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This study describes the rational development and synthesis of a benzothiazole-salicylaldehyde Schiff base probe 1. This probe is designed to function as a ratiometric fluorescent probe specifically for detecting ClO− ions, utilizing the imine bond as the fluorophore unit. Upon interaction with ClO− ions, probe 1 exhibits a redshift in its absorption spectrum from 435 nm to 450 nm. Moreover, in its emission spectrum, there is a ratiometric emission enhancement observed at 610 nm, providing a clear indication of the presence of ClO− ions. The sensitivity of probe 1 for detecting ClO− ions is quantified, revealing a lowest detection limit of 5.5 μM, indicating its potential for sensitive detection even at low concentrations of ClO− ions. Additionally, it has been successfully utilized for biological imaging purposes, demonstrating low cytotoxicity, which is crucial for its applicability in biological systems. [ABSTRACT FROM AUTHOR]

The increasing frequency of drug-resistant pathogens poses serious health issues to humans around the globe, leading to the development of new antibacterial agents to conquer drug resistance and bacterial infections. In view of this, we have synthesized a series of bis-naphthalimides to respond to awful drug resistance. Bioactivity assay and structure–activity relationship disclosed that compounds 5d and 5o exhibit potent antibacterial activity against E. faecalis, outperforming the marketed antibiotics. These drug candidates not only inhibit the biofilm formation of E. faecalis but also display rapid bactericidal properties, thus delaying the development of drug resistance within 20 passages. To explore the mechanism of antibacterial activity against E. faecalis, biofunctional examination was carried out which unveiled that 5d and 5o effectively disrupt bacterial cell membranes, causing the leakage of cytoplasmic contents and metabolic activity loss. Concurrently, 5d and 5o effectively intercalate with DNA to block DNA replication, causing the build-up of excessive reactive oxygen species and inhibiting the glutathione activity, ultimately leading to oxidative damage of E. faecalis and cell death. In addition, these compounds readily bind with HSA with a high binding constant, indicating that these drug candidates could be easily delivered to the target site. The above finding manifested that these newly synthesized bis-naphthalimides with multitargeting antibacterial properties offer a new prospect to overcome drug resistance. [ABSTRACT FROM AUTHOR]

Corrosion inhibition mechanism of two aromatic amino acids, phenylalanine (Phe) and tryptophan (Trp), was explored for steel in an alkaline pore solution simulating a carbonated concrete environment. The electrochemical impedance spectroscopy and potentiodynamic polarization test results revealed that both compounds can be used effectively as corrosion inhibitors for carbonated concrete environments with high inhibition efficiency. The dissolution of steel got controlled as Phe and Trp acted as anodic‐type inhibitors. Phe and Trp adsorbed on the steel surface by physiochemisorption process following the Langmuir isotherm. The inhibitive solution analysis through UV–visible technique confirmed the formation of inhibitor–Fe complexes. The surface of steel was analyzed after submergence in corrosive solutions with and without inhibitors by means of optical microscopy, scanning electron microscopy–energy‐dispersive X‐ray spectroscopy, Fourier transformed infrared, and X‐ray photoelectron spectroscopy, which highlights the formation of a compact, barrier layer comprised of metal–inhibitor complex. Subsequently, with the help of the aforementioned techniques, an inhibition mechanism for Phe and Trp was conjectured, which revealed that the presence of additional heterocycle in amino acids can raise the chances of chelation and formation of a more adherent and thermodynamically stable layer. Phe bound with Fe ions through the carboxylate functional group only, while Trp chelated the Fe ions via a nitrogen atom of the pyrrole ring and carboxylate functional group. [ABSTRACT FROM AUTHOR]

This paper presents the performance of a multifunctional generic compound, 4-Aminobenzoic acid (4ABA) as migratory inhibitor applied on hardened concrete surface to curb corrosion due to combined chloride and carbonated environment. Electrochemical techniques (LPR and EIS), gravimetric analysis were applied to evaluate the corrosion performance and the inhibition mechanism of 4ABA. Chloride and carbonation profiles were developed to investigate the dominant cause of corrosion during the exposure. Visual and microscopic analysis of concrete surface and rebar surface was also done. Compressive strength test was performed to study the effect of corrosion inhibitor on strength property of hardened concrete. Results confirm that 4ABA prolonged the passive state of rebar when used as preventive measure and restrained the on-going corrosion process when employed as repair strategy. Combined exposure by chlorides and CO2 leads to redistribution of chloride ions in concrete matrix. The results also conclude that during the combined exposure, chloride ions initiate the corrosion process and carbonation aggravates this process. Application of 4ABA does not influence the strength properties of concrete. ABA has performed the inhibition by protective layer development and shield formation against the negatively charged corrosive ions. Blended cement concrete system which was observed to be more vulnerable to corrosion was seen to attain similar corrosion resistance as OPC concrete after inhibitor application. [ABSTRACT FROM AUTHOR]

Palladium‐catalyzed [4+2] oxidative annulation of coumarin‐benzimidazoles with olefins for the synthesis of polycyclic aromatic hydrocarbons have been achieved. This synthetic protocol gives access to a wide range of structurally distinct imidazo[1,2‐a]chromeno[3,4‐c]pyridines in moderate to good yield with wide functional group tolerance. Further, photophysical properties of annulated scaffolds have been examined, which discloses their interesting solvatochromic emission behaviors. [ABSTRACT FROM AUTHOR]

