This thesis provides the first example of coordination of a 1,2,3-dithiazolyl (1,2,3-DTA) ligand through a N, O bidentate pocket that is reproducible in high purity and bulk quantities. More importantly, it reports the first magnetometry measurements on metal complexes of a 1,2,3-DTA ligand. The radical ligand 1,2,3-dithiazolyl-6,7-dimethyl-1,4-naphthoquinone (6,7-Me2DTANQ) has been prepared and fully characterized. Coordination complexes of 6,7-Me2DTANQ have also been prepared and the resulting species’ structural and magnetic properties are presented. The transition metal ions Ni2+ and Mn2+ produce volatile trinuclear M(hfac)2-Rad-M(hfac)2-Rad-M(hfac)2 complexes. The spin ground state of the trinuclear Mn complex ST = 13/2 results from antiferromagnetic (AFM) coupling. Short sulfur-sulfur contacts and sulfur-oxygen contacts between trinuclear complexes produce weak AFM coupling interactions between trimer units. The lanthanide ions Nd3+, Gd3+ and Dy3+ produce volatile [Ln(hfac)3-Rad]n complexes. The spin ground state of the Gd polymer is ST = 3 per monomeric unit due to Gd3+‒radical AFM coupling.

A 1,2,3-dithiazolyl radical, [1,2,3]dithiazolyl[4,5-f][1,10]phenanthroline, has been prepared and characterized. The EPR spectrum in toluene supports a delocalized structure with an experimental g-factor of 2.0081. Cyclic voltammetry in CH2Cl2 reveals an Ecell of 1.30 V vs. SCE with a reversible +1/0 and irreversible 0/-1 redox couple. The structure belongs to the space group P-1. Complexes of the radical with Mn2+ and Dy3+ have been obtained. The mononuclear Mn2+ complex was confirmed by elemental analysis; however, no structure was determined. The structure of the mononuclear Dy3+ complex was determined by X-ray crystallography and belongs to the space group C2/c. An isopropyl-substituted oxobenzene-bridged bis-1,2,3-dithiazolyl radical has been prepared and characterized by EPR and cyclic voltammetry. The EPR in toluene supports a delocalized structure with an experimental g-factor of 2.0091. Cyclic voltammetry in CH3CN reveals an Ecell of 0.64 V vs SCE with a reversible +1/0 and irreversible 0/-1 and +2/+1 redox couples.

Neutral molecular radicals have received increasing attention as building blocks for functional molecular materials owing to their intrinsic conductive and magnetic properties. However, for these systems to be technologically viable, the molecular framework must be capable of stabilizing the unpaired electron, but also enable a degree of control and modulation of the desired properties. To achieve these goals, the design of the radical template requires consideration of the intrinsic effects on the electronic structure and those from a supramolecular perspective. In that regard, thiazyl radicals are promising candidates, as their physical attributes can be tuned systematically for the application at hand. In the pursuit of tunable thiazyl frameworks, two thiatriazinyl radicals have been synthesized and functionalized with heteroaromatic substituents. The contrasting nature between the attached thienyl and pyridyl substituents was evident upon establishing the preparative routes towards the neutral radical, and further demonstrated when the radicals were characterized spectroscopically. Structural analysis has emphasized the ability for the heteroaromatic moieties to direct the assembly of molecules into different supramolecular arrangements, in addition to self-associating into tightly bound structures. While dimerization voids the spin properties of these radicals, the redox-versatile thiatriazinyls were designed to explore the physical properties originating from metal coordination. Using the more robust anionic precursor, a dinuclear dysprosium complex was isolated and structurally analyzed, where oxidation of the ligand occurred in the process. A mechanism towards the self-assembly of the complex has been proposed by NMR studies using the isostructural yttrium analogue, which has provided insights on the metal-ligand reactivity. Furthermore, single-molecule magnet behaviour was observed for the dysprosium complex following magnetic investigations. In contrast to thiatriazinyls, the resonance-stabilized pyridine-bridged bisthiadiazinyls can remain undimerized in the solid state. Three derivatives have been developed with thienyl attachments and vary by the atomic substitution at the basal carbon position (i.e., R = H, F, Cl). Solution measurements illustrated spin delocalization extending across the π-framework, while halogenation provided a handle to fine-tune the energies of frontier molecular orbitals. Moreover, the ability of the thienyl rings to engage in various interactions was manifested in the polymorphic behaviour for each derivative. The solid-state structures were analyzed from single-crystal X-ray diffraction and highlighted the range of supramolecular architectures afforded by these systems. Lastly, two crystallographic phases of a bisdithiazolyl derivative were isolated selectively, such that the low-temperature phase possess an unprecedented high-symmetry trigonal space group. The mix-matched sizes of the beltline substituents afforded a honeycomb arrangement of stacked radicals. Magnetic measurements depicted a transition to an antiferromagnetically ordered state below 8 K, from which a high-temperature series expansion function was developed to model the magnetic data. Analysis of the results suggest the presence of two equivalent spin-spiral sublattices spanning across the crystal lattice three-dimensionally.

