Structural integrity of single bis(phthalocyaninato)-neodymium(iii) molecules on metal surfaces with different reactivity

Magnetic molecules are auspicious candidates to act as functional units in molecular spintronics. Integrating molecules into a device environment providing mechanical support and electrical contacts requires their deposition as intact entities onto substrates. Thermal sublimation is a very clean deposition process that, however, thermally decomposes molecules of insufficient stability leading to the deposition of molecular fragments. Here, we show that the molecule-surface interaction of chemisorbed molecules affects the intramolecular bonding and can lead depending on the surface reactivity to either molecular decomposition or enhanced stability. We study the integrity of single bis(phthalocyaninato)-neodymium(III) molecules (NdPc₂) deposited by sublimation on differently reactive surfaces, namely Au(111), Cu(100), and two atomic layers of Fe on W(110), on the single molecular level by scanning tunneling microscopy (STM) and spectroscopy. We find a strongly substrate-dependent tendency of the NdPc₂ molecules to decompose into two Pc molecules. Surprisingly, the most reactive Fe/W(110) surface shows the lowest molecular decomposition probability, whereas there are no intact NdPc₂ molecules at all on the least reactive Au(111) surface. We attribute these findings to substrate-dependent partial charge transfer from the substrate to the Pc ligands of the molecule, which strengthens the intramolecular bonding mediated predominantly by electrostatic interaction.