A bis-NHC-CAAC dimer derived dicationic diradical.

The isolation of carbon-centered diradicals is always challenging due to synthetic difficulties and their limited stability. Herein we report the synthesis of a -1,4-cyclohexylene bridged bis-NHC-CAAC dimer derived thermally stable dicationic diradical. The diradical character of this compound was confirmed by EPR spectroscopy.

Push and Pull Effect of Methoxy and Nitro Groups Modifies the Spin-State Switching Temperature in Fe(III) Complexes.

We have explored the impact of electron-donating (methoxy) and electron-withdrawing (nitro) substituents on SalEen ligand based spin crossover (SCO) behavior of Fe(III) complexes. Thus, 3-X-substituted SalEen ligands were employed to prepare [Fe(3-X-SalEen)]·NCSe, where X = OMe (), H (), and NO () (3-X-SalEen is the condensation product of 3-substituted salicylaldehyde and -ethylethylenediamine). The characteristic spin transition temperature ( ) is shown to shift to a lower temperature when an electron-donating substituent (OMe) is used and to a higher temperature when an electron-withdrawing substituent (NO) is used.

Carbodicarbenes and Striking Redox Transitions of their Conjugate Acids: Influence of NHC versus CAAC as Donor Substituents.

Herein, a new type of carbodicarbene (CDC) comprising two different classes of carbenes is reported; NHC and CAAC as donor substituents and compare the molecular structure and coordination to Au(I)Cl to those of NHC-only and CAAC-only analogues. The conjugate acids of these three CDCs exhibit notable redox properties. Their reactions with [NO][SbF ] were investigated.

Short peptide-based cross-β amyloids exploit dual residues for phosphoesterase like activity.

Herein, we report that short peptides are capable of exploiting their anti-parallel registry to access cross-β stacks to expose more than one catalytic residue, exhibiting the traits of advanced binding pockets of enzymes. Binding pockets decorated with more than one catalytic residue facilitate substrate binding and process kinetically unfavourable chemical transformations. The solvent-exposed guanidinium and imidazole moieties on the cross-β microphases synergistically bind to polarise and hydrolyse diverse kinetically stable model substrates of nucleases and phosphatase.

Selective and rapid water transportation across a self-assembled peptide-diol channel the formation of a dual water array.

Achieving superfast water transport by using synthetically designed molecular artifacts, which exclude salts and protons, is a challenging task in separation science today, as it requires the concomitant presence of a proper water-binding site and necessary selectivity filter for transporting water. Here, we demonstrate the water channel behavior of two configurationally different peptide diol isomers that mimic the natural water channel system, , aquaporins. The solid-state morphology studies showed the formation of a self-assembled aggregated structure, and X-ray crystal structure analysis confirmed the formation of a nanotubular assembly that comprises two distinct water channels.

Tetra-Coordinated Boron-Functionalized Phenanthroimidazole-Based Zinc Salen as a Photocatalyst for the Cycloaddition of CO and Epoxides.

A unique B-N coordinated phenanthroimidazole-based zinc salen was synthesized. The zinc salen thus synthesized acts as a photocatalyst for the cycloaddition of carbon dioxide with terminal epoxides under ambient conditions. DFT study of the cycloaddition of carbon dioxide with terminal epoxide indicates the preference of the reaction pathway when photocatalyzed by zinc salen.

Fe spin crossover complexes containing NO donor ligands.

Spin crossover (SCO) is one of the most studied magnetic bistable phenomena because of its application in the field of multifunctional magnetic materials. Fe complexes in a N coordination environment have been the most well-studied in terms of their SCO behaviour. Other coordination environments, notably the NO coordination environment, has also been quite effective in inducing SCO behaviour in the corresponding Fe complexes.

Role of water structure in alkaline water electrolysis.

Herein, with the help of experimental and first-principles density functional theory (DFT)-based studies, we have shown that structural changes in the water coordination in electrolytes having high alkalinity can be a possible reason for the reduced catalytic activity of platinum (Pt) in high pH. Studies with Pt electrodes indicate that electrocatalytic HER activity reduces in terms of high overpotential required, high Tafel slope, and high charge transfer resistances in concentrated aqueous alkaline electrolytes (say 6 M KOH) in comparison to that in low alkaline electrolytes (say 0.1 M KOH), irrespective of the counter cations (Na, K, or Rb) present.

Rigid NO-Pentadentate Ligand-Assisted Octacoordinate Mononuclear Ln(III) Complexes: Syntheses, Characterization, and Slow Magnetization Relaxation.

