The Relationship Between Structure And Interaction In Noble Metal Phosphine Complexes

This text includes multiple interconnected projects that explore the chemistry of gold(I) phosphine complexes for purposes of elucidating the interactions of monovalent gold centers both with and without aurophilic attractions. These studies expressly focus upon the solid state properties, where structural determination via X-ray crystallography is key. The first chapter focuses on the series of complexes Au2([mu]-dppe)X2 (dppe is 1,2-bis(diphenylphosphino)ethane, X = Cl, Br, I) and Au2([mu]-dcpe)X2 (where dcpe is 1,2-bis(dicyclohexylphosphino)ethane). Previous work had focused on luminescent characteristics of similar complexes, but the phosphine ligands contained fluorophoric phenyl moieties that could be identified as contributors to this phenomenon. In addition, prior comparable studies had similar ligands that displayed a propensity towards polymeric or pseudo-polymeric structures, and the increased steric bulk of cyclohexyl groups was utilized to inhibit the formation of such aggregation. This study clarifies and infers the innocent nature of the dppe ligand with regards to luminescence displayed in monovalent gold complexes containing aurophilic interactions, allowing the emissions to be more confidently attributed to the metal-metal interactions. The second chapter focuses on the synthesis and interconversion of a series of complexes comprised of triphos (bis(2-diphenylphosphinoethyl)phenylphosphine), bridging monovalent gold atoms, and non-coordinating anions. Helicate ([Au3(Triphos)2]3+) systems may form monomeric units, or dimerize with bridging chloride anions, but do not display tendencies towards polymeric formations. Gold box systems ([Au6(Triphos)4Cl]5+) may form with EF6− type anions, with a complex packing structure displaying a fascinating dependency upon cavity occupancy on the molecule's surface as well as its interior. Each of these systems display distinct luminescence and these may be readily interconverted through mechanical stimuli or a recrystallization that is sensitive to specific solvent systems. The third chapter focuses on a series of complexes analogous to those in the second chapter, but utilizing bromide ions in the places previously occupied by chloride. The same helicate,bridged dimer, and gold box interconversions are observed, with the additional possibility of a second encapsulated bromide anion. These systems display much more selective luminescence with greater diversity, and mechanical stimuli resulted in the observation of transformation through negative mechanochromism where the previous case was positive mechanochromism. The box moieties and their transitions appear to be dictated by localized interactions with anions and solvent resting within nested formations of phenyl rings. Within these studies, the box has been identified as a viable luminescent molecular container for small anions with the assistance of appropriately sized solvent molecules (e.g. toluene), but the di-bromo box system implies a greater variation for content size. A system of such extreme lability and fluxionality may have excellent potential as a selective capture agent, especially with such simplistic conformation away from a container room temperature mechanical grinding at room temperature or dissolving in a solvent that inhibits box formation such as methanol.