Chemically Selective Imaging of Individual Bonds through Scanning Electron Energy-Loss Spectroscopy: Disulfide Bridges Linking Gold Nanoclusters
As proof-of-principle of chemically selective, spatially resolved imaging of individual bonds, we carry out electron energy-loss spectroscopy in a scanning transmission electron microscopy instrument on atomically precise, thiolate-coated gold nanoclusters linked with 5,5'-bis(mercaptomethyl)-2,2'-bipyridine dithiol ligands. The images allow the identification of bridging disulfide bonds (R-S-S-R) between clusters, and X-ray photoelectron spectra support the finding.
Atomically Precise Nanocluster Assemblies Encapsulating Plasmonic Gold Nanorods.
The self-assembled structures of atomically precise, ligand-protected noble metal nanoclusters leading to encapsulation of plasmonic gold nanorods (GNRs) is presented. Unlike highly sophisticated DNA nanotechnology, this strategically simple hydrogen bonding-directed self-assembly of nanoclusters leads to octahedral nanocrystals encapsulating GNRs. Specifically, the p-mercaptobenzoic acid (pMBA)-protected atomically precise silver nanocluster, Na4 [Ag44 (pMBA)30 ], and pMBA-functionalized GNRs were used. High-resolution transmission and scanning transmission electron tomographic reconstructions suggest that the geometry of the GNR surface is responsible for directing the assembly of silver …
Covalent and non-covalent coupling of a Au102 nanocluster with a fluorophore: energy transfer, quenching and intracellular pH sensing
Interactions between an atomically precise gold nanocluster Au102(p-MBA)44 (p-MBA = para mercaptobenzoic acid) and a fluorescent organic dye molecule (KU, azadioxatriangulenium) are studied. In solution, the constituents form spontaneously a weakly bound complex leading to quenching of fluorescence of the KU dye via energy transfer. The KU can be separated from the complex by lowering pH, leading to recovery of fluorescence, which forms a basis for an optical reversible pH sensor. However, the sensor is not a stable entity, which could be delivered inside cells. For this purpose, a covalently bound hybrid is synthesized by linking the KU dye to the ligand layer of the cluster via an ester b…
Small hydrocarbon cyclophanes: Synthesis, X-ray analysis and molecular modelling
Small hydrocarbon cyclophanes, such as [2.2.0]m,m,m-cyclophane (20) and [2.2.0]p,m,m-cyclophane (21), are strained analogues of the well-known π-prismand [2.2.2]p,p,p-cyclophane (1). The synthetic route to these molecules is based on well-established cyclophane methodology which offers a general access to a whole family of hydrocarbon cyclophanes. Single crystal X-ray analysis and molecular modelling showed that the reduction of the ring size from 18-membered (1) to 14-membered (21) or 13-membered (20) has a substantial effect on the size and the shape of the cyclophane’s cavity, thus blocking its ability to complex Ag+ ions. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)
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. A probe, a derivative of Pleconaril, was developed and conjugated to various labels that enabled the visualization of enteroviruses under light and electron micros…
Dithiol-Induced Oligomerization of Thiol-Protected Gold Nanoclusters
Controlled synthesis of nanostructure oligomers requires detailed understanding of their wet chemistry and the forces driving the polymerization process. In this paper, we report the main factors affecting the reaction yields of a dithiol-induced synthesis of covalently bound nanocluster dimers and oligomers and present a detailed analysis of possible reaction mechanisms. We synthesize the nanocluster oligomers using monodisperse para-mercaptobenzoic acid (p-MBA)-protected gold nanoclusters with a nominal composition of Au∼250(p-MBA)n to minimize ensemble effects on size, shape, and surface structure. Ligand exchange was performed on the nanoclusters with five different dithiol linkers: 5,5…
(E)-7-(Pyren-1-yl)hept-6-enoic acid
The title compound, C23H20O2, is a precursor of a pyrene-based supramolecular element for non-covalent attachment to a carbon nanotube. The asymmetric unit contains three independent molecules. The carboxylic acid group in each of these molecules serves as an intermolecular hydrogen-bond donor and acceptor, generating the commonly observed double O—H...O hydrogen-bond motif in an eight-membered ring. Weaker C—H...O, π–π [centroid–centroid distance = 3.968 (4) Å] and C—H...π interactions are also found in the crystal structure.
