A new donor for charge-transfer systems: synthesis and properties of 2,4,7,9-tetramethyl-1,6-dithiapyrene (TMDTP) and structure of (TMDTP)(PF)·2THF and TMDTP-TCNQ.

The heterocyclic donor molecule 2,4,7,9-tetramethyl-1,6-dithiapyrene (TMDTP) has been synthesized in five steps. Oxidation of TMDTP is facile ( = 0.27 V and = 0.

Hydrolytic Stability of 3-Aminopropylsilane Coupling Agent on Silica and Silicate Surfaces at Elevated Temperatures.

3-Aminopropylsilane (APS) coupling agent is widely used in industrial, biomaterial, and medical applications to improve adhesion of polymers to inorganic materials. However, during exposure to elevated humidity and temperature, the deposited APS layers can decompose, leading to reduction in coupling efficiency, thus decreasing the product quality and the mechanical strength of the polymer-inorganic material interface. Therefore, a better understanding of the chemical state and stability of APS on inorganic surfaces is needed.

Excited state kinetics of anthracene-bridge-aniline intramolecular exciplexes.

We report on the synthesis and characterization of fluorescent halogen substituted anthracene-bridge-aniline (ABA) supermolecules that undergo structural reorganization on photoexcitation to form transient complexes. The syntheses were achieved in high yields on a large scale and the molecular structures were confirmed by single crystal X-ray diffraction. The photophysics of the ABA supermolecules were investigated using steady state and time resolved optical spectroscopy.

Introducing a standard method for experimental determination of the solvent response in laser pump, X-ray probe time-resolved wide-angle X-ray scattering experiments on systems in solution.

In time-resolved laser pump, X-ray probe wide-angle X-ray scattering experiments on systems in solution the structural response of the system is accompanied by a solvent response. The solvent response is caused by reorganization of the bulk solvent following the laser pump event, and in order to extract the structural information of the solute, the solvent response has to be treated. Methodologies capable of doing so include both theoretical modelling and experimental determination of the solvent response.

The metallic transport of (TMTSF)2X organic conductors close to the superconducting phase.

Comparing resistivity data of the quasi-one-dimensional superconductors (TMTSF)2PF6 and (TMTSF)2ClO4 along the least conducting c(⋆)-axis and along the high conductivity a-axis as a function of temperature and pressure, a low temperature regime is observed in which a unique scattering time governs the transport along both directions of these anisotropic conductors. However, the pressure dependence of the anisotropy implies a large pressure dependence of the interlayer coupling. This is in agreement with the results of first-principles density functional theory calculations implying methyl group hyperconjugation in the TMTSF molecule.

Tracking single coccolith dissolution with picogram resolution and implications for CO2 sequestration and ocean acidification.

Coccoliths are micrometer scale shields made from 20 to 60 individual calcite (CaCO(3)) crystals that are produced by some species of algae. Currently, coccoliths serve as an important sink in the global carbon cycle, but decreasing ocean pH challenges their stability. Chalk deposits, the fossil remains of ancient algae, have remained remarkably unchanged by diagenesis, the process that converts sediment to rock.

Fulleropyrrolidine end-capped molecular wires for molecular electronics--synthesis, spectroscopic, electrochemical, and theoretical characterization.

In continuation of previous studies showing promising metal-molecule contact properties a variety of C(60) end-capped "molecular wires" for molecular electronics were prepared by variants of the Prato 1,3-dipolar cycloaddition reaction. Either benzene or fluorene was chosen as the central wire, and synthetic protocols for derivatives terminated with one or two fullero[c]pyrrolidine "electrode anchoring" groups were developed. An aryl-substituted aziridine could in some cases be employed directly as the azomethine ylide precursor for the Prato reaction without the need of having an electron-withdrawing ester group present.

Binding of ethanol on calcite: the role of the OH bond and its relevance to biomineralization.

The interaction of OH-containing compounds with calcite, CaCO(3), such as is required for the processes that control biomineralization, has been investigated in a low-water solution. We used ethanol (EtOH) as a simple, model, OH-containing organic compound, and observed the strength of its adsorption on calcite relative to OH from water and the consequences of the differences in interaction on crystal growth and dissolution. A combination of atomic force microscopy (AFM) and molecular dynamics (MD) simulations showed that EtOH attachment on calcite is stronger than HOH binding and that the first adsorbed layer of ethanol is highly ordered.

Structure of a short-lived excited state trinuclear Ag-Pt-Pt complex in aqueous solution by time resolved X-ray scattering.

The present communication describes the identification and structural characterization of a photo-induced transient trinuclear Ag-Pt-Pt complex, in which a pronounced internal structural change of the excited-state PtPOP moiety is observed upon complexation with the Ag ion.

Solution-based fabrication of single-crystalline arrays of organic nanowires.

Organic single-crystalline nanowire arrays, with a length of several hundreds of micrometers and controllable width, are grown on a substrate surface by vertically pulling the substrate out of an organic solution of the molecule of interest. Optical microscopy and atomic force microscopy show that the large-scale arrays are oriented parallel to the pulling direction and are well adhered to the substrate surface. Cross-polarized microscopy, polarized UV-vis absorption, and grazing incidence X-ray diffraction confirm that the arrays have high crystal quality.

Structural tracking of a bimolecular reaction in solution by time-resolved X-ray scattering.

