NEAR-INFRARED EMITTING LANTHANIDE METAL-ORGANIC FRAMEWORKS WITH TUNABLE PHOTOPHYSICAL PROPERTIES

White, Kiley Ann (2011) NEAR-INFRARED EMITTING LANTHANIDE METAL-ORGANIC FRAMEWORKS WITH TUNABLE PHOTOPHYSICAL PROPERTIES. Doctoral Dissertation, University of Pittsburgh.

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Abstract

In this thesis, we present a MOF-based method for modulating the photophysical properties of near-infrared (NIR) emitting lanthanide cations, specifically their excitation and emission properties. We designed and synthesized a ligand, H2-PVDC, that is capable of sensitizing four NIR lanthanide cations: neodymium, holmium, erbium, and ytterbium. Reacting H2-PVDC with Yb(NO3)3 produced an Yb3+-MOF, Yb-PVDC-1, that demonstrated NIR lanthanide luminescence via the antenna effect. We tuned the synthesis of Yb-PVDC-1 to prevent coordination of water molecules to Yb3+, as seen in Yb-PVDC-1, and yielded a material, Yb-PVDC-2, with higher quantum yields. The removal of water molecules allowed for coordination of more PVDC ligands and a subsequent increase in their π−π interactions, resulting in a lower excitation energy for Yb-PVDC-2. The first example of a barcoded MOF was synthesized by incorporating Er3+ cations into the synthesis of Yb-PVDC-1, generating materials ErxYb1-x-PVDC-1. We demonstrate the controlled preparation of a luminescent barcoded MOF whereby Yb3+ and Er3+ emission intensities vary linearly with the lanthanide composition of ErxYb1-x-PVDC-1. These materials display luminescence while dispersed in a polymer coating. We further elaborate on the potential applications of bi-metallic MOFs by demonstrating an improvement of the Er3+ emission upon tuning the dopant amount of Yb3+ within ErxYb1-x-PVDC-1. A series of water-stable MOFs, Ho-PVDC-3, Tb-PVDC-3, Nd-PVDC-3, Er-PVDC-3, Yb-PVDC-3, and barcoded MOFs, ErxYb1-x-PVDC-3, NdxYb1-x-PVDC-3, ErxNdYYbz-PVDC-3 were also synthesized. These MOFs appear stable in water for at least a one month duration, rendering these materials potentially more suitable for biomedical applications. Nd-PVDC-3 and Yb-PVDC-3 exhibit Nd3+ and Yb3+ luminescence while suspended under water, respectively. The barcoded MOFs are synthesized in a controlled fashion, including the potential 3-component tag, ErxNdYYbz-PVDC-3. To further modulate these materials for potential biomedical applications, we utilized a synthesis to make the nanocomposite materials, Nd-PVDC-3 nMOF, Yb-PVDC-3 nMOF, and barcoded NdxYb1-x-PVDC-3 nMOFs. These exhibit luminescence and barcoded emission intensities while suspended under water. Finally, we present a strategy for assembling macrocycles into permanently porous 3-D crystalline structures that relies on strong inter-macrocycle π-π interactions. We created a highly stable mesoporous macrocycle by utilizing another chromophore, H-TPY. To our knowledge, this is the first mesoporous macrocycle-based crystalline material.

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