International audienceReaction of [Fe2{μ-S(CH2)3S}(CO)6] (1) at room temperature with the N-heterocyclic carbenes IMe-(CH2)2-L (IMe = 1-methylimidazol-2-ylidene, L = NMe2, SMe) afforded the pentacarbonyl carbene derivatives [Fe2{μ-S(CH2)3S}(CO)5{IMe-(CH2)2-NMe2}] (2a) and [Fe2{μ-S(CH2)3S}(CO)5{IMe-(CH2)2-SMe}] (2b). Reaction of 1 with IMe-CH2-IMe at room temperature provided the dimer [{Fe2(μ-S(CH2)3S)(CO)5}2{μ-(IMe-CH2-IMe)}] (3) together with the chelated bis-NHC complex [Fe2{μ-S(CH2)3S}(CO)4{IMe-CH2-IMe}] (4a) as the major product. The analogous reaction of 1 with IMe-(CH2)2-IMe yielded the chelated bis-NHC complex [Fe2(μ-S(CH2)3S)(CO)4{IMe-(CH2)2-IMe}] (4b). Addition of HBF4 to compound 4a afforded the stable bridging hydride complexes [Fe2(μ-H){μ-S(CH2)3S}(CO)4{IMe-CH2-IMe}](BF4) (5a,b) with NHC ligands in a basal/basal and basal/apical mode of coordination in 5a,b, respectively. The molecular structures of 2a, 3, 4a,b, and 5a were confirmed by X-ray diffraction studies. Low-temperature NMR studies on the protonation of 4a showed spectroscopic evidence for the formation of a very unstable terminal hydride and a bridging hydride species with a NHC ligand having a non classical mode of coordination via a C-4(5) bond. Cyclic voltammetry revealed that 4a is a catalyst for proton reduction

We demonstrate a new platform, convex lens-induced nanoscale templating (CLINT), for dynamic manipulation and trapping of single DNA molecules. In the CLINT technique, the curved surface of a convex lens is used to deform a flexible coverslip above a substrate containing embedded nanotopography, creating a nanoscale gap that can be adjusted during an experiment to confine molecules within the embedded nanostructures. Critically, CLINT has the capability of transforming a macroscale flow cell into a nanofluidic device without the need for permanent direct bonding, thus simplifying sample loading, providing greater accessibility of the surface for functionalization, and enabling dynamic manipulation of confinement during device operation. Moreover, as DNA molecules present in the gap are driven into the embedded topography from above, CLINT eliminates the need for the high pressures or electric fields required to load DNA into direct-bonded nanofluidic devices. To demonstrate the versatility of CLINT, we confine DNA to nanogroove and nanopit structures, demonstrating DNA nanochannel-based stretching, denaturation mapping, and partitioning/trapping of single molecules in multiple embedded cavities. In particular, using ionic strengths that are in line with typical biological buffers, we have successfully extended DNA in sub-30-nm nanochannels, achieving high stretching (90%) that is in good agreement with Odijk deflection theory, and we have mapped genomic features using denaturation analysis.single-molecule manipulation | polymer confinement | genomic mapping | CLIC imaging | nanotechnology N anoconfinement-based manipulation is a powerful approach for controlling the conformation of single DNA molecules on chip. When single polymer chains are squeezed into environments confined at length scales below their diameter of gyration in free solution, the polymer equilibrium conformation will be molded by the surrounding nanoscale geometry. Nanochannel arrays can be used for massively parallel extension of DNA across an optical field, serving as the basis for a highthroughput optical mapping of genomes (1, 2). More varied manipulations can be performed based on the design of the surrounding nanotopology, such as using nanocavities embedded in a nanoslit to trap single DNA molecules (3). Nanoconfinementbased manipulation, compared with competing techniques for single-molecule manipulation such as tweezer technology and surface/hydrodynamic-based stretching, has three key advantages (4): (i) It is highly parallel, providing the high throughput essential for mapping gigabase-scale mammalian genomes (1); (ii) it can be efficiently integrated with microfluidics to rapidly cycle molecules through the channel arrays for upstream/downstream pre-and postprocessing of DNA; and (iii) it does not require applied flow or electric force to maintain the DNA extension.Nanoconfinement-based approaches have, however, a key difficulty inherent to the use of nanoscale dimensions: the need to bridge length scales differing by up to 5 orders...

