Externally controlled spin state switching in metal-organic complexes.

Recent transport experiments have demonstrated that a manipulation of the charge of individual molecules is feasible using electromigrated metal junctions [1] or electrochemical gates in conjunction with the STM [2]. Using elaborated density functional theory calculations, we will discuss a possibility to induce -- by means of charging or applied stress -- a switching between low and high spin states in certain metal-organic systems, [Fe(bpp)$_2$]$^{2+}$ (bpp:\ bispyrazolyl pyridine) and [Mn(tpy)$_2$]$^{2+}$ (tpy:\ terpyridine). Based upon a recent success of the single molecular conduction experiment through Ru(II) complex [3], we anticipate the transport properties of Fe(II) and Mn(II) complexes to be gate controlled via exploiting their spin degree of freedom. \medskip \newline [1] E.\ A.\ Osorio {\it et al.}, J.\ Phys.:\ Condens.\ Matter{\bf 20}, 374121 (2008); [2] F.\ Chen {\it el al.}, Ann.\ Rev.\ Phys.\ Chem.\ {\bf 58}, 535 (2007); Li {\it et al.}, Nanotechnology {\bf 18}, 044018 (2007). [3] M.\ Ruben, A.\ Landa, E.\ L{\"o}rtscher, H. Riel, M. Mayor, H.\ G{\"o}rls, H.\ Weber, A.\ Arnold, and F.\ Evers, Small (online), {\small DOI}: 10.1002/smll.200800390 (2008).