Crystal structures and 166Er Moessbauer spectra for some β-diketonatoerbium(III) complexes

The crystal structures and 166Er Moessbauer spectra for some β-diketonatoerbium(III) complexes have been investigated. The geometries around the Er(III) ions in [Er(dpm)3(H2O)] (1; Hdpm=2,2,6,6-tetramethyl-3,5-heptanedione), [Er(pta)3(H2O)] (2; Hpta=1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione) and [Er2(pta)6] (3) are distorted monocapped trigonal prisms. 3 is a dimeric structure in which one of the chelating oxygen atoms of the pta ligand bridges between the Er(pta)3 fragments. The 166Er Moessbauer spectra for those β-diketonatoerbium(III) complexes show paramagnetic relaxation patterns at 12 K. The estimated relaxation time (τ) is spread out from 0.1 to 1 ns. For the seven-coordinated complexes, τ decrease among with a decrease in the Er(III)-Er(III) distance. τ for the six-coordinated complex of [Er(dpm)3] is as short as 0.4 ns in spite of having a rather long distance of Er(III)-Er(III) ions, suggesting that the τ also depends on the coordination number. (author)