Surface-induced thermal decomposition of [Ru(dcbpyH)2-(CN)2] on nanocrystalline TiO2 surfaces: Temperature-dependent infrared spectroscopy and two-dimensional correlation analysis

Thermal degradation mechanism of the self-assembled thin films of [Ru(dcbpyH)2-(CN)2] (Ruthenium 505, R505) anchoring on TiO2 surfaces via its carboxylate group has been examined by temperature-dependent diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The CN stretching bands of R505 at 2000–2100 cm−1 appeared to change drastically at ≈140 °C on TiO2 surfaces, whereas a major CN peak at ∼2090 cm−1 disappeared at a much higher temperature above ≈250 °C in their solid states. Two-dimensional (2D) correlation analysis was introduced to explain the thermal desorption behaviors of the Ruthenium dye. Multiple peaks of the CN stretching vibrations are more clearly resolved in the 2D correlation analysis. More complicated features in the CN stretching vibrational spectra on TiO2 than those of the solid states suggest a substantial interaction of the CN groups with the TiO2 surfaces.