The Photophysical Studies of Transition Metal Polyimines Encapsulated in Metal Organic Frameworks (MOF’s)

Light harvesting systems provide a platform that converts solar energy into other forms of energy. One of the most common examples of photon capturing and conversion into chemical energy is observed in photosynthetic organisms in both Eurkaroyic and Prokaryotic domains. Nature provides a model for successful light harvesting platforms which includes the compartmentalization of antenna complexes that contain separated donor and acceptor pairs that participate in efficient electron transfer processes. In order to mimic such systems, crystalline porous materials that exhibits regular cavities and pore dimensions provides an excellent starting place. Metal organic frameworks (MOFs) are a class of porous organic and inorganic materials that exhibit highly crystalline cavities that are ideal for the encapsulation of donor-acceptor pairs. The non-covalent encapsulation of a photoactive guest results in photoactive metal organic frameworks (PMOFs). The regular cavity sizes and geometries of MOF’s allow for one to study the effects of encapsulation on guest photophysics. A class of prototypical photoactive guests including the group 8 transition metal polyimines including iron (II), ruthenium (II), and osmium (II) complexes. One in particular is ruthenium (II) tris-(2,2’-bipyridine) (RuBpy) which exhibits a low spin ground state electron configuration (1GS) and prominent photophysical properties such as broad visible light absorption, a high luminescent quantum yield, and long emission lifetime. These properties are advantageous in many solar chemistry applications. Presented is this dissertation are the photophysical studies of Ru (II) polyimines encapsulated in Zr (IV), Zn (II), and Cd (II) metal organic frameworks. The chosen Zr (IV) and Zn (II) MOF’s are well known structures and exhibit cavities sizes and geometries capable of accommodating the Ru (II) complex. These studies are compared to Ru (II) templated Cd (II)-carboxylate MOF’s which are only formed in the presence of either heteroleptic and homoleptic Ru (II) complexes. From all three studies, relationships between cavity size and guest photophysics are examined. Furthermore, similar photophysical studies are performed on other transition metal polyimines including Os (II), Fe (II), and Ir (III) complexes in Zn (II)-carboxylate MOF’s. The purpose of these studies is that by understanding the steric and electrostatic effects on the guest photophysics, improvement on future solar cell development can be achieved