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An efficient strategy has been developed for the deformylative halogenation of carbaldehyde imidazo-fused heterocycles in the presence of TBHP controlled by temperature. A convenient and sequential functionalization (C8 to C3) portrays the synthetic utility of the current method. N-Heterocycle benzamide products were also observed via the ring opening of imidazopyridines through the cleavage of C–C bond at high temperatures. Features of this method include temperature-controlled excellent regioselectivity, mild conditions and functional group tolerance. [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]

We report here the design and syntheses of a naphthalenediimide (NDI)-N functionalized organic fluorophore, 1, and its supramolecular CT complexes [(1·2H)2+·(PA−)2] (2) and [(1·2H)2+·(3,5-DNSA−)2] (3), self-assembled from 1 as an electron acceptor (A) and picric acid (PA) or 3,5-dinitrosalicylic acid (3,5-DNSA) as a donor (D), with a very large Stokes shift (>170 nm) and significant fluorescence lifetime (∼1.55 ns). NDI is functionalized with phenylpyridyl units (chromophore) to extend the π-conjugation and thus provide a suitable platform for strong C–H---π and π⋯π stacking interactions, which are the prime requirements for any compound to be used as a fluorescent probe. The organic fluorophore, 1, and its supramolecular CT complexes 2 and 3 exhibit decent electronic properties as suggested by DFT, cyclic voltammetry, and fluorescence studies. Moreover, compounds 1–3 were also exploited as fluorescent probes for cell imaging under normal cell isolation and with time-bound exposure. [ABSTRACT FROM AUTHOR]

Chemosensors that demonstrate a ratiometric change in fluorescence are in demand, but are scarce for nitroaromatic compounds owing to fluorescence quenching by nitro-aromatic compounds (NACs). Here, we report that the aggregates of the tricationic fluorescent-red chemosensor DMAS-TP in buffer undergo simultaneous fluorescence quenching at 615 nm and an increase in fluorescence intensity between 510–540 nm, revealing an unprecedented ratiometric behaviour for 2,4,6-trinitrophenol (TNP). The amplified fluorescence change in the FI615nm/FI521nm ratio from 57.67 to 30.18 (∼50%) with only 0.2 equivalents (2 μM) of TNP allows determination of TNP at a concentration as low as 2 nM. Paper strips coated with DMAS-TP differentiate TNP from other NACs through a fluorescence colour change from pink-red to blue with TNP only and provide unprecedented recognition of TNP from other NACs. In comparison to the only reported ratiometric probe for TNP, DMAS-TP provides advantages in terms of its usability in water and lower limit of detection. Furthermore, DMAS-TP adsorbed on silica nano-particles (10–20 nm) reveals a high fluorescence quantum yield (φ = 10.72%) with an emission maxima at approximately 615 nm, in the far-red region. These fluorescent silica nanoparticles NPs can be used to visualize latent fingerprints on a variety of substrates such as aluminium foil, metal sheets, coins, ceramic tiles and so on, with a high resolution and could be used in modern forensic applications. [ABSTRACT FROM AUTHOR]

The nitroaromatic compounds (NACs) show absorption maxima below 400 nm and their determination using absorption and colour change requires probes with absorption beyond this region. Herein, we report a stilbazolium-based probe DMAS-DP, which undergoes aggregation in HEPES buffer with an absorption maximum at 475 nm (red colour) and these aggregates demonstrate a highly selective and sensitive change in their colour from red to light yellow with 2,4,6-trinitrophenol (TNP). The LOD for the determination of TNP is 100 pM, the lowest in the literature by using visible spectroscopy. Moreover, the aggregates of DMAS-DP emit fluorescence in the red region with a maximum at 615 nm (red under 365 nm light), which is quenched selectively by TNP. 2,4,6-Trinitrotoluene (TNT) and other NACs show insignificant changes in the visible spectrum of the aggregates of DMAS-DP, even when present in excess. Density functional theory (DFT)-based structure optimization studies reveal that the DMAS-DP attains the Z-conformation and its dimethylamino moieties form strong interaction with the protons of TNP and are responsible for the reduced force constant (color). This constitutes the first probe where a stilbazolium dye has been used for constructing a TNP-selective chromogenic and red-fluorescent probe. [ABSTRACT FROM AUTHOR]

