Showing papers on "Xanthene published in 2021"
TL;DR: A comprehensive review of the synthetic applications of photocatalyzed d-HAT can be found in this article, where the authors provide a comprehensive overview of the main applications of PCHAT.
Abstract: Direct photocatalyzed hydrogen atom transfer (d-HAT) can be considered a method of choice for the elaboration of aliphatic C-H bonds. In this manifold, a photocatalyst (PCHAT) exploits the energy of a photon to trigger the homolytic cleavage of such bonds in organic compounds. Selective C-H bond elaboration may be achieved by a judicious choice of the hydrogen abstractor (key parameters are the electronic character and the molecular structure), as well as reaction additives. Different are the classes of PCsHAT available, including aromatic ketones, xanthene dyes (Eosin Y), polyoxometalates, uranyl salts, a metal-oxo porphyrin and a tris(amino)cyclopropenium radical dication. The processes (mainly C-C bond formation) are in most cases carried out under mild conditions with the help of visible light. The aim of this review is to offer a comprehensive survey of the synthetic applications of photocatalyzed d-HAT.
261 citations
TL;DR: In this article, the adsorption of Rhodamine B (Rh.B) was achieved by Zeolite imidazolate framework-8 (ZIF-8) in the dark condition, and the adaption rate was noticeably increased under visible and UV light irradiations.
68 citations
TL;DR: In this article, an Ag-Mg-MOF was synthesized through a one-step approach using solvothermal technique and the as-synthesized Bimetallic MOFs were characterized by TEM, SEM, EDS, XRD, FTIR and N2 adsorption.
Abstract: Removing of heavy metal ions from aqueous solutions has become a serious challenge from both biological and environmental viewpoints. Recently, metal-organic frameworks (MOF) including two metal ions in its framework have been enhanced as promising structure in the capture of various hazardous and toxic substances. Herein, Ag-Mg-MOF were synthesized through a one-step approach using solvothermal technique. Then, the as-synthesized Bimetallic MOFs were characterized by TEM, SEM, EDS, XRD, FTIR and N2 adsorption. The as-synthesized Ag-Mg-MOF samples were used for heavy metal removal. The results showed that the adsorption of cadmium, lead and Cupper ions on MOF was improved by the pH increasing. The experimental data were examined through Freundlich and Langmuir models. The fabricated Ag-Mg MOFs exhibit enhanced decontaminant performance toward Cu2+, Cd2+and Pb2 ions in terms of high adsorption capacities, Pb2+ (350 mg/g)> Cd2+ (270 mg/g)> Cu2+ (202 mg/g), and ultrafast kinetics compared to the monometallic Mg-MOF. FT-IR spectra of adsorbed pyridine methods and non-aqueous potentiometric titration were used for measuring surface acidity of the prepared MOF. It was observed that the surface acidity and the catalytic activity were increased in bimetallic MOF compared to monometallic MOF. The catalytic results of the formation of free solvent 14-aryl-14-Hdibenzo[a,j]xanthene compound by Ag-Mg MOF showed a high yield at a lower time. Also, the prepared MOF catalysts still preserved their initial catalytic activity even after the 4th run. The results of this work demonstrate that the novel Ag-Mg MOFs nanocatalysts have great potential for applications in environmental protection, especially in heavy metal ions removal present in wastewaters and in the synthesis of pharmacologically and biologically active compound.
35 citations
TL;DR: In this article, the synthesis, characterization, and evaluation of inhibiting performance of two xanthene derivatives, namely 3-oxo-3H-spiro[isobenzofuran-1,9′-xanthene]-3′,6′-diyl (3-dibenzoate) (NAR2), on mild steel immersed in 1-M HCl solution are performed.
