Photophysical study of Ruthenium (II) Tris (1,10-Phenanthroline) encapsulated in zirconium based Uio-66 and derivatives

Jacob M. Mayers and Randy W. Larsen

University of South Florida

Uio-66 metal organic frameworks are thermally stable porous materials that provide an excellent environment for the encapsulation of photoactive guests. The guest of particular interest is Ruthenium (II) Tris-(1,10-Phenanthroline) (RuPhen) due to the relatively long lifetime and photostability of this class of complexes. Presented here is a photophysical study of RuPhen encapsulated Uio-66 MOFs and derivatives. The RuPhen encapsulated in each of the MOF frameworks were fit to a biexponential decay function. A bathochromatic shift is also observed in both the steady state emission and FT-IR spectrum of each framework. The consequences of adding an amine or hydroxyl substituent to the organic ligand exhibits photophysical changes different from the parent Uio-66 such as lower lifetimes and longer wavelength emissions. Electron transfer or intermolecular hydrogen bonding between the RuPhen and the amine or hydroxyl substituent might be a plausible explanation of such spectroscopic variation. It is shown that the photophysical properties of RuPhen be altered through the adjustments of the Uio-66 framework by modifying the organic linkers supporting the inorganic Zr6O4(OH)4 clusters.