Fig 5 - uploaded by Kayambu Namitharan
Content may be subject to copyright.
Source publication
A remarkable role of Lewis acid additives in syntheses of bis-N-sulfonylcyclobutenes via copper(I) catalyzed (3 + 2)/(2 + 2) cycloaddition cascade of sulfonyl azides and terminal alkynes is described. In addition, these cyclobutenes display a unique aggregation-induced emission enhancement (AIEE), reported for the first time, arising predominantly...
Context in source publication
Context 1
... crystal X-ray analysis also provides evidence for the AIEE behaviour of 3a. The bond lengths of both the imine groups (1.31 A°) were found to be higher than the normal imines (1.27 A°). This decrease in bond order from the normal value is attributed to the effective delocalization of electrons between the two sulfonyl groups at the opposite diagonals of cyclobutenes, Consequently, we believe photoisomerization is easier, when compared to the normal unconjugated CvN double bonds and this becomes the major non-radiative channel of twisted intramolecular charge transfer (TICT) state in chloroform solution. In contrast, as evident from crystal packing diagram (Fig. 5), molecules are tightly packed in the solid state as a rigid supramolecular network. Consequently, the CvN photoisomeri- zation is greatly slowed down in solid state and thus, 3a in this aggregated state exhibits significantly enhanced fluorescence emission compared to its weak emission when molecularly dis- persed in dilute ...
Citations
... 94 Conversely, the emission enhancement at high water fraction or aggregated state can be attributed to the restricted >C=N-isomerization or the locked intramolecular rotations of the anthracene and quinoline rings, which deactivated the non-radiative relaxation pathway leading to the enhanced red shifted emission. [95][96][97] The enhancement in emission intensity with a red-shift could be due to the combined effect of increased water polarity and the formation of self-assembled agglomerates. 98 Fig. 7. Time-resolved fluorescence spectra of AnQn in pure CH 3 CN and different CH 3 CN-water mixtures (Violet: pure CH 3 CN; blue: 30% water; green: 40% water; yellow: 50% water and red: 60% water). ...
A Schiff base probe AnQn is demonstrated for selective chromofluorogenic recognition of Al ³⁺ /Ga ³⁺ ions. AnQn exhibited AIE behavior in semi-aqueous medium to give highly fluorescent aggregates which were utilized to detect Pd ²⁺ and picric acid.
... A Lewis acid catalyzed cycloaddition cascade of substituted sulfonyl azides and terminal alkynes to a variety of highly substituted bis-N-sulfonylcyclobutenes under mild reaction conditions was described by Pitchumani and Namitharan (Fig. 63). The use of a copper(I)-Y zeolite as a heterogeneous copper(I) source allows for the fast and easy isolation of the reaction products by simple filtration, in addition to other advantages such as catalyst recyclability, ambient temperature, and minimization of metallic wastes [71]. ...
... .(71). Copper-catalyzed cascade reaction of sulfonyl azides with alkynyl imines. ...
The ketenimines represent an interesting class of organic intermediates which has undergone a regrowth as a consequence of recent extensions of copper catalyzed azide alkyne cycloaddition (CuAAC) to other synthetic fields. This review summarizes the most recent generation methods of ketinimines from CuAAC reaction, highlighting chemical properties focused to the synthesis of cyclic compounds among others, affording a general outlook towards the development of new biologically active compounds.
... Schiff base derivatives can serve as optical sensors [23,24]. They display -C = Nisomerization and on conjugation with fluorophores can become the lead compounds with AIE/AIEE properties [25]. ...
A new aggregation induced enhanced emission (AIEE) active probe (1) has been synthesized via single step condensation reaction of 2-amino-3-benzyloxypyridine with 3-allylsalicylaldehyde in methanol. Probe 1 has been fully characterized by various spectroscopic techniques i.e. IR, NMR (1 H and 13 C), HRMS and X-ray crystallography. 1 displays a large stokes shift of 190 nm. It recognizes Cu 2+ ions colorimetrically and fluorescence intensity enhances on the addition of Zn 2+ ions. 1 form nanoaggregates in H 2 O:CH 3 OH (80:20, v/v) which detects Cu 2+ ions selectively. 1 in the presence of Zn 2+ ions and its nanoaggregates n1 show switch on behaviour of green fluorescence comparable to mitochondrial membrane potential indicator, Mitotracker-Red, in larval gut tissues of Drosophila melanogaster.
The introduction of more facile and atom efficient methods for the synthesis of organic linear and cyclic compounds is the aim of various researchers worldwide. N-sulfonyl ketenimine is an interesting intermediate in modern organic synthesis. N-sulfonyl ketenimine is capable of selective production of various heteroatom containing compounds, based on the functional groups in the structure of this intermediate. Several linear and cyclic compounds are synthesized from this intermediate. In this review, the role of N-sulfonyl ketenimine is studied as an intermediate in several organic syntheses.
