Bathochromic Research Articles

Multiparametric Investigations on Solvation Behaviour and Spectral Shifts of Symmetric Aromatic Diselenides: A case study of Diphenyldiselenide

ABSTRACT Decorating symmetric aromatic diselenide motif such as in diphenyldiselenide (DPDSe) with diverse supra-functionalities provides a plethora of bioactivities for pharmacological applications. Solvent studies of bioactive molecules are vital descriptors for their drug development as these can predict the drug–target interaction. This study aims to evaluate the influence of intermolecular interactional forces on the solvation behaviour and spectral shifts of DPDSe. The solvation behaviour of DPDSe was evaluated primarily via solvent polarity and solvent parameters. The observed solvatochromic shifts were analysed with various solvent study models, of which Kamlet–Taft and Catalan models were found to be most suitable for describing intermolecular interactions of DPDSe. The experimental data suggest an overall red shift with increasing solvent polarity. Moreover, data analysis using solvatochromic models predict negative coefficients for solvent dipolarity (π*) and solvent polarisabilities (SP) and (SdP). The studied dipole moment values indicate the more polar nature of DPDSe in the excited state relative to the ground state, further corroborating the observed bathochromic shift with increasing solvent polarity.

Isolation of Amyloid-like Protein Aggregates (APA) from white bread and their characterisation

High temperature, acidic pH, and physical agitation are commonly observed during cooking or industrial food processing, which are often considered as favorable conditions, at least for some proteins, to misfold and form amyloid-like protein aggregates (APA). The proteins in various bakery products generally experience high temperatures that might lead to the formation of APA. To test this hypothesis, the presence of APA in white bread was examined in this study. The APA isolated from white bread displayed typical characteristics of amyloids, like bathochromic shift in Congo red (CR) absorbance maxima, increased fluorescence of Thioflavin T (ThT) & 8-anilino-1-naphthalene sulfonic acid (ANS), fibrillar morphology of >200 nm long with average diameter of 10–12 nm and negative minima at 223 nm in Circular Dichroism (CD) spectrum. The SDS- and native PAGE revealed the presence of gliadin and glutenin as the constituent proteins in the isolated protein aggregates. Although, the presence of amyloid-like structures in white bread is evident, further studies would be essential to establish their functional role and health implications.

Multiple phases of yttrium-doped molybdenum trioxide nanorods as efficient dye degrader and bactericidal agents with molecular docking analysis

Contaminants removal is usually becoming an exciting subject of research from water considering their environmental and ecological effects. This work provides pathways to remove organic pollutants from water via nanomaterials and is used as an antibiotic against bacteria like Escherichia coli (E. coli). In this study, molybdenum trioxide (MoO3) and yttrium (Y) doped (2 and 4%) MoO3 nanorods were synthesized by co-precipitation method. Advanced characterization techniques have been introduced to study textural structures, morphological developments, and optical characteristics of produced products. X-ray diffraction studied multiple crystalline structures of prepared samples as hexagonal, orthorhombic, and monoclinic of pure MoO3 with decrease in crystallinity and crystallite size upon Y doping. UV–visible spectroscopy unveiled a redshift (bathochromic effect) in absorption pattern attributed to band gap energy (Eg) decreases. Photoluminescence spectra examined the recombination rate of electrons (e−) and holes (h+) as charge carriers. A sufficient catalytic activity (CA) was observed against methylene blue (MB) dye in an acidic medium (99.74%) and efficient bactericidal action was studied against (E. coli) with zone of inhibition (5.20 mm) for 4% Y-doped MoO3. In addition, in silico docking demonstrated potential inhibitory effect of produced nanomaterials on FabH and FabI enzymes of fatty acid biosynthesis.

Dabcyl as a Naked Eye Colorimetric Chemosensor for Palladium Detection in Aqueous Medium.

