Design, synthesis and study of photophysical properties of Re(I) and Ru(II) metal center organometallic complexes as dyes for harvesting sunlight.
Komreddy, Venugopal R.
AdvisorRillema, D. Paul
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Due to fascinating physical and photophysical properties, the Re(I) and Ru(II) metal complexes coordinated with small organic molecules, such as 2,2'-bipyridine, 1,10-phenanthroline, 2,2'-bipyrazine derivatives, are very promising class of compounds in Dye Sensitized Solar Cells (DSSC) or (Grätzel Cell) for solar energy conversion for next-generation photovoltaic devices. Herein, we successfully prepared a series of Re(I) complexes [Re(dcbpy)(CO)3X, Re(dcbpz)(CO)3X, Re(5-COOHphen)(CO)3Cl, [Re(phen)(CO)3(py-CH3COO)Re(phen)(CO)3]+ where X=Cl, Br, I, CN, SCN; dcbpy = 4-4'-dicarboxyl-2,2'-bipyridine; dcbpz = 5-5'-dicarboxyl-2,2'-bipyrazine; py-pyridine; 5-COOH-phen = 5-carboxyl-1,10-phenanthroline, dafo =4,5 diazo fluorene-9-one], rhenium (I) tricarbonyl complexes with bipyrazine derivatives, [Re(bpz)(CO)3Cl, Re(Me-bpz)(CO)3Cl, Re(Me2-bpz)(CO)3Cl, Re((COOCH3)2-bpz)CO)3Cl, Re(pypz)(CO)3Cl] and Ru(II) metal complexes where 2,2'-bipyrazine (bpz), 5-methyl-2,2'-bipyrazine (Me-bpz), 5,5'-dimethyl-2,2'-bipyrazine(Me2-bpz), dimethyl [2,2'-bipyrazine]-5,5'-dicarboxylate ((COOCH3)2-bpz), and 2-(pyridine-2-yl)pyrazine (pypz). A simple and efficient synthetic route is presented for the synthesis of a series of pyrazine compounds coupled with bromo derivatives, which lead formation of the C-C bridged dimers. The structural, physical and photophysical properties of these compounds were thoroughly investigated by various analytical techniques. The band at lower energy observed, which shows the typical metal-to-ligand charge transfer (MLCT) due to the d (PI) -> (PI) * transitions consistent with Re(I) dicarboxylate-bipyridine systems located in the 390 nm to 436 nm region. Very interestingly these compounds showed long lifetimes (τ > 50 ns) that can be attributed to anchoring dicarboxylate groups to TiO2 in DSSC. The optimum efficiency of these DSSC system is about 1%.
Thesis (Ph.D.)-- Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry