Asymmetric Dyes Research Articles

Pentamethine cyanine dyes with alkynyl group as perspective structure for conjugation with targeting moiety

We report a modified carbocyanine-based asymmetric fluorescent dye, suitable for the azide-alkyne cycloaddition reaction, that possesses promising photochemical properties (Φfl = 0,49). As an example of usage of the new fluorophore, it was conjugated to a ligand targeting prostate-specific membrane antigen (PSMA), one of the widely utilized prostate cancer markers.

Asymmetric BODIPY Dyes Enabling Triplet-Triplet Annihilation Upconversion.

The construction of triplet-triplet annihilation upconversion (TTA-UC) systems with upconversion (UC) emission efficiency at low power densities is still under continuing exploration. From an environmental point of view, the utilization of purely organic pairs is more beneficial than the involvement of transition-metal complexes. In this context, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes, which can be found in a wide range of applications, have been previously used as suitable sensitizers in TTA-UC systems. The versatility of these scaffolds makes them magnificent objectives for designing and synthesizing potential entities with different target abilities. Herein, we prepared several asymmetric BODIPY dyes with excellent optical properties to be applied to a bimolecular TTA-UC system. In the presence of 2,5,8,11-tetra-tert-butylperylene (TBPe) as a suitable annihilator, a green-to-blue light conversion was clearly observed by means of detailed spectroscopic investigations. The results revealed a high UC emission efficiency (ηUC) of ∼8%, together with a low threshold intensity (I th) of ∼40-50 mW/cm2. All data indicated that these asymmetric BODIPY dyes were ideal sensitizers for TTA-UC, providing a particular design for further investigations.

Erythrocyte nano-ghosts with dual optical and magnetic resonance characteristics.

Fluorescent organic dyes provide imaging capabilities at cellular and sub-cellular levels. However, a common problem associated with some of the existing dyes such as the US FDA-approved indocyanine green (ICG) is their weak fluorescence emission. Alternative dyes with greater emission characteristics would be useful in various imaging applications. Complementing optical imaging, magnetic resonance (MR) imaging enables deep tissue imaging. Nano-sized delivery systems containing dyes with greater fluorescence emission as well as MR contrast agents present a promising dual-mode platform with high optical sensitivity and deep tissue imaging for image-guided surgical applications. We have engineered a nano-sized platform, derived from erythrocyte ghosts (EGs), with dual near-infrared fluorescence and MR characteristics by co-encapsulation of a brominated carbocyanine dye and gadobenate dimeglumine (Gd-BOPTA). We have investigated the use of three brominated carbocyanine dyes (referred to as BrCy106, BrCy111, and BrCy112) with various degrees of bromination, structural symmetry, and acidic modifications for encapsulation by nano-sized EGs (nEGs) and compared their resulting optical characteristics with nEGs containing ICG. We find that asymmetric dyes (BrCy106 and BrCy112) with one dibromobenzene ring offer greater fluorescence emission characteristics. For example, the relative fluorescence quantum yield ( ) for nEGs fabricated using of BrCy112 is -fold higher than nEGs fabricated using the same concentrations of ICG. The dual-mode nEGs containing BrCy112 and Gd-BOPTA show a nearly twofold increase in their as compared with their single optical mode counterpart. Cytotoxicity is not observed upon incubation of SKOV3 cells with nEGs containing BrCy112. Erythrocyte nano-ghosts with dual optical and MR characteristics may ultimately prove useful in various biomedical imaging applications such as image-guided tumor surgery where MR imaging can be used for tumor staging and mapping, and fluorescence imaging can help visualize small tumor nodules for resection.

Functionalized Palygorskite as a Delivery Platforms for Bioactive Asymmetric Beta-Diketone Dyes

Natural clay minerals are among the most versatile materials used in the biomedical field. Palygorskite has found various applications in this field, from the treatment of diarrheal diseases in the past to materials with antibacterial properties and platforms carrying bioactive compounds used in the treatment of diseases, cosmetic and healthcare products in the present. In this study, a possible delivery method of some bioactive asymmetric β-diketonic compounds is presented. Palygorskite modified with amphionic groups (P) and copper ions (PCu) was used as a platform to load bioactive curcumin derivatives (1 and 2). By varying the copper ions, the amounts of charged active compounds were monitored. Studies have shown that the hybrid materials resulting from the loading of 1 and 2 compounds on palygorskite with 30% copper ions (PCu30) can be used as delivery methods for these asymmetric curcumin derivatives, while palygorskite with 50% copper ions(PCu50) loaded with the same type of bioactive compounds has antibacterial properties.

