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Three new dinuclear lanthanide complexes [Ln2L2(μ2‐benzoate)2(MeOH)2] ⋅ 4MeOH (H2L=2‐Bis(2‐hydroxybenzyl)aminomethyl]pyridine); Ln=Nd (1), Tb (2), Dy (3)) have been synthesized and structurally characterized by single‐crystal X‐ray diffraction analyses. Compounds 1, 2 and 3 are isomorphous and thus the framework connectivity features are the same for all the three compounds. In the dimeric form of the complexes, each metal centre is octacoordinated with square antiprism (D4d symmetry) geometry, which is completed by a coordinated methanol molecule. In addition, the methanol that present in the structural voids also acts as linkers of paddle‐wheel like complexes. Magnetic properties of the compounds have been investigated in detail using direct‐current and alternating‐current susceptibility measurements. From the analysis of all three complexes, the decrease of susceptibility value at low temperatures is due to the depopulation of Stark sublevels and the existence of intramolecular antiferromagnetic interactions. In addition, complex 3 shows slow relaxation of magnetization behavior, a characteristic feature of single molecule magnets (SMMs). An effective energy barrier value (Ueff) of 38.87 K and relaxation time (τ0) of 1.665×10−7 s for the magnetic relaxation process was obtained for 3. Solid state luminescence spectra for complex 2 show characteristic green emission peaks at 543 nm region having potential for applications in the solid state as light emitting diodes and photoluminescent materials. [ABSTRACT FROM AUTHOR]

Organometallic Re(I)‐BODIPY compounds have recently received attention as metal‐based photosensitizers for photodynamic therapy (PDT) applications owing to their strong absorption in the visible region. We synthesized and characterized an organometallic [ReI(L)2(CO)3Br] (ReL) complex containing a BODIPY ligand (L) and prepared nanoparticles of the ligand (NPL) as well as the complex (NPReL). The formation of nanoparticles was confirmed by dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM), and energy dispersive X‐ray (EDX) analyses. Single‐crystal structure of ReL showed octahedral environment around Re center, and the BODIPY chromophore was placed at distances of around 12 Å. Detailed photophysical properties of ReL were investigated which showed strong visible absorption at 551 nm (ε = 1.46 × 105 M−1 cm−1) owing to π‐conjugation of BODIPY with the metal center Re(I). Efficient intersystem crossing (ISC) and formation of triplet‐excited states with lifetimes of 0.80 and 0.65 μs for L and ReL, respectively, were confirmed through nanosecond‐laser flash photolysis and density functional theory (DFT) calculations. The photosensitization efficiency of ReL was observed to be ϕΔ = 0.77. In vitro biological studies of NPReL showed negligible toxicity and reactive oxygen species (ROS) generation in the dark as compared with NPL despite the good photosensitization ability of NPL. Therefore, NPReL showed coordination‐enhanced cytotoxicity under irradiation conditions and interestingly found to be nontoxic to normal NIH3T3 cell lines in comparison with L. Flow cytometry studies further indicated that the major cause of cell death by NPReL was via apoptotic pathways (54%), which authenticates its potential as a PDT agent. [ABSTRACT FROM AUTHOR]

The design of molecular compounds that exhibit flexibility is an emerging area of research. Although a fair amount of success has been achieved in the design of plastic or elastic crystals, realizing multidimensional plastic and elastic bending remains challenging. We report herein a naphthalidenimine–boron complex that showed size‐dependent dual mechanical bending behavior whereas its parent Schiff base was brittle. Detailed crystallographic and spectroscopic analysis revealed the importance of boron in imparting the interesting mechanical properties. Furthermore, the luminescence of the molecule was turned‐on subsequent to boron complexation, thereby allowing it to be explored for multimode optical waveguide applications. Our in‐depth study of the size‐dependent plastic and elastic bending of the crystals thus provides important insights in molecular engineering and could act as a platform for the development of future smart flexible materials for optoelectronic applications. [ABSTRACT FROM AUTHOR]

