Obtained by synthesis at high temperatures, Mo or W octahedral cluster compounds of general formula A2[M6Xi8Xa6] with A: alkali cation, Xi: inner ligand; Xa: apical ligand are known to be phosphorescent in the red-near infrared with quantum yields of up to unity.[1] This family of compounds has demonstrated its interest in a wide range of applications, including healthcare, energy and sustainable development. The CSM team's work in this area has led to the production of materials for optics, optoelectronics, photocatalysis, photovoltaic cells and oxygen detection; we have integrated these luminescent clusters into liquid crystals or polymers, for anti-counterfeiting purposes and for applications in photodynamic therapy.[2]

While the functionalisation of the clusters apical positions (covalent approach) is very well documented in the literature, in particular through the creation of M-carboxylate, alcoholate, thiolate, phosphinate and M-pyridine bonds,[3] their functionalisation with phosphine oxide derivatives has still been little exploited and the photophysical properties of the resulting compounds little studied. However, our initial work on this family of compounds showed that air/temperature stable complexes could be obtained and that the emission properties of the original cluster could be retained.[4]

 The objectives of this PhD work will therefore be:

1) to functionalise octahedral molybdenum and tungsten clusters with custom-synthesised organic molecules containing one or more phosphine oxide groups,

2) characterise them using all available techniques (NMR, mass spectrometry, vibrational and optical spectroscopy, X-ray diffraction, etc.)

3) study the physico-chemical properties of the resulting complexes, in particular their sensitivity to oxygen and their stability in aqueous media

4) incorporate them into nanocomposites to take advantage of their emission properties

The aim of this multidisciplinary, fundamental project will be also to explore the influence of the electron-withdrawing/electron-donating effects of apical ligands on the emission properties of cluster compounds, in order to select the most emissive/stable cluster compounds and exploit them in the fields of sustainable development and biology. The CSM team's cluster group at the Institut des Sciences Chimiques de Rennes is an international group that works with teams in Brazil, the USA, Spain, Germany, the Czech Republic, Cambodia and Japan to develop the materials it studies in the fields of energy, anti-counterfeiting, optoelectronics, photovoltaics and the fight against cancer.

[1]              K. Kirakci, K. Fejfarová, M. Kučeráková, K. Lang, Eur. J. Inorg. Chem. 2014, 2014, 2331.

[2]              a) A. Verger, G. Dollo, S. Martinais, Y. Molard, S. Cordier, M. Amela-Cortes, N. Brandhonneur, J. Pharm. Sci. 2022, 111, 3377-3383; b) M. Amela-Cortes, N. Dumait, F. Artzner, S. Cordier, Y. Molard, Nanomaterials 2023, 13; c) M. Ebert, I. Carrasco, N. Dumait, W. Frey, A. Baro, A. Zens, M. Lehmann, G. Taupier, S. Cordier, E. Jacques, Y. Molard, S. Laschat, Chem. - Eur. J. 2022, 28, e202103446; d) I. Carrasco, P. Ehni, M. Ebert, N. Dumait, G. Taupier, M. Amela-Cortes, C. Roiland, S. Cordier, J. A. Knöller, E. Jacques, S. Laschat, Y. Molard, ACS Appl. Mater. Interfaces 2023, 15, 39752-39764.

[3]              L. F. Szczepura, E. Soto, in Ligated Transition Metal Clusters in Solid-state Chemistry : The legacy of Marcel Sergent (Ed.: J.-F. Halet), Springer International Publishing, Cham, 2019, pp. 75-108.

[4]              V. Cîrcu, Y. Molard, M. Amela-Cortes, A. Bentaleb, P. Barois, V. Dorcet, S. Cordier, Angew. Chem. Int. Ed. 2015, 53, 10921-10925.

Funding category: Contrat doctoral

Contrat doctoral ordianaire

PHD title: Doctorat de Chimie, PhD in Chemistry

PHD Country: France