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theses

This thesis describes utilizing spectroscopy techniques, such as Resonance Raman spectroscopy and X-ray absorption spectroscopy, for some fundamental studies of transition metal complexes. Firstly, a series of Fe-Pt-Fe trinuclear complexes are investigated by resonance Raman spectroscopy. The spectroscopic studies can provide insight into the ground state and excited state of the related complexes, and help us to understand the charge ligand and conformation effect on photoinduced charge transfer. Three trinuclear complexes were compared: [(NC)5FeCN-Pt-(L)n-NCFe(CN)5]4- (abbreviated as [Fe2Pt-(L)2]4-), where L= NH3, (n=4); cyclam, (n=1); ethylenediamine(en), (n=2). The crystal structures reveal that the cyclam complex has an eclipsed configuration, while the ammonia ligands yield a staggered one. The crystal structure of [Fe2Pt-(en)2]4- is not available, so the twist angle between the CN and en equatorial ligands is not known. By doing the Raman frequency analysis, we concluded that the eclipsed conformation allows more electronic delocalization across the Fe-CN-Pt bridge. The resonance Raman intensity analysis provides us that the largest contribution to the vibrational barrier to electron transfer were those modes associated with the Fe-CN-Pt bridge. Comparing the Raman data of those trinuclear complexes, we assumed that the conformation of [Fe2Pt-(en)2]4- might in between of the [Fe2Pt-(NH3)4]4- and [Fe2Pt-cyclam]4-. Secondly, some Copper(I) diimine coordination complexes have the ability to flatten out in the metal-to-ligand charge transfer (MLCT) state after populating through photoexcitation. This ability is crutial to the subsequent dynamics and structures present in the excited state. A series of Cu(I) complexes which have different ligand environments has been synthesized. We propose to use resonance Raman to investigate how the coupling of two Cu(I) atoms through a bridging bisphenanthroline ligand affects the nature of the MLCT excited state. Thirdly, some ruthenium polypyridine sulfoxide complexes exhibit photochromic behavior. The photo-triggered isomerization of this kind of complex involves the transformation of sulfoxide from Ru-S to Ru-O bonded. This photo-induced isomerization dramatically changed the spectroscopic and electrochemical properties of the metal complexes. In our project, intermediate-energy X-ray absorption spectroscopy (XAS) was used to characterize the series of Ru-S/SO complexes related to their photochromic analogues. By collecting sulfur K-edge XAS data for this series of structurally similar complexes exhibiting diverse photochemical reactivity, and combining with TD-DFT calculations, an attempt was made to characterize the σ and ᴨ contributions to the HOMO correlate them with their reactivity.

ETD_8267

M.S.

Includes bibliographical references

by Qiaoqiao Xie

doi:10.7282/T3FB561D

ETD graduate

The author owns the copyright to this work.