A highly sensitive and selective coumarin based chemosensor H 2 L for the efficient detection of Al 3+ has been developed. The synthesized chemosensor H 2 L is efficient in detecting Al 3+ over other metal ions which are commonly obtained in various physiological and environmental samples. H 2 L shows fluorescence ‘turn-on’ response at 610 nm in presence of Al 3+ , without the interference of other metal ions. The resulting H 2 L-Al 3+ complex behave as a sequential chemosensor for F − , by showing quenching of emission intensity upon addition of F − to it. This quenching of emission intensity is only specific for F − and is not hampered due to the presence of other anions that commonly coexist with F − in various environmental solutions. Theoretical calculations using DFT/B3LYP method has been used to get insight into the sensing mechanism as well as electronic structure of the synthesized chemosensor H 2 L. H 2 L is efficient in detecting Al 3+ in the intracellular region of human A549 cell and also exhibits an INHIBIT logic gate with Al 3+ and F − as chemical inputs by monitoring the emission mode at 610 nm.

A novel coumarin based molecular switch for the sequential detection of Al3+ and F−: Application in lung cancer live cell imaging and construction of logic gate

Two novel water-soluble coumarin-based compounds (OC7, NC7) were designed and synthesized as two-photon fluorescent probes for biological Mg2+ detection. The compounds feature a β-keto acid as a high selective binding site for Mg2+ and the coumarin framework as the two-photon fluorophore. OC7 and NC7 show significant “off-on” detecting signals (9.05-fold and 23.8-fold fluorescence enhancement) and lower detection limits compared with previous reported two-photon fluorescent probes for Mg2+. Moreover, OC7–Mg2+ and NC7–Mg2+ exhibit large two-photon absorption cross sections (340 and 615 GM) at the near-infrared wavelengths (740 and 860 nm), which indicates that the probes are very suitable for detection of Mg2+ in vivo. Both OC7 and NC7 are pH-insensitive and of low cytotoxicity and can be applied to image intracellular Mg2+ under two-photon microscopy (TPM). Our results provide a strategy to modify the coumarin fluorophore to get better two-photon fluorescent properties. And the results also suggest that e...

Two-Photon Fluorescent Probes for Biological Mg2+ Detection Based on 7-Substituted Coumarin

Even though numerous thermochromic fluorescent materials (TFMs) have been reported, effective and universal strategies for the development of ideal TFMs with simple preparation, low cost, excellent performance and practicability are still urgently required. Herein, we report a simple and general platform for such TFMs via taking biomimetic lipid like fatty acids (FAs) as an effective matrix which is applicable to abundant simple fluorophores. Change of crystallinity of FAs induced by phase transition regulates the reversible interconversion between non-dispersion and dispersion states of fluorescent dyes (e.g., coumarins), thus leading to obvious fluorescence (FL) change of the TFMs based on both. The reaction mechanism was proved in detail by FL spectra, XRD and SEM techniques. The substituent effect of coumarins and the nature of FAs play important roles in adjusting the properties of the TFMs, such as FL colour and responsive temperature. Additionally, their multiple feasible potential applications (i.e., in situ thermometers, thermal response FL papers, FL colour change crayon, anti-counterfeiting and encryption, erasable or long-preservative thermal printing) with selective multi-mode (i.e., groove-fill, writable pen, loading on paper substrate) were developed. These TFMs with the merit of easy preparation, low cost, obvious colour change (ca. 100 nm shifts), fast response speed, good reversibility and high adjustability are very close to industrial application requirements. The design and preparation principles from this work should facilitate the development of other novel stimuli-responsive fluorescent materials.

Simple and general platform for highly adjustable thermochromic fluorescent materials and multi-feasible applications

A series of unsymmetrical and symmetrical push–pull phenothiazines (3–7) were designed and synthesized by the Pd-catalyzed Sonogashira cross-coupling reaction and subsequent [2 + 2] cycloaddition–retroelectrocyclization reaction with tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). The effect of systematic variation of the number and nature of cyano-based acceptor TCNE and TCNQ units on the photophysical, electrochemical, and computational studies was investigated. The single-photon absorption on phenothiazines 3–7 reveals that substitution of 1,1,4,4-tetracyanobutadiene (TCBD) and a cyclohexa-2,5-diene-1,4-diylidene-expanded TCBD unit results in strong intramolecular charge transfer and lowering of the LUMO energy level. The TCBD-linked and cyclohexa-2,5-diene-1,4-diylidene-expanded TCBD-linked phenothiazines 3–7 exhibit multiredox waves. The computational studies on phenothiazines 3–7 exhibit substantial stabilization of the LUMO with the increase in acceptor strength, which result...

Unsymmetrical and Symmetrical Push–Pull Phenothiazines

A fluorescence quenching-based mechanism for the determination of hypochlorite was proposed based on spectroscopic and chromatographic studies on the hypochlorite-sensing potency of three structurally similar and highly fluorescent coumarins. The mode of action was found to rely upon a chlorination of the coumarin-based probes resulting from their reaction with sodium hypochlorite. Importantly, the formation of chlorinated derivatives was accompanied by a linear decrease in the fluorescence intensities of the probes tested. The results obtained suggest the applicability of a coumarin-dependent hypochlorite recognition mechanism for the detection of, as well as for quantitative determination of, hypochlorite species in vitro.

https://arrow.tudublin.ie/cgi/viewcontent.cgi?article=1066&context=ittsciart

Fluorescence Quenching-Based Mechanism for Determination of Hypochlorite by Coumarin-Derived Sensors

Synthesis of coumarin based fluorescent compounds

Synthesis and photophysical study of novel coumarin based styryl dyes

Reaction of 7-substituted-4-styrylcoumarins and N-phenylmaleimide in nitrobenzene under reflux conditions affords mainly 7-substituted-2,11-diphenyl-3a,10,11,11a-tetrahydro(1)- benzopyrano(3,4-e)isoindole-1,3,4(2 H)-triones. The same reaction in o-dichlorobenzene in the presence of DDQ gives the corresponding aromatized dibenzopyranones. The dibenzopyranones are fluorescent and their UV and fluorescence spectra are reported.

Synthesis of fluorescent dibenzopyranones by the Diels-Alder reaction of 4-styrylcoumarins and N-phenylmaleimide and in situ aromatization using DDQ

Condensation of 7-methylcoumarin-4-carbaldehyde with different anilines affords 7-methylcoumarin-4-azadienes. The 7-methylcoumarin-4-azadienes do not undergo normal electron demand Diels–Alder reaction with N-phenylmaleimide, but react with dihydropyran, dihydrofuran, and styrene via inverse electron demand Diels–Alder reaction in the presence of anhydrous ZnCl2. The diene involves the azomethine group and the aniline ring. The product is a mixture of two diastereomers in which the major diastereomer has all the hydrogens at the ring junction in cis configuration.

Kailas K. Sanap

Papers

Synthesis of coumarin based fluorescent compounds

Synthesis and photophysical study of novel coumarin based styryl dyes

Synthesis of fluorescent dibenzopyranones by the Diels-Alder reaction of 4-styrylcoumarins and N-phenylmaleimide and in situ aromatization using DDQ

Regiospecific inverse electron demand Diels–Alder reactions of 7-methylcoumarin-4-azadienes

Investigation of Diels–Alder Reaction of 7‐Substituted 4‐Styrylcoumarins with Symmetrical Dienophiles Leading to 3,4‐Annulated Coumarins