Synthesis and structure of nonacoordinated tris-chelate lanthanide (III) complexes with tridentate 2,4,6,8-tetrakis(tert-butyl)-9-hydroxyphenoxazin-1-one ligands

A series of new nonacoordinated tris-chelate lanthanide (III) complexes was prepared by the reaction of the reduced form of the tricyclic 2,4,6,8-tetrakis(tert-butyl)-9-hydroxyphenoxazin-1-one ligand with Ln(III) acetates (Ln = La, Pr, Sm, Eu, Gd, Tb, Dy, Yb). The coordination polyhedron in all complexes, the molecular structures of which were established by X-ray diffraction studies, is the tricapped trigonal prism composed by six oxygen and three nitrogen atoms of the deprotonated ligand. Electronic absorption spectra of the deeply colored complexes contain a broad long wavelength absorption band ranging from 600 to 900 nm. The values of effective magnetic moments μeff (at 300 K) were found to be equal to 1.78, 3.41, 3.50, 4.35, 7.85, 9.22 and 10.32 μB for the Sm(III), Pr(III), Eu(III), Yb(III), Gd(III), Tb(III) and Dy(III) complexes, respectively.