This thesis addresses the synthesis of a new mix-metal trimetallic nitride template endohedral metallofullerene (TNT-EMF) and the functionalizations of M3N@C80 (M = Sc, Gd, Ho) under the high-speed vibration milling (HSVM) condition. In addition, this thesis discusses the internal motion of the cluster, Sc3N inside three different carbon cages, C68, C78 and C80. Water-soluble derivatives of endohedral metallofullerenes possess a unique potential for medical applications, such as magnetic resonance imaging (MRI) contrast agents, X-ray contrast agents and nuclear medicine. The TNT-EMFs have inherent advantages over other endohedral metallofullerenes, such as M@C60 and M@C82, due to the encapsulation of up to three metal atoms inside the carbon cages. M3N@C80(OH)m(O)n (M = Sc, Gd, Ho) were synthesized under the HSVM condition and characterized by FT-IR, MALDI-TOF and XPS. The relaxivity studies on these water-soluble derivatives have shown that Gd-based metallofullerols have significantly higher relaxivities than commercially used MRI contrast agents (e.g. OmniscanTM) and can be the next generation MRI contrast agent. The Ho containing species has a high R2/R1 ratio compared to other samples showing the potential to be a T2 agent. In contrast to homonuclear M3N clusters, there is a paucity of mixed-metal cluster cases of TNT-EMFs reported to date because the mixed-metal metallofullerenes are difficult to be separated and purified. In this thesis, CeSc2N@C80 was synthesized, separated in pure form and fully characterized. Single-crystal X-ray diffraction shows that CeSc2N@C80 consists of a four atom asymmetric top (CeSc2N) inside a C80 (Ih ) carbon cage and the nitride ion is not located at the center of the carbon cage but is offset by 0.36 Å. The NMR studies, together with the XPS results, show that CeSc2N@C80 is a weakly paramagnetic system with a single buried f electron spin. A new cage isomer of the Sc3N@C80 (D5h) metallofullerene was also isolated from the Ce-Sc mixture and the cage symmetry was confirmed by single-crystal X-ray diffraction. The internal motion of the metal-nitride cluster, Sc3N within the carbon cages (C68, C78 and C80) was studied at various temperatures using 45Sc NMR spectroscopy. The reorientation barriers (presumably dominated by motion internal to the cage) were calculated for these three TNT-EMFs. The preliminary results show that the quadrupole coupling constant of Sc3N@C80 (Ih) is quite close to that of Sc3N@C68. / Master of Science

Gadolinium endohedral metallofullerenes (EMFs) have shown the potential to become next generation magnetic resonance imaging (MRI) contrast agents due to their significantly improved efficiency and safety, as well as multi-day body retention which allows for a longer surgery and observation compared to current contrast agents. In Chapter 1, I have reviewed the development of gadolinium EMF based MRI contrast agents. In Chapter 2, I have described my study of Gd3N@C80 and Gd3N@C84 metallofullerenols as next generation MRI contrast agents. The metallofullerenols are synthesized and characterized utilizing UV-vis, IR, X-ray photoelectron spectroscopy (XPS) and dynamic light scattering (DLS). In addition, relaxivity data were obtained for the two metallofullerenes, and the results showed that Gd3N@C84 metallofullerenol had enhanced relaxivity compared to Gd3N@C80 metallofullerenol. This result is consistent with the observation of magnetic resonance images of the samples at different concentrations. The enhanced relaxivity was attributed to the special "egg shape" of the Gd3N@C84 cage. In Chapter 3, I have described the relaxivity study of Gd3N@C80 (without functionalization) in oleic acid, which could be used as an MRI contrast agent for more hydrophobic bioenvironments. The results show that Gd3N@C80 has a reasonable relaxation effect (relaxivity ~10 mM-1S-1 at 1.4 T) in oleic acid and could be a viable contrast agent even without functionalization. In Chapter 4, I have discussed the outlook of gadolinium EMF-based MRI contrast agents and suggested several directions for future work. / Master of Science

