Coverage- and Temperature-Dependent Metalation and Dehydrogenation of Tetraphenylporphyrin on Cu(111)

• Published in: Chemistry : a European journal 2014-07, Vol.20 (29), p.8948-8953
• Main Authors: Röckert, Michael, Franke, Matthias, Tariq, Quratulain, Ditze, Stefanie, Stark, Michael, Uffinger, Patrick, Wechsler, Daniel, Singh, Upendra, Xiao, Jie, Marbach, Hubertus, Steinrück, Hans-Peter, Lytken, Ole
• Format: Article
• Language: English
• Subjects: Chemistry; copper; Copper - chemistry; Dehydrogenation; Hydrogen storage; Hydrogenation; Islands; Metalloporphyrins - chemistry; Microscopy, Scanning Tunneling; Nitrogen atoms; Photoelectron Spectroscopy; porphyrinoids; Porphyrins - chemistry; Scanning tunneling microscopy; self-metalation; Temperature; Temperature programmed desorption; X-ray photoelectron spectroscopy; X-rays
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201402420

Using temperature‐programmed desorption, supported by X‐ray photoelectron spectroscopy and scanning tunneling microscopy, a comprehensive overview of the main reactions of 5,10,15,20‐tetraphenyl‐21H,23H‐porphyrin (2HTPP) on Cu(111) as a function of coverage and temperature is obtained. Three reactions were identified: metalation with Cu substrate atoms, stepwise partial dehydrogenation, and finally complete dehydrogenation. At low coverage the reactions are independent of coverage, but at higher coverage metalation becomes faster and partial dehydrogenation slower. This behavior is explained by a weaker interaction between the iminic nitrogen atoms and the Cu(111) surface in the high‐coverage checkerboard structure, leading to faster metalation, and the stabilizing effect of T‐type interactions in the CuTPP islands formed at high coverage after metalation, leading to slower dehydrogenation. Based on the amount of hydrogen released and the appearance in STM, a structure of the partially dehydrogenated molecule is suggested. Small loss: The release of hydrogen during the metalation and dehydrogenation of tetraphenylporphyrin on Cu(111) has been followed with temperature‐programmed desorption, and supported by X‐ray photoelectron spectroscopy and scanning tunneling microscopy. The results provide a detailed overview of the reactions as a function of coverage and temperature and identify the structure of the partially dehydrogenated intermediate.