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Instruments / Technical Area	Publication Details	Published	Actions
	On-surface synthesis of nonmetal porphyrins Aleksandr Baklanov , Manuela Garnica , Anton Robert , Marie-Laure Bocquet , Knud Seufert , Johannes T. Kuchle , Paul T. P. Ryan , Felix Haag , Reza Kakavandi , Francesco Allegretti , Willi Auwärter Journal Of The American Chemical Society DOI: 10.1021/jacs.9b10711 Show Abstract ▼ Abstract: We report the on-surface synthesis of a nonmetal porphyrin, namely, silicon tetraphenylporphyrin (Si-TPP), by the deposition of atomic silicon onto a free-base TPP layer on a Ag(100) surface under ultrahigh vacuum (UHV) conditions. Scanning tunneling microscopy provides insights into the self-assembly of the TPP molecules before and after Si insertion. Silicon coordinates with all four nitrogen atoms of the TPP macrocycle and interacts with a silver atom of the substrate as confirmed by scanning tunneling spectroscopy, X-ray photoelectron spectroscopy, and complementary density functional theory calculations. The Si-TPP complex presents a saddle-shaped conformation that is stable under STM manipulation. Our study shows how protocols established for the on-surface metalation of tetrapyrroles can be adopted to achieve nonmetal porphyrins. Complementary experiments yielding Si-TPP and Ge-TPP on Ag(111) highlight the applicability to different main group elements and supports. The success of our nonmetal porphyrin synthesis procedure is further corroborated by a temperature-programmed desorption experiment, revealing the desorption of Ge-TPP. This extension of interfacial complex formation beyond metal elements opens promising prospects for new tetrapyrrole architectures with distinct properties and functionalities.	Jan 2020
I09-Surface and Interface Structural Analysis	Direct quantitative identification of the “surface trans-effect” Peter Deimel , Reda M. Bababrik , Bin Wang , Philip Blowey , Luke Rochford , Pardeep K. Thakur , Tien-lin Lee , Marie-laure Bocquet , Johannes V. Barth , Phil Woodruff , David Duncan , Francesco Allegretti Chem. Sci. DOI: 10.1039/C6SC01677D Diamond Proposal Number(s): [8940] Open Access Show Abstract ▼ Abstract: The strong parallels between coordination chemistry and adsorption on metal surfaces, with molecules and ligands forming local bonds to individual atoms within a metal surface, have been established over many years of study. The recently proposed “surface trans-effect” (STE) appears to be a further manifestation of this analogous behaviour, but so far the true nature of the modified molecule–metal surface bonding has been unclear. The STE could play an important role in determining the reactivities of surface-supported metal–organic complexes, influencing the design of systems for future applications. However, the current understanding of this effect is incomplete and lacks reliable structural parameters with which to benchmark theoretical calculations. Using X-ray standing waves, we demonstrate that ligation of ammonia and water to iron phthalocyanine (FePc) on Ag(111) increases the adsorption height of the central Fe atom; dispersion corrected density functional theory calculations accurately model this structural effect. The calculated charge redistribution in the FePc/H2O electronic structure induced by adsorption shows an accumulation of charge along the σ-bonding direction between the surface, the Fe atom and the water molecule, similar to the redistribution caused by ammonia. This apparent σ-donor nature of the observed STE on Ag(111) is shown to involve bonding to the delocalised metal surface electrons rather than local bonding to one or more surface atoms, thus indicating that this is a true surface trans-effect.	Jun 2016

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