First examples of carbacylamidophosphate pentanuclear hydroxo-complexes: Synthesis, structure, luminescence and magnetic properties

Abstract

The first representatives of pentanuclear carbacylamidophosphate complexes of composition Ln5L6(μ-L)4(μ3-OH)4(μ4-OH) (LnIII=Eu (1), Gd (2), Tb (3), L−=dimethylbenzoylamidophosphate ion [C6H5C(O)–N–P(O)(OCH3)2]−) were obtained. The single crystal X-ray analysis revealed that polynuclear core of 1 contains five europium ions, connected by the μ3- and μ4-hydroxo groups and carbacylamidophosphate ligands. Compounds 1–3 were found to be isostructural. Temperature dependencies of magnetic susceptibility (χM) of the compounds 1 and 2 could be explained by spin-orbit coupling of EuIII ions or antiferromagnetic exchange interactions of four GdIII ions located in the base of Gd5 pyramid, respectively. In the case of 3, the value of χM increases with temperature decreasing from 300K to 50K, and then falls down during temperature decrease till 2K. Such behavior can be explained by comparable contribution of spin-orbit coupling and exchange interactions. No signs of single-molecule magnet behavior for 3 were found at 2K. Phosphorescence, emission and excitation spectra at 298K and 77K for the complexes were measured, as well as luminescence decay times were determined. The compounds 1 and 3 showed intense luminescence with decay time at 298K equal to 0.66 and 1.44ms respectively. Intrinsic quantum yield for 1 determined from its emission spectrum was found to be 25%.