| The study of nitrogen heterocyclic ligands in coordination chemistry has experienced a steady increase in the last thirty years. The increasing versatility of synthetic methods used in the preparation of ligands has permitted increasingly more complex molecules to be assembled. The work reported in this thesis involves the systematic study of the chemistry of five diimine ligands that have not been investigated thoroughly to date. These are 2-2-pyridyl-1,8-naphthyridine (pynp), 3,6-bis-pyridyl-tetrazine (bptz), 2,2′-bis-bipyridyl-azo (abpy), 1,3,6-trispyridyl-triazine (tptaz), and 2,3,5,6 tetrapyridyl pyrazine (tppz).; The chemistry of the bptz ligand was explored with a variety of first row transition metals, with the result being the high yield syntheses of cyclic coordination compounds metallocyclophanes). The formation of these cyclic entities rather than polymeric materials or dinuclear complexes is attributed, in great degree, to the choice of the anion which functions as a template in the self-assembly of the cationic metallocyclophanes. Anions that we similar in size and geometry, e.g. [BF4]− and [ClO 4]−, yield molecular squares, whereas the larger anion, [SbF6]−, leads to the assembly of a molecular pentagon.; The existence of these species in solution was demonstrated by 19F NMR studies conducted on the diamagnetic metallocyclophane, [Zn 4(bptz)4(CH3CN)8][BF4] 8), the results of which indicate that the encapsulated anion is present in the solution form of the compound. Electrospray mass spectrometry revealed that the formation of these metallocyclophanes with other transition metals such as MnII, FeII, CoII and CuII feasible, but that they are not as stable as the Ni II and ZnII analogs.; The chemistry of tppz has languished for almost two decades, most likely due to reports that coordination of more than one metal center was not possible. We embarked on the synthesis and characterization of a series of mononuclear tppz compounds [M(tppz)2]n+ that can potentially be used as building blocks for the synthesis of higher nuclearity species. In addition, a new application for this ligand was discovered in our laboratory, namely as a linker for metal-metal compounds to give molecular rectangles. In this vein, the compound [RH4(O2CCH3) 2(tppz)2(CH3OH)4][PF6] 6 was prepared which is the first of its kind in the M-M bond field.; Naphthyridine based ligands have been used relatively infrequently compared to phosphine, halide or carboxylate derivatives in metal-metal bond chemistry. The presence of two pynp ligands in the dimetal units [M2] 4+ (M = MoII, RuII and RhII) allows for a rich electrochemistry that is not observed for most metal-metal compounds with more electronically “innocent” ligands. In the case of two of the new compounds in this study, four reversible one electron ligand based reductions, are observed. The compound [Ru2(O 2CCH3)2(pynp)2][PF6] 2 shows Class III Robin-Day behavior with all four electrons being fully delocalized throughout the molecule, whereas in the [Mo2] 4+ derivative, Class II behavior is found. |