We have designed and synthesized a novel pyrene-naphthalene sulphonyl conjugate, 1-((1Z)-(4-((Z)-4-(pyrene-1-yl)methyleneamino)phenylsulfonyl)phenylimino)methyl)naphthalene-2-ol (PSN) through a facile two-step reactions. It was characterized by various spectral techniques. Fluorescence spectral studies showed that compound PSN featured fluorescence enhancement upon increasing the water content in THF. This can be attributed to the phenomena of aggregated induced emission (AIE), which is confirmed by SEM and AFM studies, due to the restriction of –CH=N isomerization of PSN. The anion sensing of PSN was examined with various anions. Among these anions, H2PO4⁻ and F⁻ ions were selectively sensing with a low detection limit of 3.52 × 10⁻⁷ M and 7.23 × 10⁻⁷ M, respectively, and an obvious color change from yellow to orange was observed by the naked eye. The mechanism of sensing involved the formation of hydrogen bonding interaction between O-H group of PSN and H2PO4⁻/ F⁻ ions. The binding of PSN with LYZ was also examined by docking studies, which shows that H-bonding and hydrophobic interactions play crucial roles for the interaction of LYZ toward PSN.
Five pyrazole-based tripodal ligands, compounds 1 – 5, based on a 1,3,5-triethylbenzene scaffold, show aggregation-induced emission enhancement (AIEE) and their application as fluorescent probes for nitroaromatics has been investigated. All five compounds are weakly fluorescent in THF, but their fluorescence intensity increases with the addition of a poor solvent (water), causing nanoaggregation, as confirmed by changes in UV-vis and emission spectra, and light scattering techniques. The nanoaggregates exhibit time-dependent emission characteristics and can serve as sensors for the detection of nitroaromatic compounds. The selective detection of picric acid (PA) over other nitroaromatic compounds by 1-3 is attributed to the photoinduced electron transfer from the trispyrazole to the quencher, as confirmed by TD-DFT calculations. Furthermore, compounds 1 and 2 were tested towards sensing of PA in the vapor and solid phases by means of changes in emission spectra observable by naked eye. The supramolecular assemblies of 1 and 3 with PA have been structurally characterized by X-ray crystallography.
Three anthracene‐based Schiff base complexes, R1–R3 (R1 = (E)‐N´‐((anthracen‐10‐yl)methylene)benzohydrazide; R2 = (E)‐1‐((anthracen‐10‐yl)methylene)‐4‐phenylsemicarbazide; and R3 = (E)‐1‐((anthracen‐10‐yl)methylene)‐4‐phenylthiosemicarbazide) were synthesized from 9‐anthracenecarboxaldehyde, benzohydrazide, 4‐phenylsemicarbazide and 4‐phenylthiosemi‐carbazide respectively, and characterized by various spectral techniques. The absorption spectral characteristics of R1–R3 were bathochromically tuned to the visible region by extending the π conjugation. These target compounds were weakly fluorescent in tetrahydrofuran (THF) solution because of rapid isomerization of the C=N double bond in the excited state. However, the aqueous dispersion of R1–R3 in the THF/water mixture by the gradual addition of water up to 90% resulted in an increase in the fluorescence intensity mainly due to aggregation‐induced emission enhancement (AIEE) properties. The formation of nanoaggregates of R1–R3 were confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The compounds R1–R3 are ideal probes for the fluorescence sensing of bovine serum albumin (BSA) and breast cancer cells by optical cell imaging.
A concise account on the use of transition metals copper (Cu) and palladium (Pd), as their cations as well as nanoparticles exchanged/immobilized onto porous frameworks such as zeolites, metal organic frameworks (MOFs), covalent organic polymers (COPs) and hollow nanostructures, functioning as catalysts in organic synthesis is presented. This biomimetic account, “focusing on catalytic systems in confinement” within zero-dimensional microenvironments and second sphere coordination covers primarily results from our group on N-sulfonylketenimine mediated cycloaddition, hydrogenation and C−C bond forming reactions, thus providing an interesting insight into the versatility and utility of these Cu and Pd catalysts. Other significant advantages and green credentials of confinement such as stability, selectivity, reusability, promotion of multicomponent reactions, use of green solvents, atom economy, and use of ambient conditions are highlighted at appropriate places. In the final section, our views on the current achievements and the future prospects in this area are summarized.
This chapter reviews the use of water as a solvent in cycloaddition and cyclization reactions. A review describing the production of Au-containing and Au-generated 1, n-dipoles and their use in the Diels-Alder, 1,3-dipolar-, and m + n-cycloaddition reactions has been published. A tutorial review covering the Diels-Alder and dipolar cycloaddition reactions of 1,2-benzoquinones has been reported. A review of organocatalytic asymmetric 2 + 2- and 4 + 2-cycloaddition reactions of ketenes has been published. A review of the 1,3-dipolar cycloaddition reactions of nitrile oxides to the C=C of unsaturated amino acid derivatives has been published. An extensive review of recent advances in transition-metal-free carbon-carbon and carbon-heteroatom cycloadditions of arynes, generated from 2-(trimethylsilyl)aryl triflates, has been presented. A review describing the recent advances in transition-metal-catalysed 2 + 2 + 2- cyclotrimerization reactions has been published. A review of use of iminium ions as dienophiles in inter- and intra-molecular aza-Diels-Alder reactions in aqueous solutions has been published.
