Tailoring and Exploiting Magnetic Anisotropy in Low Coordinate 3d Transition Metal Complexes.
by Ting-Yi Chen
Date of Examination:2023-06-08
Date of issue:2023-07-04
Advisor:Prof. Dr. Franc Meyer
Referee:Prof. Dr. Franc Meyer
Referee:Prof. Dr. Eliseo Ruiz
Referee:Prof. Dr. Ricardo Mata
Referee:Dr. Silvia Gómez-Coca
Referee:Prof. Dr. Anna Jun.-Krawczuk
Referee:Dr. Michael John
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EnglishAmong 3d transition metal based SMMs, Co(II) SMMs is the most-studied group owning to the high-spin electronic configuration (CoII, d7) which yields second-order spin-orbit coupling or even first-order spin-orbit coupling. A variety of Co-based SMMs were synthesized with coordination number from seven coordination to two coordination. Nevertheless, Co-based mononuclear SMMs with three coordination and two coordination remain scares because of the challenging synthesis the instability. In this study, we focus on three and two coordinated Co complexes for their potentially interesting electronic structures and magnetic properties. To stabilize low-coordination 3d transition metal complexes, bulky anionic ligands and bulky carbene ligands with steric alkyl side substituents are commonly used. The first part (chapter. 2) and the second part (chapter. 3) of this study contain a family of three-coordinated Co(II) mononuclear SMMs and a series of two-coordinated Co(II) SMMs respectively. With different steric amide ligands and NHC ligands, a number of Co(II) complexes were successfully synthesized and characterized by X-ray diffractometer, NMR spectroscopy, UV-Vis spectroscopy and IR spectroscopy. The magnetic properties were examined by SQUID magnetometry. The magneto-structural correlation was elucidated by theoretical studies. In addition, the comprehensive relaxation processes analysis was investigated both with experiments and computational methods. The last part (chapter. 4) entails the investigation of a low-coordinated high-spin dinitrogen-bridged dicobalt complex which was obtained from the a putative two-coordinated Co(I) specie under N2 atmosphere. The dinitrogen-bridged complex was characterized by X-ray diffractometer, NMR spectroscopy, X-ray absorption spectroscopy, Raman spectroscopy and SQUID magnetometer. Interesting magnetic behavior was observed and was elucidated by comprehensive computational method suggesting an unprecedented electronic configuration. Additionally, such complex also displays SMM property.
Keywords: Single Molecule Magnet; SMMs; Molecular Magnetism; Nitrogen activiation; Nitrogen fixation