Molecular movies: Time-resolved X-ray scattering provides direct structural information on an electronically excited complex while it is formed in the bimolecular reaction between excited octahydrogen[tetrakis-mu-diphosphito-1kappaP:2kappaP'-diplatinate](4-) (PtPOP*) and thallium ions. In the exciplex one thallium(I) and two platinum(II) ions are found to be collinear.

Time-resolved X-ray scattering of an electronically excited state in solution. Structure of the 3A(2u) state of tetrakis-mu-pyrophosphitodiplatinate(II).

The structure of the (3)A(2u) excited state of tetrakis-mu-pyrophosphitodiplatinate(II) in aqueous solution is investigated by time-resolved X-ray scattering on a time scale from 100 ps to 1 micros after optical pumping. The primary structural parameter, the Pt-Pt distance, is found to be 2.74 A, which is 0.

Anomalous in-plane anisotropy of the onset of superconductivity in (TMTSF)2ClO4.

We report the magnetic-field amplitude and field-angle dependence of the superconducting onset temperature Tconset of the organic superconductor (TMTSF)2ClO4 in magnetic fields H accurately aligned to the conductive ab' plane. We revealed that the rapid increase of the onset fields at low temperatures occurs both for H || b' and H || a, irrespective of the carrier confinement. Moreover, in the vicinity of the Pauli-limiting field, we report a shift of a principal axis of the in-plane field-angle dependence of Tconset.

Superconducting state of the organic conductor (TMTSF)2ClO4.

(TMTSF)2ClO4 is a quasi-one-dimensional organic conductor and superconductor with Tc=1.4 K, and one of at least two Bechgaard salts observed to have upper critical fields far exceeding the paramagnetic limit. Nevertheless, the 77Se NMR Knight shift at low fields reveals a decrease in spin susceptibility chi(s) consistent with singlet spin pairing.

Structural study of four complexes of the M-N2S2 type derived from diethylphenylazothioformamide and the metals palladium, platinum, copper and nickel.

The four electron-transfer complexes trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-kappaS,kappaN2))nickel, trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-kappaS,kappaN2))copper, trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-kappaS,kappaN2))palladium and trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-kappaS,kappaN2))platinum have been crystallized, and their structures have been determined at low temperature. All the complexes are of the M-N2S2 type. The crystals of both the nickel and the copper complex belong to the tetragonal P4(1)2(1)2 system, in which the central metal ion lies on a twofold axis.

2,6,10-Tris(dialkylamino)trioxatriangulenium salts: a new promising fluorophore. Ion-pair formation and aggregation in non-polar solvents.

The D3h symmetric tris(dialkylamino)trioxatriangulenium ((R2N)3TOTA+) ions are structurally related to classical stains and fluorophores such as triphenylmethane dyes and rhodamines. New derivatives of (R2N)3TOTA+, in which long flexible alkyl chains surround the planar and rigid aromatic core, have been synthesized and isolated as hexafluorophosphate salts. In contrast to short-chain derivatives of triphenylmethane dyes, the new compounds described here are soluble in hydrocarbon solvents.

Preparation and structural properties of 7,8-dioxa[6]helicenes and 7a,14c-dihydro-7,8-dioxa[6]helicenes.

The potentially chiral 7,8-dioxa[6]helicenes 1-1c have been prepared by oxidation of their precursors the 7a,14c-dihydro-7,8-dioxa[6]helicenes 3. The crystal structure determination of 3b cis-7a,14c-dihydro-3,12-dibromo-7,8-dioxa[6]helicene unambiguously confirms the cis configuration of the 7a,-14c hydrogens in compounds 3 as previously implied from NMR measurements and also shows that 3b crystallizes in a chiral conformation in the solid state. Selective deuteration of the sterically crowded 1,14 positions of 7,8-dioxa[6]helicene 1 influenced the crystal structure.

Low-temperature structure of indium quantum chains on silicon.

The array of quasi-one-dimensional indium chains in the Si(111)- (4x1)-In surface reconstruction exhibits a phase transition to a low-temperature (8x2) phase. It has been suggested that this phase transition is related to a charge density wave (CDW) formation. The x-ray diffraction results presented here demonstrate that at 20 K the CDW has not yet condensed into a superstructure even though good transverse coupling was established.

Hall effect in the normal phase of the organic superconductor (TMTSF)2PF6.

We report accurate Hall effect measurements performed in the normal phase of the quasi-one-dimensional organic conductor (TMTSF)2PF6 at ambient pressure. The Hall coefficient is found to be strongly temperature dependent all the way from 300 K down to the spin density wave onset arising around 12 K. These new results emphasize the existence of a high temperature regime above 130 K where the Fermi liquid model is not satisfactory.

The geometry and structural properties of the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo.

The geometry of the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrene system in the cationic state was established by X-ray structural resolution of the salts formed between the cation and various anions. The geometry was found to be planar for the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenylium and 2,6,10-tri(tert-butyl)-4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenylium cations with the monovalent anions I(-), BF(4)(-), PF(6)(-), AsF(6)(-), HNO(3).NO(3)(-) and CF(3)SO(3)(-), and the divalent anions S(2)O(6)(2-) and Mo(6)Cl(14)(2-).

Easy access to 3,8-Diaryldifurano[2,3-a:2',3'-f]naphthalenes. A new extended aromatic system.

3,8-Diaryldifurano[2,3-a:2',3'-f]naphthalenes were prepared in two simple steps. First, 1,5-dihydroxynaphthalene and 1-aryl-2-bromodecan-1-ones were condensed to the corresponding naphthalene 1,5-diethers. Second, these intermediates were cyclized using methanesulfonic acid in methylene chloride.