Obiettivo MOLSWITCH aimed to develop molecular materials with applications in the field of microelectronics. Highly ordered materials are made from organic chemical compounds. The name "molecular materials" is used in order to distinguish them from the commonly used semi-conductive inorganic materials. The Action has focused on the construction of molecules which can be switched between two metastable states primarily activated by electromagnetic irradiation. The switch molecules contain electron donor and acceptor groups connected by a linker. Molecular structures with mobile electrons serving as connecting wires were also studied. The specification and design of the molecules is performed with the assembly of highly ordered stable systems in mind.Organic materials with potential transistor-like switching properties have been designed and prepared. Donor and acceptor structures of, respectively, the TTF and bianthrone type were prepared and synthesic methods developed for attaching linkers for combining donors and acceptors. Hydrocarbon chains of various lengths were attached to the donor and acceptor groups to allow mono and multilayer films to be prepared by the Langmuir Blodgett technique of the combined molecular switch (molswitch) molecule. A donor acceptor system based on bianthrone has been demonstrated to act as a molswitch in solution. In films inactive due to steric hindrance, the obstacle is overcome by addition of spacers in the films. Donor and acceptor modified polyenes with different chain lengths have been prepared with benzoid donors and acceptors. Synthesis was achieved of symmetrical and polarised molecular wires based on caroviologens, with the molecules incorporated in artificial lipid membranes. Electron transfer by binding of inorganic ions was demonstrated. Equipment for picosecond time-resolved spectroscopy was constructed. Picosecond and nanosecond time-resolved spectroscopy was carried out on molswitch molecules, yielding information on the charge transfer process. A redox sensor system with flourescence readout was synthesised and studied. Theoretical evaluation by quantum chemical calculations of the stability of polaron and exiton transport mechanisms in polyene chains was performed. Calculations of electronic properties for the ground state and lowest singlet and triple excited state of molecular switches have been performed and compared with experimental results. A good agreement was found between the calculations and the experiments.APPROACH AND METHODS Different types of switching mechanisms for blocking the back-flow of electrons were investigated. Blocking of the back-flow of electrons was attempted by a change in conformation. Blocking in both directions was attempted by switching a bistable group inserted between the donor and the acceptor group in a molecular triad. Both types of switches were activated by electromagnetic radiation. A third type of switching mechanism was based upon ion complexation. Chemical synthesis of potentially switching molecules includes the preparation of TTF-like donors connected to bianthrone acceptors by electronically partly delocalised linkers, mixed valence caroviologen molecules and long-chain polyenes substituted by benzoid donors with simple electron-attracting groups at the chain terminals. The properties of the molecules are evaluated by spectroscopic and electrochemical methods. Ground- and excited-state properties were calculated and the results used to adjust the designs of the types of molecules mentioned above. The techniques used for preparing highly ordered materials are film formation by the Langmuir-Blodgett technique, membrane formation, and epitaxial growth. The structure and stability of the material were investigated by methods such as spectroscopy and X-ray techniques. The transport and switching properties were evaluated by spectroscopic, electrical and electrochemical techniques, pico- and nano-second, time-resolved spectroscopy and chemical measurements. PROGRESS AND RESULTS The Action has lead to a strongly increased insight into the basic requirements for a molecular switch. -Donor and acceptor structures of, respectively, the TTF and bianthrone type were prepared and synthesic methods developed for attaching linkers for combining donors and acceptors. -Hydrocarbon chains of various lengths were attached to the donor and acceptor groups to allow mono and multilayer films to be prepared by the Langmuir Blodgett technique of the combined molswitch molecule. -A donor-acceptor system based on bianthrone has been demonstrated to act as a molswitch in solution. However, in fims inactive due to steric hindrance, the obstacle is overcome by addition of spacers in the films. -Donor and acceptor modified polyenes with different chain-lengths have been prepared with benzoid donors and acceptors. -Synthesis of symmetrical and polarised molecular wires based on caroviologens, with the molecules incorporated in artificial lipid membranes. Electron transfer by binding of inorganic ions was demonstrated. -Equipment for pico-second time resolved spectroscopy was constructed. Pico- and nano-second time resolved spectroscopy was carried out on molswitch molecules yielding information on the charge transfer process. -A redox sensor system with fluorescence read-out was synthesised and studied. -Theoretical evaluation by quantum chemical calculations of the stability of polaron and exiton transport mechanisms in polyene chains was performed. -Calculations of electronic properties for the ground state and lowest singlet and triplet excited state of molecular switches have been performed and compared with experimental results. A good agreement was found between the calculations and the experim ents. POTENTIAL An increase in knowledge about the behaviour of electrons in organic compounds and materials is a prerequisite for the exploitation of the tremendous potential of molecular materials in applications such as sensor technology and computer and communication devices. The results of MOLSWITCH, combined with the outcome of similar efforts by other research groups, will lead to improved possibilities for designing molecular materials for microelectronic applications including strongly miniaturized sensors. Mor e specifically, the work contributes to clarifying the possibilities for constructing switching mechanisms on the molecular level. Campo scientifico natural scienceschemical sciencesorganic chemistryhydrocarbonsnatural sciencesbiological sciencesbiochemistrybiomoleculeslipidsengineering and technologymaterials engineeringcoating and filmsnatural sciencesphysical scienceselectromagnetism and electronicsmicroelectronicsnatural sciencesphysical sciencesopticsspectroscopy Programma(i) FP2-ESPRIT 2 - European strategic programme (EEC) for research and development in information technologies (ESPRIT), 1987-1992 Argomento(i) Data not available Invito a presentare proposte Data not available Meccanismo di finanziamento Data not available Coordinatore KOBENHAVNS UNIVERSITET Contributo UE Nessun dato Indirizzo NJALSGADE, 94 2300 COPENHAGEN Danimarca Mostra sulla mappa Costo totale Nessun dato Partecipanti (3) Classifica in ordine alfabetico Classifica per Contributo UE Espandi tutto Riduci tutto Max-Planck-Gesellschaft zur Förderung der Wissenschaften eV Germania Contributo UE Nessun dato Indirizzo Heisenbergstraße 1 70569 Stuttgart Mostra sulla mappa Costo totale Nessun dato UNIVERSITY OF UPPSALA Svezia Contributo UE Nessun dato Indirizzo 75121 UPPSALA Mostra sulla mappa Costo totale Nessun dato Université de Strasbourg I (Université Louis Pasteur) Francia Contributo UE Nessun dato Indirizzo 4 rue Blaise Pascal 67070 Strasbourg Mostra sulla mappa Costo totale Nessun dato
