Conductive Self-Assembled Monolayers of Paramagnetic {Co } and { } Coordination Clusters on Gold Surfaces.

Two polynuclear cobalt(II,III) complexes, [Co(N)(--bda)(bza·SMe)] () and [Co(N)(--bda)(bza·SMe)(MeOH)]Cl (), where Hbza·SMe = 4-(methylthio)benzoic acid and --Hbda = --butyldiethanolamine, were synthesized and fully characterized by various techniques. Compound exhibits an unusual, approximately -symmetric {Co } core of two isosceles Co triangles with perpendicularly oriented planes, sharing a central, high-spin Co ion residing in a distorted tetrahedral coordination environment. This central Co ion is connected to four outer, octahedrally coordinated low-spin Co ions oxo bridges. Compound comprises a semi-circular { } motif of four non-interacting high-spin Co and two low-spin Co centers in octahedral coordination environments. Self-assembled monolayers (SAMs) of and were physisorbed on template-stripped gold surfaces contacted by an eutectic gallium-indium (EGaIn) tip. The acquired current density-voltage () data revealed that the cobalt-based SAMs are more electrically robust than those of the previously reported dinuclear {CuLn} complexes with Ln = Gd, Tb, Dy, or Y (Schmitz et al., 2018a). In addition, between 170 and 220°C, the neutral, mixed-valence compound undergoes a redox modification, yielding a {Co}-based coordination cluster () with five non-interacting, high-spin octahedral Co centers as indicated by SQUID magnetometry analysis in combination with X-ray photoelectron spectroscopy and infrared spectroscopy. Solvothermal treatment of results in a high-nuclearity coordination cluster, [Co(N)(--bda)(bza·SMe)] (), containing 10 virtually non-interacting high-spin Co centers.