Electrochemistry of Dinuclear Re(I) Complexes with Bridging 1,2 Heteroaromatic Chromophore Ligands

In the last years we have been developing [1-3] a new class of photoluminescent complexes with high quantum yields, having a dinuclear Re2􀀋􀈝-X)2(CO)6 scaffold with: (a) a bridging 1,2 heteroaromatic ligand, either a pyridazine (with many combinations of electron donating or electron attractor substituents R, R'; R'', R''' on the aromatic ring) or an oxadiazole; (b) two ancillary bridging ligands X and X' (either halides Cl, Br, or I; and/or H; or OH, OCH3, OC6H5, OC6F5, SC6H5). The nature of the ligands greatly influences (a) the electrochemical properties of the molecule, in terms of energies of the HOMO (localized on the dinuclear Re2􀀋􀈝-X)2 (CO)6 core) and LUMO (localized on the heteroaromatic ring), and (b) the electrochemical and chemical reversibility of the electron transfers. These features will be discussed in detail also in comparison with the electrochemical reactivity of the free heteroaromatic ligands, and with the functional properties of these molecules. The electrochemical study, combined with other techniques, is important for interpretation and prediction purposes, in order to develop electroluminescent devices based on these new classes of Re(I) complexes. Nevertheless, it also looks attracting (in some cases intriguing) in itself, since the wide, systematic compound family now available provides an unusually complete and neat model case of multivariate electrochemical reactivity in a complex system. References [1] D. Donghi; G. D'Alfonso, M. Mauro, M. Panigati; P. Mercandelli, A. Sironi, P. Mussini, L. D'Alfonso. Inorganic Chemistry 47 (2008) 4243. [2] M. Mauro, M. Panigati, D. Donghi, P. Mercandelli, P. Mussini, A. Sironi, G. D'Alfonso. Inorg. Chem. 47 (2008) 11154. [3] M. Mauro; E. Quartapelle Procopio; Y. Sun; C.-H. Chien; D. Donghi; M. Panigati, Monica; P. Mercandelli; P.Mussini; G. D'Alfonso; L. De Cola, Adv. Funct. Mat. 19 (2009) 2607.