Variable temperature STM study of Co deposition on a dodecanethiol self assembled monolayer

The present scanning tunneling microscopy study reports on the growth processes of Co vapor-deposited on a dodecanethiol (DDT) self-assembled monolayer (SAM)/Au(111). We observe strongly modified surface and depth diffusions of Co adatoms depending on the growth temperature. Co deposited at 300 K shows an extremely incomplete regime of condensation on the organic layer. Besides, Co penetrates the DDT monolayer and resides at the DDT/Au(111) interface as 2D clusters. This phenomenon takes place through defects in the SAM which are transient channels. In contrast, Co deposited at 50 K shows a complete condensation and nucleates on defects of the SAM layer as 3D islands sitting most likely on top of the DDTs. These results are of interest in the growing field of organic spintronics where the quality of the organic/ferromagnetic interface is a key issue.     

Blocking and invasion for reaction–diffusion equations in periodic media

We investigate the large time behavior of solutions of reaction–diffusion equations with general reaction terms in periodic media. We first derive some conditions which guarantee that solutions with compactly supported initial data invade the domain. In particular, we relate such solutions with front-like solutions such as pulsating traveling fronts. Next, we focus on the homogeneous bistable equation set in a domain with periodic holes, and specifically on the cases where fronts are not known to exist. We show how the geometry of the domain can block or allow invasion. We finally exhibit a periodic domain on which the propagation takes place in an asymmetric fashion, in the sense that the invasion occurs in a direction but is blocked in the opposite one.     

Wermer Examples and Currents

We give the first examples of positive closed currents T in ${{\mathbb C}^2}We give the first examples of positive closed currents T in \mathbb C²{{\mathbb C}^2} with continuous potentials, T ùT = 0{T \wedge T = 0}, and whose supports do not contain any holomorphic disk. This gives in particular an affirmative answer to a question of Forn?ss and Levenberg. We actually construct examples with potential of class C ^1,α for all α < 1. This regularity is expected to be essentially optimal.     

Synthesis of symmetrically modified α-cyclodextrins: an efficient and easy method

Efficient and simple synthetic methods of designed specific synthons of cyclodextrins are fundamental for the further development of more sophisticated supramolecular devices. Here, a new two step synthesis was proposed for the obtention of the 6^A,6^C,6^E-triazido-6^A,6^C,6^E-trideoxy-6^B,6^D,6^F-tri-O-methylhexakis-(2,3-di-O-methyl)cyclomaltohexaose on a large scale.     

Isomer effects in the excess enthalpies of mixtures of alkanes and cycloalkanes

Using the Picker flow calorimeter, excess molar enthalpies H ^E have been obtained at 25°C for mixtures of 1,2-, 1,3- and 1,4-cis- and trans-dimethylcyclohexane and cis- and trans-decalin with n-hexadecane and the highly branched C₁₆ isomer, 2,2,4,4,6,8,8-heptamethylnonane. Values of H ^E are also obtained for cis- and trans-decalin mixed with C₆, C₇, and C₉ isomers. Anomalously low values of H ^E occur for normal alkanes mixed with cycloalkanes in the di-equatorial configuration, suggesting the presence of a negative contribution in H ^E possibly due to a restriction of n-alkane molecular motion by the flat, plate-like cycloalkane.     

Demonstration of the utility of DOS-derived fragment libraries for rapid hit derivatisation in a multidirectional fashion

Organic synthesis underpins the evolution of weak fragment hits into potent lead compounds. Deficiencies within current screening collections often result in the requirement of significant synthetic investment to enable multidirectional fragment growth, limiting the efficiency of the hit evolution process. Diversity-oriented synthesis (DOS)-derived fragment libraries are constructed in an efficient and modular fashion and thus are well-suited to address this challenge. To demonstrate the effective nature of such libraries within fragment-based drug discovery, we herein describe the screening of a 40-member DOS library against three functionally distinct biological targets using X-Ray crystallography. Firstly, we demonstrate the importance for diversity in aiding hit identification with four fragment binders resulting from these efforts. Moreover, we also exemplify the ability to readily access a library of analogues from cheap commercially available materials, which ultimately enabled the exploration of a minimum of four synthetic vectors from each molecule. In total, 10–14 analogues of each hit were rapidly accessed in three to six synthetic steps. Thus, we showcase how DOS-derived fragment libraries enable efficient hit derivatisation and can be utilised to remove the synthetic limitations encountered in early stage fragment-based drug discovery.

Fragment-based screening of a shape-diverse collection yielded four hits against three proteins. Up to 14 analogues of each hit were rapidly generated, enabling four fragment growth vectors to be explored using inexpensive materials and reliable synthetic transformations.     

Reactivity of ditert-butyldimethoxystannane with carbon dioxide and methanol: X-ray structure of the resulting complex

The synthesis of dimethyl carbonate from carbon dioxide and methanol was studied with ditert-butyldimethoxystannane under pressure at temperatures ?423 K. The formation of dimethyl carbonate is accompanied by transformation of the stannane into a trinuclear complex, the structure of which has been determined by single-crystal X-ray diffraction technique. The relevance of this specie in the catalytic cycle is demonstrated by conducting recycling runs. A preliminary kinetic study underlines the steric influence of the tert-butyl ancillary ligands in the stabilisation of intermediates, by comparison with the n-butyl homologue.