Photodynamics of a Molecular Water-Soluble Nanocluster Identified as Au130(pMBA)50
Photodynamics of a highly monodisperse sample of a water-soluble gold nanocluster tentatively identified as Au130(pMBA)50 (pMBA = p-mercaptobenzoic acid) was studied by mid-IR transient absorption spectroscopy with visible excitation. The observed long-lived excited states (>1 ns) indicate a molecular behavior of the cluster. By combining the transient absorption data with DFT calculation results the observed relaxation dynamics could be fully explained by identifying several relaxation processes involving singlet and triplet manifolds. The results indicate that the cluster may have interesting transient magnetic properties due to a long-lived triplet population.
Template-Free Supracolloidal Self-Assembly of Atomically Precise Gold Nanoclusters : From 2D Colloidal Crystals to Spherical Capsids
We report supracolloidal self-assembly of atomically precise and strictly monodisperse gold nanoclusters involving p-mercaptobenzoic acid ligands (Au102-pMBA44) under aqueous conditions into hexagonally packed monolayer-thick two-dimensional facetted colloidal crystals (thickness 2.7 nm) and their bending to closed shells leading to spherical capsids (d ca. 200 nm), as controlled by solvent conditions. The 2D colloidal assembly is driven in template-free manner by the spontaneous patchiness of the pMBA ligands around the Au102-pMBA44 nanoclusters preferably towards equatorial plane, thus promoting inter-nanocluster hydrogen bonds and high packing to planar sheets. More generally, the findin…
Structural characterization of site-modified nanocapsid with monodispersed gold clusters
AbstractHepatitis E Virus-like particles self-assemble in to noninfectious nanocapsids that are resistant to proteolytic/acidic mucosal delivery conditions. Previously, the nanocapsid was engineered to specifically bind and enter breast cancer cells, where successful tumor targeting was demonstrated in animal models. In the present study, the nanocapsid surface was modified with a solvent-exposed cysteine to conjugate monolayer protected gold nanoclusters (AuNC). Unlike commercially available gold nanoparticles, AuNCs monodisperse in water and are composed of a discrete number of gold atoms, forming a crystalline gold core. Au102pMBA44 (Au102) was an ideal conjugate given its small 2.5 nm s…
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) 0.5-1.5 ps electronic relaxation, (2) 6.8 ps vibrational cooling, (3) intersystem crossing from the low…
All-Solid-State Ag+-ISE Based on [2.2.2]p,p,p-Cyclophane
All-solid-state ion-selective electrodes (ISEs) based on two ionophores with similar structure, i.e., [2.2.2] p,p,p-cyclophane and [2.2.2]m,p,p-cyclophane, were prepared and investigated. The ion-selective membranes were composed of the corresponding ionophore (1 %), potassium tetrakis(4-chlorophenyl)borate (0.5 %), 2-nitrophenyl octyl ether (65–66 %), and PVC (33 %). The ion-selective membrane was placed on top of a layer of the conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), working as ion-to-electron transducer. The resulting all-solid-state ISEs were conditioned in 0.01 M AgNO3 and investigated as Ag+-ISEs. The results show that [2.2.2] p,p,p-cyclophane is much more select…
Concave π-prismand hydrocarbon [2.2.2]cyclophanes and their crystalline Ag-triflate complexes
New small concave hydrocarbon cyclophanes were prepared via the well-known HD-2SO2-method. The cyclophanes obtained are isomers of the very well-known [2.2.2]p,p,p-cyclophane, C24H24, a π-prismand efficiently complexing Ag+-ion. X-ray crystal structure determinations showed the bis-sulfide 7 (1,10-dithia[3.3.2]m,p,p-cyclophane) to be helically chiral and that the conformation of the parent hydrocarbon cyclophane 13 ([2.2.2]m,p,p-cyclophane) does not change dramatically upon complexation with the Ag+-ion. The 16- and 17-membered [2.2.2]m,m,p- and [2.2.2]m,p,p-cyclophane (15 and 16) also act as π-prismands and form surprisingly similar crystalline 1:1 Ag-triflate complexes (π-prismates) as th…
ChemInform Abstract: Concave π-Prismand Hydrocarbon [2.2.2]Cyclophanes and Their Crystalline Ag-Triflate Complexes.
