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Symmetry of octa-coordination environment has a substantial influence on dinuclear TbIII triple-decker single-molecule magnets.

ABSTRACT: Single-molecule magnet (SMM) properties of terbium(iii)-phthalocyaninato and porphyrinato mixed ligand triple-decker complexes, [(TTP)Tb(Pc)Tb(TTP)] (1) and [(Pc)Tb(Pc)Tb(TTP)] type (2), were studied and were compared with those of the TbIII homoleptic triple-decker complex [(obPc)Tb(obPc)Tb(obPc)] (3) in order to elucidate the relationship between octa-coordination environments and SMM properties (TbIII = terbium(iii), TTP2- = tetraphenylporphyrinato, Pc2- = phthalocyaninato, obPc2- = 2,3,9,10,16,17,23,24-octabutoxyphthalocyaninato). By combining TTP2- and Pc2- with TbIII ions, it is possible to make three octa-coordination environments: SP-SP, SAP-SP and SAP-SAP sites, where SAP is square-antiprismatic and SP is square-prismatic. The direction and magnitude of the ligand field (LF) strongly affect the magnetic properties. Complexes 2 and 3, which have SAP-SAP sites, undergo dual magnetic relaxation processes in the low temperature region in a direct current magnetic field. On the other hand, 1, which has an SP-SP environment, undergoes a single magnetic relaxation process, indicating that the octa-coordination environments strongly influence the SMM properties. The SMM behaviour of dinuclear TbIII SMMs 1-3 were explained by using X-ray crystallography and static and dynamic susceptibility measurements. This work shows that the SMM properties can be fine-tuned by introducing different octa-coordination geometries with the same TbIII-TbIII distances.

SUBMITTER: Katoh K

PROVIDER: S-EPMC6013818 | biostudies-other | 2016 Jul

REPOSITORIES: biostudies-other

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Symmetry of octa-coordination environment has a substantial influence on dinuclear TbIII triple-decker single-molecule magnets.

Katoh Keiichi K Breedlove Brian K BK Yamashita Masahiro M

Chemical science 20160329 7

Single-molecule magnet (SMM) properties of terbium(iii)-phthalocyaninato and porphyrinato mixed ligand triple-decker complexes, [(TTP)Tb(Pc)Tb(TTP)] (1) and [(Pc)Tb(Pc)Tb(TTP)] type (2), were studied and were compared with those of the TbIII homoleptic triple-decker complex [(obPc)Tb(obPc)Tb(obPc)] (3) in order to elucidate the relationship between octa-coordination environments and SMM properties (TbIII = terbium(iii), TTP2- = tetraphenylpor ...[more]

PMID: 30155079

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Project description:The preparation of η-cyclopentadienyl (η5-C5R5), η-arene (η6-C6R6), and η-cyclooctatetraenyl (η8-C8R8) bridging motifs are common in organometallic chemistry; however, the synthetic preparation of η-cycloheptatrienyl (η7-C7R7) bridging motifs has remained a synthetic challenge in 4f chemistry. To this end, we have developed a synthetic route towards a series of rare dinuclear organolanthanide inverse sandwich complexes containing the elusive η7-C7H7 bridge. Herein, we present the structures and magnetic properties of the lanthanide inverse sandwich complexes [KLn2(C7H7)(N(SiMe3)2)4] (Ln = GdIII (1), DyIII (2), ErIII (3)) and [K(THF)2Er2(C7H7)(N(SiMe3)2)4] (4). These compounds are the first single-molecule magnets (SMMs) to feature this type of bridging motif. Furthermore, η7-C7H7 was found to efficiently promote ferromagnetic exchange interactions between metal ions. Variable temperature dc magnetic susceptibility measurements and subsequent simulations give significant exchange constants of J = +1.384, +1.798, and +3.149 cm-1 and dipolar constants of J = -0.603, -0.601, and -0.475 cm-1 for compounds 2-4, respectively. Frequency dependent ac susceptibility measurements under an applied static field resulted in the observation of dual relaxation processes, and brought forth a greater understanding of the intermolecularly driven process at high frequency. In particular, this type of analysis of compound 3 under 800 Oe elicited an energy barrier of Ueff = 58 K. Ab initio calculations were performed in order to understand the nature of magnetic coupling and the origin of slow relaxation of magnetisation. Through these studies, the effect of the amido ancillary ligands on the magnetic axiality of the lanthanide ions was found to be competitive with the crystal field of the η7-C7H7 π-electron cloud. Our findings suggest that the tunability of the dipolar and exchange components of the magnetic interactions lie within the dihedral angle imposed by the amido ligands, thus offering potential for the development of new exchange coupled lanthanide systems.

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Symmetry of octa-coordination environment has a substantial influence on dinuclear TbIII triple-decker single-molecule magnets.

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Symmetry of octa-coordination environment has a substantial influence on dinuclear Tb<sup>III</sup> triple-decker single-molecule magnets.

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