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A new carbazole-coupled tetrakis-(1 H-pyrrole-2-carbaldehyde) anion receptor 1 has been designed and synthesized. Anion binding studies in organic media using fluorescence and UV-vis spectroscopy revealed that receptor 1 is capable of sensing HP2O73- with high selectivity. Addition of HP2O73- to THF solution of 1 resulted in the emergence of a new broad band at longer wavelength along with quenching of the original emission band forming a ratiometric response. Based on dynamic light scattering (DLS) experiment and fluorescence lifetime measurement, we propose that the emergence of new emission band in the presence of HP2O73- ion is due to the aggregation-induced excimer formation. [ABSTRACT FROM AUTHOR]

Sometimes unusual redox chemistry and modulation of enzyme activity Cu‐proteins can be encountered by the presence of a trace amount of Cu−Tris interaction (Tris‐(hydroxymethyl) aminomethane) during vitro studies. Herein, we addressed a redox chemistry of CuII−Tris with variable stoichiometric ratios in the presence of ascorbic acid (H2A) and O2. The redox chemistry of Bs3 (Cu : Tris; 1 : 3) with H2A/O2 was passed through several intermediates with progress on time yielding initially yellow precipitate, (Yp3), then green solution, (Gs3) and finally cyan solution (Cs3). The UV‐Vis spectra of Bs3, Gs3 and Cs3 displayed peaks at 640, 690 and 710 nm respectively suggesting CuII. The redox potential of CuII/CuI in Bs3, Gs3 and Cs3 were −0.18 V, −0.15 V and −0.19 V (vs. Ag/AgCl) respectively. The EPR spectrum of Bs3 showed an axial signal with g∥,⊥=2.483/2.105&A∥=160×10−4 cm−1 whereas Gs3 and Cs3 showed rhombic signal with g1,2,3=2.302/2.063/2.018&A∥=177×10−4 cm−1 and g1,2,3=2.274/2.064/2.016&A∥=164×10−4 cm−1 respectively suggesting a distorted tetragonal geometry. ESI−MS data indicated the probable composition of Bs2‐Bs5, Gs3 and Cs3 in solution. Integration of all spectroscopies data demonstrated the probable composition and redox mechanism. [ABSTRACT FROM AUTHOR]

Strategies for clean energy are important components of the United Nation's Sustainable Development Goals (SDGs). To this end, we have studied the conductivity of a Cd(II)-based 3D coordination polymer, [Cd(succ)(pcih)(H2O)]n (1) (H2succ = succinic acid; pcih = pyridine-4-carboxaldehyde iso-nicotinoyl hydrazone). Compound 1 was structurally characterized by single-crystal X-ray diffraction. The bridging groups, succ2− and pcih, self-assembled via H-bonding and π∙∙∙π interactions. The optical band gap calculated from a Tauc's plot was determined to be 3.71 eV which is consistent with semiconducting behavior. The experimental barrier height, 0.71 eV (dark phase); 0.49 eV (light phase) and series resistance, 358.48 Ω (dark); 133.73 Ω (light), also support the photoinduced enhancement of conductivity. The non-ohmic relation, I α V2, showed an enhancement of conductivity by 2.5 times upon light irradiation [3.36 × 10−6 S m−1 (dark) and 8.37 × 10−6 S m−1 (light)]. DFT computations employing the crystallographic parameters of 1 indicated a HOMO/LUMO energy gap of 4.06 eV, within the range of semiconducting materials. The optical stability of 1 was examined by fluorescence measurements and lifetime data. [ABSTRACT FROM AUTHOR]

Petasis aryl and allyl borations were accomplished using substituted ninhydrins, boronic acids or 2-allyl-4,4,5,5-tetramethyl-1,3,2-dioxaborolane and 1,2-aminophenols in Hexafluoroisopropanol (HFIP) without any catalysts to synthesize different aryl and allyl derivatives of ninhydrins. The nature of substitution in the boronic acids and 1,2-amino phenols was the key factor in determining the diastereo-regioselectivity and the type of product distributions. The products were isolated and characterized by HMBC, HSQC, 1H, 13C NMR experiments and X-ray single crystallographic analysis. A probable reaction pathway involves in situ formation of acyclic and cyclic ninhydrin-amino alcohol adducts, with the positioned hydroxyl group determining the stereo-regioselective outcome via tetracoordinated boron intermediates. A metal free diastereo- and regioselective Petasis aryl and allyl boration of ninhydrins. [ABSTRACT FROM AUTHOR]

During the past few decades, the synthesis of coordination complexes that exhibit high catalytic efficiencies has received significant attention from bio-inorganic chemists. In this context, two trinuclear mixed-valence manganese complexes, namely [MnIII2MnII(L1)2(OAc)4(H2O)2]·5H2O (1) and [MnIII2MnII(L2)2(OAc)4(CH3OH)2]·3CH3OH (2) [OAc = acetate] have been synthesized and structurally characterized. These complexes are shown to retain their nuclearity in acetonitrile medium, unveiling a new area of catecholase-like activity. In fact, both complexes showed an efficient oxidizing activity in acetonitrile using 3,5-di-tert-butylcatechol (3,5-DTBC) as the model substrate, and they were able to bring about complete oxidation of the substrate at a catalyst-to-substrate ratio of up to 1 : 600. To the best of our knowledge, the catecholase-like activity of trinuclear species is explored here for the first time. Interestingly, pseudo-zero-order kinetics with respect to the substrate are identified for both complexes, which represents the second report of this type of activity and the first report observed for a mixed-valence manganese complex. Details from experimental investigations of the mechanistic pathway revealed that the formation of oxygen radicals is believed to be the rate-limiting step, which supports the observation of the pseudo-zeroth-order kinetics. [ABSTRACT FROM AUTHOR]

