Design of a Family of Ln3 Triangles with the HAT Ligand (1,4,5,8,9,12-Hexaazatriphenylene): Single-Molecule Magnetism

Ismael F. Díaz-Ortega, Juan Manuel Herrera, Tulika Gupta, Gopalan Rajaraman, Hiroyuki Nojiri, Enrique Colacio

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

A series of trinuclear Ln3 complexes (LnIII = Yb (1), Er (2), Dy (3) and Gd (4)) were prepared from the tris-chelate bidentate ligand 1,4,5,8,9,12-hexaazatriphenylene (HAT). 1 and 2 exhibited field-induced single-molecule-magnet (SMM) behavior with estimated Ueff values of 21.30 and 13.86 K, respectively. Complex 3 behaved as a SMM even at zero field, and two different thermally assisted relaxation processes were detected with Ueff values of 29.6 K (fast relaxation process, FR) and 69 K (slow relaxation process, SR) due to the existence of two magnetically different DyIII centers in the molecule. Ab initio studies reveal that all the Dy3+ centers have almost an Ising ground state. The local anisotropy axes are not coplanar but form angles with the Dy3 plane in the range 58-78°. The magnetic interaction between the anisotropic Dy3+ ions is antiferromagnetic in nature and very weak in magnitude. However, due to the extreme feebleness of the magnetic interaction with regard to the local excitation energies, the magnetization blockade is most probably of single-ion origin. Calculations support the existence of two relaxation processes, which take place through the first excited state following an Orbach/Raman mechanism. Finally, for complex 4, the magnetocaloric effect was simulated using the magnetic parameters extracted from the fit of the magnetization and susceptibility data and demonstrated that the simulated -ΔSm values were almost coincident with those extracted from the integration of the field dependence of the magnetization. The simulated MCE value at 2 K and 5 T (20.46 J kg-1 K-1) makes complex 4 an attractive candidate for cryogenic magnetization.

Original languageEnglish
Pages (from-to)5594-5610
Number of pages17
JournalInorganic chemistry
Volume56
Issue number10
DOIs
Publication statusPublished - 2017 May 15

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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