Abstract: The synthesis, characterization, and evaluation of inhibiting performance of two xanthene derivatives, namely 3-oxo-3H-spiro[isobenzofuran-1,9′-xanthene]-3′,6′-diyl (3-dibenzoate) (NAR2) and 3-oxo-3H-spiro[isobenzofuran-1,9′-xanthene]-3′,6′-diyl (3-diacetate) (NAR3) on mild steel immersed in 1 M HCl solution are performed. The in vivo tests were carried out to confirm the non-toxicity of NAR2 and NAR3. The solutions corrosive was analyzed using UV visible Spectroscopy. The recorded spectra confirm the adsorption capacity of these molecules on the surface of iron and thereby a formation of Fe–inhibitor complex film. A combination of Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) Spectroscopy were performed to characterize the surface of mild steel, with and without the NAR2 or NAR3 inhibitors; and Electrochemical techniques were evaluated (EIS) to determine the corresponding corrosion inhibition efficiencies of NAR2 and NAR3. The Density Functional Theory (DFT)- based total energy calculations and Monte Carlo simulations were also performed to get further theoretical insights into the inhibition mechanism. The obtained results confirmed that both organic inhibitors exhibit non-toxicity, with an inhibition efficiency of 93% and 89% for NAR2 and NAR3 at 10−4 M concentrations, respectively. Also, the both inhibitor function as mixed (cathodic and anodic) type inhibitors, displace water molecules from mild steel, and form an heterogeneous films on the mild steel surface to protect against corrosion.
34 citations
TL;DR: In this article, the authors found that the fluorescence quenching of neutral form of fluorescein derivatives in acidic medium resulted from a dark nπ* state, whereas the anionic fluorescence of the anions in the gas phase and alkaline solutions was tuned by minimal energy conical intersection (MECI).
Abstract: Although a large number of fluorescein derivatives have been developed and applied in many different fields, the general mechanisms for tuning the fluorescence of fluorescein derivatives still remain uncovered. Herein, we found that the fluorescence quenching of neutral form of fluorescein derivatives in acidic medium resulted from a dark nπ* state, whereas the fluorescence of the anionic form of fluorescein derivatives in the gas phase and alkaline solutions was tuned by minimal energy conical intersection (MECI). The formation of MECI involved significant rotation of benzene ring and flip-flop motion of xanthene moiety, which would be restricted by intermolecular hydrogen bonding and lowering temperature. The energy barrier for reaching MECI depended on the substituents in the benzene moiety in accordance with experimentally observed substituent effects. These unprecedented mechanisms would lead to a recognition of fluorescein derivatives and could provide a correct and instructive design strategy for further developing new fluorescein derivatives.
33 citations
TL;DR: In this paper, a mesoporous MCM-41 was synthesized via a solgel method and then grafted by adding the appropriate amount of citric acid (CA).
Abstract: Order mesoporous MCM-41 was synthesized via a sol-gel method and then grafted by adding the appropriate amount of citric acid (CA). The structure and morphology of pure and grafted mesoporous MCM-41 were investigated by XRD, BET, TEM, and FT-IR measurements. TEM measurements confirm that MCM-41 particles display an ordered structure with uniform mesoporous arranges into a hexagonal, honeycomb-like lattice and still preserved their mesoporous structure after grafting with different weight contents of CA. The pore sizes and volume of the CA/MCM-41 samples were found to vary markedly within CA contents. The surface acidity and the type of acid sites (Bronsted and Lewis) were determined using the potentiometric titration method and the FTIR of pyridine adsorption. In this work, it was found that the textural, acidic properties and the activities of catalysts could be improved by citric acid treatment The results illustrated that the surface acidity and acidic strength of CA/MCM-41 gradually increased with increasing the CA amount up to 50 wt.%. Also, the prepared catalysts showed both Bronsted and Lewis acid sites and the number of Bronsted acid sites increased largely compared with Lewis acid sites with increasing the CA content which indicates the role of carboxylic groups in enhancing the Bronsted acid sites. The catalytic performance of the samples was tested by the synthesis of 14-Phenyl-14H-dibenzo [a, j] xanthene (xanthene). In this reaction, the sample with 50 wt.% of CA displayed the highest acidity and catalytic activity. The adsorption activity was examined for removing Cd2+ and Pb2+ from aqueous solution with varying parameters such as pH, concentration, temperature and time. The equilibrium adsorption data obtained fitted with the Langmuir model and the adsorption kinetics favored the pseudo 2nd order model. Also, the adsorption was spontaneous and exothermic.
