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The development of inexpensive and efficient bifunctional electrocatalysts for water splitting is very important but still a challenging task. In the present research, a mixed-valent molecular cluster, [Mn9L4(μ2-O)4(μ3-Cl)2] (1; 5MnII, 4MnIII) possessing cubic Ia3¯d symmetry has been synthesized as an efficient bifunctional water-splitting electrocatalyst for the first time. This synthesis is achieved by adopting a molecular library approach that utilizes an inorganic metal salt, MnCl2·4H2O and a multidentate organic linker, H3L as building blocks (H3L = N,N′-bis[2-carboxybenzomethyl]-N,N′-bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol). The organic linker is so flexible and the inclination towards cubic symmetry is so high that this cluster is readily formed through subcomponent self-assembly. Structural investigation reveals that the metallic hub of 1 consists of a central [MnII(μ2-O)4(μ3-Cl)2] backbone that connects four MnII and four MnIII ions, located at eight vertices of a body-centered cubic (BCC) structure, via the μ2-oxido and μ3-chlorido groups. A total of 24 discrete [Mn9] cluster units are packed together in the unit cell through a number of intramolecular π⋯π stacking interactions among the adjoining benzoate and pyridyl moieties, forming aesthetically attractive 3D polyhedral topologies with essentially large unit cell dimensions, and a cell volume of 113 112(9) Å3. When working as both a hydrogen evolution reaction (HER) and an oxygen evolution reaction (OER) catalyst, 1 exhibits excellent activity with overpotential values of 209 mVHER and 410 mVOER to attain a current density of 10 mA cm−2, and the Tafel slopes of 180 mV decHER−1 and 113.54 mV decOER−1. The chronoamperometric studies reveal the commendable stability of 1, accompanied by minimal degradation of current density which is the key yardstick for HER and OER activities. The mechanistic insight obtained from DFT calculations on the intermediate species show that the MnII–Ooxido–MnIII linkage is the active site for the formation of H2 and O2. [ABSTRACT FROM AUTHOR]

A series of copper (II) (1 and 3) and cobalt (II/III) (2, 4 and 5) complexes comprising different imino‐phenolate ligands DCH, DTH and DBH2 (where DCH = 2,4‐dichloro‐6‐((mesitylimino)methyl)phenol, DTH = 2,4‐di‐tert‐butyl‐6‐((mesitylimino)methyl) phenol and DBH2 = 2,4‐dibromo‐6‐((mesitylimino)methyl)phenol) have been prepared with excellent yield and high purity. By utilizing different spectroscopic tools such as UV–visible, electrospray ionization (ESI)‐mass, Fourier‐transform infrared (FTIR) spectrometry and elemental analysis, the prepared complexes (1–5) were thoroughly characterized. The molecular structure of the synthesized complexes was ascertained by using single‐crystal X‐ray diffraction studies (SCXRDs). The experiment reveals that Complexes 1–5 bind to calf thymus DNA (CT‐DNA) through non‐intercalative way with good interacting abilities. However, 1–5 are excellent quenchers of the fluorescence intensity of bovine serum albumin (BSA) following the static pathway. Additionally, they had shown remarkable cytotoxic potential against MCF‐7 (mammary gland adenocarcinoma) and A549 (lung adenocarcinoma) cell lines. The IC50 values associated with these complexes were much lower than the conventional drug cisplatin. Apoptosis‐induced cell death was confirmed from the DNA fragmentation studies and Hoechst 33342 staining. The 2′,7′‐dichlorofluorescein diacetate (DCFDA) assay indicates that the complex mediated reactive oxygen species (ROS) generation is accountable for governing the apoptosis mechanism via oxidative cell distress. Apart from these studies, by carrying out density functional theory (DFT) method, highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) energy gap calculations and optimized structures of the synthesized complexes were accomplished. [ABSTRACT FROM AUTHOR]

A series of six lanthanide‐containing germanotungstates of the formula: [(Ln2GeW10O38)4(W3O8)(OH)4(H2O)2]26− (Ln=Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6) have been synthesized under ambient conditions. The synthetic procedure involves the use of trilacunary Na10[A‐α‐GeW9O34]⋅16H2O as a preformed precursor along with lanthanide salts in 0.5 M potassium chloride solution. The interaction of the trilacunary Na10[A‐α‐GeW9O34]⋅16H2O with the lanthanide salts leads to the formation of a tetrameric structure with four [GeW10O36]8− dilacunary Keggin units incorporating eight lanthanide ions and three additional tungsten atoms. All the polyanions were structurally characterized by Fourier‐transform infrared spectroscopy (FT‐IR), Single Crystal X‐ray Diffraction (SC‐XRD), UV/Visible spectroscopy, thermogravimetric analysis (TGA), electrochemistry, Electron‐spray ionization mass spectroscopy (ESI‐MS), Powder X‐ray diffraction (PXRD) and photoluminescence. FT‐IR spectroscopy reveals that all the polyanions are isomorphous and SC‐XRD shows that all the polyanions are isostructural and crystalize in the triclinic crystal system with P1‾ space group. Some of the polyanions show good photoluminescence properties. The cyclic voltammograms (CVs) of all the six compounds exhibit the same shape, each being composed of a pronounced reduction wave. [ABSTRACT FROM AUTHOR]

Protonation of trans-1,2-bis(4-pyridyl)ethylene (4,4′-bpe) with dilute sulfuric acid (33 %) afforded a protonated adduct [{4,4′-bpe⋅2 H+}2{HSO4}−2{SO4}−2{H2O}2] ( 1). The neighboring olefinic bond in 1 is in a suitable range (3.931-4.064 Å) to undergo a photochemical [2+2] cycloaddition reaction. Upon irradiation with UV light (365 nm), 1 undergoes a molecular sliding involving the 4,4′-bpe⋅2 H+ units, affording 2, stabilized through OSO4⋅⋅⋅π interactions. Heating 1 to 50° C leads to a 3D hydrogen-bonded organic framework (HOF) ( 3). This process occurs through thermal dissociation of the bisulfate anion. Diffusion of iodine through the crystal lattice of 1 and 3 enables the reduction of sulfate to bisulfate, affording a 1D hydrogen-bonded chain ( 4). Solid-state 13C CPMAS NMR, IR, DSC, and powder XRD studies further support stimuli-responsive structural tuning through crystal-to-crystal transformation. All these conversions occur with significant translational and rotational movements along with a series of bond-breaking and bond-forming processes. [ABSTRACT FROM AUTHOR]