We report the syntheses and structural characterization of a Zn(II) metallacycle [Zn2{(L)2(DMF)2(NO3)2}]·(NO3)2 (1) along with a Cd(II) coordination polymer [{Cd1(L)2(DMF)2}·(NO3)2]n (2) (where L = N,N′-bis-(3-pyridyl)terephthalamide; DMF = dimethylformamide) and their utilization as fluorescent probes for highly selective recognition (turn-off) of Fe3+ and CrO42− ions. Compounds 1 and 2 were prepared by utilizing ligand L and the nitrate salt of zinc and cadmium, respectively. Single crystal X-ray analysis reveals that 1 adopts an overall Zn(II) metallacycle architecture, whereas 2 displays a one-dimensional (1D) polymeric structure. Both 1 and 2 showed high fluorescence stability in aqueous solution and selectively detected Fe3+ and CrO42− ions with high quenching constants and low detection limits of 2.34 × 106 M−1 and 0.153 μM for Fe3+, 6.72 × 105 and 0.205 μM for CrO42− (for 1); 3.25 × 106 and 0.193 μM for Fe3+, 6.94 × 105 and 0.155 μM for CrO42− (for 2). Notably, ligand L itself did not display any type of recognition for any ions in DMF as well as in aqueous media. Moreover, 1 and 2 were also employed as heterogeneous catalysts for the ring-opening reaction (ROR) of epoxides with various assorted amines and up to 95% yield (TON, 47.5 and TOF, 11.9 h−1) was observed with perfect regioselectivity in the case of styrene oxide. [ABSTRACT FROM AUTHOR]

This work presents the synthesis and characterization of two Cu(ii)-based coordination polymers prepared by utilizing two different Co(iii)-based metalloligands offering appended arylcarboxylic acid groups. Both coordination polymers are three-dimensional in nature and present pores and channels filled with water molecules. Both coordination polymers function as heterogeneous catalysts for the epoxidation of various olefins using O2 while employing isobutyraldehyde as the coreductor and for peroxide-mediated oxidation of assorted benzyl alcohols. The catalytic results illustrate efficient oxidation reactions, whereas the hot-fltration test and leaching experiments indicate the true heterogeneous nature of the catalysis. [ABSTRACT FROM AUTHOR]

We report the synthesis of probe 2 for the fluorescence “turn-on” detection of Al3+ ions in CH3OH. Probe 2 has been designed via utilizing the aggregation-induced emission properties of the tetraphenylethylene unit, with further enhancement from Schiff base units for the ESIPT phenomenon. Probe 2 exhibits emission at 548 nm (λex = 360 nm), with a large Stokes shift of 188 nm, indicating the ESIPT phenomenon. Probe 2 also exhibits emission enhancement via increasing the H2O ratio up to 70–90% H2O/THF (v/v) and altering the spherical morphology to needle shapes. Probe 2 has been found to be highly selective and sensitive towards Al3+ ions over other metal ions in pure CH3OH using absorption and emission spectroscopy. FESEM analysis revealed that the size of probe 2 increases upon the addition of Al3+ ions. Thus, the fluorescence “turn-on” behaviour of probe 2·Al3+ is due to metal-induced aggregation. [ABSTRACT FROM AUTHOR]

A donor–π–acceptor (D–π–A) dyad 1 has been successfully synthesized by linking phenanthrenequinone as an electron donor unit and anthraquinone as an electron acceptor unit through a phenyl ring. Dyad 1 exhibits intramolecular charge transfer and this is a key factor for the detection of Hg2+ and of the pyrophosphate ion (P2O74−, PPi) in a semi-aqueous medium. Dyad 1 exhibits absorption peaks at 430, 370, and 337 nm and an emission peak at 530 nm (λex = 430 nm). Dyad 1 exhibits a new absorption peak at 390 nm ratiometrically along with emission quenching in the presence of Hg2+ ions while the presence of PPi results in drastic ratiometric changes in the absorption and emission spectra with new peaks at 495 nm and 620 nm, respectively. The quantum yield of dyad 1 on complexation with PPi was also increased from 0.1 (free dyad) to 0.69 (dyad 1·PPi). The lowest detection limits for Hg2+ and PPi were found to be 31 nM and 46.5 nM, respectively. DFT calculations have been performed to develop a mechanism for PPi and Hg2+ ion binding with dyad 1. [ABSTRACT FROM AUTHOR]

A BINOL (1,1′-bi-2-naphthol)-based probe 1 with a diamide group has been synthesized and investigated for its photophysical behavior towards various cations and anions. Probe 1 has been used for the estimation of Al3+ and Cu2+ ions in the presence of other metal ions, signaling the binding event through the formation of new absorption bands at 415 and 430 nm. Differential emission bands are formed in the presence of Al3+ at 515 nm and Zn2+ at 485 nm, while quenching is observed in case of Cu2+ ion. Probe 1 shows selective estimation for CN− ion among all other anions by forming a new absorption band at 395 nm and new emission band at 495 nm, with the lowest detection limit of 2 μM. Based on these results, the anion/cation as well as cation/cation 2-to-1 encoder and 1-to-2 decoder have been formed. Moreover, a 4-to-2 encoder has also been established by using various cations as inputs. [ABSTRACT FROM AUTHOR]

This work illustrates two Ni2+ based coordination polymers (CPs, 1-Ni and 2-Ni) synthesized using two related Co3+ based metalloligands offering appended arylcarboxylate groups. The crystal structure of 1-Ni displays a porous 3D network having well-defined major and minor pores whereas 2-Ni exhibits a somewhat densely packed structure. Both CPs supported the exchange of coordinated water molecules and the inclusion of iodine within their porous structure whereas binding studies illustrated that the Ni(ii) ion in these CPs can bind thiophenol, a reagent used in the C–S cross coupling reactions. The two CPs functioned as the reusable heterogeneous catalysts for the C–S cross coupling reactions between substituted aromatic halides and thiophenol as well as cyclohexanethiol and ethanethiol. [ABSTRACT FROM AUTHOR]