27 citations
TL;DR: In this article, the incorporation of sulfamic acid (SA) into mesoporous silica (MCM-41) introduced an effective approach in numerous multicomponent reactions, such as 3,4-dihydro-pirimidin-2(1H)-ones (DHPs), 7-hydroxy-4-methylcoumarin and 14-Phenyl-14H-dibenzo [a, j] xanthene.
27 citations
TL;DR: In this article, a near-infrared phosphorescent Ir(iii) complex conjugated to a xanthene dye, NIR-Ir-XE, is reported with highly favourable properties for mitochondria-targeted imaging and cancer phototherapy.
Abstract: Iridium(iii) complexes are potent candidates for photodynamic therapy (PDT), but some key drawbacks still hamper clinical translation, such as poor operability in the phototherapeutic window, high dark toxicity, and low reactive oxygen species (ROS) production efficiency. In this work, a near-infrared phosphorescent Ir(iii) complex conjugated to a xanthene dye, NIR-Ir-XE, is reported with highly favourable properties for mitochondria-targeted imaging and cancer phototherapy. The generation of the triplet excited state of a xanthene moiety endows the NIR-Ir-XE to form singlet oxygen (1O2) for use as a photodynamic therapy agent after irradiation with visible light. Compared with the xanthene-free Ir(iii) counterpart (NIR-Ir-bpy), the xanthene-modified cyclometalated Ir(iii) photosensitizer NIR-Ir-XE exhibits higher 1O2 generation efficiency, negligible dark toxicity and a better therapeutic effect. Importantly, a clear correlation between cell death and intracellular generation of 1O2 derived from NIR-Ir-XE after light irradiation was demonstrated. The corresponding in vivo photo-antitumor performance was further demonstrated to be effective in tumor-bearing mice. The observed properties of NIR-Ir-XE qualify it as a promising PDT agent.
21 citations
TL;DR: In this article, the mononuclear compound (bpy)Re(CO)3Cl(bpy-Re, with bpy = 2,2′-bipyridine) was shown to activate CO2.
Abstract: Mechanistic studies on dinuclear complexes that can activate CO2 are rare. Based on the investigations done for the mononuclear compound (bpy)Re(CO)3Cl (bpy-Re, with bpy = 2,2′-bipyridine), many re...
16 citations
TL;DR: A series of novel pH-sensitive fluorescent sensors for monitoring acidic lysosomes was developed by structure-pKa relationship study of Rh–OMe derivatives with various substituents in an alkoxy group on xanthene ring, which showed excellent fluorescence transition triggered by acidic pH.
15 citations
TL;DR: In this article, 3-phosphonofluorescein has been used to synthesize a new class of xanthene fluorophores called Phosphono-VF2.1.Cl.