A rapid, efficient, selective, and sensitive ratiometric chemosensor has been developed to detect dopamine. The sensor is based on coumarin fluorophore incorporating an aldehyde binding site to detect catecholamines. Here, the fluorescence quenching was observed after the reaction of compound 6 with dopamine. This fluorescence sensor relies on rapid detection of dopamine in aqueous medium by iminium ion formation between aldehyde and amine analytes at neutral pH. The reaction product gives the emission maximum at 420 nm on excitation at 280 nm. The proposed method allows the determination of dopamine upto 9.7×10−7 M. Furthermore, this method has good selectivity and sensitivity towards dopamine. [ABSTRACT FROM AUTHOR]

In this paper, we studied the effect of increasing the conjugation in compound 3 on the proton transfer and aggregation‐induced emission properties. Compound 3 exhibited the dual absorption peak at 420 nm and 320 nm, which was redshifted by 50 nm compared to compound 2 (previous report). Compound 3 emits exhibited a peak at 530 nm with a Stokes' shift of 110 nm after photoexcitation at 420 nm. In a high polarity medium, the absorption and emission spectra of compound 3 showed redshifts of 50 nm and 20 nm, respectively. Further, compound 3 displayed the aggregation‐induced emission enhancement in THF/H2O (60 % v/v). Additionally, the proton transfer process in compounds 2 and 3 was evaluated through theoretical calculations via determining the relative free energies of possible tautomeric forms. It was determined that the small energy barriers for compound 2 in the S1 state suggested the presence of the proton transfer process; however, high energy barriers and high stabilization and Boltzmann population of 3.KK tautomeric form at S0 and S1 state for compound 3 discommoded the proton transfer process. Further, the aggregated form of compound 3 (20 μM; CH3OH/HEPES buffer (4 : 1; v/v) pH=7.04) was utilized to recognize Cu2+ ions with the lowest detection limit of 1.5 nM and Stern‐Volmer binding constant of 2.8×105 M−1. A noted decrease in the hydrodynamic size of compound 3 from 400 nm to 40 nm in the presence of Cu2+ ions confirmed the disaggregation with a decrease in emission intensity. Compound 3 was also employed as a Cu2+ ions recognizer in different collected samples with good percentage recovery. [ABSTRACT FROM AUTHOR]

N-Benzothiazolyl-1,8-naphthalimide based fluorescent probes were designed and synthesized for selective detection of human serum albumin (HSA) and bovine serum albumin (BSA) among various bioanalytes and further studied for their in vitro anti-proliferative activity against 60 human cancer cell lines. Binding interactions of naphthalimide derivative 2-(benzo[d]thiazol-2-yl)-6-(4-methoxyphenyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione bearing an electron-donating group (8) and 2-(benzo[d]thiazol-2-yl)-6-(2-flourophenyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione having an electron-withdrawing group (12) with HSA and BSA were explored by spectroscopic as well as molecular modeling techniques. Amongst these two derivatives, probe 12 showed better binding affinity with human serum albumin and bovine serum albumin as compared to 8 and the limit of detection for 12 toward HSA was found to be 4.3 μM. Moreover, compound 12 with fluoro positioned at the phenyl ring displayed potent cytotoxic activity over other derivatives. Thus, the effects of both substituent and position account for the binding interactions of the compounds with serum albumin. These fluorescent probes can be used effectively for the quantification of HSA in clinical diagnosis. [ABSTRACT FROM AUTHOR]

A 2-(2-hydroxyphenyl)benzothiazole based probe BTNN undergoes a drastic upsurge (∼146-fold, Φ = 69%) in fluorescence intensity (bright green, λem 530 nm) on going from pH 7 to 2. MG-63 cells and E. coli bacteria internalize BTNN without toxicity and its fluorescence intensity is directly correlated to the pH in the cells/bacteria. This response to pH is instantaneous, reversible and stable for over a week. The protonation of the diethylamino nitrogen followed by efficient normal and excited state intramolecular proton transfer (ESIPT) processes of protonated BTNN are responsible for remarkable increase in fluorescence intensity and quantum yield under acidic conditions. Furthermore, polystyrene-BTNN thin films can be used for efficient detection of HCl vapour (2 ppm). This is first example where 2-(2-hydroxyphenyl)benzothiazole derivative can image strong acidic conditions. [ABSTRACT FROM AUTHOR]

Latent fingerprints (LFPs) identification is of paramount importance for national security and criminal investigations. We designed and synthesized fluorescent organic molecule HPBI for the rapid fluorescence imaging of latent fingerprints on various surfaces such as aluminium foil, currency paper, brick, and glass, which did not require any post treatment. The HPBI exhibits a combination of ESIPT and AIE properties and forms green fluorescent nano-aggregates in CH3CN–H2O (1 : 1) mixture, as evaluated by DFT, SEM, TEM, and fluorescent microscopic studies. Spraying the solution of spherical HPBI nanoaggregates (50–100 nm size) on various surfaces resulted in fluorescence display of LFPs in <2 minutes. LFPs clearly revealed level-2 (ridge ending, islands, bifurcation) and level-3 (ridges path deviation, edge contours, sweat pores) details with high contrast and no background interference. The relocation of fluorescent fingerprints on cello tape provides an efficient and clean method for carrying fingerprints to the forensic laboratory. [ABSTRACT FROM AUTHOR]