New 1,2,3,5-dithiadiazolyl (DTDA), 1,2,3,5-diselenadiazolyl (DSDA) radicals and their resulting metal complexes were synthesized and characterized. The overarching theme of this thesis is the utility of intermolecular interactions for facilitating previously unseen magnetic behaviours in thiazyl radical-metal complexes. This thesis contains the first examples of thiazyl radical metal complexes acting as molecule based magnets. The 4-benzoxazol-2′-yl-1,2,3,5-dithiadiazolyl (boaDTDA) radical and its selenium analogue 4-benzoxazol-2′-yl-1,2,3,5-diselenadiazolyl (boaDSDA) were coordinated to several paramagnetic metal ions including transition metal ions Mn(II), Co(II) and Ni(II). The Ni(hfac)2(boaDTDA) and Ni(hfac)2(boaDSDA) complexes are isomorphous and both demonstrate step like π-stacking leading to additional ferromagnetic (FM) intermolecular interactions. The Mn(hfac)2(boaDTDA) (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato) complex was the first DTDA metal complex to conclusively show that intermolecular S(DTDA)…O(hfac) contacts can lead to intermolecular anti-ferromagnetic (AF) interactions which, in turn, can lead to a large spin ground state. Based on the magnetic properties of the Mn(hfac)2(boaDTDA) complex, a new DTDA biradical ligand, 4,6-bisDTDApyrimidine (bisDTDApym), was developed and coordinated to Mn(hfac)2. The resulting dinuclear Mn(II) complex, [Mn(hfac)2]2(bisDTDApym), is arranged in the solid state by short S(DTDA)…O(hfac) interactions forming two dimensional ferrimagnetic sheets. These ferrimagnetic sheets AF couple to one another, giving rise to AF ordering below 4.5 K. The [Mn(hfac)2]2(bisDTDApym) is the first thiazyl metal complex to magnetically order and is a unique example of a molecular coordination complex which magnetically orders. This thesis also presents the synthesis and characterization of precursor materials of the form Ln(hfac)3(DME) (DME = dimethoxyethane) for coordination reactions to thiazyl radical ligands. The Dy(hfac)3(boaDTDA) and Dy(hfac)3(pyDTDA) (pyDTDA = 4-(2′-pyridyl)-1,2,3,5-DTDA) complexes demonstrate single molecule magnetism with energy barriers of 100 K and 70 K respectively. Ten-coordinate Ln(hfac)3(pyDTDA)2 (Ln = La, Ce, Pr) complexes demonstrate phase transition behaviour between dimerized and undimerized phases and were studied by X-ray crystallography and magnetometry. The aforementioned compounds are some of the over 50 new compounds which have been synthesized and fully characterized in this thesis.

Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-08-11T12:02:32Z No. of bitstreams: 1 hebersilaspires.pdf: 1057538 bytes, checksum: a1059a1d408dc6d11e6268b18f3dd3af (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-08-11T12:54:04Z (GMT) No. of bitstreams: 1 hebersilaspires.pdf: 1057538 bytes, checksum: a1059a1d408dc6d11e6268b18f3dd3af (MD5) / Made available in DSpace on 2017-08-11T12:54:04Z (GMT). No. of bitstreams: 1 hebersilaspires.pdf: 1057538 bytes, checksum: a1059a1d408dc6d11e6268b18f3dd3af (MD5) Previous issue date: 2008-01-14 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este trabalho descreve a síntese e caracterização de três ligantes, N-(2-piridil)oxamato de etila (OPy), N-(3-piridil)oxamato de etila (MPy) e N-(4-piridil)oxamato de etila (PPy). Estes ligantes contêm pontes do tipo oxamato e encontram-se descritos na literatura; são isômeros e apresentam algumas propriedades em comum, como por exemplo, solubilidade. A partir destes ligantes, quatro novos precursores foram sintetizados e caracterizados, três deles contendo cátions tetrametilamônio, [Me4N]2[Cu(OPy)2].9H2O (MeCuOPy), [Me4N]2[Cu(MPy)2].2H2O (MeCuMPy) e [Me4N]2[Cu(PPy)2].4H2O (MeCuPPy), e um contendo o cátion sódio em sua composição, Na2[Cu(MPy)2].4H2O (NaCuMPy). Usando estes precursores, três cadeias inéditas foram obtidas, sendo elas CoCu(OPy)2.4H2O (CoCuOPy), CoCu(MPy)2.6H2O (CoCuMPy) e CoCu(PPy)2.7H2O (CoCuPPy). As cadeias são insolúveis na maioria dos solventes orgânicos e inorgânicos, decompondo-se em soluções ácidas. As propriedades magnéticas também foram investigadas sendo que os resultados indicaram que as cadeias comportam-se como sistemas magnéticos unidimensionais. Todos os compostos obtidos neste trabalho foram caracterizados por análise elementar, espectroscopia vibracional na região do IV e solubilidade. Os ligantes também foram caracterizados por ponto de fusão e ressonância magnética nuclear para carbono (RMN-13C) e hidrogênio (RMN-1H). Para os precursores, foi também utilizada espectroscopia de absorção na região do ultravioleta e visível. Para a determinação do número de moléculas de solvente, no caso dos precursores e das cadeias, foi utilizada análise térmica. / This work describes the synthesis and characterization of three ligands, ethyl N-(2-pyridyl)oxamate (OPy), ethyl N-(3-pyridyl)oxamate (MPy) and ethyl N-(4-pyridyl)oxamate (PPy). These ligands have oxamato bridges and are described in the literature; they are isomers and present some properties in common, for example, solubility. From these ligands, four novel precursors have been synthesized and characterized, three of them containing tetramethylamonium cations (Me4N+), [Me4N]2[Cu(OPy)2].9H2O (MeCuOPy), [Me4N]2[Cu(MPy)2].2H2O (MeCuMPy) and [Me4N]2[Cu(PPy)2].4H2O (MeCuPPy), and one containing the Na+ cation in its composition, Na2[Cu(MPy)2].4H2O (NaCuMPy). Using these precursors, three new chains have been obtained, CoCu(OPy)2.4H2O (CoCuOPy), CoCu(MPy)2.6H2O (CoCuMPy) and CoCu(PPy)2.7H2O (CoCuPPy). The chains are insoluble in most organic and inorganic solvents, decomposing in diluted acid solutions. The magnetic properties have been also investigated. The results indicated that the chains behave as onedimensional magnetic molecular systems. All compounds obtained in this work were characterized by elemental analysis, vibrational spectroscopy (IR) and solubility. The ligands were characterized also by melting point and nuclear magnetic resonance for carbon (NMR-13C) and hydrogen (NMR-1H). For the precursors, UV-Vis spectroscopy was used. To determine the number of solvent molecules in precursors and chains, thermal analysis has been used.