Endohedral metalofullerenes (EMFs) have emerged as an important class of nanomaterials with vast promise in applications of molecular devices and nanomedicines. This dissertation addresses the EMF research span from synthesis to application, with an emphasis of work on trimetallic nitride template (TNT) EMF and carbide clusterfullerenes (CCFs). As a general introduction, chapter 1 reviews the main literature in TNT EMF studies. Also key works in CCF area are highlighted to show the common feature and uniqueness of this class of EMF in comparison with other EMFs. In the last part of the chapter a list of milestone progress in EMF area has been summarized. Chapter 2 is devoted to the synthetic work on EMFs. Especially, for isotopic modification, the trial and actual EMF syntheses in efforts to introduce 13C, 89Y and 177Lu are described. The next three chapters address the structural characterization of EMFs. Chapter 3 focuses on structural studies of CCFs. With detailed interpretation of 13C NMR and DFT computational results for selected members of the Y2C2@C2n family, the influence of fullerene cage on the size and shape of the yttrium carbide cluster (Y2C2)4+ is investigated. It has also been established that the carbide cluster prefers a linear shape in sufficiently large fullerene cages but adopts a compressed butterfly shape in smaller cages where space is constrained. Chapter 4 presents a systemic examination of dipole moments in TNT EMFs. The first 13C NMR study of M3N@C2(22010)-C78 is achieved on Y3N@C2(22010)-C78. In addition, dipole moments of the M3N@C2n (n=39-44) family are probed by interpretation of chromatographic retention behavior, DFT computational results and single-crystal data. It has been found that TNT EMFs with pentalene motifs exhibit enhanced dipole moments due to the cluster-cage interplay. Chapter 5 provides full characterization of the M2C2@C1(51383)-C84 (M=Y, Gd) molecule, which contains the first example of an asymmetric fullerene cage with fused pentagons. Furthermore, it is suggested that the C1(51383)-C84 cage is capable of a cascade of rearrangements into high symmetry and stable fullerene cages via well-established mechanistic steps, namely, extrusion of C2 units from pentalene or indene motifs and Stone-Wales transformations. As an important intermediate in the formation of high symmetry fullerene cages, the C1(51383)-C84 represents a missing link that implies the "top-down" fullerene formation mechanism. Chapter 6 describes the endeavor to functionalize two exotic EMFs, the room-temperature radical heterometallofullerene Gd2@C79N, and the egg-shaped TNT EMF Gd3N@C84. The reactivity of Gd2@C79N is directly compared to Y2@C79N, Gd3N@C80 and Sc3N@C80 in two reactions and the paramagnetic Gd2@C79N is proven to be very inert toward many known common fullerene cage reactions. Eventually both EMFs have been successfully functionalized via the Bingel reaction, and the derivatives are characterized with HPLC and mass-spectrometry. Chapter 7 compares the effective magnetic moment of Gd3N@C80 and Gd3N@C84, together with the previously reported Gd@C82. The magnetic moment has a second-order contribution to the T1 relaxivity and thereby is an important factor to evaluate an EMF's value in application as MRI contrast agents. Furthermore the influence of cluster motion to magnetic behavior in TNT EMF is discussed. / Ph. D.

Nous avons synthétisé différentes dyades donneurs-accepteurs (D-A) π-conjuguées à base de fullerène pour des applications photovoltaïques dans lesquelles les unités D étaient soit des oligophenylenevinylenes (OPV) soit des oligophenyleneethynylene (OPE) et les unités A étaient le C60 ou un endofullerène du type Y3N@C80. Il y avait une exigence supplémentaire pour nos matériaux, à savoir qu’ils devaient s’auto-organiser en phases liquides-cristallines. Pour ce faire, toutes les unités D contenaient un promoteur mésogène afin d'induire le mésomorphisme de la dyade D- et donc de contrôler la morphologie des couches minces nécessaires à l’élaboraiton des cellules photovoltaïques grâce à une organisation supramoléculaire. En dehors de cela, nous avons étudié l’influence de la nature chimique du donneur (par exemple lyophile ou amphiphile), de la longueur des oligomères et de la multiaddition sur les propriétés photophysiques et sur l'auto-assemblage. Nous avons synthétisé une dyade OPE-Y3N@C80 qui est le premier dérive mésomorphe et photosensible de ce type de métallofullerène endohédral. / We have synthesized different π-conjugated system-fullerene dyads for photovoltaic applications, where the donor units were either oligophenylenevinylene (OPV) or oligophenyleneethynylene (OPE) derivatives and for the acceptor, C60 or Y3N@C80 was used. There was an additional requirement for our materials: liquid crystallinity. All the donor units contained a mesogenic promoter in order to induce mesomorphism in the D-A dyad and to control the morphology of the prepared film through supramolecular organization. Apart from that, we investigated the effect of the chemical nature of the donor moiety (ie. lyophilic or amphiphilic), the oligomeric length and multiaddition on the photophysical properties and on the self-assembly. We have synthesized an OPE-Y3N@C80 dyad which is the first trimetallic nitride template endohedral metallofullerene derivative with mesomorphic and photoactive properties.