Syntheses structures and magnetic properties of heterometallic iron(III)-lanthanide coordination clusters

  • 曾 琛

Student thesis: Master's Thesis

Abstract

This work contains three parts First a new family of heterometallic tetranuclear Fe2Ln2 (Ln = Y Dy Ho and Er) complexes were synthesized using the β-diketone ligand L1 Four metals are linked together with a μ4?O atom The geometries of both lanthanides are distorted triangular dodecahedron The dc magnetic studies reveal that the presence of strong antiferromagnetic interaction between two Fe3+ ions Dynamic magnetic susceptibility measurements indicate that slow relaxation of magnetization is present in dysprosium(III) and holmium(III) analogues at the absence of external dc field Moreover complex 2‧Dy possesses the highest energy barrier (Ueff) over 180 K among all the FeIII–LnIII SMMs to date For the second part a series of Fe4Ln2 compounds were synthesized using two different β-diketone ligands L2 and L3 ([FeIII4LnIII2(μ4-O)2(μ2-OMe)2(μ2-OH)2(L2)4 (OAc)2Cl2(MeOH)2]Cl2‧2MeCN‧xH2O (Ln = Y (5‧Y) Gd (6‧Gd) Tb (7‧Tb) Ho (8‧Ho) and Er (9‧Er)) and [FeIII4DyIII2(μ4-O)2(μ2-OMe)4(L3)4(OAc)2Cl2(H2O)2] Cl2‧10H2O (10‧Dy)) All these seven complexes possess a {Fe4Ln2O10(CO2)2} core with a strictly coplanar Fe4 unit The lanthanides possess distorted biaugmented trigonal prismatic geometries Static magnetic susceptibility measurements show that the dominant antiferromagnetic interactions within Fe4 unit In the alternating current magnetic measurements complex 10‧Dy also possesses a larger reversal magnetization barrier The phenomenon of slow magnetic relaxation was also observed in complexes 7‧Tb and 8‧Ho under a zero dc filed In the final chapter the unprecedented heterohexnuclear FeIII–LnIII clusters (Ln = Y (11‧Y) Gd (12‧Gd) Tb (13‧Tb) and Dy (14‧Dy)) were synthesized using β-diketone ligand L4 The structure model is similar to the Fe4Ln2 compounds mentioned in previous section In contrast to the last chapter (Fe4Ln2) with the complexes herein (Fe2Ln4) the two lanthanides were replaced by irons and the coplanar Ln4 unit is in the central position Different coordination spheres on the two individual lanthanides one is eight-coordinated (biaugmented trigonal prism) while the other is nine-coordinated (among mono-capped square antiprism spherical tricapped trigonal prism and muffin) Direct current (dc) susceptibility measurements indicate that the presence of antiferromagnetic interactions for four complexes The Curie-Weiss equation also suggests that the intermolecular antiferromagnetic interactions due to the negative Weiss constant (θ) Alternating current (ac) magnetic susceptibility studies show that only composing highly anisotropic lanthanides e g TbIII and DyIII exhibit slow magnetic relaxation
Date of Award2017 Sep 4
LanguageEnglish
SupervisorHui-Lien Tsai (Supervisor)

Cite this

Syntheses structures and magnetic properties of heterometallic iron(III)-lanthanide coordination clusters
琛, 曾. (Author). 2017 Sep 4

Student thesis: Master's Thesis