Blends of polypropylene (PP) and polyamide 6 (PA6) with multiwalled carbon nanotubes (MWNTs) were prepared using different processing strategies in a twin-screw micro-compounder. The effect of MWNTs on the crystallization behaviour of the PP phase and the PA6 phase of the blend has been investigated through non-isothermal crystallization studies by differential scanning calorimetric analysis. Furthermore, the effect of the addition of the compatibilizer (PP-g-MA) and the modification of MWNTs (m-MWNTs) with a non-covalent organic modifier (Li-salt of 6 amino hexanoic acid, Li–AHA) has also been studied in context to the crystallization behaviour of the PP and PA6 phase in the blend. The crystallization studies have indicated a significant increase in bulk crystallization temperature of the PP phase in the blend in the presence of MWNTs. Moreover, the formation of ‘trans-lamellar crystalline’ structure consisting of PA6 ‘trans-crystalline lamellae’ on MWNTs surface was facilitated in the case of blends prepared via‘protocol 2’ as compared to the corresponding blends prepared via‘protocol 1’. Wide angle X-ray diffraction analysis has showed the existence of a β-polymorph of the PP phase due to incorporation of the PA6 phase in the blend. Addition of MWNTs in the blends has facilitated further β-crystalline structure formation of the PP phase. In the presence of m-MWNTs, a higher β-fraction was observed in the PP phase as compared to the blend with pristine MWNTs. Addition of PP-g-MA has suppressed the β-phase formation in the PP phase in the blend. X-ray bulk texture analysis revealed that incorporation of PA6 as well as pristine/modified MWNTs has influenced the extent of orientation of the PP chains towards specific crystalline planes in various blend compositions of PP and PA6. [ABSTRACT FROM AUTHOR]

Amide-based ligands H2L¹, H2L² and H2L³ containing thiazole, thiazoline and benzothiazole appended groups have been used to synthesize Zn2+ (1 and 3), Cd2+ complexes (2 and 4), and a Mn2+ complex (5). In all cases, potentially multidentate ligands create a meridional N3 coordination environment around the M(II) ion whereas additional sites are occupied by labile nitrate ions in 1-4 and MeOH in 5. Interestingly, metal complexation caused the migration of protons from amidic N-H sites to the appended heterocyclic rings in complexes 1-4. Structural studies show that the protonated heterocyclic rings in these complexes create a hydrogen bond based cavity adjacent to the metal ion. Importantly, binding studies confirm that the substrates are bound within the complex cavity closer to the Lewis acidic metal in all complexes including the oxidation-sensitive Mn ion in complex 5. All complexes have been utilized as the reusable and heterogeneous catalysts for ring-opening reactions of assorted epoxides, cyanation reactions of various aldehydes, and epoxidation reactions of several olefins. [ABSTRACT FROM AUTHOR]

2-Arylquinazolines with a range of alkyl polyamines as side chain/ring functional motifs at the 4th-position were considered for antileishmanial study with the rationale that related heterocyclic scaffolds and polyamine functionalities are present in drugs, clinical trial agents, natural products and anti-parasitic/leishmanial agents. Synthesis involves construction of the 2-arylquinazolin-4-one ring and deoxyamination via deoxychlorination followed by S N Ar-based amination or a methodology of S N Ar-deoxyamination driven by BOP-mediated hydroxyl-activation. Various alkyl-polyamines important for activities were incorporated. A total of 26 compounds were prepared and screened against Leishmania donovani ( Ld ) promastigote cells using the MTT assay. Most of the investigated series of compounds showed characteristic leishmanicidal properties. Several compounds showed pronounced leishmanicidal activities (IC 50 : 5-6.5 μM) with higher efficiency than the antileishmanial drug miltefosine (IC 50 : 10.5 μM), and relatively less cytotoxicity to macrophage host cells (SI: 9.27-13.5) compared to miltefosine (SI: 3.42). Important pharmacophoric skeletons were identified., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The different rotameric conformations of imidazo-[1,2- a ]pyrazine have been synthesized and characterized by means of different experimental techniques, such as NMR, FTIR, and absorption spectroscopy and quantum chemical calculations. The different conformations were stabilized by hydrogen bonds, such as OH⋯N, ArH⋯N and ArH⋯ArH. The ground state optimizations and potential energy surface (PES) scanning profiles produced using density functional theory (DFT) show two stable rotameric forms for each molecule. The relative population of the conformations is affected by the strength of the hydrogen bonds. The calculated absorption spectra and isotopic shielding constants were acquired by time-dependent density functional theory (TD-DFT) and gauge invariant atomic orbitals (GIAO)-DFT, respectively. The strength of the hydrogen bonding interactions that resulted in the different conformations was studied by quantum theory of atoms in molecules (QTAIM)., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)