Industrial activity has raised significant concerns regarding the widespread pollution caused by metal ions, contaminating ecosystems and causing adverse effects on human health. Therefore, the development of sensors for selective and sensitive detection of these analytes is extremely important. In this regard, an azo dye, Dabcyl 2, was synthesised and investigated for sensing metal ions with environmental and industrial relevance. The cation binding character of 2 was evaluated by colour changes as seen by the naked eye, UV-Vis and 1H NMR titrations in aqueous mixtures of SDS (0.02 M, pH 6) solution with acetonitrile (99:1, v/v). Out of the several cations tested, chemosensor 2 had a selective response for Pd2+, Sn2+ and Fe3+, showing a remarkable colour change visible to the naked eye and large bathochromic shifts in the UV-Vis spectrum of 2. This compound was very sensitive for Pd2+, Sn2+ and Fe3+, with a detection limit as low as 5.4 × 10-8 M, 1.3 × 10-7 M and 5.2 × 10-8 M, respectively. Moreover, comparative studies revealed that chemosensor 2 had high selectivity towards Pd2+ even in the presence of other metal ions in SDS aqueous mixtures.

A smart probe for multi-analyte signaling: Cascade detection of HSA mediated by N2H4

Human serum albumin (HSA) and hydrazine (N2H4) are known biomarkers and damage agents of liver function activity, respectively. However, the mechanism of association between HSA and N2H4 in the liver remains unexplored. Herein, we report a naphthalimide-based smart fluorescent probe NI-2 for the N2H4 mediated cascade detection of HSA (N2H4 ∩HSA). Results showed that the levulinate recognition group on NI-2 is ammonolyzed within seconds in response to N2H4, releasing the compound NI-OH, triggering a hypsochromic shift of the emission to 400 nm; while with the coexistence of HSA, the entry of NI-OH into the hydrophobic cavity of HSA, resulting a bathochromic emission shift to 670 nm. We have further revealed the reaction mechanism of NI-2 cascade reacting with N2H4 ∩HSA through HRMS, replacement experiment and molecular docking method. NI-2 has been successfully applied in detecting N2H4 ∩HSA in human urine quantitatively and N2H4 in water samples or plants. A qualitative test paper strip model for quick response of N2H4 and N2H4 ∩HSA has also been established. Moreover, NI-2 can be applied in bioimaging of HepG2 cells and zebrafish, indicating that NI-2 can be a potential tool for the study of liver damage.

A combined theoretical and experimental study of ratiometric fluorescent Schiff base chemosensor for detection of Fe3+ ion and its anticancer activity

Schiff-base fluorescent chemosensor (E)-N-(4-(dimethylamino)benzylidene)quinolone-3-amine (DBQA) was synthesized and characterized by FT-IR,1H NMR,13C NMR, ESI-MS spectrometry and Single X-ray crystallographic studies. The synthesized chemosensor (DBQA) was used for the detection of Fe3+ successfully. UV-visible and fluorescence spectra of (DBQA) exhibits a ratiometric behaviour along with a bathochromic shift upon the successive addition of Fe3+. The fluorescence spectra of chemosensor (DBQA) were recorded followed by addition of concentrations of different metal ions and NH3. The chemosensor (DBQA) showed a favourable linear relationship between the fluorescence intensity and concentration of Fe3+ ion. DBQA exhibits a ratiometric response and illustrates high sensitivity (with a detection limit of 0.4 ​μM) and good selectivity for the Fe3+ ion over other transition metal ions. DBQA shows 0.6 ​μM detection limit for NH3 along with ratiometric behaviour also. The association constant (Ka) of chemosensor (DBQA) was found to be 1.455×102 ​M-1/2 for Fe3+. The mechanism of sensing of the present ratiometric fluorescent chemosensor (DBQA) was explained by ICT (Intra-molecular charge transfer) using DFT calculations. The interaction model of chemosensor (DBQA) with Fe3+ was determined to be 2:1 stoichiometry using Job's plot analysis and ESI-MS spectra which further confirms DFT studies. Moreover, tested DBQA ​+ ​Fe3+ was showed that remarkable anticancer activity against the HCT116 colon cancer cells by MTT assay. Novelty and importance of DBQA as it can be investigate, test or analyse of detect Fe3+ rapidly as compared to other tested ions. Lastly, DBQA can be investigate, test or analyse of Fe3+ in environmental and biological samples.

