Synthesis and properties of an Au cluster supported by a mixed N-heterocyclic carbene-thiolate ligand.

The preparation of a novel Au cluster bearing a bidentate mixed carbene-thiolate ligand is presented. The length of linker between the central benzimidazole and thiolate has a strong effect on the formation of cluster products, with a C chain giving an Au cluster, while a C chain results in no evidence of cluster formation. Density functional theory analysis predicts a non-metallic cluster with a large HOMO-LUMO (3.

N-heterocyclic carbene-functionalized magic-number gold nanoclusters.

Magic-number gold nanoclusters are atomically precise nanomaterials that have enabled unprecedented insight into structure-property relationships in nanoscience. Thiolates are the most common ligand, binding to the cluster via a staple motif in which only central gold atoms are in the metallic state. The lack of other strongly bound ligands for nanoclusters with different bonding modes has been a significant limitation in the field.

Water-Soluble N-Heterocyclic Carbene-Protected Gold Nanoparticles: Size-Controlled Synthesis, Stability, and Optical Properties.

NHC-Au complexes were used to prepare stable, water-soluble, NHC-protected gold nanoparticles. The water-soluble, charged nature of the nanoparticles permitted analysis by polyacrylamide gel electrophoresis (PAGE), which showed that the nanoparticles were highly monodisperse, with tunable core diameters between 2.0 and 3.

Exploring the atomic structure of 1.8nm monolayer-protected gold clusters with aberration-corrected STEM.

Monolayer-protected (MP) Au clusters present attractive quantum systems with a range of potential applications e.g. in catalysis.

Jahn-Teller effects in Au(SR).

The relationship between oxidation state, structure, and magnetism in many molecules is well described by first-order Jahn-Teller distortions. This relationship is not yet well defined for ligated nanoclusters and nanoparticles, especially the nano-technologically relevant gold-thiolate protected metal clusters. Here we interrogate the relationships between structure, magnetism, and oxidation state for the three stable oxidation states, -1, 0 and +1 of the thiolate protected nanocluster Au(SR).

Conformation and dynamics of the ligand shell of a water-soluble Au102 nanoparticle.

Inorganic nanoparticles, stabilized by a passivating layer of organic molecules, form a versatile class of nanostructured materials with potential applications in material chemistry, nanoscale physics, nanomedicine and structural biology. While the structure of the nanoparticle core is often known to atomic precision, gaining precise structural and dynamical information on the organic layer poses a major challenge. Here we report a full assignment of (1)H and (13)C NMR shifts to all ligands of a water-soluble, atomically precise, 102-atom gold nanoparticle stabilized by 44 para-mercaptobenzoic acid ligands in solution, by using a combination of multidimensional NMR methods, density functional theory calculations and molecular dynamics simulations.

Hydrophobic pocket targeting probes for enteroviruses.

Visualization and tracking of viruses without compromising their functionality is crucial in order to understand virus targeting to cells and tissues, and to understand the subsequent subcellular steps leading to virus uncoating and replication. Enteroviruses are important human pathogens causing a vast number of acute infections, and are also suggested to contribute to the development of chronic diseases like type I diabetes. Here, we demonstrate a novel method to target site-specifically the hydrophobic pocket of enteroviruses.

Molecule-like photodynamics of Au102(pMBA)44 nanocluster.

Photophysical properties of a water-soluble cluster Au102(pMBA)44 (pMBA = para-mercaptobenzoic acid) are studied by ultrafast time-resolved mid-IR spectroscopy and density functional theory calculations in order to distinguish between molecular and metallic behavior. In the mid-IR transient absorption studies, visible or near-infrared light is used to electronically excite the sample, and the subsequent relaxation is monitored by studying the transient absorption of a vibrational mode in the ligands. Based on these studies, a complete picture of energy relaxation dynamics is obtained: (1) 0.

Solvation chemistry of water-soluble thiol-protected gold nanocluster Au₁₀₂ from DOSY NMR spectroscopy and DFT calculations.

The hydrodynamic diameter of Aum(pMBA)n [(m, n) = (102, 44) and (144, 60)] clusters in aqueous media was determined via DOSY NMR spectroscopy. The apparent size of the same (n, m) cluster depends on the counter ion of the deprotonated pMBA(-) ligand as explained by the competing ion-pair strength and hydrogen bonding interactions studied in DFT calculations. The choice of the counter ion affects the surface chemistry and molecular structure at the organic/water interface, which is relevant for biological applications.

The structural diversity of benzofuran resorcinarene leads to enhanced fluorescence.

An unexpected and previously unknown resorcinarene mono-crown with a fused benzofuran moiety in its macrocyclic core was obtained as a byproduct from a bridging reaction of tetramethoxy resorcinarene with tetraethylene glycol ditosylate. The formation of the fused benzofuran moiety in the resorcinarene macrocycle resulted in a unique rigid and puckered boat conformation, as shown by XRD studies in the solid state. Modification of the macrocycle was also observed to affect the photophysical properties in solution by enhancing the fluorescence brightness compared with a conventional resorcinarene macrocycle.

