Date of Award

2013

Document Type

Thesis

First Advisor

Assefa, Dr. Zerihun

Abstract

Coordination of several chromophoric ligands capable of sensitizing Tb3+ and Eu3+ ions have been studied. Four new complexes of Eu3+ and Tb3+ ions were achieved by coordinating Eu with 4’, 4’’’’- (1-4 phenylene) bis (2, 2’:6’, 2-terpyridine) , pyridino [2-3-b] pyrazines and 6,6′′ dibromo-2,2′:6′,2′′-terpyridine.The crystal structure of [Tb(TPAO)2(H2O)4(Au(CN)2)3], was determined and shows a polymeric three-dimensional coordination with a monoclinic space group Cc, Z=4. The unit cell parameters are a = 17.4266(14) Å, b = 10.8224(10) Å, c = 18.0270(16) Å, α = 90° β = 109.309(3)° γ = 90°. The structure exhibits an equilateral Au-Au-Au interaction bridged to a terbium core by the C-N groups. Three other complexes, viz [Eu(ppz)2(H2O)n]Cl3, [Eu(ptpy)(H2O)n]Cl3 and [Eu(bbterp)(H2O)n]Cl3, have also been synthesized and characterized using IR and luminescence spectroscopy, although no crystal was obtained suitable for X-ray diffraction analysis. The ligand tetra(2‘-pyridyl)pyrazine (tppz) was also crystallized and its crystal structure solved. The results herein, elaborate the mode of dual donor sensitization from ligand groups to the lanthanide ions. The efficiency of energy transfer that occurs in the Ln3+ complexes has been calculated, taking into account the radiative and non radiative relaxation processes, and the limitation encountered. A broad excitation spectrum at 369, 366 and 380 nm were observed for [Eu(ppz)2(H2O)n]Cl3 , [Eu(bbterp)(H2O)n]Cl3 and [Eu(ptpy)(H2O)n]Cl3 complexes, respectively upon monitoring the Eu3+ emission indicating the presence of ET in a donor-acceptor type interaction.

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