Precisely Constructing Renal-Clearable and LAP-Activatable Ratiometric Molecular Probes for Early Diagnosis of Acute and Chronic Kidney Injury Via Optimizing Asymmetric DPP Dyes.

Fluorescence analysis is an increasingly important contributor to the early diagnosis of kidney diseases. To achieve precise visualization of the kidneys and early diagnosis of related diseases, an asymmetric pyrrolopyrrolidone (DPP) dye platform with C-aromatic substituents and N-lipophilic/hydrophilic modification was constructed. Based on these, we developed the renal-clearable, water-soluble, and kidney injury biomarker leucine aminopeptidase (LAP) activated ratiometric fluorescent probe DPP-S-L. In the mouse model of cisplatin-induced acute kidney injury and during the development of type 2 diabetes to diabetic kidney disease, we visualized for the first time the upregulation of LAP in the kidney and urine by dual-channel ratiometric fluorescence signal and diagnosed the kidney injury earlier and more sensitively than blood/urine enzyme detection and tissue analysis. This study showcases an excellent asymmetric DPP dye platform and renal-clearable ratiometric fluorescent probe design strategy that is extended to determination and visualization of other biomarkers for early disease diagnosis.

Aggregation induced nucleic acids recognition by homodimeric asymmetric monomethyne cyanine fluorochromes in mesenchymal stem cells

In the light of recent retrovirus pandemics, the issue of discovering new and diverse RNA-specific fluorochromes for research and diagnostics became of acute importance. The great majority of nucleic acid-specific probes either do not stain RNA or cannot distinguish between DNA and RNA. The versatility of polymethine dyes makes them suitable as stains for visualization, analysis, and detection of nucleic acids, proteins, and other biomolecules. We synthesized the asymmetric dicationic homodimeric monomethine cyanine dyes 1,1′-(1,3-phenylenebis(methylene))bis(4-((3-methylbenzo[d]thiazol-2(3H)-ylidene)methyl)pyridin-1-ium) bromide (Т1) and 1,1′-(1,3-phenylenebis(methylene))bis(4-((3-methylbenzo[d]thiazol-2(3H)-ylidene)methyl)quinolin-1-ium) bromide (M1) and tested their binding specificity, spectral characteristics, membrane penetration in living and fixed cells, cellular toxicity, and stability of fluorescent emission. Mesenchymal cells have diverse phenotypes and extensive proliferation and differentiation properties. We found dyes T1 and M1 to show high photochemical stability in living mesenchymal stem cells from apical papilla (SCAP) with a strong fluorescent signal when bound to nucleic acids. We found M1 to perform better than control fluorochrome (Hoechst 33342) for in vivo DNA visualization. T1, on the other hand, stains granular cellular structures resembling ribosomes in living cells and after permeabilization of the nuclear membrane stains the nucleoli and not the chromatin in the nucleus. This makes T1 suitable for the visualization of structures rich in RNA in living and fixed cells.

Electronic Structure and Excited-State Dynamics of DNA-Templated Monomers and Aggregates of Asymmetric Polymethine Dyes.

Aggregates of conjugated organic molecules (i.e., dyes) may exhibit relatively large one- and two-exciton interaction energies, which has motivated theoretical studies on their potential use in quantum information science (QIS). In practice, one way of realizing large one- and two-exciton interaction energies is by maximizing the transition dipole moment (μ) and difference static dipole moment (Δd) of the constituent dyes. In this work, we characterized the electronic structure and excited-state dynamics of monomers and aggregates of four asymmetric polymethine dyes templated via DNA. Using steady-state and time-resolved absorption and fluorescence spectroscopy along with quantum-chemical calculations, we found the asymmetric polymethine dye monomers exhibited a large μ, an appreciable Δd, and a long excited-state lifetime (τp). We formed dimers of all four dyes and observed that one dye, Dy 754, displayed the strongest propensity for aggregation and exciton delocalization. Motivated by these results, we undertook a more comprehensive survey of Dy 754 dimer and tetramer aggregates using steady-state absorption and circular dichroism spectroscopy. Modeling these spectra revealed an appreciable excitonic hopping parameter (J). Lastly, we used femtosecond transient absorption spectroscopy to characterize τp of the dimer and tetramer, which we observed to be exceedingly short. This work revealed that asymmetric polymethine dyes exhibited μ, Δd, monomer τp, and J values promising for QIS; however, further work is needed to overcome excited-state quenching and achieve long aggregate τp.