Abstract: Xanthene fluorophores, like fluorescein, have been versatile molecules across diverse fields of chemistry and life sciences. Despite the ubiquity of 3-carboxy and 3-sulfonofluorescein for the last 150 years, to date, no reports of 3-phosphonofluorescein exist. Here, we report the synthesis, spectroscopic characterization, and applications of 3-phosphonofluoresceins. The absorption and emission of 3-phosphonofluoresceins remain relatively unaltered from the parent 3-carboxyfluorescein. 3-Phosphonofluoresceins show enhanced water solubility compared to 3-carboxyfluorescein and persist in an open, visible light-absorbing state even at low pH and in low dielectric media while 3-carboxyfluoresceins tend to lactonize. In contrast, the spirocyclization tendency of 3-phosphonofluoresceins can be modulated by esterification of the phosphonic acid. The bis-acetoxymethyl ester of 3-phosphonofluorescein readily enters living cells, showing excellent accumulation (>6x) and retention (>11x), resulting in a nearly 70-fold improvement in cellular brightness compared to 3-carboxyfluorescein. In a complementary fashion, the free acid form of 3-phosphonofluorescein does not cross cellular membranes, making it ideally suited for incorporation into a voltage-sensing scaffold. We develop a new synthetic route to functionalized 3-phosphonofluoresceins to enable the synthesis of phosphono-voltage sensitive fluorophores, or phosVF2.1.Cl. Phosphono-VF2.1.Cl shows excellent membrane localization, cellular brightness, and voltage sensitivity (26% ΔF/F per 100 mV), rivaling that of sulfono-based VF dyes. In summary, we develop the first synthesis of 3-phosphonofluoresceins, characterize the spectroscopic properties of this new class of xanthene dyes, and utilize these insights to show the utility of 3-phosphonofluoresceins in intracellular imaging and membrane potential sensing.
TL;DR: In this article, the bridging group was harnessed to sterically shield the central methane carbon from incoming nucleophiles and render high stability and synthesized xantheno-xanthene dyes.
TL;DR: In this article, the Zr-based metal-organic framework, UiO-66-NH2, was modified with ionic liquid (dibutylimidazolium bromide) to generate a platform for supporting an organocatalyst of guanidine.
Abstract: In this study, the Zr-based metal–organic framework, UiO-66-NH2, was modified with ionic liquid (dibutylimidazolium bromide) to generate a platform for supporting an organocatalyst of guanidine. After an anion exchange, the prepared hybrid system was denoted as UiO-66-NH2-ILPF6–-guanidine. The catalyst was characterized by different techniques such as PXRD, FTIR, TEM, SEM–EDS, TGA, and BET. The basic heterogeneous catalyst was then utilized for the synthesis of xanthene derivatives via a reaction of aldehydes with dimedone. Various types of aromatic aldehydes were employed for the synthesis with medium to high yield. The study of catalytic activities showed that the heterogenization of guanidine significantly promotes catalytic performance in comparison with guanidine in a homogeneous form. The heterogeneous catalyst is stable in the reaction medium and can be recycled for at least four times without significant reduction in activity. The stability of the catalyst was also investigated by XRD, FTIR, SEM/elemental mapping, and leaching test.
TL;DR: The analysis in different environments shows that the interactions of EOS and its derivatives with biomembranes can be modulated based on the hydrophobicity of the xanthene derivative and the cell membrane charge.
TL;DR: In this paper, a review of green catalytic routes for the synthesis of 1,8-dioxo-octahydroxanthenes, 1,6-decahydroacridines and related heterocyclic molecules with catalysts such as metal oxides, mixed metal oxide, resins, supported organocatalysts, heteropolyacids, carbon-based materials, zeolites, sulfides and ionic liquids are discussed.
Abstract: Xanthene and acridine-based heterocyclic compounds find applications in cancer chemotherapy, biological staining and laser dyes and are known for their antibacterial and anti-tumor properties. Here we review green catalytic routes for the synthesis of 1,8-dioxo-octahydroxanthenes, 1,8-dioxo-decahydroacridines and related heterocyclic molecules with catalysts such as metal oxides, mixed metal oxides, resins, supported organocatalysts, heteropolyacids, carbon-based materials, zeolites, sulfides and ionic liquids. We compare protocols for their catalytic activities, and proposed mechanisms are discussed.
TL;DR: XanthCR-880 as mentioned in this paper is a xanthene-based near-infrared (NIR) photoacoustic (PA) dyes with absorbance > 800 nm.
TL;DR: In this article, a series of new xanthene dyes containing dimethylamidine group were synthesized and the influence of this fragment in the composition of these dyes on their spectral characteristics was investigated.