New small concave hydrocarbon cyclophanes were prepared via the well-known HD-2SO2-method. The cyclophanes obtained are isomers of the very well-known [2.2.2]p,p,p-cyclophane, C24H24, a π-prismand efficiently complexing Ag+-ion. X-ray crystal structure determinations showed the bis-sulfide 7 (1,10-dithia[3.3.2]m,p,p-cyclophane) to be helically chiral and that the conformation of the parent hydrocarbon cyclophane 13 ([2.2.2]m,p,p-cyclophane) does not change dramatically upon complexation with the Ag+-ion. The 16- and 17-membered [2.2.2]m,m,p- and [2.2.2]m,p,p-cyclophane (15 and 16) also act as π-prismands and form surprisingly similar crystalline 1:1 Ag-triflate complexes (π-prismates) as th…
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 1.7, 2.2, and 3.1 nm for the Au25(PET)18, Au38(PET)24, and Au144(PET)60 nanoclusters, respectively, which were shown to agree well with the average diameters of the corresponding single crystal or t…
Covalent and non-covalent coupling of a Au102 nanocluster with a fluorophore : energy transfer, quenching and intracellular pH sensing
Interactions between an atomically precise gold nanocluster Au102(p-MBA)44 (p-MBA = para mercaptobenzoic acid) and a fluorescent organic dye molecule (KU, azadioxatriangulenium) are studied. In solution, the constituents form spontaneously a weakly bound complex leading to quenching of fluorescence of the KU dye via energy transfer. The KU can be separated from the complex by lowering pH, leading to recovery of fluorescence, which forms a basis for an optical reversible pH sensor. However, the sensor is not a stable entity, which could be delivered inside cells. For this purpose, a covalently bound hybrid is synthesized by linking the KU dye to the ligand layer of the cluster via an ester b…
Chemically Selective Imaging of Individual Bonds through Scanning Electron Energy-Loss Spectroscopy : Disulfide Bridges Linking Gold Nanoclusters
As proof-of-principle of chemically selective, spatially resolved imaging of individual bonds, we carry out electron energy-loss spectroscopy in a scanning transmission electron microscopy instrument on atomically precise, thiolate-coated gold nanoclusters linked with 5,5′-bis(mercaptomethyl)-2,2′-bipyridine dithiol ligands. The images allow the identification of bridging disulfide bonds (R–S–S–R) between clusters, and X-ray photoelectron spectra support the finding. peerReviewed
Covalently linked multimers of gold nanoclusters Au102(p-MBA)44 and Au∼250(p-MBA)n
We present the synthesis, separation, and characterization of covalently-bound multimers of para-mercaptobenzoic acid (p-MBA) protected gold nanoclusters. The multimers were synthesized by performing a ligand-exchange reaction of a pre-characterized Au102(p-MBA)44 nanocluster with biphenyl-4,4′-dithiol (BPDT). The reaction products were separated using gel electrophoresis yielding several distinct bands. The bands were analyzed by transmission electron microscopy (TEM) revealing monomer, dimer, and trimer fractions of the nanocluster. TEM analysis of dimers in combination with molecular dynamics simulations suggest that the nanoclusters are covalently bound via a disulfide bridge between BP…
Covalently linked multimers of gold nanoclusters Au102(p-MBA)44and Au∼250(p-MBA)n
We present the synthesis, separation, and characterization of covalently-bound multimers of para-mercaptobenzoic acid (p-MBA) protected gold nanoclusters. The multimers were synthesized by performing a ligand-exchange reaction of a pre-characterized Au102(p-MBA)44 nanocluster with biphenyl-4,4′-dithiol (BPDT). The reaction products were separated using gel electrophoresis yielding several distinct bands. The bands were analyzed by transmission electron microscopy (TEM) revealing monomer, dimer, and trimer fractions of the nanocluster. TEM analysis of dimers in combination with molecular dynamics simulations suggest that the nanoclusters are covalently bound via a disulfide bridge between BP…
Opiskelijoiden kokemuksia kemian opiskelusta koronakevään aikana
Koronapandemia sulki korkeakoulut keväällä 2020 hyvin nopealla aikataululla. Jyväskylän yliopiston kemian laitoksella siirryttiin etäopiskelujaksolle ja tehtiin nopea digiloikka etäopiskelun mahdollistamiseksi. Opiskelijoiden kokemuksia kevään 2020 etäopiskelujaksosta kartoitettiin kolmen eri kyselyn avulla. Kyselyiden tulosten perusteella kemian etäopetusta pyrittiin kehittämään nopealla aikataululla paremmin opiskelijoiden tarpeita vastaavaksi. Vastausten perusteella kemian opiskelijat pitivät kemian laitoksen etäopiskelun toteutustapaa pääosin onnistuneena. Etäopiskelujakson aikana haasteeksi nousivat opiskelijoiden omien opiskelutaitojen kehittäminen, kurssien sopivien työmäärien asetta…
