Temperature-dependent and time-resolved emission studies of cis-Ru(bpy)2(N3)2
Abstract
The electronic properties of a RuII cyclometalated dye complex, cis-Ru(bpy)2(N3)2 , were examined with time-resolved and temperature-dependent visible emission measurements. Compared to two related solar cell dye-sensitizer species, cis-Ru(bpy)2(NCS)2 and cis-Ru(bpy)2(CN)2, the azide (N3) pseudohalide ligand dramatically changes the electronic properties of the dye. The uv-vis absorption spectra of cis-Ru(bpy)2(N3)2 in various solvents reveal that its metal-to-ligand charge transfer band (MLCT) is located more than 50 nm to the red of the MLCT bands found for the other two complexes. Furthermore, while room temperature emission is readily observed for cis-Ru(bpy)2(NCS)2 and cis-Ru(bpy)2(CN)2, the emission is much weaker for cis-Ru(bpy)2(N3)2 . We report the first observation of luminescence from cis-Ru(bpy)2(N3)2 by measuring it in 4:1 EtOH:MeOH matrices at temperatures below 140 K. Emission bands are observed at 665 nm and 620 nm (514 nm excitation). The quantum yield of this species was estimated by comparing the integrated emission signal of cis-Ru(bpy)2(N3)2 to that of cis-Ru(bpy)2(CN)2 at 77 K and was determined to be exceptionally low (6 x 10-4). The luminescence lifetime of cis-Ru(bpy)2(N3)2 at 77 K was measured to be approx. 800 ns, implying an extremely slow radiative rate of 780 s-1. The long radiative rate and low quantum yield led us to further investigate the photolability and electrochemical behavior of the azide complex.
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2013
- Bibcode:
- 2013APS..MARY43009G