Molecular Metal Complexes as Defined Spin Impurities for Kondo Physics

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The interaction of molecules with metals has recently attracted increasing attention due to the appearance of molecular electronics as a candidate for future nanoelectronics. In this project, we will create and investigate systems where a molecule carries an unpaired spin. We propose to investigate two types of interaction between the spin degree of freedom and the conduction electrons in the metal: The first experiment is dedicated to the dynamical screening of the spin degree of freedom by the conduction electrons of the metal, a phenomenon which is closely related to the Kondo effect known in solid state metals with magnetic impurities. For that purpose, we will immobilize spin-bearing coordination compounds (e.g. FeII and CoII compounds) in single-molecule junctions. Thereby, the main observable parameter will be the I/V dependence of a current passing through the spin-bearing molecule. Second, we will investigate binuclear compounds with two spin degrees of freedom. Here, more complicated variations of Kondo physics can be explored. As a further reaching goal (and presumably beyond the two-year period for this grant), this research will guide towards Spintronics on the single-molecule level, where the electron transport can be controlled by the relative orientation of the two spins. The requirements to the molecules and the experiment are delicate and imperatively need a close cooperation between synthetic chemistry and experimental physics.