Using a dicarboxylic acid, [1,1′-biphenyl]-4,4′-dicarboxylic acid (H2L1) and an exobidentate ligand, (1E,1′E)-N,N′-(1,4-phenylene)bis(1-(pyridin-4-yl)methanimine) (L2), two 3D interpenetrated networks, {[Zn3(L1)3(L2)]·9H2O}n (Zn-MOF) and {[Co3(L1)3(L2)(DMF)]·0.5DMF}n (Co-MOF), have been prepared in good yields. The crystal structure analysis of Zn-MOF and Co-MOF revealed that both have a 3D pillared-layer structure based on pinwheel trinuclear metal–carboxylate clusters as secondary building units (SBUs). Furthermore, the structures also exhibited three-fold interpenetration. Although the overall networks in Zn-MOF and Co-MOF showed significant resemblances, there are marked differences in their crystal structures, which are associated with the coordination environment of the metal centre and the binding modes of the carboxylates. Gas adsorption studies (N2 at 77 K and 1 bar) indicated that Co-MOF is more porous than Zn-MOF. Magnetic measurements on Co-MOF indicate a significant antiferromagnetic interaction (45 K to 303 K) between trimeric Co(II) S = 3/2 spins through syn–syn carboxylato bridges. Both MOFs were studied for the Lewis acid catalyzed Knoevenagel condensation reactions between benzaldehydes and malononitrile with an active methylene group, where Zn-MOF was found to be a better catalyst than Co-MOF. This was supported by the Monte Carlo simulations indicating the better substrate binding ability of Zn-MOF than Co-MOF. [ABSTRACT FROM AUTHOR]

A phenylazo appended ortho‐vanillin Schiff base scaffold (HAZ) has been used for selective colorimetric sensing of Cu2+ in semi‐aqueous medium (methanol–water, 1:1, v/v) in the presence of 16 cations and 20 anions, and the limit of detection is 1.8 × 10−7 M. The structures of HAZ and Cu (II) complex, [Cu(AZ)2], have been characterised by spectroscopic data (UV–Vis, Fourier transform infrared and electron paramagnetic resonance) and established by the single crystal X‐ray diffraction measurement. The Job's plot from the absorption studies has also confirmed the 1:2 stoichiometry of Cu2+:HAZ. The absorption spectrum of [Cu (AZ)2] has returned to the spectrum of HAZ on the addition of Na2EDTA solution which is again recovered upon the addition of Cu2+ solution. Discrete Fourier transform computations were carried out using the coordinates of the X‐ray structures of the compounds, and the molecular functions were used to correlate the solution spectroscopic properties. In addition to this, the probe is treated on MDA‐MB 231 breast cancer cells to check the cytotoxicity. The probe is used for the detection of trace quantity of Cu2+ in the cancer cell. [ABSTRACT FROM AUTHOR]

In the age of sustainable development, the exploration of multifunctional materials is of high priority due to their economic benefits and environmental suitability. A stable luminescent coordination polymer, [Zn2(tdc)4(pdiq)3] (1), (pdiq = pyridyl-imidazoquinazoline; H2tdc = 2,5-thiophenedicarboxylic acid) has been prepared and structurally confirmed by single-crystal X-ray diffraction analysis. The 3D framework consists of a distorted octahedral geometry with a ZnO4N2 coordination sphere where four carboxylato-O donations come from two tdc2− as bridging ligands and two pyridyl-Ns come from two pdiq. The π⋯π interactions between the imidazolium and phenyl groups bestow robustness on the architecture. The compound is chemically stable to water, shows tolerance to acid/base aqueous solutions (pH = 2–12), and is stable to the impact of organic solvents. The high dispersibility of Zn-MOF (1) in acetonitrile may enhance the fluorescence intensity compared to that in water, which prompted fluorescence measurements in the former solvent and it is used for the efficient and selective turn-off ratiometric sensing of Al3+ ions (LOD, 1.39 × 10−7 M). In addition, the fluorescence emission of 1 is instantly quenched by trinitrophenol (TNP) and the LOD is 1.54 × 10−7 M. The Tauc's plot is used to measure the semiconducting band gap (3.33 eV) and the electrical conductivity is significantly increased upon illumination (Λ: 1.14 × 10−3 S m−1 (dark), 5.35 × 10−3 S m−1 (light)) and the energy barrier declines marginally (FB: 0.57 (dark), 0.49 (light)). Transit time (τ) and diffusion length (LD) at the quasi-Fermi level were analyzed to offer information on the charge transport mechanism of the compound. The better performance on photo-irradiation signifies the enhanced charge transfer kinetics of a Zn-MOF coated thin-film device (TFD 1), which encourages its application in semiconductor devices. [ABSTRACT FROM AUTHOR]