Coordination polymers and metal-organic frameworks (MOFs) are a class of solid-state materials where metal centers are connected through coordination with multifunctional organic compounds and propagate into a higher-dimensional material. The topology of these materials is governed by the coordination preferences of the metal center and those of the organic compound or through the use of a structure-directing agent (a qtemplateq). The primary focus of this dissertation has been to develop methods of topological manipulation in various MOF systems. Herein, the use of 4, 4'-bipyridine and related molecules have been explored throughout a series of lanthanide-aliphatic and calcium-adipate systems. As such, a series of guidelines for template occlusion in MOFs was developed including hard-soft acid-base considerations, hydrophobic/hydrophilic interactions, hydrogen bonding, and template size and flexibility. This template, 4'4-bipyridine was also observed to affect the physical properties of the MOF in that it acts to stimulate lanthanide luminescence through a process known as the antenna effect. Quantum yield and lifetime measurements were recorded in order to quantify the effects that 4, 4'-bipyridine has on overall luminescent properties. GWMOF-6:Eu has a quantum yield of 23% with a lifetime of 726mus, and GWMOF-6:Tb with a 32% quantum yield and a lifetime of 1395mus. If both elements are incorporated into GWMOF-6 in a 50/50 ratio, Tb(III) emission is almost completely quenched by transferring its energy to the Eu(III) center, increasing overall quantum yield to 39% (lifetime Eu(III) increased to 768mus and Tb(III) decreased to 523mus). Other lanthanide combinations were explored with promising preliminary results. Another route to topological control that was developed in this dissertation was to reduce the typically high coordination number of the lanthanide to promote the formation of more familiar coordination geometries (e.g., octahedral) and to create more accessibility to the ion. It was observed that organic linkers that could provide a significant degree of steric hindrance thwarted coordination to the lanthanide ion, thus decreasing overall coordination number. These structural systematics and photophysical properties of these various systems are discussed in detail.... Figure 1.2 MO diagrams for Hard-Hard and Soft-Soft interactions in HSAB theory...................9 Scheme 1.3 CP formation in a templated lanthanide-adipate system................................................8 Figure 2.1 Examples of lanthanide coordinationanbsp;...
|Title||:||Host-guest Interactions and Photophysical Properties Within 4,4'-bipyridine-derived Templated and Non-templated Metal-organic Framework Materials of the Lanthanide Elements and Calcium|
|Publisher||:||ProQuest - 2008|