Functionalized tris(3-cyanoacetylacetonato)metal(III) complexes as sensitizers for lanthanide-centered luminescence

The reaction of LnCl3 (Ln = Sm, Eu, Tb, Yb) with M(acacCN)3 (with M = Al, Cr, acacCN = 3-cyanoacetylacetonate) in ethanolic solution yields a series of novel 3d-4f heterodinuclear complexes [(acacCN)2M(μ-acacCN)LnCl3]. For M = Al the complexes display strong 4f–4f lanthanide-centered luminescence due to energy transfer from the triplet state of the ligand acacCN to the lanthanide. Photophysical measurements of the complexes with M = Cr show efficient sensitization of both Ln(III) and Cr(III) through ligand excitation at 77 K. Luminescence measurements indicate strong interactions between Ln(III) and Cr(III) and the degree of energy transfer between the two metals depends on the energy gap of the donor and acceptor levels.