An efficient, metal free, direct and selective deoxygenation of α‐hydroxy carbonyl compounds is achieved with the aid of catalytic amount of aqueous HClO4 (70 %) and triethylsilane as hydride source. A variety of α‐hydroxy‐α,α‐diaryl carbonyl compounds are selectively deoxygenated to give α,α‐diaryl carbonyl compounds in good to excellent yields. Intermediacy of α‐keto carbenium ion is proposed on the basis of some control experiments and atmospheric pressure chemical ionization mass spectral analysis. [ABSTRACT FROM AUTHOR]

Development of chemosensors for metal ions is an active area of research. Fluorescent chemosensors capable of detecting multiple metal ions are valuable because of their potential utility in diagnostics and environmental science. We have synthesized a Schiff‐base chemosensor based on the tetraphenylethylene chromophore. It was observed that the chemosensor interacts with Cu(II) and Zn(II) in acetonitrile with high association constants of 2.33 × 1021 and 1.33 × 1021 M−4, respectively. Moreover, the interaction of these metal ions with the chemosensor resulted in visual colour and fluorescence changes. Nanoaggregates of this molecule, on the other hand, were observed to be selective towards Cu(II) in the aqueous medium. It is also noteworthy that the binding of Cu(II) activates photosensitization property of this molecule and generates singlet oxygen efficiently. [ABSTRACT FROM AUTHOR]

To learn how a preorganized peptide-based molecular template, together with diverse weak non-covalent interactions, leads to an effective self-association, we investigated the conformational characteristics of a simple γ,α-hybrid model peptide, Boc-γ-Abz-Gly-OMe. The single-crystal X-ray diffraction analysis revealed the existence of a fully extended β-strand-like structure stabilized by two non-conventional C−H⋅⋅⋅O=C intramolecular H-bonds. The 2D 1H NMR ROESY experiment led us to propose that the flat topology of the urethane-γ-Abz-amide moiety is predominantly preserved in a non-polar environment. The self-association of the energetically more favorable antiparallel β-strand-mimic in solid-state engenders an unusual 'flight of stairs' fabricated through face-to-face and edge-to-edge Ar⋅⋅⋅Ar interactions. In conjunction with FT-IR spectroscopic analysis in chloroform, we highlight that conformationally semi-rigid γ-Abz foldamer in appositely designed peptides may encourage unusual β-strand or β-sheet-like self-association and supramolecular organization stabilized via weak attractive forces. [ABSTRACT FROM AUTHOR]

Friedel-Crafts arylation of α-hydroxy ketones such as 2-hydroxy-1,2,2-triarylethanones has been achieved with a variety of arenes and heteroarenes in the presence of Lewis or Brønsted acids. Both sterically hindered and unhindered 1,2,2,2-tetrarylethanones are formed in good to excellent yields by using a stoichiometric amount of triflic acid. The intermediacy of an α-keto carbenium ion has been proposed. [ABSTRACT FROM AUTHOR]

Porous coordination polymers (CPs) with partially uncoordinated pyridyl rings based on rationally designed polypyridyl linkers are appealing from the point of view of their application as nucleophilic catalysts. A D2 d-symmetric tetradentate organic linker L, that is, 2,2′,6,6′-tetramethoxy-3,3′,5,5′-tetrakis(4-pyridyl)biphenyl, was designed and synthesized for metal-assisted self-assembly aimed at porous CPs. Depending on the nature of the metal ion and the counter anion, the ligand L is found to function as a 3- or 4-connecting building block leading to porous CPs of diverse topologies. The reaction of L with Zn(NO3)2 and Cd(NO3)2 yields porous 2 D CPs of ' fes' topology, in which the tetrapyridyl linker L serves as a 3-connecting unit with its free pyridyl rings well exposed into the pores. The functional utility of these porous CPs containing uncoordinated pyridyl rings is demonstrated by employing them as efficient heterogeneous nucleophilic catalysts for acetylation of a number of phenols with varying electronic properties and reactivities. [ABSTRACT FROM AUTHOR]

A highly efficient and cost-effective green method for the synthesis of complex glycopeptides and ureas mediated by carbonyl diimidazole under solvent-free conditions is reported. The reactions could be performed conveniently in a planetary ball mill by dry grinding, and the isolation of the novel sugar derivatives thus produced could be very efficiently achieved by size exclusion chromatography with environmentally benign substances. A diacetone galactose based diamide, upon crystallization, could be examined by X-ray crystallography and was found to possess a heart-shaped structure. Although the 4-aminophenyl galactoside based diamide synthesized formed spherical particles, the alanine-based diamide formed nanofilamentous/-tubular structures as analyzed by TEM imaging. [ABSTRACT FROM AUTHOR]

