Phosphorus and molecular materials

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Organic oligomers and polymers have been applied successfully as active components in electro-optical devices (field effect transistors, organic light emitting diodes). The performance of these devices is related to electronic properties of the molecular organic material and their ordering in the solid state. Therefore, tuning the electronic structure of conjugated systems and controlling their structural order on the molecular level is crucial for the development of improved new materials. The project proposes the development of a novel family of conjugated systems incorporating phosphole rings. The presence of the P-heterocycles potentially offers several ways to control the organisation and the electronic properties of these systems. We first propose to control the molecular arrangement by tailoring the P-substituent of phospholes which is perpendicular to the conjugated backbone. Self-assembling of the molecules at the liquid/solid or water/air interface are expected by introduction of ordering elements (long alkyl and alkoxy chains, polar groups). Another possibility offered by the presence of the reactive P-atom is the ordering of phosphole-containing oligomers through stereoselective coordination on transition metal centers. Different shapes imposed by the geometry of the metal coordination sphere (square-planar, octahedral..), can be attained. The introduction of metal centers with different electronic properties (oxidation states, orbital levels) will allow a fine tuning of the opto-electronic properties of the conjugated systems. A crucial part of this project is the elucidation of valuable structure-properties relationships through UV/vis/nir, fluorescence and electrochemical (cyclic voltammetry, differential pulse voltammetry, spectroelectrochemistry) studies. Fluorescence quenching experiments will be conducted to elucidate energy or electron transfer processes in the metal complex containing oligomers. Finally, the preparation of electro-active materials by electropolymerisation will be explored. Transition metal-containing polymers with sensor properties are expected.