Spectral and photophysical characteristics of asymmetric polymethine dyes in polyurethane matrices

Effects of the polymer matrix polarity on the spectral and photophysical properties of asymmetric polymethine dyes were investigated. Asymmetrical cyanines of the LDS (laser dye styryl) series were used, which were introduced into elastic polyurethane matrices by an auxiliary solvent. Polymer media were synthesized by: a polyaddition reaction based on macrodiisocyanate from oligoethylene glycol adipinate, hexamethylene diisocyanate, trimethylolpropane, and a photopolymerization reaction of oligourethane acrylate with benzoin isobutyl ether. Polyurethane polarity influence on the absorption and luminescence band maxima, and the Stokes shift of the dye spectra was studied, and the obtained spectral parameters of dyes in the polymer matrices were compared with the corresponding characteristics of their ethanol solutions. The observed spectral peak positions of the absorption and luminescence bands, changes in the Stokes shift value for the LDS dyes in different environments indicated the presence of positive solvatochromism. The presented results demonstrated the possibility of the significant increase in photostability of asymmetric polymethine dyes in the polymer polyurethane matrix of high polarity, obtained by means of the polyaddition reaction.

Engineering an asymmetric rhodamine dye suitable for developing ratiometric fluorescent probe

AbstractFluorescent probes based on rhodamine skeleton are extensively used in biological imaging. However, the construction of ratiometric fluorescent probes based on the rhodamine skeleton without introducing additional fluorophores is still challenging. Herein, we propose an effective method to construct a rhodamine‐based ratiometric fluorescent probe through the regulation of electron cloud density. A ratiometric fluorescent probe RDQF‐RB‐NTR was successfully constructed for the detection of nitroreductase (NTR). RDQF‐RB‐NTR exhibits good sensitivity, high selectivity, and ratiometric response to NTR. Cell imaging experiments showed that RDQF‐RB‐NTR can rapidly and accurately detect the fluctuation of NTR in cells and difference of NTR levels between normal cells and cancer cells. In addition, RDQF‐RB‐NTR was successfully applied to the imaging of NTR in liver tissue slices, and we found that the level of NTR was upregulated in liver cirrhosis.

Intramolecular Charge Transfer and Ultrafast Nonradiative Decay in DNA-Tethered Asymmetric Nitro- and Dimethylamino-Substituted Squaraines.

Molecular (dye) aggregates are a materials platform of interest in light harvesting, organic optoelectronics, and nanoscale computing, including quantum information science (QIS). Strong excitonic interactions between dyes are key to their use in QIS; critically, properties of the individual dyes govern the extent of these interactions. In this work, the electronic structure and excited-state dynamics of a series of indolenine-based squaraine dyes incorporating dimethylamino (electron donating) and/or nitro (electron withdrawing) substituents, so-called asymmetric dyes, were characterized. The dyes were covalently tethered to DNA Holliday junctions to suppress aggregation and permit characterization of their monomer photophysics. A combination of density functional theory and steady-state absorption spectroscopy shows that the difference static dipole moment (Δd) successively increases with the addition of these substituents while simultaneously maintaining a large transition dipole moment (μ). Steady-state fluorescence and time-resolved absorption and fluorescence spectroscopies uncover a significant nonradiative decay pathway in the asymmetrically substituted dyes that drastically reduces their excited-state lifetime (τ). This work indicates that Δd can indeed be increased by functionalizing dyes with electron donating and withdrawing substituents and that, in certain classes of dyes such as these asymmetric squaraines, strategies may be needed to ensure long τ, e.g., by rigidifying the π-conjugated network.

Retraction Note: Fabrication of hexagonal shaped CuCo2S4 nanodiscs/graphene composites as advanced electrodes for asymmetric supercapacitors and dye sensitized solar cells (DSSCs)

Retraction Note: Fabrication of hexagonal shaped CuCo2S4 nanodiscs/graphene composites as advanced electrodes for asymmetric supercapacitors and dye sensitized solar cells (DSSCs)

A New Ratiometric Fluorescent Probe Based on BODIPY for Highly Selective Detection of Hydrogen Sulfide.

Hydrogen sulfide (H2S) as small molecular signal messenger plays key functions in numerous biological processes. The imaging detection of intracellular hydrogen sulfide is of great significance. In this work, a ratiometric fluorescent probe BH based on an asymmetric BODIPY dye for detection of H2S was designed and synthesized. After the interaction with hydrogen sulfide, probe display colorimetric and ratiometric fluorescence response, with its maximum emission fluorescence wavelength red-shifted from 542 nm to 594 nm, which is attributed to the sequential nucleophilic reaction of H2S leading to enhanced molecular conjugation after ring formation of the BODIPY skeleton. A special response mechanism has been fully investigated by NMR titration and MS, so that the probe has excellent detection selectivity. Furthermore, probe BH has low cytotoxicity and fluorescence imaging experiments indicate that it can be used to monitor hydrogen sulfide in living cells.

