Abstracts

Near-infrared (NIR) lanthanide luminescent molecular materials are of interest for their wide applications such as lasers, optical telecommunication, bioimaging, quantum technologies. Due to the forbidden nature of the f-f transitions, it is difficult to directly excite lanthanide ions due to their low molar absorption coefficients. To overcome this problem, organic molecules are used to form molecular complexes, where the organic moiety acts as an antenna, absorbing light and undergoing energy transfer to nearby lanthanide ion. On the other hand, the gain of a more efficient excitation of lanthanide ions comes at the cost of having shorter emission lifetimes and lower quantum yields as a consequence of vibrational quenching phenomena by strong oscillators such as C-H and O-H groups present in the coordination environment. First, we will present a quantitative study of vibrational quenching in a series of NIR-luminescent beta-diketonate complexes. We elucidate the influence of the number, orientation and donor-acceptor distance of C-H and O-H groups on quenching and propose a semi-empirical predictive model based on the Förster’s resonance energy transfer (FRET) theory of general validity for NIR-emitting lanthanide complexes. Second, we propose the use of 3d complexes as metalloligands to afford d-f heterometallic molecular materials. This strategy allows for reducing the proximity of the high energy oscillators such as C-H, N-H and O-H groups to the lanthanide center and, at the same time, obtain efficient dual emitters in the Visible and NIR region thanks to the combined properties of transition metal and lanthanide ions.