Bright NIR-Emitting Styryl Pyridinium Dyes with Large Stokes' Shift for Sensing Applications.

Two NIR-emitting donor-π-acceptor (D-π-A) type regioisomeric styryl pyridinium dyes (1a-1b) were synthesized and studied for their photophysical performance and environment sensitivity. The two regioisomers, 1a and 1b, exhibited interesting photophysical properties including, longer wavelength excitation (λex ≈ 530-560 nm), bright near-infrared emission (λem ≈ 690-720 nm), high-fluorescence quantum yields (ϕfl ≈ 0.24-0.72) large Stokes' shift (∆λ ≈ 150-240 nm) and high-environmental sensitivity. Probe's photophysical properties were studied in different environmental conditions such as polarity, viscosity, temperature, and concentration. Probes (1a-1b) exhibited noticeable changes in absorbance, emission and Stokes' shift while responding to the changes in physical environment. Probe 1b exhibited a significant bathochromic shift in optical spectra (∆λ ≈ 20-40 nm) compared to its isomer 1a, due to the regio-effect. Probes (1a-1b) exhibited an excellent ability to visualize bacteria (Bacillus megaterium, Escherichia coli), and yeast (Saccharomyces cerevisiae) via fluorescence microscopy.

Concerted Intramolecular and Intermolecular Charge Transfer for High‐Efficiency Near‐Infrared Thermally Activated Delayed Fluorescent Materials Approaching 900 nm

AbstractHindered by the energy gap law, the development of high‐efficiency near‐infrared (NIR) thermally activated delayed fluorescence (TADF) emitters with emission peaks over 800 nm remains challenging. The conventional strategy of enhancing intramolecular charge transfer for bathochromic shift commonly results in low radiative decay rates (kr) and emission efficiency. Herein, a superior strategy of concerted intramolecular CT (intra‐CT) and intermolecular CT (inter‐CT) for high‐efficiency NIR‐TADF materials is demonstrated. As a proof‐of‐concept, two novel emitters DTPZ and DtBuTPZ are developed based on a new acceptor phenazine‐2,3‐dicarbonitrile (PZ). High kr is achieved by large oscillator strength from appropriate intra‐CT property in monomers and effective electronic couplings between inter‐CT and intra‐CT states in aggregates. Suppressed nonradiative decay processes are realized through strong inter‐CT properties, abundant intermolecular attractive interactions, and negligible π∙∙∙π stacking. Consequently, organic light‐emitting diodes based on those emitters showed record‐high maximum external quantum efficiencies and radiances of 2.28%, 24.18 W Sr−1 m−2 at 817 nm, 0.57%, 14.38 W Sr−1 m−2 at 877 nm for DTPZ, and 2.34%, 23.55 W Sr−1 m−2 at 807 nm for DtBuTPZ, respectively.

Quantum Dot-Based Fluorometric Sensor for Hg(II) in Water Customizable for Onsite Visual Detection.

An easy naked-eye detection technique for mercuric ions in water using silanized quantum dots is demonstrated. Cadmium selenide quantum dots were synthesized and rendered water soluble by silica overcoating. The quantum dot emission was instantly turned off by the mercuric ions in the analyte, enabling visual detection. The emission quenching was associated with a concomitant bathochromic shift, both in the absorption and emission profiles. The underlying mechanism is a permanent surface modification of quantum dots by mercuric ions, altering the electronic structure and, in turn, the photophysical properties. The results confirmed the potential of this simple system to be customized for on-site visual detection of mercury contamination in water bodies, biological fluids, and soil with high selectivity and sensitivity.