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.

A series of binuclear coordination complexes of 4-(2′-pyrimidal)-1,2,3,5-dithiadiazolyl and its selenium analogue have been prepared to examine their structural and magnetic properties. The zinc(II) coordination complex is the first example of a DTDA radical ligand N-coordinated to a diamagnetic metal center. The magnetic properties reveal that it exhibits Curie behaviour and can be used as a benchmark to compare the analogous coordination complexes which possess paramagnetic metal ions. The nickel(II) coordination complex of the selenium containing radical pymDSDA was shown to dimerize in the solid state and is the only binuclear complex thus far that has done so. The manganese(II) complex of pymDSDA is by far the most interesting and is isomorphous to the DTDA analogue. For both complexes, one of the two molecules in the asymmetric unit form chains in the solid state joined by intermolecular contacts between a sulfur or selenium atom from the radical, and an oxygen atom coordinated to a neighbouring molecule. This feature gives rise to a ground state spin greater than that of an individual binuclear coordination complex. The radical ligand is however disordered in the solid state and so these random chain lengths are dependent on the orientation of the ligands in adjacent complexes. The 1,2,3-DTA species examined herein are related to the 4,5-dioxo-4,5-dihydronaphtho[1,2-d][1,2,3]dithiazolyl radical and the related protonated species 4-hydroxy-5H-naphtho[1,2-d][1,2,3]dithiazol-5-one. The proton from this latter compound has shown that it can be substituted with alkyl groups and this was achieved using acetyl chloride to place an acetyl group in this position. The above radical did not exhibit the strong donor properties required for metal coordination and preliminary investigations of the radical dianionic suggest that it is chemically irreversible by cyclic voltametry. The acetyl group unfortunately did not provide the chemically reversibility of interest although has established a potential route toward the substitution chemistry of this compound. The other 1,2,3-DTA compounds discussed herein are not complete, although the data acquired on the precursor compounds leading up to the radical will be discussed.

Cette thèse décrits la synthèse et caractérisations de chaines métalliques étendues (EMACs:extended metal atom chains) construite à partir des ligands dipyridylamine (dpa) etdipyridylformamidinate (DpyF). Le Chapitre I fait une brève introduction sur les liaisons métalmétalet sur les chaines métalliques étendues. Le Chapitre II présente les propriétés de conversionde spin (SCO: spin crossover) d’une série d’EMACs de tris-cobalt de formule générale[Co3(dpa)4X2]. L’influence des ligands axiaux et de la symétrie des molécules a été examinée etcorrélée aux propriétés de conversion de spin. Le Chapitre III porte sur la résolutionénantiomérique et activité RX optique de l’EMAC tris-cobalt [Co3(dpa)4(MeCN)2]2+. Dans lechapitre IV, La chimie de coordination du ligand N,N’-di(2-pyridyl)formamidinate (DpyF), quiconduit à des complexes présentant des propriétés structurales and magnétiques remarquable,est explorée. Finalement, le chapitre V présente nos études préliminaires pour obtenir despolymères unidimensionnelles d’EMAC de tris-cobalt en utilisant des radicaux de type thiazyle. / This thesis describes the synthesis and characterizations of extended metal atom chains (EMACs)supported by dipyridylamine (dpa) and dipyridylformamidinate (DpyF) ligands. Chapter Iprovides a brief introduction to metal-metal bonds and extended metal atom chains. In Chapter IIspin crossover properties of series of tricobalt EMACs based on [Co3(dpa)4X2] motifs arepresented. The influence of the axial ligands and the symmetry of the molecule was examined andcorrelated with the SCO properties. Chapter III describes the enantiomeric resolution and X-rayoptical activity of tricobalt EMAC, [Co3(dpa)4(MeCN)2]2+. In chapter IV, the coordination chemistryof N,N’-di(2-pyridyl)formamidinate, (DpyF) is explored, a ligand which gives rise to complexeswith remarkable structural and magnetic properties Finally, chapter V presents our initial effortsto obtain one-dimensional coordination polymers of tricobalt EMAC using thiazyl radicals.