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We present a simple, fast, solvent-free, environmentally benign, one-pot technique to synthesize nanoflakes/nanoplatelets of transition metal dichalcogenides [i.e., molybdenum disulfide (MoS2), tungsten disulfide (WS2), and vanadium disulfide (VS2)]. In this technique, the precursor powder was prepared by simply mixing a transition metal source, a sulfur source, and multiwall carbon nanotubes (MWCNTs) in a mortar and pestle and heating in a microwave oven for 10 min under atmospheric conditions. MWCNTs were used as a microwave absorber. Microwaves interacted strongly with the precursor and induced localized arcing and plasma. Synthesized nanomaterials were studied using electron microscopy, X-ray and electron diffraction, Raman and photoelectron spectroscopy, and thermogravimetric analysis. The crystalline nanostructures were found to have mixed semiconducting and metallic phases. The as-synthesized MoS2, WS2, and VS2 showed impressive electrocatalytic activity for the hydrogen evolution reaction. MoS2 exhibited the lowest overpotential with a typical value of about 262 mV at a current density of 10 mA cm–2 and a Tafel slope of 84 mV dec–1, along with long-term stability. The proposed method is time- and energy-efficient and does not demand vacuum or a gaseous atmosphere, stringent temperature–pressure conditions, multiple steps or lengthy procedures, complex instrumentations, or expert manpower. [ABSTRACT FROM AUTHOR]

Research has been conducted on the multi-pyrazolyl cyclotriphosphazene containing a polymerized group. The preparation of this compound from a corresponding chloro derivative is described.

A family of metallaquartets generated through interaction of silver and modified adenine nucleobase is described. The complex is found to remain unaffected by subtle substitutions in the purine ring and counteranions.

The synthesis and characterization of [C.sub.2]- and [C.sub.3]-symmetric D-biotin conjugates is described that is followed by examining the solution state self-assembly behavior of the conjugates by various microscopy methods. The [C.sub.2]-symmetric conjugate has produced the formation of fibrous structures, while the [C.sub.3]-symmetric conjugate has disclosed the formation of marigold flower-like spherical morphologies.

The synthesis and characterization of adenine-single-walled carbon nanotube (SWCNT) hybrid materials are described, where the nucleobases are covalently attached to the exosurface of SWCNTs. The coordinating ability of these hybrid materials toward silver ions is evaluated and a pattern of silver nanoparticles localized over the surface of the carbon nanotube network is found.

The synthesis of two dodecanuclear copper(II) cages by a multicomponent reaction strategy involving a copper(II) salt, an ancillary pyrazole ligand and triethyl amine is described. The nuclease activity of these cages is studied and has disclosed that both of them are effective nucleases in the presence of an external oxidant.

A novel lipophilic tetranuclear copper phosphonate possessing an unprecedented double-four-ring (D4R) core structure is prepared. The tetranuclear cage has functioned as a very effective artificial nuclease in the presence of an external oxidant, magnesium monoperoxyphthalate.

The systematic analysis of high-resolution protein structures which identified geometry of carbonyl oxygen and aromatic centers with [pi]...[pi] and a lone pair...[pi] interaction that could play a stabilizing role in protein secondary structures is demonstrated.

A glycine-rich, short pentapeptide conjugate is derived from the highly conserved copper-binding octarepeat region of the prion proteins and has displayed a tendency to self-aggregate in a time-dependent fashion. The results have shown that the antimitotic agent colchicine has afforded disaggregation of aged peptide conjugate solutions.

The interfacial electron transfer (ET) dynamics of 5,10,15-trisphenyl-20-(3,4-dihydroxybenzene) porphyrin (TPP-cat) adsorbed on TiO2 nanoparticles are analyzed by using femtosecond transient absorption spectroscopy in the visible and near-infrared (IR) region exciting at 400 and 800 nm. The reaction path in the TPP-cat/TiO2 system after exciting with both 400 and 800 nm laser light is discussed and the ET dynamics are compared by exciting at both wavelengths.

The synthesis and characterization of novel lipophilic free-base and Cu(II)-metalated hexaporphyrin assemblies that are supported on a central drumlike stannoxane core are discussed. A highly efficient and successful synthetic strategy based on approaches available in organostannoxane chemistry to conduct hexaporphyrin assemblies in a single step and in nearly quantitative yields is described.

The molecular structure of a novel mixed-coordinate silver-adenine helicate is described. The results indicated the usefulness of shape-persistent coordination motifs for fabricating functionalized surfaces for advanced nanoscale applications.

The molecular structure of a silver-adenine metallamacrocycle, its propensity to aggregate and its luminescent properties are investigated. The unusual coordination mode, resemblance to biological purine quartets and the presence of silver-mediated helical motifs represents an example of metal-nucleobase interaction.

A proton-coupled electron transfer (PCET) reaction in a hydrogen-bonded charge-transfer (CT) complex of 4-([2,2′-bipyridin]-4-yl)phenol (bpy-phenol) with a F- ion has been investigated by ultrafast time-resolved transient absorption spectroscopy. The phenolic receptor molecule, bpy-phenol, binds to the F- ion through a hydrogen bond and senses the F- ion via the Stokes-shifted CT band. Upon photoexcitation, CT from the phenol residue to the bpy residue promotes proton transfer from the phenol radical cation (ArOH•+) to the fluoride ion at ultrafast time scales of <150 fs (instrument response function limited) and 3 ps, separately. The fast and slow proton-transfer times are linked to two different types of hydrogen-bonding networks between the phenol residue and fluoride ion. Crystalline water in the fluoride salt hydrates mediates the proton-transfer reaction. This work demonstrates the participation of a hydrogen-bonded water bridge within a PCET reaction in a water-restricted environment. [ABSTRACT FROM AUTHOR]