Red light photocatalysis of conjugated microporous polymers based on fused thiophenes for selective oxidation of amines

By virtue of tailorable building blocks, the band gaps and electronic structures of conjugated microporous polymers (CMPs) can be readily adjusted at the molecular level. Generally, the building blocks possessing extended π-conjugations result in exceptional photocatalytic performances. In this work, the direct CH arylation of fused thiophenes, thieno[3,2-b]thiophene (TT) and dithieno[3,2-b:2′,3′-d]thiophene (DTT), with 1,3,6,8-tetrabromopyrene affords two CMPs, namely TT-Py-CMP and DTT-Py-CMP. The expansion of π-conjugations of the fused thiophenes from TT to DTT gives rise to a bathochromic shift about 30 nm from TT-Py-CMP to DTT-Py-CMP. Besides, systematic characterizations suggest the optoelectronic properties of DTT-Py-CMP are better than that of TT-Py-CMP. Furthermore, DTT-Py-CMP drives better red light photocatalysis than TT-Py-CMP for the selective oxidation of amines with molecular oxygen. The selective oxidation of benzyl amines by red light photocatalysis of DTT-Py-CMP progresses via an electron transfer pathway with high selectivities for imines. This work provides new insights that fused thiophenes could be the stepping stone in designing CMPs for expansive visible light photocatalysis.

Imidazole appended rotatable hydroxy quinoline scaffold as dual signaling fluorescent chemosensor: Detection of silver ions with hypsochromic shift and hydroxide ions with bathochromic shift and their LFP’s, anticounterfeiting, soil analysis and bio-imaging

An imidazole conjugated hydroxy quinoline based chemosensor (QBI) was developed for the specific dual detection of silver (Ag+) and hydroxide (OH−) ions by fluorimetric technique. QBI had weak fluorescent emission, upon binding with Ag+ and OH−, fluorescence intensity enhanced with a large hypsochromic shift for Ag+ ion and notable bathochromic shift for OH− ions respectively. Three modes of possible mechanistic pathways accounts for the detection of the Ag+ ions, restriction of the C–C free rotation between the quinoline and imidazole scaffolds, blocking of photoinduced electron transfer (PET) process assisted by the Intramolecular charge transfer (ICT) process. On other hand, the –OH moiety of QBI gets deprotonated during the process of detecting OH− ions. The binding stoichiometry of complexations was confirmed by Jobs plot, Benesi-hildebrand, 1H NMR titration, DFT analysis and ESI-TOF. The limit of detection (LOD) of QBI with Ag+ and OH− was found to be 3.53 × 10−8 M for Ag+ and 1.5 × 10−7 M respectively. Latent fingerprintvisualization (LFP), anti-counterfeiting applications, and soil analysis are merely a few instances of where QBI has been effectively put to use in the real world for the specific detection of Ag+ and OH− ions. Furthermore, receptor QBI was utilized in bacterial imaging against E.coli and pseudomonas pathogens for the detection of both ions.

Short-wave infrared fluorescence imaging of near-infrared dyes with robust end-tail emission using a small-animal imaging device.

Commercially available near-infrared (NIR) dyes, including indocyanine green (ICG), display an end-tail of the fluorescence emission spectrum detectable in the short-wave infrared (SWIR) window. Imaging methods based on the second NIR spectral region (1,000-1,700 nm) are gaining interest within the biomedical imaging community due to minimal autofluorescence and scattering, allowing higher spatial resolution and depth sensitivity. Using a SWIR fluorescence imaging device, the properties of ICG vs. heptamethine cyanine dyes with emission >800 nm were evaluated using tissue-simulating phantoms and animal experiments. In this study, we tested the hypothesis that an increased rigidity of the heptamethine chain may increase the SWIR imaging performance due to the bathochromic shift of the emission spectrum. Fluorescence SWIR imaging of capillary plastic tubes filled with dyes was followed by experiments on healthy animals in which a time series of fluorescence hindlimb images were analyzed. Our findings suggest that higher spatial resolution can be achieved even at greater depths (>5 mm) or longer wavelengths (>1,100 nm), in both tissue phantoms and animals, opening the possibility to translate the SWIR prototype toward clinical application.

