New chiral heteroleptic Eu(III)/Tb(III)/Yb(III)-based luminescent complexes designed for different applications.

The chemistry of luminescent complexes of trivalent lanthanide (Ln) ions is gaining remarkable attention thanks to their promising applications in several technological fields, such as the biomedicine as optical probes or biosensors and the realization of OLED1 or solar concentrators [2]. For instance, heteroleptic complexes bearing both β-diketonates and chiral ligands[3,4] are capable to emit left and right circularly-polarized (CP) light with different intensities. Such complexes can find a possible application as phosphors in CP-OLED, emitting CP light in the visible spectral range. Thus, we recently have focused on the synthesis of a new class of chiral Ln(III)-based complexes of the type [Ln(bpcd)(tta)] and [Ln(bpcd)(cum)] (Figure 1) wherein bpcd = 2,2'-(((1R,2R or 1S,2S)-cyclohexane-1,2-diyl)bis((pyridin-2-ylmethyl)azanediyl))diacetate; tta = 2-thenoyltrifluoroacetyl acetonate; cum = 3-acetyl-4-hydroxy-2H-chromen-2-one in order to evaluate them as luminescent species in CP-OLED devices. It is worth highlighting that the use of Yb(III)-based complexes would propel the circularly polarized emission in the near infrared (NIR) region, thus increasing the versatility and applicability of such a technique (e.g., design of advanced security inks [5] ). All the complexes have been spectroscopically characterized both in solution and in the solid state, leading to promising preliminary data. Their stability (by spectrophotometric titration experiments), structure (by DFT calculations) and CP luminescence are currently under investigation. [1] S. K. Behzad, M. M. Amini, M. Ghanbari, M. Janghouri, P. Azenbacher Jr., S. W. Ng, Eur. J. Inorg. Chem. 2017, 3644. [2] M. M. Nolasco, P. M. Vaz, V. T. Lima, P. S. Andre, R. A. S. Ferreira, P. D. Vaz, P. Ribeiro Claro, L. D. Carlos, J. Mater. Chem. A 2013, 1, 7339. [3] M. Leonzio, M. Bettinelli, L. Arrico, M. Monari, L. Di Bari, F. Piccinelli, Inorg. Chem. 2018, 57, 10257. [4] L. Arrico, C. De Rosa, L. Di Bari, A. Melchior, F. Piccinelli, Inorg. Chem. 2020, 59, 5050. [5] L.E. MacKenzie, R. Pal, Nat. Rev. Chem. 2021, 5, 109.