The single-crystal X-ray diffraction analysis of a β,γ-hybrid model peptide Boc-β-Ala-γ-Abu-NH2 revealed the existence of four crystallographically independent molecules ( A, B, C and D conformers) in the asymmetric unit. The analysis revealed that unusual β-turn-like folded structures predominate, wherein the conformational space of non-proteinogenic β-Ala and γ-Abu residues are restricted to gauche- gauche- skew and skew- gauche- trans- skew orientations, respectively. Interestingly, the U-shaped conformers are seemingly stabilised by an effective unconventional CH ⋅⋅⋅O intramolecular hydrogen bond, encompassing a non-covalent 14-membered ring-motif. Taking into account the signs of torsion angles, these conformers could be grouped into two distinct categories, A/ B and C/ D, establishing the incidence of non-superimposable stereogeometrical features across a non-chiral one-component peptide model system, that is, 'mirror-image-like' relationships. The natural occurrence of β-Ala and γ-Abu entities in various pharmacologically important molecules, coupled with their biocompatibilities, highlight how the non-functionalised β,γ-hybrid segment may offer unique advantages for introducing and/or manipulating a wide spectrum of biologically relevant hydrogen bonded secondary structural mimics in short synthetic peptides. [ABSTRACT FROM AUTHOR]

In the compound [C6H6O2]3C60, hydroquinone (C6H6O2) forms a three-dimensional hydrogen-bonded network enclosing roughly spherical cages with point symmetry &3macr;m and a diameter of 13.2 Å at 100 K. Although C60 fits tightly into these cages, it shows threefold orientational disorder, the molecular site symmetry being 2/m. The disorder has been studied with single-crystal Mo Kα X-ray data at four temperatures, 100, 200, 293 and 373 K. In the refinement, C60 was restrained to the icosahedral molecular symmetry m&35macr; and to rigid-body translational and librational displacements including third- and fourth-order cumulants to account for curvilinear atomic movements, R(/F/) = 3.2-4.7%. At 100 K, bond lengths in C60 refine to the expected values 1.450 (1) and 1.388 (1) Å. The ratio of these values increases with increasing temperature, but the radius of the molecule remains constant at 3.537 (2) Å. The r.m.s. libration amplitudes of C60 are relatively small (5.5° at 373 K) and the probability function of orientations of C60 inside the cage shows large values only at the refined positions, indicating that the energy barrier of reorientation is large. Refinement of an ordered twinned structure was unsuccessful; the orientations of neighboring C60 appear to be uncorrelated. [ABSTRACT FROM AUTHOR]

In the compound [C6H6O2]3C60, hydroquinone (C6H6O2) forms a three-dimensional hydrogen-bonded network enclosing roughly spherical cages with point symmetry &3macr;m and a diameter of 13.2 Å at 100 K. Although C60 fits tightly into these cages, it shows threefold orientational disorder, the molecular site symmetry being 2/m. The disorder has been studied with single-crystal Mo Kα X-ray data at four temperatures, 100, 200, 293 and 373 K. In the refinement, C60 was restrained to the icosahedral molecular symmetry m&35macr; and to rigid-body translational and librational displacements including third- and fourth-order cumulants to account for curvilinear atomic movements, R(/F/) = 3.2-4.7%. At 100 K, bond lengths in C60 refine to the expected values 1.450 (1) and 1.388 (1) Å. The ratio of these values increases with increasing temperature, but the radius of the molecule remains constant at 3.537 (2) Å. The r.m.s. libration amplitudes of C60 are relatively small (5.5° at 373 K) and the probability function of orientations of C60 inside the cage shows large values only at the refined positions, indicating that the energy barrier of reorientation is large. Refinement of an ordered twinned structure was unsuccessful; the orientations of neighboring C60 appear to be uncorrelated. [ABSTRACT FROM AUTHOR]

The article presents chemical equations related to the article "Indium(III) Bromide Catalyzed Direct Azidation of α-Hydroxyketones Using TMSN3" by A. Kumar and others, published in the periodical "Tetrahedron" in 2013.