Bis(phosphine) platinum(II) supramolecular coordination complexes: a structural, photophysical, and computational investigation
Creators: name: Pollock, James Bryant
Publisher: name: University of Utah
Year: 2014
Subjects: Photophysics
Platinum
Self-assembly
Supramolecular

description: Since pioneering work in the early 1990s, supramolecular coordination complexes (SCCs) have attracted attention from researchers because complex, discrete systems can readily be self-assembled from highly symmetric, complementary molecular subunits that display a high-level of modularity and fidelity. Classically, in the Stang lab, SCCs are synthesized using bis(phosphine) platinum(II) metal nodes and rigid, pyridyl-based organic ligands. Flexible SCCs, however, are very rare and are attractive for host-guest applications due to their fluid cavity sizes and shapes that can autonomously adapt to specific substrates. Utilizing a recently developed methodology for constructing multicomponent SCCs that exploits the electronic nature of the coordinating ligands and platinum metal center, a series of 2D and 3D flexible SCCs was synthesized using alkylbased dicarboxylic acid and pyridyl-based subunits. Moreover, insight into the thermodynamic preference for the coordination motif was explored using computational methods, which was determined to originate from orbital effects in conjunction with shape complementarily and electrostatic effects. Platinum-based SCCs have been proposed for photon emitting applications due to the assumed preservation of the unique and attractive photophysical properties of known mononuclear platinum complexes. However, reports on the photophysical properties of platinum-based SCCs are rare, which severely limits their utility. Platinum-based SCCs that display low-energy optical transitions, have high quantum yields, and are readily tunable need to be developed if they are to fulfill this purpose. Using aniline-based core scaffolds, a series of SCCs that emit above 500 nm with quantum yields greater than 20% was synthesized. Utilizing computational methods, the nature of the observed optical transitions were determined to arise from n-type molecular orbitals that are ligand centered with modest contributions from the metal center. By functionalizing the periphery of the aniline-based core scaffolds, a series of rhomboidal-shaped SCCs was synthesized that emit from 500 to 600 nm. The low-energy absorption and emission band of the series was determined to be tunable in a predictive manner by altering the Hammett sigma constants of the peripheral functional group. This dissertation describes our investigations into bis(phosphine) platinum(II) SCCs. In particular, a novel series of flexible SCCs was synthesized and the construction method was probed via molecular modeling. Then, a series of highly emissive endohedral functionalized SCCs is described, characterized, and investigated via computational methods. Model complexes were synthesized to further investigate the nature of the observed photophysical properties for the endohedral functionalized SCCs, culminating with a series of SCCs that displayed facile tunability in a predictive manner with emission profiles spanning the visible spectral window.