A series of air-stable mononuclear octacoordinate Ln(III) complexes, [(L)Ln(TPPO)]OTf (Ln = Y (); Gd (); Tb (); Dy (); Ho (); and Er ()) and [(L)Ln(TPPO)(NO)] (Ln = Y () and Dy ()), are synthesized employing a rigid NO-pentadentate chelating ligand as the basis ligand and meridional ancillary ligands (where HL = 2,6-diacetylpyridine -benzoylhydrazone, TPPO = triphenylphosphine oxide, and OTf = trifluoromethanesulfonate). All the complexes are synthesized under aerobic conditions and characterized comprehensively by spectroscopic and X-ray crystallographic techniques. Magnetic property investigation on the polycrystalline solid samples of (Ln = Gd, Tb, Dy, Ho, and Er) and are reported.

Synthesis, Structure, and Zero-Field SMM Behavior of Homometallic Dy2, Dy4, and Dy6 Complexes.

The synthesis, structure, and magnetic properties of three Dy complexes of different nuclearity, [Dy(HL)(NO)] [NO]·2HO·CHOH (), [Dy(HL)(piv)(OH)] (), and [Dy(HL)(μ-OH)(μ-CO)(CHOH)(HO)] 5Cl·3HO () [(HL) = 6-((bis(2-hydroxyethyl)amino)-'-(2-hydroxybenzylidene)picolinohydrazide)], are described. This variety of complexes with the same ligand could be obtained by playing with the metal-to-ligand molar ratio, the type of Dy salt, the kind of base, and the presence/absence of coligand. is a dinuclear complex, while is a tetranuclear assembly with a butterfly-shaped topology.

The oxidation state in low-valent beryllium and magnesium compounds.

Low-valent group 2 (E = Be and Mg) stabilized compounds have been long synthetically pursued. Here we discuss the electronic structure of a series of Lewis base-stabilized Be and Mg compounds. Despite the accepted zero(0) oxidation state nature of the group 2 elements of some recent experimentally accomplished species, the analysis of multireference wavefunctions provides compelling evidence for a strong diradical character with an oxidation state of +2.

Actin-driven Golgi apparatus dispersal during collective migration of epithelial cells.

As a sedentary epithelium turns motile during wound healing, morphogenesis, and metastasis, the Golgi apparatus moves from an apical position, above the nucleus, to a basal position. This apical-to-basal repositioning of Golgi is critical for epithelial cell migration. Yet the molecular mechanism underlying it remains elusive, although microtubules are believed to play a role.

Minimalist De Novo Design of an Artificial Enzyme.

We employed a reductionist approach in designing the first heterochiral tripeptide that forms a robust heterogeneous short peptide catalyst similar to the "histidine brace" active site of lytic polysaccharide monooxygenases. The histidine brace is a conserved divalent copper ion-binding motif that comprises two histidine side chains and an amino group to create the T-shaped 3N geometry at the reaction center. The geometry parameters, including a large twist angle (73°) between the two imidazole rings of the model complex, are identical to those of native lytic polysaccharide monooxygenases (72.

Ligand-Controlled Ruthenium-Catalyzed Borrowing-Hydrogen and Interrupted-Borrowing-Hydrogen Methodologies: Functionalization of Ketones Using Methanol as a C1 Source.

Herein we report simple, highly efficient, and phosphine-free N,C-Ru and N,N-Ru catalysts for ligand-controlled borrowing-hydrogen (BH) and interrupted-borrowing-hydrogen (I-BH) methods, respectively. This protocol has been employed on a variety of ketones using MeOH as a green, sustainable, and alternative C1 source to form a C-C bond through the BH and I-BH methods. Reasonably good substrate scope, functional group tolerance, and good-to-excellent yields at 70 °C are the added highlights of these methodologies.

Separation of Branched Alkanes Feeds by a Synergistic Action of Zeolite and Metal-Organic Framework.

Zeolites and metal-organic frameworks (MOFs) are considered as "competitors" for new separation processes. The production of high-quality gasoline is currently achieved through the total isomerization process that separates pentane and hexane isomers while not reaching the ultimate goal of a research octane number (RON) higher than 92. This work demonstrates how a synergistic action of the zeolite 5A and the MIL-160(Al) MOF leads to a novel adsorptive process for octane upgrading of gasoline through an efficient separation of isomers.

Mechanism of selective polarization exchange amongst chemically similar and distinct protons during weak rf irradiation at fast magic angle spinning.

Band Selective Spectral Spin-Diffusion (BASS-SD) is a method to obtain selective H-H contacts between chemically similar protons within a distance range of 5-6 Å in fully protonated proteins. BASS-SD combines low-amplitude proton spinlock radio frequency (rf) pulses with fast MAS frequency to enable selective polarization exchange in fully protonated molecules. The selectivity of transfer is dictated by the bandwidth of the spinlock pulse and has been used to observe selective H-H, H-Η and H-H correlations.

Role of processing parameters in CVD grown crystalline monolayer MoSe.

The quality of as-synthesized monolayers plays a significant role in atomically thin semiconducting transition metal dichalcogenides (TMDCs) to determine the electronic and optical properties. For designing optoelectronic devices, exploring the effect of processing parameters on optical properties is a prerequisite. In this view, we present the influence of processing parameters on the lattice and quasiparticle dynamics of monolayer MoSe.

