Adsorption of Dipyrrin-Based Dye Complexes on a Rutile TiO2(110) Surface

The adsorption of two ruthenium-based dye complexes containing dipyrrin-based ligands has been studied on the rutile TiO2(110) surface using synchrotron-based electron spectroscopy. The dye complexes studied were bis(5-(4-carboxyphenyl)-4,6-dipyrrin)bis(dimethyl sulfoxide)ruthenium(II) and bis(5-(4-carboxyphenyl)-4,6-dipyrrin)(2,2′-bipyridine)ruthenium(II). The dye molecules were deposited using in situ electrospray deposition, which allows for the deposition of thermally fragile molecules in ultrahigh vacuum. Photoemission studies were used to provide experimental data on the bonding geometry of the dye complexes to the rutile TiO2(110) substrate and to provide data on molecular orbitals involved in the charge transfer process. DFT calculations of the molecules adsorbed onto the rutile TiO2(110) surface have also been performed to identify the most energetically favorable bonding geometry.