Adsorption of [Mn19] Aggregates with S = 83/2 onto HOPG Surfaces

Abstract

AbstractA structural analogue of the previously reported record‐high‐spin (S = 83/2) mixed‐valence [Mn19] coordination cluster [MnIII12MnII7(μ4‐O)8(μ3‐η1‐N3)8(HLMe)12(MeCN)6]Cl2·10MeOH·MeCN (1) {H3LMe = 2,6‐bis(hydroxymethyl)‐4‐methylphenol} was prepared in which the methyl group at the 4‐position on the phenyl ring was replaced by a methoxy group to give the compound [Et3NH]2[MnIII12MnII7(μ4‐O)8(μ3‐η1‐N3)7.4(μ3‐Cl)0.6(HLOMe)12(MeOH)6]Cl4·14MeOH (2). Single‐crystal X‐ray diffraction analysis of 2 confirms that the molecular structure motif found for 1, comprising two supertetrahedral {MnIII6MnII4} units sharing a common MnII vertex, was retained. Magnetic susceptibility measurements on 2 show that the ferromagnetic spin structure, which results in the maximum ST = 83/2 spin ground state for 1, is largely robust with respect to the change in ligand substituent in 2. Molecules of compounds 1 and 2 were deposited onto highly oriented pyrolytic graphite (HOPG) substrates and were investigated by scanning tunneling microscopy (STM) andcurrent imaging tunneling spectroscopy (CITS). By usingextremely dilute solutions (10–9 mol L–1), one‐dimensionalarrangements as well as isolated single molecules of [1]Cl2·10MeOH·MeCN were observed with STM topography, generally at the step edges or at defects of the HOPG surfaces, while small groups of molecules of 2 were observed. The size of the individual molecules was consistent with the X‐ray crystallographic data. In the CITS images of the single molecules, a strong tunneling current contrast was observed at the positions of the metal ions.