Electronic and magnetic properties of single molecules at the metallic interface

The electronic and magnetic properties of organic compounds are in most cases strongly modified by the presence of a metallic interface [1]. The subtle correlation between these properties and the bonding configuration at the interface is in fact the responsible for the lack of reproducibility in the transport properties of molecular films and junctions [2]. In that respect, the STM presents as an ideal tool to correlate conformational and spectroscopic properties at the atomic scale.

Here I will present a systematic study of molecule-metal interaction by using phthalocyanine molecules with different metal centers. I will show how a careful choice of molecule-metal interaction can lead to interesting phenomena such as the induction of chiral molecular orbitals in achiral molecules [3], and of magnetism in organic compounds [4]. Depending on the active orbitals, the magnetic moment can either be quenched or enhanced [5]. The molecular properties can be further manipulated extrinsically by doping them atom by atom with alkali dopants. The role of the metallic interface here will be to act as electron reservoir that regulates charge transfer and to impose bonding configurations different from thin films that allow selective charge transfer to either metal or ligand orbitals [6,7]. As we depart from the interface by growing thicker films, the semiconducting behaviour of the molecules is recovered, and new features characteristic of electronically decoupled systems arise in the tunnelling conductance.

References:

[1] S. Sanvito, Chem. Soc. Rev. 40, 3336 (2011).

[2] L. Bogani and W. Wernsdorfer, Nat. Mater. 7, 179 (2008).

[3] A. Mugarza et al., Phys. Rev. Lett. 105, 115702 (2010).

[4] A. Mugarza et al., Nature Comm. 2:490 (2011).

[5] A. Mugarza et al., Phys. Rev. B 85, 155437 (2012).

[6] C. Krull et al., Nature Mater. 12, 337 (2013).

[7] S. Stepanow et al., J. Am. Chem. Soc. 136, 5451 (2014).