Ines dos Santos Vieira

Mechanism of the Living Lactide Polymerization Mediated by Robust Zinc Guanidine Complexes

Zinc bis(chelate) guanidine complexes promote living lactide polymerization at elevated temperatures. By means of kinetic and spectroscopic analyses the mechanism has been elucidated for these special initiators that make use of neutral N-donor ligands. The neutral guanidine function initiates the polymerization by a nucleophilic ring-opening attack on the lactide molecule. DFT calculations on the first ring-opening step show that the guanidine is able to act as a nucleophile. Three transition states were located for ligand rearrangement, nucleophilic attack, and ring-opening. The second ring-opening step was modeled as a representation for the chain growth because here, the lactate alcoholate opens the second lactide molecule via two transition states (nucleophilic attack and ring-opening). Additionally, the resulting reaction profile proceeds overall exothermically, which is the driving force for the reaction. The experimental and calculated data are in good agreement and the presented mechanism explains why the polymerization proceeds without co-initiators.

Synergistic Empirical and Theoretical Study on the Stereoselective Mechanism for the Aluminum Salalen Complex Mediated Polymerization of rac‐Lactide

[a] I. d. S. Vieira, Prof. Dr. S. Herres-PawlisAnorganische ChemieTechnische Universitt DortmundOtto-Hahn-Strasse, 644221 Dortmund (Germany)[b] Dr. E. L. Whitelaw, Dr. M. D. JonesDepartment of ChemistryUniversity of BathClaverton Down, Bath, BA2 7AY (UK)Fax: ( +44)1225-386231E-mail: mj205@bath.ac.uk[c] Prof. Dr. S. Herres-PawlisDepartment ChemieLudwig-Maximilians-Universitt MnchenButenandtstrasse 5–13, 81377 Mnchen (Germany)E-mail: sonja.herres-pawlis@cup.uni-muenchen.deSupporting information for this article is available on the WWWunder http://dx.doi.org/10.1002/chem.201203973.

Workflow-enhanced conformational analysis of guanidine zinc complexes via a science gateway

The new science gateway MoSGrid (Molecular Simulation Grid) enables users to submit and process molecular simulation studies on a large scale. A conformational analysis of guanidine zinc complexes, which are active catalysts in the ring-opening polymerization of lactide, is presented as an example. Such a large-scale quantum chemical study is enabled by workflow technologies. Two times 40 conformers have been generated, for two guanidine zinc complexes. Their structures were optimized using Gaussian03 and the energies processed within the quantum chemistry portlet of the MoSGrid portal. All meta- and post-processing steps have been performed in this portlet. All workflow features are implemented via WS-PGRADE and submitted to UNICORE.

Novel Tin(IV) Complexes with the Hybrid Guanidine Ligand DMEGqu

Novel Sn(IV) complexes with the guanidine-quinoline hybrid ligand DMEGqu are reported. With SnCl4, SnBr4, Me2SnCl2, Me2SnBr2, and the 3,5-di-tert-butyl-catecholate coligand complexes with different donor sets were synthesized. Four of these tin compounds have been modelled by density functional theory. Additionally, a tetranuclear Sn(IV) oxocluster with a novel structure motif, a distorted hetero-adamantane with bridging oxido and hydroxido ligands, is presented Graphical Abstract Novel Tin(IV) Complexes with the Hybrid Guanidine Ligand DMEGqu

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].

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.