Tetrathiafulvalene-annulated phenanthroline and its complexes with transition metals

Recent interest in designing multifunctional transition metal complexes that incorporate the redox-active tetrathiafulvalene (TTF) molecule stems from the perspective of embedding specific localized properties of transition metal ions into TTF-containing substructures characterized by extended delocalized conduction pathways. This dissertation reports on the synthesis of tetrathiafulvalene, a ubiquitous component of organic conductors, fused directly to 1,10-phenanthroline, one of the most popular ligands in transition metal chemistry. We have devised and implemented a synthetic pathway to this unique ligand, which then was used to obtain complexes with Ru(II) and Fe(II) ions. Chapter 1 of this dissertation provides an introduction to the chemistry of TTF and its metal complexes. Chapter 2 describes the most important methods of characterization employed in this research project. Chapter 3 is devoted to the preparation and properties of the TTF-annulated phenanthroline ligands. Chapter 4 describes a detailed study of a Ru(II) complex of TTF phenanthroline, including its structural, photophysical, and electrochemical properties. [Ru(bpy) 2(edt-TTF-phen)](PF6)2 exhibits a unique helical packing of molecules in the crystal structure. In contrast to its TTF-free analogues, this complex contains a TTF-centered highest occupied molecular orbital, and the electrochemical data show that the first two oxidations of the complex are TTF-based. Examination of the photophysical properties revealed that this Ru(II) complex experiences excited-state luminescence quenching via reductive electron transfer from the TTF to the Ru3+ center, which opens up a path for non radiative relaxation to the ground state through the low-lying intra-ligand charge transfer state. We also describe an unusual photoreactivity of this complex that leads to the cleavage of the central C=C bond of the TTF unit in solution. Such reactivity was monitored by the evolution of NMR, UV-visible, emission, and transient absorption spectra. Chapter 5 describes spin-crossover behavior of [Fe(NCS)2(L) 2] (L = edt-TTF-phen or hexS2-TTF-phen) and parent Fe(II) complexes. The complex with hexyl substituents is highly soluble and exhibits reversible oxidations centered on the TTF fragments. The observed spin transition was elucidated with variable-temperature Mossbauer and infrared spectroscopies.