Electrochromic conjugated polymers containing benzotriazole and thiophene performing sub-second response time and 916 cm2 C−1 superb coloration efficiency

In pursuit of high-performance electrochromic conjugated polymers (ECPs), three benzotriazole-thiophene ECPs employing benzotriazole as acceptor and different thiophene repeating units as donors, namely, PBTz-T, PBTz-BT, and PBTz-TT, were synthesized via direct (hetero)arylation polymerization (DHAP). Meanwhile, following the above ECPs model, we investigated the effect of corresponding conjugated chain length of monomers on their optical, electrochemical and electrochromic properties. The results showed that along with the increase of the numbers of thiophene in the repeating unit of ECPs, the electronic and optical band gaps decreased, the UV–Vis absorption and fluorescence spectra showed significant bathochromic shift, and the electrochemical cycle stability gradually improved. PBTz-T exhibited giant coloration efficiency (916 cm2 C−1 at 530 nm), which is one of the best results in the visible region. And higher coloration efficiency means less energy consumption, which holds great potential for various applications, including electrochromic back covers of smartphones. PBTz-BT displayed the highest transmittance (28% at 550 nm), and BTz-TT illustrated the fastest switching time (0.6 s/0.5 s for doping/dedoping process). Flexible electrochromic device (ECD) fabricated employed PBTz-T as functional layer gradually changed from red (reduction) to dark green (oxidation), and maintained good cycling stability.

An ependymin-related blue carotenoprotein decorates marine blue sponge

Marine animals display diverse vibrant colors, but the mechanisms underlying their specific coloration remain to be clarified. Blue coloration is known to be achieved through a bathochromic shift of the orange carotenoid astaxanthin (AXT) by the crustacean protein crustacyanin, but other examples have not yet been well investigated. Here, we identified an ependymin (EPD)-related water-soluble blue carotenoprotein responsible for the specific coloration of the marine blue sponge Haliclona sp. EPD was originally identified in the fish brain as a protein involved in memory consolidation and neuronal regeneration. The purified blue protein, designated as EPD-related blue carotenoprotein-1, was identified as a secreted glycoprotein. We show that it consists of a heterodimer that binds orange AXT and mytiloxanthin and exhibits a bathochromic shift. Our crystal structure analysis of the natively purified EPD-related blue carotenoprotein-1 revealed that these two carotenoids are specifically bound to the heterodimer interface, where the polyene chains are aligned in parallel to each other like in β-crustacyanin, although the two proteins are evolutionary and structurally unrelated. Furthermore, using reconstitution assays, we found that incomplete bathochromic shifts occurred when the protein bound to only AXT or mytiloxanthin. Taken together, we identified an EPD in a basal metazoan as a blue protein that decorates the sponge body by binding specific structurally unrelated carotenoids.

A Multistimuli Responsive, Flexible Luminescent Framework and Its Applicability in Anticounterfeiting.

A linear distyrylanthracene derivative (DDATAn) with two diaminotriazine (DAT) groups acting as the hydrogen bond (H-bond) units was designed and synthesized in order to construct flexible organic porous crystals. H-bonds between the DAT moieties helped the molecules to construct a double interpenetrated two-dimensional layer, and the stacking between layers provided a H-bonded organic framework (X-HOF-3) with one-dimensional solvent channels. When X-HOF-3 was placed in contact with methanol, the fluorescent colors of the HOF exhibited an apparent bathochromic shift. More interestingly, the methanol-activated HOF was able to rapidly adsorb water from the air, which was accompanied by a change in fluorescent color from yellow to red. Under heating, water was released from the HOF and the fluorescent color returned to yellow. Water molecules in the pores were also able to be released after an applied mechanical force disrupted the ordered structure of the HOF. Based on these stimuli-responsive properties, these HOFs can be used as advanced functional materials in anticounterfeiting applications.