TL;DR: Experimental solubility data are reported for anthracene, biphenyl, benzil, benzoin, 1-chloroanthraquinone, phenothiazine, pyrene, salicylamide, thioxanthen-9-one, xanthene, and benzoic acid.
Abstract: Experimental solubility data are reported for anthracene, biphenyl, benzil, benzoin, 1-chloroanthraquinone, phenothiazine, pyrene, salicylamide, thioxanthen-9-one, xanthene, benzoic acid, 4-tert-bu...
TL;DR: In this paper, a metal-organic framework (MOF) possessing dual Lewis acidic Cr sites and sulfonic acid sites (MIL-101(Cr)-SO3H) was reported as an efficient catalytic material for direct cross-coupling of xanthene and different nucleophiles using O2 as the oxidant.
Abstract: Cross-dehydrogenative coupling (CDC) is an effective tool for carbon-carbon bond formation in chemical synthesis. Herein, we report a metal-organic framework (MOF) possessing dual Lewis acidic Cr sites and sulfonic acid sites (MIL-101(Cr)-SO3H) as an efficient catalytic material for direct cross-coupling of xanthene and different nucleophiles using O2 as the oxidant. The highly porous structure of MIL-101(Cr)-SO3H enables the free access of reactants to the catalytic active sites inside MOF pores. Kinetic studies indicated that the Cr sites of MOF accelerate the rate-limiting autoxidation reaction of xanthene, which synergistically work with the sulfonic acid group on MOF ligands in promoting the CDC reactions. Besides, the catalytic system shows excellent functional group compatibility, and a variety of valuable xanthene derivatives were synthesized with satisfactory yields. Furthermore, MIL-101(Cr)-SO3H can be reused and its catalytic activity and crystal structure remain after six consecutive runs.
TL;DR: In this article, the authors demonstrate different synthetic methodologies for the construction of various dibenzo[a,i]xanthene derivatives by one-pot three-component reactions of lawsone, naphthols, and aldehydes or isatins or ninhydrin under different conditions.
Abstract: Xanthenes are a class of natural and synthetic heterocyclic compounds that exhibit a broad spectrum of biological properties and synthetic applications. The purpose of this current review is to demonstrate different synthetic methodologies for the construction of various dibenzo[a,i]xanthene, spiro-dibenzo[a,i]xanthene, dibenzo[b,i]xanthene, spiro dibenzo[b,i]xanthene, and dibenzo[b,h]xanthene derivatives by one-pot three-component reactions of lawsone, naphthols, and aldehydes or isatins or ninhydrin in the presence of homogeneous and heterogeneous catalysts under different conditions.
TL;DR: In this paper, two diamine monomers containing ether linkages, polar trifluoromethyl (-CF3), and xanthene segments were prepared through condensation polymerization with applying diverse aliphatic and aromatic dicarboxylic acids.
Abstract: Two series of new diamine monomers containing ether linkages, polar trifluoromethyl (-CF3), and xanthene segments were prepared. In addition, relevant high-performance polyamides (PAs) were synthesized through condensation polymerization with applying diverse aliphatic and aromatic dicarboxylic acids. The structure of compounds were characterized by Fourier transform infrared (FT-IR), proton nuclear magnetic resonance (1H NMR), and elemental analysis. The inherent viscosities values of the polymers were from 0.48 dL/g to 0.67 dL/g. The PAs indicated the glass transition temperatures (Tg), and 10% weight loss temperatures recorded within the range of 187–244 °C and 395–497 °C in N2 atmosphere, respectively. Polyamides showed a well antibacterial activity, with respect to the presence of xanthene segments in their structure. The polymeric nanocomposite was prepared through a combination of one of the synthesized polyamides with modified graphene oxide nanoparticles (m-GO NPs). The formation of potent chemical linkage across (m-GO) NPs and polymer chains caused photoluminescence intensity to enhance, thermal stability, and antibacterial properties of the nanocomposite than pure polyamide. The study of chromium ions adsorption from aqueous solutions was also performed at 25 °C and pH 7–8.
