Site-Specific Coordination Chemistry and Beyond: Novel Properties in Low Dimensional Supramolecular Architectures of Porphins at Surfaces

In our work, we establish porphin based on-surface architectures which exhibit extraordinary properties e.g. electronic, magnetic and quantum properties originating from the reduced dimensionality of the self-assembled and atomically precise architectures. Unconventional H-bonding as well as the direct site-specific interaction of the porphin’s center metal with the substrate direct the 2D architectures. The coordination and magneto-chemistry of binary 2D assemblies can be investigated by combining scanning probe microscopy / spectroscopy, photoelectron and photoabsorption spectroscopy and density functional theory. Complex electronic [1] and magnetic [2] interactions arise from the 2D periodicity which are also dependent on the state of adsorbed to physisorption and chemical reactivity. Sub-lattices in 2D ‘checkerboard’ architectures of magnetic molecules on magnetic substrates can be selectively switched by chemical ligation [3]. Also we have observed the first example of 2D ferrimagnetic long-range order and remanence for such a 2D architecture on non-magnetic Au(110) [2]. Uniquely, self-assembled 2D architectures contribute to our understanding of fundamental interactions involved in host-guest systems and allow for the specific operation of quantum states with a partial delocalization across the supramolecular on-surface architecture [4]. Thereby we unravel more and more of the on-surface chemistry [5] required to engineer low dimensional materials with unprecedented properties by controlling their architecture. In particular this involves the on-surface supramolecular, the on-surface coordination and the on-surface magneto-chemistry. [1] Lobo-Checa, J. et al., Science 325:300 (2009) [2] Girovsky, J. et al., Nat. Commun., DOI: 10.1038/ncomms15388 (2017). [3] C. Waeckerlin et al, 10.1002/adma.201204274 [4] Nowakowska, S. et al., 10.1021/acsnano.7b07989 [5] Ballav N., et al., JPCL 4:2303 (2013) [4] Figure 1