Optimizing the SYBR green related cyanine dye structure to aim for brighter nucleic acid visualization
In recent years, the studies of RNA and its use for the development of RNA based vaccines have increased drastically. Although cyanine dyes are commonly used probes for studying nucleic acids, in a wide range of applications, there is still a growing need for better and brighter dyes. To meet this demand, we have systematically studied the structure of SYBR green-related cyanine dyes to gain a deeper understanding of their interactions with biomolecules especially how they interact with nucleic acids and the structural components which makes them strongly fluorescent. Herein, five new dyes were synthesized, and their photophysical properties were evaluated. Observations of photophysical cha…
Development of functionalized SYBR green II related cyanine dyes for viral RNA detection
Abstract Fluorescent probes for sensing nucleic acids have found widespread use in the field of cell and molecular biology. However, probes combined with potential for post-synthetic conjugation, e.g. for intra-endosomal measurements of RNA, are unavailable. Herein we developed cyanine dyes that can be conjugated to viral capsid or other targets. First, we solved the crystal structure of SYBR Green II. The structural elucidation of this commonly used RNA probe provided the basis for synthesizing similar molecules with much desired function for post-synthetic conjugation. To address this need, cyanine dyes were prepared using an alternative synthesis protocol. All studied compounds showed co…
Crystal structure of 5-{3-[2,6-dimethyl- 4-(5-methyl-1,2,4-oxadiazol-3-yl)phenoxy]propyl}- N-(11-hydroxyundecyl)isoxazole-3-carboxamide hemihydrate
The crystal structure and supramolecular features of 5-{3-[2,6-dimethyl-4-(5-methyl-1,2,4-oxadiazol-3-yl)phenoxy]propyl}-N-(11-hydroxyundecyl)isoxazole-3-carboxamide hemihydrate, a derivative of antiviral ‘WIN compounds’, are reported.
Ultrafast electronic relaxation and vibrational cooling dynamics of Au 144(SC2H4Ph)60 nanocluster probed by transient mid-IR spectroscopy
Energy relaxation dynamics of a gold nanocluster with atomically precise composition, Au144(SC2H4Ph)60, is studied by transient mid-IR spectroscopy. The experiment is designed to simultaneously pro...
Liquid-phase alkali-doping of individual carbon nanotube field-effect transistors observed in real-time
The carbon nanotube (CNT) is known to be very sensitive to changes in its surrounding environment. Our study is on the effects of mild, liquid-phase alkali-doping on electronic transport in individual CNTs. We find clear and consistent reversal from p- to n-type behavior, with all seven investigated CNT field-effect transistors (FETs) retaining a similar ON/OFF ratio and subthreshold slope. We have also measured the realtime electronic response during liquid-phase doping, and demonstrate detection of alkali cations with a signal response that ranges over more than three orders of magnitude. The doping is fully reversible upon exposure to oxygen, and the doping cycle is repeatable. We also c…
Towards Controlled Synthesis of Water-Soluble Gold Nanoclusters : Synthesis and Analysis
Water-soluble gold nanoclusters with well-defined molecular structures and stability possess particular biophysical properties making them excellent candidates for biological applications as well as for fundamental spectroscopic studies. The currently existing synthetic protocols for atomically monodisperse thiolate-protected gold nanoclusters (AuMPCs) have been widely expanded with organothiolates, yet the direct synthesis reports for water-soluble AuMPCs are still deficient. Here, we demonstrate a wet-chemistry pH-controlled synthesis of two large water-soluble nanoclusters utilizing p-mercaptobenzoic acid (pMBA), affording different sizes of plasmonic AuMPCs on the preparative scale (∼7 …
N-Benzyl-2,3,4,5,6-pentafluorobenzamide
In the title compound, C14H8F5NO, the dihedral angle between the planes of the pentafluorophenyl and phenyl rings is 18.34 (5)°. An intermolecular N—H...O hydrogen bond between the amide groups connects these molecules to form an infinite chain through the crystal structure. One weak intermolecular C—H...O contact and one π–π interaction [centroid–centroid distance = 3.772 (3) Å] are also involved in crystal structure stabilization between the phenyl rings.