Janus-Type AIE Fluorophores: Synthesis and Properties of π-Extended Coumarin-Bearing Triskelions.

Janus-type triskelion-shaped fluorophores comprising coumarins bearing various electron-donating substituents (1aad, 1add, 1ccd, and 1cdd) were successfully synthesized via an intramolecular Ullmann coupling. Density functional theory (DFT) calculations indicated that all the compounds presented two different molecular surfaces, similar to Janus-type molecules. The absorption and fluorescence spectra of asymmetrical derivatives 1aad, 1add, 1ccd, and 1cdd exhibited a bathochromic shift due to their narrow highest occupied molecular orbital (HOMO) -lowest unoccupied molecular orbital (LUMO) gap. Natural transition orbital (NTO) analysis indicated that the excited state orbital overlaps differ among the C3 symmetrical and asymmetrical dyes. These triskelion-shaped fluorophores were found to form molecular nanoaggregates in THF/H2O mixtures and demonstrated aggregation-induced emission (AIE) enhancement characteristics as a result of restricting their molecular inversion. These results indicate that Janus-type AIE fluorophores are potentially applicable as solid-state fluorescent chiral materials, which can be optimized by controlling their molecular rearrangement in the solid state.

Colorimetric and fluorescent probe for highly selective and sensitive recognition of Cu2+ and Fe3+ based on asymmetric squaraine dye

An asymmetric squaraine, (Z)-2-((3-ethyl-1,1-dimethyl-1,3-dihydro-2H-benzo -[e]indol-2-ylidene)methyl)-4-((5-fluoro-3,3-dimethyl-3H-indol-1-ium-2-yl)methylene)-3-oxocyclobut-1-en-1-olate (FSQ) with high sensitivity and selectivity for detecting Cu2+ and Fe3+ has been synthesized. Compared with other tested metal cations (Hg2+, Ni2+, Mg2+, Pb2+, Al3+, Ag+, K+, Cr3+, Co2+, Ca2+,Ba2+,Na+, Zn2+, Cd2+), the colorimetric and fluorescence behaviors of the FSQ chemical sensors are significantly different in the presence of Cu2+and Fe3+. When Cu2+ was added, the color of FSQ solution turned from blue to purple, and the absorbance and fluorescence intensity decreased obviously. When Fe3+ was added, the color of FSQ solution turned from blue to yellow. The intensity of the maximum absorption peak at 657 nm decreased and the fluorescence intensity increased. Moreover, the binding mode of FSQ-Cu2+ and FSQ-Fe3+ was supporting by Job’s plot, FT-IR and 1H NMR. Therefore, the FSQ chemosensor maybe provide colorimetric and fluorescent methods for selective and sensitive detection of Cu2+ and Fe3+.

One-pot synthesis and applications of two asymmetrical benzoxanthene dyes

Two asymmetrical benzoxanthene dyes (BP-1 and BP-2) were designed and synthesized by a convenient one-step procedure from naphthaldehyde and m-aminophenol precursors. These dyes showed long-wavelength absorption, near-infrared emission (>650 nm), and large Stokes shifts (>90 nm) because of the asymmetrical introduction of the benzene ring into the xanthene structure. BP-1 exhibited high fluorescence quantum yield in organic solvents, whereas BP-2 showed very weak fluorescence due to the photoinduced electron transfer of 9-substituted groups. Cell experiments indicated that BP-1 with crescent-shape structure showed lower cytotoxicity and higher photostability than BP-2 and could rapidly stain RNA in nucleoli at low concentration.

RETRACTED ARTICLE: Fabrication of hexagonal shaped CuCo2S4 nanodiscs/graphene composites as advanced electrodes for asymmetric supercapacitors and dye sensitized solar cells (DSSCs)

RETRACTED ARTICLE: Fabrication of hexagonal shaped CuCo2S4 nanodiscs/graphene composites as advanced electrodes for asymmetric supercapacitors and dye sensitized solar cells (DSSCs)

Single- and co-sensitization of triphenylamine-based and asymmetrical squaraine dyes on the anatase (001) surface for DSSC applications: Periodic DFT calculations