Design, synthesis, and single crystal structure elucidation of modified purine ligands 2-(2-amino-9H-purin-9-yl) acetic acid (L1) and 2-(2,6-diamino-9H-purin-9-yl) acetic acid (L2) and their interaction with certain d10 transition metal ions is described. Copper complex 1 (C28H34Cu2N22O19) afforded a two-dimensional polymeric structure composed of metallaquartets, while corresponding silver complex 2 (C14H20AgN10O8) was formed as a discrete dimer. Complexes 3 (C14H24CdN10O10) and 5 (C14H22CdN12O8), cadmium complexes of L1 and L2, respectively, afforded different coordinating modes, where 3 resulted in a two-dimensional (2D) polymeric structure consisting of metallaquartets and 5 as a discrete dimeric structure, with an octahedral coordination geometry. Complex 4 (C14H13Cl13Hg6N10O8) afforded a unique hexanuclear, 2D polymeric structure, supported by mercury-chloride bridges, presenting as interconnected dimeric, trimeric, and hexameric mercury halide (μ2double, μ3triple, and μ6six) clusters. The potential of halide ions as bridges is interesting. We have also studied the fluorescence properties of ligand L1 and L2 along with complexes 1-5. [ABSTRACT FROM AUTHOR]

Adenine presents an interesting preformednatural heterocyclic skeleton to bind metal ions with well-definedangles with the possibility of multisite intraligand coordinationto afford a myriad of complex architectures. This article describescrafting of additional coordination sites by introducing a Schiffbase linkage on adenine nucleobase. As envisaged, this approach willexpand opportunities for the construction of dynamic self-assembled,metal-assisted frameworks on the adenine platform. Based on crystalstudies, we find that ligand (HL) affords ML2type coordination with Cd(II) and M2L2typecomplexes with Zn(II) and Co(II), while presenting a linear 1D polymericstructure with Cu(II) ions. Interestingly, Ag(I) hydrolyzed the iminebond to afford interconnected metallacycles. Photophysical propertiesof Cd and Zn complexes exhibited enhanced fluorescence compared withthe ligand alone. [ABSTRACT FROM AUTHOR]

This communication describes thesynthesis and structure of zinc,cadmium, and mercury complexes of modified N9-substituted 2-aminopurine(2AP) analogues. 2AP is an inherently fluorescent heterocyclic nucleobasewith wide applications in biochemical reactions. Herein, we reporta one-dimensional (1D) polymeric helical chain and discrete arrangementsfor zinc complexes [C8H11N5Cl2Zn] (1) and [C12H15N5O5Zn] (2), a 1D polymeric helicalchain for a Cd complex [C8H11CdI2N5] (3), and a unique example of supported2AP-Hg(II) two-dimensional clusters [C16H21Cl6Hg3N10] (4). The photoluminescenceproperties of free ligand Land complexes 1–4are also presented. [ABSTRACT FROM AUTHOR]

Detailed crystallographic analysis of four silver complexesof N9-benzyl-N6-methoxyadenine, 1, on the basis of three differentcounteranions and silver ion stoichiometry, is discussed in this article. 1is a rare tautomer of adenine, which exhibits promutagenicbehavior as it partly mimics hydrogen bond donor and acceptor propertiesof guanine and mispairs with cytosine. Complexes 2and 4exhibit discrete Ag2L2dimer, whilecomplex 3shows two AgL2units in additionto a Ag2L2dimer, all in a head-to tail fashion.Complex 5, on the other hand, shows four AgL2units coordinated in a head-to-head fashion affording a three-dimensional latticestabilized by CH···F interactions. Various noncovalentinteractions such as hydrogen bonding, CH-π interactions, argentophilicinteractions, and Ag-π interactions stabilize these complexes. [ABSTRACT FROM AUTHOR]

We have synthesized a new photoactive ruthenium(ll) complex having a pendant catechol functionality (K2[Ru(CN)4(L)] (1) (L is 4-[2-(4'-methy-2,2'-bipyridinyl-4-yl)vinyl]benzene-1,2-diol) for studying the dynamics of the interfadal electron transfer between nanopartiwlate TiO2 and the photoexcited states of this Ru(lI) complex using ferrosecond transient absorption spectroscopy. Steady-state absorption and emission studies revealed that the complex 1 showed a strong solvatochromic behavior in solvents or solvent mixtures of varying polarity. Our steady-state absorption studies further revealed that 1 is bound to TiO2 surfaces through the catectrol functionality, though 1 has two different types of functionalities (catetholate and cyanato) for binding to TiO2 surfaces. The longer wavelength absorption band tail for 1, bound to TiO2 through the proposed catechotate functionality, could also be explained on the basis of the DFT calculations. Dyrrarnics of the interfadat electron transfer between 1 and TiO2 nanopartides was investigated by studying kinetics at various wavelengths in the visible and near-infrared region. Electron injection to the conduction band of the nanoparticulate TiO2 was confirmed by detection of the conduction band electron in TiO2 ([e-]TiO2CB) and cation radical of the adsorbed dye (1∙+) in real time as monitored by transient absorption spectroscopy. A single exponential and pulse-width limited (<100 fs) electron injection was observed. Back electron transfer dynamics was determined by monitoring the decay kinetics of 1∙+ and [e-]TiO2CB. This is the first report on uitrafast ET dynamics on TiO2 nanopartide surface using a solvatodiromic sensitizer molecule. [ABSTRACT FROM AUTHOR]