Date of Award

5-1-2010

Degree Type

Dissertation

University or Center

Clark Atlanta University(CAU)

School

School of Arts and Sciences

Degree Name

Ph.D.

Department

Chemistry

First Advisor

Dr. Eric Mintz

Second Advisor

Dr. Yi Pang

Third Advisor

Dr. Issifu Harruna

Abstract

The research presented in this dissertation focuses on the design, synthesis, photophysical characterization, and metal ion sensing properties of a conjugated polymer and enhancing the photophysical and acid-base properties of Ru(mtpy)(tpycooh)- a transition metal complex. All the synthesized compounds were based on terpyridine ligans.

The objective of the first project is to investigate the effect of positioning the terpyridine unit in the meta position, which does not allow extended conjugation through the polymer backbone, on the metal ion sensing ability of this conjugated Poly(phenylenevinylene) (PPV) material. A novel PPV containing meta-linked pendant terpyridine ligand was synthesized. Absorption and fluorescence studies indicated that Fe2+ was coordinate in 1:2 ratio to the terpyridyl groups and Cu2+ bound in 1:1 ratio to the terpyridyl groups. A more selective response was observed for this meta-derivative compared to para derivative. Cu2+ selectively quenches the fluorescence of the polymer, with slight interference from Zn2+, Cd2+ and Hg2+. These ions induce partial fluorescence quenching accompanied by a broad new emission band due to the complex formation between the terpyridine (tpy) ligand and the metal ion. The objective of the second project is to synthesize a new mixed-ligand comllex [Ru(mtpy)(tpycooh)](la), where mtpy = 4'- methy1-2,2' : 6'2" - terpyridine and tpycooh = 2,2':6',2"- terpyridine-4' - carboxylic acid. This new complex incorporated mixed ligands to enhance the photophysical propertics of Ru(II) terpyrine complex like its bypyridine analog. The methyl group on tpy acts as an electron-donating group (EDG) while COOH group on tpy acts as an electron-withdrawing group (EWG). The new enhanced complex showed redshifted Metal Ligand Charge Transfer (MLCT) band in the absorption and emission spectra, larger quantum yield and improved redox properties over the non-enhanced model terpyridine-Ru compex. These results implied that the combination of mixed ligands of electron donating and electron withdrawing substituents on tpy ligand improved the luminescence and the photophysical properties of the complex.

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Chemistry Commons

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