Klaus-Dieter Warzecha

Photoinitiated domino reactions: N-(adamantyl)phthalimides and N-(adamantylalkyl)phthalimides.

Phthalimides 1-6 undergo photochemical reactions upon direct irradiation as well as triplet sensitization and give rise to new products. Besides formation of the primary photoproducts, the first photochemical step initiates a subsequent thermal domino reaction or a domino sequence of a thermal and a photochemical reaction. The latter, involving two photochemical intramolecular gamma-H abstractions, was observed with phthalimides 1, 3, and 6 and delivered stereospecifically the hexacyclic benzazepine products 12, 19, and 27, respectively. The lowest triplet states of 1-6 were characterized in several solvents upon direct and acetone-sensitized excitation. The intermolecular electron transfer from triethylamine and DABCO was studied, and the radical anions were observed. Electrochemical measurements showed that intramolecular electron transfer from the adamantyl group of 1-6 to the lowest triplet state of the phthalimides is not feasible. The formation of products can be explained by intramolecular H-abstraction from the (alkyl)adamantane to the excited phthalimide, either from the excited singlet state or a hidden upper excited triplet state.

Photocyclization of terpenoid polyalkenes upon electron transfer to a triphenylpyrylium salt A time-resolved study

Photoinduced electron transfer to 2,4,6-triphenylpyrylium tetrafluoroborate (P + BF 4 - ) from terpenoid polyalkenes bearing electron-withdrawing substituents, e.g. 2,6-dimethylhepta-1,5-diene-1,1-dicarbonitrile (D-1) and homologues thereof (D-2, D-3) as well as from other donors, such as 1,1′-biphenyl (BP) and trans-stilbene, has been studied in solution by laser flash photolysis. The main transient in the presence of D-n (n=1, 2, 3) is the triphenylpyranyl radical (P ). Fluorescence quenching of 1* P + by D-n in acetonitrile occurs with rate constants of (0.6–1.7)×10 10 dm3 mol -1 s -1 , whereas those for quenching of the triplet state ( 3* P + ) are significantly smaller, (0.5–3)×10 9 dm3 mol -1 s -1 . The corresponding half-concentrations for fluorescence and triplet quenching are [D] 1/2 =20–40 and 0.02–0.2 mmol dm -3 , respectively. BP and trans-stilbene were used as donors since their radical cations can be detected spectroscopically (λ max =660 and 460 nm, respectively). In addition, the role of BP as a co-donor was examined; the [D] 1/2 values for the quenching of its radical cation are similar to those for the quenching of 3* P + . These findings demonstrate the existence of the polyalkene radical cation (e.g. D-1 + ), although it is not directly detectable, even upon photoionization (λ exc =248 nm). The quantum yields of photodecomposition of D-1 and formation of photoproducts were measured in acetonitrile in the presence of either water or methanol. P + is not directly restored from P . Two mechanisms for electron back-transfer involving the dimer P 2 are proposed and consequences for preparative work are discussed.

Molecular simulation grid

MoSGrid is the acronym for Molecular Simulation Grid, a BMBF funded joint research project with the aim to offer grid services for the broad field of molecular simulations in the D-Grid infrastructure. Besides tendering various codes ranging from quantum molecular calculations (e.g. Gaussian, Turbomole) via molecular dynamics (e.g. Gromacs) to docking approaches (e.g. FlexX) for high performance computing, one of the main goals is the integration of metadata annotation for data mining and knowledge generation. Molecular simulation codes and computational resources are accessed via the MoSGrid portal (http://www.mosgrid.de), which will offer intuitive access to various tools and will support the users with workflows, for an easy import of molecular data, a simple setup and submission of calculations as well as extraction of relevant results. The portal will hide the complexity of the underlying technology by providing a unified user interface making computational chemistry in general more readily available. MoSGrid’s server-based portal is available as open-access and open-source software. Users are relieved from software installations and do not need to have knowledge about the underlying infrastructure. The portal includes portlets specifically set up for the various simulation programs. Commonly used workflows, simple or complex, can be stored in recipe repositories and are available for every user. Moreover, users can develop, improve, publish, and use workflows for their everyday tasks.

MoSGrid: efficient data management and a standardized data exchange format for molecular simulations in a grid environment

The MoSGrid (Molecular Simulation Grid) project is currently establishing a platform that aims to be used by both experienced and inexperienced researchers to submit molecular simulation calculations, monitor their progress, and retrieve the results. It provides a web-based portal to easily set up, run, and evaluate molecular simulations carried out on D-Grid resources. The range of applications available encompasses quantum chemistry, molecular dynamics, and protein-ligand docking codes. In addition, data repositories were developed, which contain the results of calculations as well as “recipes” or workflows. These can be used, improved, and distributed by the users. A distributed high-throughput file system allows efficient access to large amounts of data in the repositories. For storing both the input and output of the calculations, we have developed MSML (Molecular Simulation Markup Language), a CML derivative (Chemical Markup Language). MSML has been designed to store structural information on small as well as large molecules and results from various molecular simulation tools and docking tools. It ensures interoperability of different tools through a consistent data representation. At http://www.mosgrid.de the new platform is already available to the scientific community in a beta test phase. Currently, portlets for generic workflows, Gaussian, and Gromacs applications are publicly accessible [1,2].

MoSGrid: Progress of Workflow driven Chemical Simulations

Motivation: Web-based access to computational chemistry grid resources has proven to be a viable approach to simplify the use of simulation codes. The introduction of recipes allows to reuse already developed chemical workflows. By this means, workflows for recurring basic compute jobs can be provided for daily services. Nevertheless, the same platform has to be open for active workflow development by experienced users. This paper provides an overview of recent developments of the MoSGrid project on providing tools and instruments for building workflow recipes. Contact: birke@uni-paderborn.de

The MoSGrid - e-science gateway: molecular simulations in a distributed computing environment

Modern tools for computational chemistry allow the calculation of a wide range of properties of all sorts of molecules applying various levels of theory. But to perform convincing and significant calculations with these tools not only requires insight into the scientific theory itself, but also knowledge and experience on how to operate the simulation tools. In addition to the general challenge of gaining access to a powerful computing environment, very often a high level of technical competence is necessary to set up and run calculations efficiently. These prerequisites often hamper scientists to routinely use computational tools to support or confirm their perceptions. To overcome some of these problems, the MoSGrid consortium develops an open source e-science portal for grid based environments with respect to computational chemistry. At present residing in the German Grid Initiative (D-Grid), MoSGrid enables users to set up, run and evaluate calculations using tools from the domains of Quantum Chemistry, Molecular Dynamics and Docking [1]. This talk underlines the basic motivation, layout, development, properties and available tools of MoSGrid as well as the procedure of gaining access to the grid environment.

N‐Isobutyl­phthalimide: unidimensional zigzag ribbons of R(10) motifs

Institute of Organic Chemistry, University ofCologne, Greinstr. 4, D-50939 Cologne,GermanyCorrespondence e-mail:klaus.warzecha@uni-koeln.deKey indicatorsSingle-crystal X-ray studyT = 100 KMean (C–C) = 0.002 A˚R factor = 0.039wR factor = 0.095Data-to-parameter ratio = 11.7For details of how these key indicators wereautomatically derived from the article, seehttp://journals.iucr.org/e.Received 28 September 2006Accepted 30 September 2006