Directing the assembly of heterometallic molecular magnets using compartmental ligands

Heras Ojea, Maria Jose (2017) Directing the assembly of heterometallic molecular magnets using compartmental ligands. PhD thesis, University of Glasgow.

Abstract

The use of multinucleating ligands capable of directing the synthesis of heterometallic single−molecule magnets (SMMs) is discussed herein. To this end, we have focused on investigating the coordination chemistry of two different ligands (H6L and H2L2) with 3d and/or 4f metal ion precursors.
The aminopolyalcohol ligand H6L has been employed in the assembly of twenty−three new complexes, ranging from simple monomers up to hexametallic systems, involving Mn(II/III), Co(II/III), Ni(II), Cu(II) and Ln(III) ions. The obtained monomers however have been utilised as building blocks in subsequent reactions to gain control over the assembly process of the polynuclear complexes. Those coordination complexes have been classified into five different families. The first one describes a series of "butterfly−like" systems ([Mn2Ni2(OH)2(H3L)2(H2O)2]Cl2 (3), [Mn2Cu2(CH3O)2(H3L)2(CH3COO)2] (4), [Mn2IIIMnIICu2O(HCOO)(H4L)(H2L)-(CH3COO)3] (5)) where the magnetic properties of the final compounds can be easily tuned by changing the starting 3d−precursor. The second group focusses on the enhancement of the SMM properties of {Ln2Cu3(H3L)2Xn} (X = CH3COO−, n = 6 for 6−7; and X = NO3−, n = 7 or 8 for 8−12), which is related to changes in the crystal field around the Ln(III) ions due to modifications in the synthetic strategy, such as the replacement of the co−ligands (CH3COO− vs. NO3−). Following on from this, the magneto−structural study performed on [LnCu4(H4L)4](Cl)2(ClO4) systems (13−16) attempts to shed light on the nature of the 3d−4f exchange interactions. The last two groups are based on the combination of Co(II) precursors with 4f ions (17−21). In both families the oxidation of the paramagnetic Co(II) centres to diamagnetic Co(III) centres was observed, thereby the overall magnetic properties were mainly defined by the lanthanide ions. One chapter discusses the single−ion magnet (SIM) features of [CoIII3Ln(H2L)2(H3L)](ClO4), while the other describes the magnetocaloric properties of the topologically novel [CoIII3GdIII3(H2L)3(acac)2(CH3COO)4(H2O)2] ring. The last experimental chapter reviews the reactivity of the Schiff base derivative H2L2. H2L2 is a compartmental ligand capable of controlling the synthesis of Ni/Ln systems (24−28, [Ln2Ni2(L2)2(CH3COO)6(H2O)2]), with the Tb analogue displaying SMM features.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Coordination chemistry, heterometallic complex, molecular magnetism.
• Subjects: Q Science > QD Chemistry
• Colleges/Schools: College of Science and Engineering > School of Chemistry
• Supervisor's Name: Murrie, Prof. Mark
• Date of Award: 2017
• Depositing User: Miss Maria Jose Heras Ojea
• Unique ID: glathesis:2017-8291
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 03 Jul 2017 09:50
• Last Modified: 11 Aug 2022 16:05
• Thesis DOI: 10.5525/gla.thesis.8291
• URI: https://theses.gla.ac.uk/id/eprint/8291