Dye aggregation causes poor performance of dye-sensitized solar cell (DSSC) applications through faster charge recombination of the photosensitizer with electrolyte. Triphenylamine (TBA)-based dyes feature a higher molar absorption coefficient and broadened wavelength but cannot absorb sunlight in the near-infrared (NIR) region. In contrast, the squaraine (SQ) photosensitizer, which is also called an NIR photosensitizer, has a maximum wavelength in the NIR region with high intensity. However, SQ dye suffers from dye aggregation due to its planar structure. The use of a co-sensitizer is one well-tested way to increase the power conversion efficiency (η) of solar cells by reducing dye aggregation and charge recombination. Using density functional theory (DFT) and time-dependent DFT (TDDFT), this work explains from a theoretical perspective the higher η values of the TZC1 and TZC2 dyes compared to that of asymmetric the SQ sensitizer (YR6) as free dyes. The electronic properties, reorganization energies, absorption and emission spectra, ICT parameters, and photovoltage parameters of the TZC1, TZC2, and YR6 dyes were computed using the M06/6-31G(d,p) level of theory in the gas phase and CH2Cl2 solvent (CPCM method). Additionally, the mono- and co-adsorption processes of TZC-based sensitizers with YR6 on the anatase (001) surface were investigated using periodic DFT calculations with the PBE + U/PAW method and the dispersion correction of the Grimme method D3. The results reveal that the use of the co−sensitized led to significant stabilization of the formed complexes by at least 1.21 eV, the panchromatic effect on the absorption spectra, and an increase in the light-harvesting ability in the NIR region, which improves the performance of DSSCs.

Dual-state emission and solvatofluorochromism properties of facile squaraine dyes with cis-3,5-dimethylpiperidine

By incorporating cis-3,5-dimethylpiperidine here we synthesized two simple asymmetrical squaraine dyes (SQ1-2), both exhibiting solution emission and crystalline-induced emission (CIE) behavior with the quantum yield (ΦPL) up to 0.36 at 541 nm and 0.48 at 579 nm in the solid state, respectively. The efficient emission in crystalline state was resulted from twisty 3,5-dimethylpiperidine which resisted intermolecular π-π stacking, while their marked intramolecular charge transfer (ICT) effect resulted into moderate emission and solvatofluorochromism behaviors.

Theoretical predictions of the spectroscopic properties of BODIPY dyes: Effects of the fused aromatic and heteroaromatic rings at the b, g bonds.

The fusion of aryl and heteroaryl moieties in the BODIPY skeleton is the important route to design BODIPYs exhibiting absorption and fluorescence in red or near infra-red regions. Despite the importance of this approach, little is known about the influence of aryl and heteroaryl rings on the position of the energy levels of the lower electronic states of such dyes. In this paper, the influence of benzene (B), thiophene (T) and furan (F) rings fused in the BODIPY core (b) at both b and g bonds on the optical properties of the symmetric BbB, TbT and FbF and asymmetric TbF, BbF and BbT dyes have been investigated by TD-CAM-B3LYP and RI-CC2 calculations. We have shown that in contrast to the locally excited (LE0-type) main vertical state, energy of which is nearly the same for all the substituents at the b and g bonds, energy of the next two states of the LE1- and LE2-type for the symmetric dyes or the charge transfer (CT1- and CT2-type) for the asymmetric dyes depends strongly on the nature of the rings at the b and g bonds. The benzene-fused dyes (BbF, BbT, BbB) have the lowest energy of the excited levels of the LE-type (or CT1-type) states, and inversion with LE0-type levels occurs. As a result, the dramatic decrease of the fluorescence quantum yield is expected in these cases. The identification of these effects provides a quality framework for understanding of how fused substituents regulate photophysical processes of BODIPYs.

Cascade recognition for Fe3+ and CO32− based on asymmetric squaraine dye：An application in mimicking an INHIBIT logic gate

Abstract A novel fluorescent and colorimetric squaraine dye (SQ) is synthesized and its cascade recognition ability for Fe3+ and CO32− is investigated by spectroscopic techniques. It has exhibited high selectivity and sensitivity for Fe3+ over the other metal ions. The CO32− ion can be consequently detected by Fe3+ displacement approach and restoring the spectral signal of SQ. The mechanism of interaction between SQ and Fe3+ and sensing performance of CO32− are supported by spectroscopic changes and other analytical methods. The limit of detection (LOD) for both Fe3+ and CO32− are found to be 0.14 μM and 0.17 μM, respectively. Both results are superior to the most literature reported examples. An INHIBIT logic gate can be constructed by this reversible bifunctional sensing system and the quantification of Fe3+ in real water samples is successfully applied as well.