HOPV12 - Blogs

4 th Hybrid and Organic Photovoltaic Conference -Uppsala 2012 276
C136 - Synthesis and Properties of an Asymmetric Binuclear Ruthenium Polypyridine
Dye
Tiago A. Matias, André Luís A. Parussulo, Sérgio H. Toma, Koiti Araki, Henrique E. Toma
Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, S˜ao Paulo, CEP 05508-000, Brazil
Supramolecular approach has been used to design more efficient photosensitizers for Dye
Sensitized Solar Cell (DSSC) with capable to harvest light by photoinduced charge separation,
higher absorptivity in the visible/infrared range thanks to antenna effect and electron-transfer
processes to enhance photoinduced charge separation, associated with slower charge
recombination processes. 1
Previously we described the symmetric binuclear complex Na6[{[Ru(dcbpy)2Cl}2(BPEB)]
(dcbpy=2,2'-bipyridine-4,4'-dicarboxylate and BPEB=trans-1,4-bis[2-(4pyridyl)ethenyl]benzene)
which exhibited good photoelectrochemical properties. 2 Here we
focused on the asymmetric binuclear species {[RuCl(dmbpy)2]-BPEB-[RuCl(dcbpyH2)2]}(PF6)2
(dmbpy=4,4’-dimetil-2,2’-bipyridine) containing a donor [RuCl(dmbpy)2] and acceptor
[RuCl(dcbpyH2)2] moieties. BPEB is a π-conjugated bridging ligand allowing intramolecular
electron-transfer or energy-transfer processes 2 increasing solar-to-electrical energy conversion
efficiency in dye sensitized solar cells, DSSCs.
The [RuCl(dmbpy)2(BPEB)](PF6) and the binuclear species were successfully prepared using a
similar procedure to literature. 3 ESI-MS spectrum of the binuclear species showed a molecular
ion peak in m/z=707.1 (Δm/z=0,5 Figure1A) and the daughter ion fragments
[RuCl(dcbpyH2)2(BPE)] 1+ m/z=909.0, [RuCl(dmbpy)2(BPE)] 1+ m/z=789.2 and
[RuCl(dmbpy)2] 1+ m/z=505.0 as expected for the MS + spectrum.
The [RuCl(dmbpy)2(BPEB)] exhibited absorption bands at 295 and 355nm, ascribed to
dmbpy and BPEB intraligand transitions (Figure1B), 3 and metal-to-ligand charge transfer
(MLCT) bands at 421 and 488nm. 3 The binuclear species exhibited bands at 295, 316 and
355nm ascribed to intraligands transitions in the dmbpy, dcbpyH2 and BPEB, respectively, and
the charge transfer bands at 419 and 499nm. These were broadened and intensified by the
contributions of the MLCT bands of both, the [RuCl(dcbpyH2)2(BPEB)] and
[RuCl(dmbpy)2(BPEB)] moieties.
The [RuCl(dmbpy)2(BPEB)](PF6) showed two reversible ligand reduction processes at E1/2= -
1.33 and -1.52V and the characteristic Ru(III/II) process at E1/2=0.80V. 3 The binuclear complex
exhibited two reversible Ru(III/II) processes at E1/2=0.84 and 1.28V respectively assigned to the
[RuCl(dmbpy)2] and [RuCl(dcbpyH2)2] bridged by BPEB (Figure1D).
© SEFIN 2012