TL;DR: The additive bactericidal ability of a combination of xanthene dyes was tested on planktonic cultures and biofilms of Streptococcus mutans when irradiated by a hand-held LED photopolymerizer unit as mentioned in this paper.
TL;DR: In this paper, a new class of macrocycles denoted as "xanthene[n]arenes" was synthesized, which facilitates the synthesis of cavitands and the self-assembly to molecular capsules via noncovalent interactions.
Abstract: A new class of macrocycles denoted as "xanthene[n]arenes" was synthesized. In contrast to most other macrocycles, they feature a conformationally restricted bowl shape due to the attached alkyl groups at the linking methylene units. This facilitates the synthesis of cavitands and the self-assembly to molecular capsules via noncovalent interactions. The derivatization potential of the novel macrocycles was demonstrated on the xanthene[3]arene scaffold. Besides a deep cavitand and an oxygen-embedded zigzag hydrocarbon belt[12]arene, a modified macrocycle was synthesized that self-assembles into a hydrogen-bonded tetrameric capsule, demonstrating the potential of xanthene[n]arenes as a new set of macrocyclic building blocks.
TL;DR: In this article, four xanthene-based fluorescent probes have been devised and synthesized for the detection of Hg2+ in biological cells, and four of them were successfully applied for detecting Hg 2+ in a strip test in the presence of various cations, anions and amino acids.
Abstract: Four new xanthene-based fluorescent probes have been devised and synthesized. These probes were well characterized by 1H NMR, 13C NMR and HRMS. UV-vis absorption and fluorescence spectroscopy indicated that these probes show high selectivity and sensitivity towards Hg2+ in the presence of various cations, anions and amino acids in PBS buffer solution containing DMSO/H2O (1 : 1, v/v). The detection limits of the probes for Hg2+ were found to be 10.4, 12.5, 16.2 and 15.4 nM, respectively. The four probes were successfully applied for the detection of Hg2+ in a strip test. Among them, probe 4 was successfully applied for the detection of Hg2+ in biological cells.
01 Jan 2021
TL;DR: In this article, the authors investigated chemical and electrochemical 4e-ORR catalyzed by Co2(μ-O2) complexes bridged by xanthene (1) and anthracene (3).
Abstract: The four-electron oxygen reduction reaction (4e--ORR) is the mainstay in chemical energy conversion. Elucidation of factors influencing the catalyst's reaction rate and selectivity is important in the development of more active catalysts of 4e--ORR. In this study, we investigated chemical and electrochemical 4e--ORR catalyzed by Co2(μ-O2) complexes bridged by xanthene (1) and anthracene (3) and by a Co2(OH)2 complex bridged by anthraquinone (2). In the chemical ORR using Fe(CpMe)2 as a reductant in acidic PhCN, we found that 1 showed the highest initial turnover frequency (TOFinit = 6.8 × 102 s-1) and selectivity for 4e--ORR (96%) in three complexes. The detailed kinetic analyses have revealed that the rate-determining steps (RDSs) in the catalytic cycles of 1-3 have the O2 addition to [CoII2(OH2)2]4+ as an intermediate in common. In the only case that complex 1 was used as a catalyst, kcat depended on proton concentration because the reaction rate of the O2 addition to [CoII2(OH2)2]4+ was so fast as compared to that of the concerted PCET process of 1. Through X-ray, Raman, and electrochemical analyses and stoichiometric reactions, we found the face-to-face structure of 1 characterized by a slightly flexible xanthene was advantageous in capturing O2 and stabilizing the Co2(μ-O2) structure, thus increasing both the reaction rate and selectivity for 4e--ORR.
TL;DR: In this article, a metal-organic framework-based Sr(II) was fabricated to achieve the desired goal for dye removal and catalysis, and the maximum adsorption capacity of crystal violet (CV) dye was reached after 90 min and well fitted the pseudo-second kinetic order and Langmuir adaption isotherm.
