Structure and emission spectrum of the o-phenanthroline adduct of tris(6-methyl-2,4-heptanedionato)europium(III)

The title compound, conveniently abbreviated Eu(MHD)(3).o-phen, has been pr epared and characterized by means of its luminescence spectrum and by compl ete structure determination by X-ray diffraction. The P-diketone ligand is unsymmetrical with a methyl group at one end and an iso-butyl group at the other. Monoclinic crystals having m.p. 186-187 degreesC were isolated from dichloromethane/isopropanol. The luminescence spectrum is typical for low-s ymmetry complexes of this type with a single sharp D-5(0) --> F-7(0) transi tion at 579.9 nm accompanied by a weak shoulder. The D-5(0) --> F-7(1) and D-5(0) --> F-7(2) transitions are completely resolved with weak additional transitions that are most likely vibronic in origin. The X-ray structure sh ows a single eight-coordinate coordination geometry that approximates a squ are antiprism. The average Eu-O and Eu-N distances are 2.358 and 2.628 Angs trom and are typical. Our initial assumption that the unsymmetrical beta -d iketone would lead to multiple sites was not substantiated. (C) 2001 Elsevi er Science B.V. All rights reserved.