Tripodal M(III) Complexes on Au(111) Surfaces : Towards Molecular “Lunar Modules”

A series of tripodal MIII complexes (M = Ga, Mn, Fe) functionalized with three methylsulfanyl end-groups for deposition on Au(111) were synthesized. The structures were designed to build rigid three-dimensional molecular structures that stand on their own with multiple attachments on the metallic surface. The coordination compounds are based on a trensal [(tris(2,2′,2"-salicylideneimino)triethylamine)] Schiff base ligand which provides stable metal complexes. The molecular structures of GaIII, FeIII, and MnIII complexes were determined by single-crystal X-ray diffraction crystallography. Magnetic properties depend on the coordinated metal ion and vary from a diamagnetic GaIII complex to paramagnetic high-spin FeIII and MnIII complexes. A submonolayer of the GaIII complex deposited on Au(111) was studied in a preliminary ultra-high-vacuum scanning tunneling microscopy (UHV-STM) investigation.