4,4-Di-fluoro-2,3;5,6-bis-(tetra-methylene)-4-bora-3a,4a-di-aza-s-indacene (LD540).

The title compound, C18H21BF2N2, is a lipophilic dye based on a BODIPY fluoro-phore backbone, which was developed for microscopic imaging of lipid droplets; the mol-ecule has a planar BODIPY core [dihedral angle between the pyrrole rings = 2.3 (3)°] and two tetra-methyl-ene substituents at the 2,3- and 5,6-positions in a half-chair conformation. One of the tetra-methyl-ene substituents is disordered over two two sets of sites with site occupancies of 0.

Site-specific targeting of enterovirus capsid by functionalized monodisperse gold nanoclusters.

Development of precise protocols for accurate site-specific conjugation of monodisperse inorganic nanoparticles to biological material is one of the challenges in contemporary bionanoscience and nanomedicine. We report here a successful site-specific covalent conjugation of functionalized atomically monodisperse gold clusters with 1.5-nm metal cores to viral surfaces.

Vibrational Perturbations and Ligand-Layer Coupling in a Single Crystal of Au144(SC2H4Ph)60 Nanocluster.

We have determined vibrational signatures and optical gap of the Au144(PET)60 (PET: phenylethylthiol, SC2H4Ph) nanocluster solvated in deuterated dichloromethane (DCM-D2, CD2Cl2) and in a single crystal. For crystals, solid-state (13)C NMR and X-ray diffraction were also measured. A revised value of 2200 cm(-1) (0.

Nondestructive size determination of thiol-stabilized gold nanoclusters in solution by diffusion ordered NMR spectroscopy.

Diffusion ordered NMR spectroscopy (DOSY) was used as an analytical tool to estimate the size of thiol-stabilized gold nanoclusters in solution, namely, phenylethanethiol (PET) stabilized Au25(PET)18, Au38(PET)24, and Au144(PET)60. This was achieved by determining the diffusion coefficient and hydrodynamic radius from solution samples that were confirmed to be monodispersed by electrospray ionization mass spectrometry. The average cluster diameters obtained by this technique were estimated to be 1.

The missing member of the partially O-alkylated resorcinarene family: synthesis and conformation of methyl tetramethoxy resorcinarene.

An improved Lewis acid catalyzed synthesis method for methyl tetramethoxy resorcinarene is described, which produced the missing lower rim methyl derivative of this partially O-alkylated resorcinarene family. Structural characterization by means of variable temperature NMR experiments and single crystal X-ray diffraction studies furthermore revealed that the resorcinarene core adopts different conformations in the solid state and in solution.

One-pot synthesis and characterization of subnanometre-size benzotriazolate protected copper clusters.

A simple one-pot method for the preparation of subnanometre-size benzotriazolate (BTA) protected copper clusters, Cu(n)BTA(m), is reported. The clusters were analyzed by optical and infrared spectroscopy, mass spectrometry and transmission electron microscopy together with computational methods. We suggest a structural motif where the copper core of the Cu(n)BTA(m) clusters is protected by BTA-Cu(i)-BTA units.

Resorcinarene bis-thiacrowns: prospective host molecules for silver encapsulation.

Mixed-donor atom tetramethoxy resorcinarene bis-thiacrown hosts, in which the crown unit contains both hard oxygen and soft sulfur donor atoms, were synthesized for soft metal cation binding. The binding properties were investigated both in solution and in the solid state by NMR spectroscopy and X-ray crystallography. It was found that the resorcinarene bis-thiacrowns were able to complex silver cations with remarkable affinity forming readily 1:2 host-guest complexes in solution.

Synthesis and structure of mono-bridged resorcinarene host: a ditopic receptor for ammonium guests.

The synthesis and structural properties of tetramethoxy resorcinarene mono-crown-5 (1) are described. The binding characteristics of 1 toward acetylcholine and tetramethylammonium salts were investigated by 1H NMR titration. It was observed that the cavity of 1 provides a better fit to acetylcholine compared to the smaller tetramethylammonium cation, as acetylcholine is able to interact with both the crown ether moiety and the free hydroxyl groups of receptor 1 simultaneously.

Novel tetramethoxy resorcinarene bis-crown ethers.

The synthesis and characterization of new tetramethoxy resorcinarene bis-crown ethers BC4 and BC5 are described. The complexation properties of the compounds toward alkali metal cations were studied by 1H NMR spectroscopy and X-ray crystallography, which revealed that BC5 can accommodate two cations simultaneously inside the crown pockets formed by the crown ether bridges and the resorcinarene skeleton. [reaction: see text].