Combined experimental and computational investigations of the fluorosolvatochromism of chromeno[4,3-b]pyridine derivatives: Effect of the methoxy substitution

Extensive research has been conducted on the spectral properties of chromeno[4,3-b]pyridine derivatives, owing to their potential applications in sensing, optoelectronic devices, and drug discovery. This study presents a comprehensive investigation into the fluorosolvatochromism of selected chromeno[4,3-b]pyridine derivatives, with a particular emphasis on the impact of methoxy substitution. Three derivatives were synthesized and subjected to spectral analysis: chromeno[4,3-b]pyridine-3-carboxylate (I) as the parent compound, and its 7-methoxy (II) and 8-methoxy (III) substituted derivatives.The UV–Vis absorption spectra of all derivatives exhibited a broad band with a maximum absorption wavelength that remained unaffected by the surrounding medium. However, distinct fluorescence properties were observed among them. Specifically, derivative II displayed notable fluorescence, while derivatives I and III exhibited no fluorescence properties. Furthermore, derivative II exhibited a fluorescence spectrum that is significantly influenced by the polarity of the medium. To investigate the fluorosolvatochromic behavior in depth, we conducted a comprehensive analysis using various neat solvents with different polarities and hydrogen bonding capabilities. The results obtained revealed a significant positive fluorosolvatochromism, with a bathochromic shift in the fluorescence spectrum as the solvent polarity increased. To understand how specific and non-specific interactions between the solute and the solvent affected the fluorosolvatochromism of II, we employed the four empirical scales model of Catalán. The obtained results demonstrated that intramolecular charge transfer played a crucial role in the fluorescence behavior of II. To provide a molecular-level explanation for the experimental spectral properties, we utilized the DFT and TD-DFT/B3LYP/6-31 + G(d) computational methods with the IEFPCM implicit solvation approach. The spectral differences between II and III were rationalized in terms of the frontier molecular orbitals (FMOs: the HOMO and LUMO), where distinct natures were observed among the examined derivatives. This study offers valuable insights into the impact of methoxy substitution on the physical and chemical properties of chromeno[4,3-b]pyridine derivatives, specifically concerning their spectral properties as elucidated by their fluorosolvatochromic behavior.

Flexible “V‐Shaped” Dibenzimidazole Amphiphile: Metal Ion‐Driven Microenvironment‐Sensitive Reversible Supramolecular Assembly in Aqueous Medium

AbstractFlexible dibenzimidazole based amphiphilic probe with indole as terminal residue has been synthesized using simple one‐step oxidative condensation. The compound formed nanoaggregates in the aqueous medium probably via extended intermolecular hydrogen bonding network involving benzimidazole moieties. The compound in monomer form (in THF) showed metal ion‐induced bathochromic shift, while in aggregate state (in water) metal coordination leads to hypsochromic shift. Moreover, in THF medium, compound interacts with large number of metal ions, whereas optical response was specifically observed with Hg2+ and Ag+ in the aqueous medium. Discrimination between Hg2+ and Ag+ was achieved using chloride as masking agent. Mechanistic investigations indicate formation of coordination‐driven supramolecular assembly where both benzimidazole and indole moieties participate in metal ion binding. The changes in microenvironment, such as local hydrophobicity, pH etc. showed distinct impact on metal ion sensing properties, both in terms of selectivity and sensitivity. Finally, the quantitative estimation of mercury, beyond its permissible level, was achieved in various natural water samples.

Exciplex luminescence of difluoroboron meta- and para-Nitrodibenzoylmethanates in solutions and polymer matrix