Abstract: There is an urgent need to improve engineering and synthetic chemistry, either through the use of eco-friendly starting materials or the proper design of novel synthesis routes. This reduces the contamination of toxic chemicals and helps the disposal of organic dyes. In the current work, a metal–organic framework-based Sr(II) was fabricated to achieve the desired goal for dye removal and catalysis. Sr-MOF-based phosphotungstic acid (PWA/Sr-MOF) was hydrothermally synthesized to study its adsorption and catalytic activities. Remarkably, about 99.9% of crystal violet (CV) dye was removed using PWA/Sr-MOF within 90 min at room temperature. Various factors have been studied to investigate the optimum conditions such as pH of solution, initial dye concentration, contact time, and temperature. The maximum adsorption capacity of CV dye was reached after 90 min and well fitted the pseudo-second kinetic order and Langmuir adsorption isotherm. Coumarin and xanthene reactions were chosen to test the catalytic activity of the prepared PWA/Sr-MOF at 373 K. Furthermore, structural and chemical characterization of the fabricated samples was obtained using FT-IR, XRD, TGA, DTA, TEM, EDX, and XPS. PWA/Sr-MOF can be considered as a promising and green framework in the material design used to study catalytic and adsorption performances.
TL;DR: In this paper, a facile and versatile strategy employing TiCl4-mediated cyclization followed by a Cannizzaro reaction has been developed for the synthesis of various xanthene derivatives.
Abstract: A facile and versatile strategy employing TiCl4-mediated cyclization followed by a Cannizzaro reaction has been developed for the synthesis of various xanthene derivatives. The reaction proceeded smoothly to afford both xanthenes/xanthones or their sulfur derivatives and tolerated a wide range of electronically diverse substrates. Using this methodology, pranoprofen was synthesized in three steps in 59% overall yield from commercially available starting materials.
TL;DR: In this paper, the authors investigated the installation of a ketone bridge at the C10' position on the xanthene scaffold to extend the absorbance maxima to 860nm and the emission beyond 1000nm, with reduced photon output.
Abstract: Imaging in the shortwave-infrared region (SWIR, λ = 1000-2500 nm) has the potential to enable deep tissue imaging with high resolution. Critical to the development of these methods is the identification of low molecular weight, biologically compatible fluorescent probes that emit beyond 1000 nm. Exchanging the bridging oxygen atom on the xanthene scaffold (C10' position) with electron withdrawing groups has been shown to lead to significant redshifts in absorbance and emission. Guided by quantum chemistry computational modeling studies, we investigated the installation of a ketone bridge at the C10' position. This simple modification extends the absorbance maxima to 860 nm and the emission beyond 1000 nm, albeit with reduced photon output. Overall, these studies demonstrate that broadly applied xanthene dyes can be extended into the SWIR range.
TL;DR: In this paper, the dual activities of six deep eutectic solvents were compared for the synthesis of 1,8-dioxooctahydroxanthenes at room temperature.
Abstract: Deep eutectic solvents are obtained by the fusion of two or more compounds: hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs). They are formed by mixing the constituents with moderate heating (via hydrogen bond interactions). In this manuscript, the dual activities (as catalysts and reaction media) of six deep eutectic solvents were compared for the synthesis of 1,8-dioxooctahydroxanthenes at room temperature. Here DES 2, a combination of ZrOCl2·8H2O with ethylene glycol at a 1 : 2 ratio, was found to be the supreme catalyst among the six DESs and was reused for five batches. The photophysical properties of the xanthene derivatives were examined by UV-vis and fluorescence spectroscopy in THF. The synthesised molecules showed absorption maxima around 285–295 nm and emission maxima around 403–404 nm. The ground state dipole moments of all the molecules were calculated by the Debye–Guggenheim method using toluene as the non-polar solvent. All the synthesised molecules showed significant dipole moment values and are in good agreement with theoretical values.