Characterization of NOM
Worldwide reports over the last few decades have shown that the amount of natural organic matter (NOM) in surface water is continuously increasing, which has an adverse effect on drinking water purification. For many practical and hygienic reasons, the presence of NOM in drinking water is undesirable. Various technologies have been proposed for NOM removal with varying degrees of success. The properties and amount of NOM, however, can significantly affect the process efficiency. To improve and optimize these processes, it is essential to characterize and quantify NOM at various points during purification and treatment. It is also important to be able to understand and predict the reactivity…
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. Water-soluble Au102(para-mercaptobenzoic acid)44 clusters, functionalized by maleimide linkers to target cysteines of viral capsid proteins, were synthesized and conjugated to enteroviruses echovirus 1 and coxsackievirus B3. Quantitative analysis of transmission electron microscopy images and the known virus structures showed …
Acid–Base Properties and Surface Charge Distribution of the Water-Soluble Au102(pMBA)44 Nanocluster
The pKa of the p-mercaptobenzoic acid (pMBA) ligands in the Au102(pMBA)44 nanocluster was measured by using acid–base and IR titration. The observed macroscopic pKa = 6.18 ± 0.05 is significantly more basic than that of free pMBA (pKa = 4.16), and the protonation behavior is anticooperative according to the Hill coefficient n = 0.64 ± 0.04. The cluster is truly water-soluble when more than 22 and insoluble when fewer than 7 ligands are in the deprotonated state. In order to obtain more insight into the anticooperative character, the cluster was modeled at pH ∼6.2 using constant pH molecular dynamics simulations. The pKa values of the individual pMBAs are in the range of 5.18–7.58, depending…
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.
Systematic study of SYBR green chromophore reveals major improvement with one heteroatom difference
Five nucleic acid binding cyanine dyes were synthesized and their photophysical properties were evaluated. Changing a single heteroatom in the chromophore causes major differences both in brightness and photostability between the dyes. With such alteration, the brightness of the chromophore increased two-fold compared to the one found in SYBR Green I.
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2-(2-Iodoethyl)isoindole-1,3-dione
The title compound, C10H8INO2, is an N-substituted phthalimide derivative in which the crystallographic intermolecular contact pattern consists of I⋯I, C—H⋯I, C—H⋯O and aromatic π–π interactions.
Polymorphic and solvate structures of ethyl ester and carboxylic acid derivatives of WIN 61893 analogue and their stability in solution
3-Ethyl ester- (1) and 3-carboxylic acid-isoxazole (2) derivatives of an antiviral drug analogue WIN 61893 were synthesized and characterized by X-ray crystallography and NMR spectroscopy. Crystallization experiments afforded two polymorphic structures for the ethyl ester derivative and two solvate structures for the carboxylic acid derivative based on their ability to form intermolecular hydrogen bonding interactions with the solvent molecules. The conformations of the derivatives depended greatly on the orientation of the planar isoxazole and phenyl-oxadiazole ring systems with respect to one another and were found to take up perpendicular, linear or tilted conformations. The carboxylic a…
Tailoring the interaction between a gold nanocluster and a fluorescent dye by cluster size : creating a toolbox of range-adjustable pH sensors
We present a novel strategy for tailoring the fluorescent azadioxatriangulenium (KU) dye-based pH sensor to the target pH range by regulating the pKa value of the gold nanoclusters. Based on the correlation between the pKa and surface curvature of ligand-protected nanoparticles, the pKa value of the gold nanoclusters was controlled by size. In particular, three different-sized para-mercaptobenzoic acid (p-MBA) protected gold nanoclusters, Au25(p-MBA)18, Au102(p-MBA)44, and Au210–230(p-MBA)70–80 were used as the regulator for the pH range of the KU response. The negatively charged gold nanoclusters enabled the positively charged KU to bind to the surface, forming a complex and quenching the …
Silver Ion-Selective Electrodes Based on π-Coordinating Ionophores Without Heteroatoms
Ion-selective electrodes (ISEs) were constructed by using spherical hydrocarbons (cyclophanes) as π-coordinating ionophores in solvent polymeric membranes. Four structurally similar cyclophanes, i. e., [2.2.2]p,p,p-cyclophane, [2.2.2]m,p,p-cyclophane, [2.2.1]p,p,p-cyclophane and [2.2.1]m,p,p-cyclophane were studied as ionophores for Ag+. The ion-selective membranes were composed of the corresponding ionophore (1%), potassium tetrakis(4-chlorophenyl)borate (0.5%), 2-nitrophenyl octyl ether (65–66%) and PVC (32–33%). The ion-selective membrane was placed on top of a layer of the conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), working as ion-to-electron transducer. The selectivit…
