Wet-Chemically Prepared Porphyrin Layers on Rutile TiO2(110)

Abstract

Porphyrins are large organic molecules that are interesting for different applications, such as photovoltaic cells, gas sensors, or in catalysis. For many of these applications, the interactions between adsorbed molecules and surfaces play a crucial role. Studies of porphyrins on surfaces typically fall into one of two groups: (1) evaporation onto well-defined single-crystal surfaces under well-controlled ultrahigh vacuum conditions or (2) more application-oriented wet chemical deposition onto less well-defined high surface area surfaces under ambient conditions. In this study, we will investigate the wet chemical deposition of 5-(monocarboxyphenyl)-10,15,20-triphenylporphyrin (MCTPP) on well-defined rutile TiO2(110) single crystals under ambient conditions. Prior to deposition, the TiO2(110) crystals were also cleaned wet-chemically under ambient conditions, meaning none of the preparation steps were done in ultrahigh vacuum. However, after each preparation step, the surfaces were characterized in ultrahigh vacuum with X-ray photoelectron spectroscopy (XPS) and the result was compared with porphyrin layers prepared in ultrahigh vacuum (UHV) by evaporation. The differences of both preparations when exposed to zinc ion solutions will also be discussed.

Porphyrin Catecholate Iron-Based Metal–Organic Framework for Efficient Visible Light-Promoted One-Pot Tandem C–C Couplings

“…25,26 The N 1s core-level spectrum involves three contributions at 397.80, 399.65, and 401.80 eV. 27,28 The high binding energy peak at 399.65 eV is assigned to pyrrolic N (sp 3 N, 49.0%) and the one at 397.80 eV to the iminic N (sp 2 N, 45.3%). 29 The binding energy at 401.8 eV (5.7%) can be attributed to N-oxides.…”

“…The main peak at 284.5 eV is originated from CC double bonds of the porphyrin linkers. The peak at 286.68 eV is assigned to C–(O,N) bonds of pyrrol and catecholate rings, and the very weak one at higher binding energies (288.39 eV) is likely due to the presence of CO groups caused by a partial oxidization of catecholate linkers. , The N 1s core-level spectrum involves three contributions at 397.80, 399.65, and 401.80 eV. , The high binding energy peak at 399.65 eV is assigned to pyrrolic N (sp 3 N, 49.0%) and the one at 397.80 eV to the iminic N (sp 2 N, 45.3%) . The binding energy at 401.8 eV (5.7%) can be attributed to N -oxides.…”

On surface chemical reactions of free-base and titanyl porphyrins with r-TiO2(110): a unified picture

“…Even metalation in solution, which is very effective for free-base porphyrins in solution and vacuum-deposited on gold, 97 does not exceed a 75% yield for a wetting layer of carboxylated TPP on TiO 2 (110). 21,25 In principle, metalation by deposition offers the advantage of leaving unaffected the 2H-TPP molecular ordering eventually established by self assembly. 92,98 This is not necessarily the case for the r-TiO 2 (110) surface, where the adsorption site appears to be driven by a direct chemical interaction of the macrocycle with the surface, even for the simple case of 2H-/4H-HTPP.…”

“…ethanol), thus facilitating the implementation of the protocols of growth on r-TiO 2 (110) by wet chemistry. 24,25 In the absence of peripheral linkers, the vdW interactions drive a flat-lying porphyrin orientation, which brings the chelated metal atom close to the surface, where it may chemically interact with the substrate, thus dictating the adsorption site (on either O br or Ti 5f rows). Simple coordination chemistry arguments suggest that chelated metal ions with coordination vacancies will be able to form bonds with undercoordinated surface atoms.…”

“…ethanol), thus facilitating the implementation of the protocols of growth on r-TiO 2 (110) by wet chemistry. 24,25…”