Publications Repository - Gdańsk University of Technology

The optical properties of a new(bipyridine)2Ru(4H-imidazole) complex presenting a remarkablebroad absorption in the visible range are investigated. Thestrong overlap of the absorption with the solar radiationspectrum renders the studied complex promising as a blackabsorber and hence as a starting structure for applications inthe field of dye-sensitized solar cells. The correlations betweenstructural and electronic features for the unprotonated andprotonated forms are studied by means of UV−vis absorptionand resonance Raman (RR) spectroscopy modeled with thehelp of time-dependent density functional theory (TDDFT) calculations. The absorption spectra show two bands in the visibleregion, which TDDFT assigns to a metal-to-ligand charge-transfer (MLCT) state and to a superposition of three excited stateswith MLCT and intraligand charge-transfer character, respectively. Additionally, the analysis of the molecular orbitals and RRspectra in resonance with the first MLCT band shows that the effects of protonation favor a charge-transfer photoexcitation tothe 4H-imidazole ligand. The RR spectra simulated for several excitation wavelengths covering the visible region are in excellentagreement with experimental data. In particular, it is noteworthy that the calculations are able to reproduce the wavelengthdependence of the RR spectra provided that corrected excitation energies are employed. Interference effects between theelectronic states contributing to the RR scattering are small for the investigated complex.

Authors

• prof. dr hab. Julien Guthmuller link open in new tab ,
• Stephan Kupfer,
• Maria Wachtler,
• Jurgen Popp,
• Benjamin Dietzek,
• Leticia Gonzalez