The function of peptide-mimetic anionic groups and salt bridges in the antimicrobial activity and conformation of cationic amphiphilic copolymers.

Herein we report the synthesis of ternary statistical methacrylate copolymers comprising cationic ammonium (amino-ethyl methacrylate: AEMA), carboxylic acid (propanoic acid methacrylate: PAMA) and hydrophobic (ethyl methacrylate: EMA) side chain monomers, to study the functional role of anionic groups on their antimicrobial and hemolytic activities as well as the conformation of polymer chains. The hydrophobic monomer EMA was maintained at 40 mol% in all the polymers, with different percentages of cationic ammonium (AEMA) and anionic carboxylate (PAMA) side chains, resulting in different total net charge for the polymers. The antimicrobial and hemolytic activities of the copolymer were determined by the net charge of +3 or larger, suggesting that there was no distinct effect of the anionic carboxylate groups on the antimicrobial and hemolytic activities of the copolymers.

CURD: a Single-Shot Strategy to Obtain Assignments and Distance Restraints for Proteins Using Solid-State MAS NMR Spectroscopy.

We present a strategy dubbed CURD (correlations using recycle delays) to acquire chemical-shift assignments and distance restraints for proteins in a single experimental block under slow-moderate magic-angle spinning conditions. This is done by concatenating the 3D-CCC and 3D-NNC experiments, both of which individually require long experimental times for sufficient resolution and sensitivity to be realized. Unlike previous approaches, the CURD strategy does not increase the amount of radio-frequency deposition on the sample and does not require lengthy procedures to optimize any of the pulse sequence elements.

Aluminium alkyl complexes supported by imino-phosphanamide ligand as precursors for catalytic guanylation reactions of carbodiimides.

Herein, we report the synthesis, characterisation, and application of three aluminium alkyl complexes, [κ-{NHIP(Ph)NDipp}AlMe] (R = Dipp (2a), Mes (2b); Bu (2c), Dipp = 2,6-diisopropylphenyl, Mes = mesityl, and Bu = -butyl), supported by unsymmetrical imino-phosphanamide [NHIP(Ph)NDipp] [R = Dipp (1a), Mes (1b), Bu (1c)] ligands as molecular precursors for the catalytic synthesis of guanidines using carbodiimides and primary amines. All the imino-phosphanamide ligands 1a, 1b and 1c were prepared in good yield from the corresponding N-heterocyclic imine (NHI) with phenylchloro-2,6-diisopropylphenylphosphanamine, PhP(Cl)NHDipp. The aluminium alkyl complexes 2a, 2b and 2c were obtained in good yield upon completion of the reaction between trimethyl aluminium and the protic ligands 1a, 1b and 1c in a 1 : 1 molar ratio in toluene the elimination of methane, respectively.

Realizing 1,1-Dehydration of Secondary Alcohols to Carbenes: Pyrrolidin-2-ols as a Source of Cyclic (Alkyl)(Amino)Carbenes.

Herein we report secondary pyrrolidin-2-ols as a source of cyclic (alkyl)(amino)carbenes (CAAC) for the synthesis of CAAC-Cu -complexes and cyclic thiones when reacted with Cu -salts and elemental sulfur, respectively, under reductive elimination of water from the carbon(IV)-center. This result demonstrates a convenient and facile access to CAAC-based Cu -salts, which are well known catalysts for different organic transformations. It further establishes secondary alcohols to be a viable source of carbenes-realizing after 185 years Dumas' dream who tried to prepare the parent carbene (CH ) by 1,1-dehydration of methanol.

Disclosing Cyclic(Alkyl)(Amino)Carbenes as One-Electron Reductants: Synthesis of Acyclic(Amino)(Aryl)Carbene-Based Kekulé Diradicaloids.

Herein, we disclose cyclic(alkyl)(amino)carbenes (CAACs) to be one-electron reductants under the formation of a transient radical cation as indicated by EPR spectroscopy. The disclosed CAAC reducing reactivity was used to synthesize acyclic(amino)(aryl)carbene-based Thiele and Chichibabin hydrocarbons, a new class of Kekulé diradicaloids. The results demonstrate CAACs to be potent organic reductants.

Solid-State NMR: Methods for Biological Solids.

In the last two decades, solid-state nuclear magnetic resonance (ssNMR) spectroscopy has transformed from a spectroscopic technique investigating small molecules and industrial polymers to a potent tool decrypting structure and underlying dynamics of complex biological systems, such as membrane proteins, fibrils, and assemblies, in near-physiological environments and temperatures. This transformation can be ascribed to improvements in hardware design, sample preparation, pulsed methods, isotope labeling strategies, resolution, and sensitivity. The fundamental engagement between nuclear spins and radio-frequency pulses in the presence of a strong static magnetic field is identical between solution and ssNMR, but the experimental procedures vastly differ because of the absence of molecular tumbling in solids.