We present the conception, fabrication, and demonstration of a versatile, computer-controlled microscopy device which transforms a standard inverted fluorescence microscope into a precision single-molecule imaging station. The device uses the principle of convex lens-induced confinement [S. R. Leslie, A. P. Fields, and A. E. Cohen, Anal. Chem. 82, 6224 (2010)], which employs a tunable imaging chamber to enhance background rejection and extend diffusion-limited observation periods. Using nanopositioning stages, this device achieves repeatable and dynamic control over the geometry of the sample chamber on scales as small as the size of individual molecules, enabling regulation of their configurations and dynamics. Using microfluidics, this device enables serial insertion as well as sample recovery, facilitating temporally controlled, high-throughput measurements of multiple reagents. We report on the simulation and experimental characterization of this tunable chamber geometry, and its influence upon the diffusion and conformations of DNA molecules over extended observation periods. This new microscopy platform has the potential to capture, probe, and influence the configurations of single molecules, with dramatically improved imaging conditions in comparison to existing technologies. These capabilities are of immediate interest to a wide range of research and industry sectors in biotechnology, biophysics, materials, and chemistry.

Single and 10-fold-twinned crystals of the C 60 1:1 solvate formed with 1,1,2-trichloroethane were examined by means of scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry and thermogravimetry. Solubility of C 60 in 1,1,2-trichloroethane was found to be 130 ( 10 mg per liter of solution in equilibrium with solvate crystals at 296 ( 2 K. The lattice metrics of the solvate is orthorhombic (a ) 10.164(3) Å, b ) 31.390(6) Å, c ) 10.130(4) Å, β ) 90.00(2)°), with axis c as a twin axis, although the symmetry is monoclinic (space group P2 1 /n). The solvate forms with a negative excess volume (-58 Å 3 per formula unit), and its packing coefficient (0.76) is higher than that for close packing of hard spheres. On heating, desolvation into cubic C 60 and TCAN vapor occurs in one step at 436 K (onset) with a related enthalpy, +48 kJ per mole of solvate, close to the sublimation enthalpy for pure solvent. On aging at room temperature in the dark, no degradation of big (≈1 × 10-3 mm 3 ) solvate crystals into fcc C 60 is observed after 4 years have elapsed.

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In the crystal of the title compound, C20H42O, the mol­ecules are packed in layers parallel to the (100) plane. The alkyl chains are parallel to the [30] direction and these molecular chains are hydrogen‐bonded into chains parallel to the c axis. All C—C bonds of the alkyl chain show an antiperiplanar (trans) conformation, with a slight deviation from the ideal value (180°) in the C—C bonds close to the hydrogen bonds. The length of the alkyl chain is 27.92 (2) Å and the tilt angle is 59.7 (2)°.

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Electrochromic organic systems that can undergo substantial variation of their optical properties upon electron stimulus are of high interest for the development of functional materials. In particular, devices based on radical dimerization are appropriate because of the effectiveness and speed of carbon-carbon bond making/breaking. Phenylmethylenepyrans are organic chromophores which are well suited for such purposes since their oxidation leads to the reversible formation of bispyrylium species by radical dimerization. In this paper, we show that the redox and spectroscopic properties of phenylmethylenepyrans can be modulated by adequate variation of the substituting group on the para position of the phenyl moiety, as supported by DFT calculations. This redox switching is reversible over several cycles and is accompanied by a significant modification of the UV-vis spectrum of the chromophore, as shown by time-resolved spectroelectrochemistry in thin-layer conditions.