and Sr2+ cations in alkaline earth metal systems, Eu3+, Tm3+ and Yb3+ cations in lanthanide systems, and Cr3+, Fe3+ and Hg2+ cations in systems containing transition and other metal cations, via obvious fluorescence quenching.

Acceptor Influence on Thiolate Sensing by Hemicyanine Dyes.

Promoting selective interactions between a nucleophile and electrophilic dye in complex environments is a central goal in nucleophilic chemosensor development. Commonly employed dyes are hemicyanines containing either the N-methylbenzothiazolium (Btz) or the N-methyl-3,3-dimethylindolium (Ind) acceptors. The dyes are related to α,β-unsaturated carbonyls and contain two sites of reactivity (C2 vs C4) with the C2-site directly attached to the quaternary nitrogen possessing greater electrophilicity. We demonstrate the regioselectivity between reactions of sodium thiomethoxide (NaSMe) with two electrophilic hemicyanine dyes bearing Btz (1) or Ind (2) in dipolar aprotic solvent-water mixtures. Adduct complexation was followed by NMR spectroscopy, and structures were optimized in the gas phase to estimate relative adduct stability. The key results include finding a preference for thiolate attachment at the C4-site to generate an enamine adduct with no evidence for attachment at the more electrophilic C2-position. Equilibration between NaSMe and water also affords NaOH that displays a thermodynamic preference for C2-attachment. Dye 1 containing the Btz moiety exhibits greater selectivity for the thiolate addition, with dye 2 being more reactive toward adventitious water to generate OH-adducts. Our data affords diagnostic 1H/13C NMR adduct signals, regioselectivity for various dye/nucleophile combinations, and suggests use of the Btz acceptor for direct thiolate detection.

Trans-4-[4-(dimethylamino)styryl]-1-methylpyridinium Iodide@Hemimethylcucurbit[6]uril Fluorescent Probe for Anion Recognition

In the present work, a host–guest system of a hemimethyl-substituted cucurbit[6]uril derived from 3α-methyl-glycoluril (HMeQ[6]) and a hemicyanine dye, trans-4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (t-DSMI) showing strong fluorescence emission has been evaluated as a fluorescent probe. The results of a preliminary systematic study on the detection of a series of inorganic anions have revealed that this Q[n]-based host–guest fluorescent probe shows clear responses to BF4− and H2PO4− anions through distinct fluorescence quenching. Application of this Q[n]-based host–guest interaction system in anion recognition or detection opens a new avenue in Q[n] chemistry.