resumo
Two mononuclear Dy-III crown ether complexes [Dy(15C5)(H2O)(4)](ClO4)(3)center dot(15C5)center dot H2O (1) and [Dy(12C4)(H2O)(5)](ClO4)(3)center dot H2O (2) have been prepared and characterized. X-ray diffraction studies show that both compounds crystallize as half sandwich type structures with muffin and pseudo-capped square antiprismatic geometries respectively. Despite the comparable local environments of the Dy-III ions they display remarkably different dynamic magnetic properties with only 1 displaying SMM properties in zero field. The solid state emission spectra for both 1 and 2 display sharp bands associated with f-f transitions. From the fine structure of the F-4(9/2) -> H-6(15/2) band, the Stark splitting of the H-6(15/2) ground state permitted the energy difference between the ground and first excited state to be determined. For 1 this value (Delta E = 58.0 +/- 3.0 cm(-1) ) is in excellent agreement with ab initio calculations and the experimentally observed SMM behaviour. For 2, the photoluminescence data and theoretical calculations support a less well isolated ground state (Delta E = 30 +/- 3.0 cm(-1)) in which a rapid relaxation process affords no SMM behaviour in zero-field.
palavras-chave
SINGLE-MOLECULE MAGNETS; ION MAGNET; SLOW RELAXATION; LANTHANIDE COMPLEXES; LUMINESCENT; SYMMETRY; SPINTRONICS; ANISOTROPY; MAGNETIZATION; EMISSION
categoria
Materials Science; Physics
autores
Gavey, EL; Al Hareri, M; Regier, J; Carlos, LD; Ferreira, RAS; Razavi, FS; Rawson, JM; Pilkington, M
nossos autores
agradecimentos
This work was supported by NSERC (DG; M. P. and J. M. R.), CRC (Tier II M. P. and Tier I J. M. R.), Brock University, CFI (New Opportunities, M. P.) and OIT (matching funds, M. P.). We wish to thank Prof. Ian Brindle and Yong Wang for ICP MS measurements. This work is partially developed in the scope of the projects CICECO - Aveiro Institute of Materials (UID/CTM/50011/2013), financed by national funds through the Fundacao para a Ciencia e a Tecnologia/Ministerio da Educacao e Ciencia (FCT/MEC) and when applicable co-financed by FEDER under the PT2020 Partnership Agreement.