Molecular systems with intense exciplex luminescence are promising for the creation of OLEDs and light-transforming materials. The luminescent properties of difluoroboron meta- and para-nitrodibenzoylmethanates (1 and 2) were studied by the steady-state and time-resolved luminescence spectroscopy methods and quantum chemistry simulation. The influence of the position of the nitro group on the spectral properties of the complexes was revealed. The nitro group withdraws the electron density upon photoexcitation in the para-isomer in contrast to the meta-isomer. The bond order of the CC bond between the phenyl and chelate rings decreases in the excited relaxed state of 2, which leads to rotation of the substituent and a low quantum yield. Formation of exciplexes of 1 and 2 in benzene, toluene and polystyrene was found. The formation of the ground and excited-state electron donor–acceptor complexes based on difluoroboron nitrodibenzoylmethanates and benzene was revealed. The TDDFT method showed that the complexes are characterized by the presence of short contacts between the fluorine atom of the dye molecule and the hydrogen atoms of the aromatic hydrocarbon molecule. These contacts shorten during the transition from the ground state to the excited state. Polymeric compositions based on polystyrene (PS) and poly(methyl methacrylate) (PMMA) doped with 1 and 2 were obtained. The luminescence intensity of dyes 1 and 2 increases during the transition from PMMA to PS. A significant bathochromic shift of the luminescence maximum of 1 is observed, which is associated with the formation of exciplexes and triplexes. The obtained polymeric materials are promising for the development of optical smart materials.

BODIPY‐based Fluorescent Indicators for Lipid Droplets

AbstractLipid droplets are essential for cellular lipid storage, playing critical roles in cellular lipid metabolism. Although lipid droplets have drawn intense research in recent years, much remains to be uncovered about the roles of this organelle in biology. Lipid droplet indicators exhibiting large Stokes shifts and improved brightness are therefore in demand. We report two asymmetric BODIPY derivatives, BoL1 and BoL2 bearing a benzothiazole group at the 6‐position, which led to bathochromic shifts of 62 nm for BoL1 and 37 nm for BoL2 in fluorescence emission when compared to the reference molecules without the benzothiazole group. The incorporation of the benzothiazole moiety also resulted in a large Stokes shift of 40 nm. BoL1 and BoL2 have been demonstrated to operate as lipid droplet indicators in both confocal and STED imaging. BoL2 showed particularly good cellular retention and was further applied to explore the impact of cellular starvation on the trafficking of lipid droplets.

Structural elucidation and spectroscopic studies of acetyl substituted piperazine nucleus tethered with 4, 5-diaryl-1 H-imidazole scaffold: DNA binding, Cu2+and Sn2+ ions sensing and cytotoxicity

In this study, we report on synthesis of new imidazole based fluorescentchemosensors2-((4-(5-bromo-2-hydroxy-3-(4,5-diphenyl-1H-imidazol-2-yl)benzyl)piperazine-1-yl)methyl)-4-bromo-6-(4,5-diphenyl-1H-imidazole-2-yl)phenol(1)and2-((4-(2-hydroxy-5-methyl-3-(4,5-diphenyl-1H-imidazol-2-yl)piperazine-1-yl)methyl)-4-methyl-6-(4,5-diphenyl-1H-imidazole-2-yl)phenol(2). The synthesized chemosensors 1 and 2 were characterized by FT-IR, 1H NMR, UV–visible and fluorescence spectral studies. Further, the single crystal X-ray diffraction analysis shows that the chemosensor 1 crystallizes in triclinic system, with space group P-1.Hirshfeld surface analysis and 2D fingerprint maps revealed that 1 have remarkable H…H, C…H/H…C, and O…H/H…O Br…H/H…Br, interactions. The chemosensors have developed for selective and sensitive detection of Sn2+ and Cu2+ions in methanol among other tested cation. A bathochromic shift and color change with respect to the intra-molecular charge transfer transition in the absorption spectra was displayed after the addition of Sn2+ and Cu2+ions. The “Turn-on” fluorescence enhancement to Sn2+ ions and “turn-off” fluorescence quenching response to Cu2+ ions at λmax 450 and 448 nm, respectively, were detected in the fluorescence emission spectra of 1 and 2 upon addition of Sn2+ and Cu2+ions⁻. The receptor senses Sn2+ and Cu2+ ions via the deprotonation of the phenolic O-H unit, which was further confirmed by 1H NMR titration. Moreover, the fluorescence imaging in A549 cells suggested that chemosensors had great potential in the application of bio-imaging. The chemosensors1 and 2 with Sn2+ ions were found to be cytotoxic against A549 cells andthe IC50 of 1 and 2 have value of 107.40 μM and 8.21 μM, respectively and could be used as an anticancer agent.