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 fluorophore backbone, which was developed for microscopic imaging of lipid droplets; the molecule has a planar BODIPY core [dihedral angle between the pyrrole rings = 2.3 (3)°] and two tetramethylene substituents at the 2,3- and 5,6-positions in a half-chair conformation. One of the tetramethylene substituents is disordered over two two sets of sites with site occupancies of 0.5. In the crystal, pairs of C—H...F interactions link the molecules into inversion dimers. Neighbouring dimers are linked by further C—H...F interactions, forming an infinite array. C—H...π and π–π [centroid–centroid distance = 4.360 (3) Å] interac…
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) (0.27 eV) was obtained for the optical gap in both phases. The vibrational spectra of solvated AU144(PET)60 closely resembles that of neat PET, while the crystalline-state spectrum exhibits significant inhomogeneous spectral broadening, frequency shifts, intensity transfer between vibrational modes, and an increase in the overtone and combination transition intensities. Spectral broa…
Exploring the atomic structure of 1.8 nm monolayer-protected gold clusters with aberration-corrected STEM
Abstract Monolayer-protected (MP) Au clusters present attractive quantum systems with a range of potential applications e.g. in catalysis. Knowledge of the atomic structure is needed to obtain a full understanding of their intriguing physical and chemical properties. Here we employed aberration-corrected scanning transmission electron microscopy (ac-STEM), combined with multislice simulations, to make a round-robin investigation of the atomic structure of chemically synthesised clusters with nominal composition Au 144 (SCH 2 CH 2 Ph) 60 provided by two different research groups. The MP Au clusters were “weighed” by the atom counting method, based on their integrated intensities in the high …
N-[1-(Silatran-1-yl)propyl]pentafluorobenzamide
In the title compound {systematic name: N-[3-(5-aza-2,8,9-trioxa-1-silabicyclo[3.3.3]undecan-1-yl)propyl]pentafluorobenzamide}, C16H19F5N2O4Si, unexpected weak anion⋯π-type C=O⋯C(aromatic) interactions form a dimer [O⋯C distances of 3.096 (3) and 3.036 (3) A]. These dimers are further connected by a normal N—H⋯O hydrogen bond [2.955 (2) A], from the amide H atom to one of the silatrane O atoms. Also, four intermolecular contacts between CH groups and silatrane O and F atoms [3.101(3)–3.406 (3) A] are observed.
An overview of the methods used in the characterisation of natural organic matter (NOM) in relation to drinking water treatment
Natural organic matter (NOM) is found in all surface, ground and soil waters. During recent decades, reports worldwide show a continuing increase in the color and NOM of the surface water, which has an adverse affect on drinking water purification. For several practical and hygienic reasons, the presence of NOM is undesirable in drinking water. Various technologies have been proposed for NOM removal with varying degrees of success. The properties and amount of NOM, however, can significantly affect the process efficiency. In order to improve and optimise these processes, the characterisation and quantification of NOM at different purification and treatment processes stages is important. It …
CCDC 999257: Experimental Crystal Structure Determination
Related Article: Kirsi Salorinne, Tanja Lahtinen, Varpu Marjomäki, Hannu Häkkinen|2014|CrystEngComm|16|9001|doi:10.1039/C4CE01152J
CCDC 999254: Experimental Crystal Structure Determination
Related Article: Kirsi Salorinne, Tanja Lahtinen, Varpu Marjomäki, Hannu Häkkinen|2014|CrystEngComm|16|9001|doi:10.1039/C4CE01152J
CCDC 999255: Experimental Crystal Structure Determination
Related Article: Kirsi Salorinne, Tanja Lahtinen, Varpu Marjomäki, Hannu Häkkinen|2014|CrystEngComm|16|9001|doi:10.1039/C4CE01152J
CCDC 999256: Experimental Crystal Structure Determination
Related Article: Kirsi Salorinne, Tanja Lahtinen, Varpu Marjomäki, Hannu Häkkinen|2014|CrystEngComm|16|9001|doi:10.1039/C4CE01152J
(E)-7-(Pyren-1-yl)hept-6-enoic acid
The title compound, C₂₃H₂₀O₂, is a precursor of a pyrene-based supramolecular element for non-covalent attachment to a carbon nanotube. The asymmetric unit contains three independent molecules. The carboxylic acid group in each of these molecules serves as an intermolecular hydrogen-bond donor and acceptor, generating the commonly observed double O-H...O hydrogen-bond motif in an eight-membered ring. Weaker C-H...O, π π [centroid-centroid distance = 3.968 (4) Å] and C-H...π interactions are also found in the crystal structure. peerReviewed