Surface Reactions and Electronic Structure of Carboxylic Acid Porphyrins Adsorbed on TiO2(110)

Wechsler D, Vensaus P, Tsud N, Steinrück HP, Lytken O, Williams FJ (2021)


Publication Type: Journal article

Publication year: 2021

Journal

Book Volume: 125

Pages Range: 6708-6715

Journal Issue: 12

DOI: 10.1021/acs.jpcc.1c01133

Abstract

We studied the coverage- and temperature-dependent proton transfer and self-metalation reactions of tetraphenylporphyrin molecules containing a carboxyl functional group (MCTPP) on rutile TiO2(110) surfaces. Furthermore, we also determined changes in the molecular geometric and electronic structures as a function of coverage and temperature. The investigation was carried out by means of synchrotron radiation X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure measurements. We found that at a coverage of 0.2 ML, most MCTPP molecules adsorb with the iminic nitrogen atoms protonated; at 0.5 ML, a decrease in the proportion of protonated molecules is observed; and at a monolayer coverage, most molecules are not protonated. Raising the temperature to above 500 K, where hydroxyl groups recombine to desorb as water, causes a decrease in the number of protonated porphyrin molecules. In roughly the same temperature range, we start to observe the self-metalation of the free-base molecules, which produces flat-lying titanyl porphyrin molecules on the TiO2(110) surface. This reaction is found to be coverage dependent: For 0.2 ML, it starts above 450 K, and for 1.0 ML, temperatures above 650 K are needed. Metalation shifts the surface state located in the semiconductor band gap to lower energies. Our results suggest that protonation and self-metalation depend on the proximity of the macrocycle to the surface and show that metalation modifies the molecular occupied and vacant electronic states.

Authors with CRIS profile

Involved external institutions

How to cite

APA:

Wechsler, D., Vensaus, P., Tsud, N., Steinrück, H.-P., Lytken, O., & Williams, F.J. (2021). Surface Reactions and Electronic Structure of Carboxylic Acid Porphyrins Adsorbed on TiO2(110). Journal of Physical Chemistry C, 125(12), 6708-6715. https://dx.doi.org/10.1021/acs.jpcc.1c01133

MLA:

Wechsler, Daniel, et al. "Surface Reactions and Electronic Structure of Carboxylic Acid Porphyrins Adsorbed on TiO2(110)." Journal of Physical Chemistry C 125.12 (2021): 6708-6715.

BibTeX: Download