SFL-PRR · New Switchable Organometallic Oligomers and Polymers

New switchable organometallic oligomers and polymers

Project objectives According to the original proposal the aim of this research project is the development of new luminescent organometallic oligomers and polymers with applications in the optoelectronic and sensor industries. These new materials contain both early and late transition metal centres linked by modulating organic groups so that electrons can flow along the polymer chains. By altering the metal oxidation state or the conformation of the organic groups it will be possible to switch 'on' and 'off' the electron flow and these materials will act as 'molecular switches'. On the other hand, the training aspects of the fellowship were explained in the personal career development plan and included: development of her experience in teaching, oral and written communication and networking by interaction with leading mentors at a top rank institution. Project results Following our planned work, during the initial part of the project we synthesised a range of platinum complexes as plausible precursors to obtain the polyyne systems and subsequently in a second stage, to achieve the coordination to the early transition metals (Mo2 systems). Therefore, after failed synthetic routes, we successfully prepared a suitable precursor ((R-CNC)Pt(dmso)). Firstly, we synthesised a new derivative of the 2,6-diphenylpyridine: ethyl 2,6-diphenylisonicotinate (EtO2C-C^N^C-H2). Its double C-H activation led to the formation of this tridentate CNC Bis-cycloplatinated derivative ((R-CNC)Pt(dmso)), in which the new ligand coordinates to the metal centre as a pincer ligand through the C and N donor atoms. This is a very promising starting material because it displays an ethylacetate group located at the back which might be easily hydrolysed, favouring the coordination to the Molybdenum systems through the carboxylate group. To fully characterise this new platinum system '(R-CNC)Pt', we prepared a series of different mononuclear, binuclear and even heterotrinuclear compounds using various ligands such as phosphines, pyridines and alkynyls derivatives. We performed a systematic study between structural and optical properties, establishing a correlation between them. These results were backed up with theoretical calculations. From density functional theory (DFT) calculations, we found out that the lowest unoccupied molecular orbital (LUMO) was always involving the pyridine ring and the ester group from the CNC tridentated ligand, which would perfectly fit with our purpose, outlined in the next step. Moving on to platinum-molybdenum metal mixed hybrid complexes: platinum / molybdenum metal mixed compounds were successfully achieved. The ester group located at the back of the pincer CNC ligand was easily hydrolysed using KtBuO, allowing the coordination to the Mo2 system through the carboxylate group. As part of a collaborative work with Doctor of Philosophy (PhD) students in Raithby's group we have also tried with different alkynyl platinum compounds ((PEt3)2PtPh(C?C-X-COOMe)). All these Pt/Mo compounds were fully characterised. Time resolved infrared experiments were carried out on these systems to study the dynamics or electronic flow between the early and late transition metals within these two completely different platinum systems. Finally, given the extraordinary results obtained in the first two parts of the project, the evaluation of the new polymeric materials to incorporate them into optical devices has remained barely explored. However, these encouraging results are opening research lines within the group. The last PhD student joining the group (October 2011) was one of her nurturing Master students that now is going on with this same research project. He has already prepared a new platinum precursor with a different pincer ligand whose optical properties seem to be more promising. As for the research training the researcher received an initial training by the technical staff of the University (nuclear magnetic resonance (NMR), mass spectrometry, X-ray, etc.) after which she developed most of her research work in an independent manner. Also, she has received a hands-in training in a hands-in training in lasers and synchrotron radiation. Numerous group and literature meetings took place during the two-year period helping to focus the research work and to identify new research areas of potential interest, but helping to also increase the chemical knowledge of the researcher. The researcher has also been involved in the active supervision and nurturing graduate and undergraduate students working in prof. Raithby's group. In summary, the excellent research results obtained together with the very good quality of the training and new skills acquired by the researcher provided her with an exceptional opportunity for the development of the professional maturity, diversity, independence and leadership qualities.

Data: CORDIS, © European Union