Emission properties of Sm complexes substituted with asymmetric β-diketonato ligands in solution

Trivalent samarium (Sm) complexes show four emission bands due to the 4f-4f transition in the visible 550-750 nm region, where the 645 nm transition has the dominant intensity. In this paper we have synthesized the three Sm complexes with varying pybox and beta-diketonato ligands, to investigate the relative intensity among the emission bands. We have shown that the beta-diketonato ligands with asymmetric molecular structures enhance the relative intensity of the 645 nm transition by approximately 20% compared to that with symmetric ligands. By virtue of such a property, Sm complexes can be used as possible candidates for deep red emitting materials. As a strategy on the molecular design, it has also been confirmed that the introduction of heavy atoms such as fluorine to the beta-diketonato moiety should be of essential to obtain a high emission quantum yield. (C) 2014 Elsevier B.V. All rights reserved.