Metal–Organic Coordination Networks of Ferric Wheels, their Surface-supported Supramolecular Architectures and STM/STS Imaging

Abstract

Six-membered ferric wheels [Fe 6 Cl 6 (L 2 ) 6 ] were generated from the corresponding N-alkylsubstituted 19 (3e)}, calcium hydride and iron(III) chloride. Compound 3d was characterized by X-ray crystal structure analysis. The lipophilic tails of 3d interdigitate to create strands that, by lateral van der Waals interactions, pack to form 2D layers. The stacking of these sheets creates the final 3D architecture of the crystal. An elementary structure formation process of complex molecule 3d on highly oriented pyrolytic graphite (HOPG) was studied. Using scanning tunneling microscopy (STM) under ambient conditions, we succeeded in combining high-resolution topography mapping with simultaneous current -voltage characteristics (scanning tunneling spectroscopy, STS) measurements on single molecules deposited on HOPG surfaces. One of the most interesting results is that the location of the individual metal ions in their organic matrix is directly addressable by STS.

STM/STS Observation of Polyoxoanions on HOPG Surfaces: the Wheel-Shaped [Cu20Cl(OH)24(H2O)12(P8W48O184)]25- and the Ball-Shaped [{Sn(CH3)2(H2O)}24{Sn(CH3)2}12(A-PW9O34)12]36-

“…Therefore, in this sense, STS spectroscopy directly addresses the metal centers. As we have found, a similar behavior for the Co centers in supramolecular [2 × 2] grid molecules 29 or for the Fe ions in ferric wheels, it is reasonable to assume that we can locate any weakly bond metal center in rather complex molecules.…”

“…As, for example, we would scan the van der Waals surface of large and complex molecules, we would see only a featureless “blob” of a large cluster of atoms. However, spectroscopic possibilities of STM allow us to probe electronic states of the molecules as a function of energy. , If there would be subunits of the molecule exhibiting a special type of chemical bonding, STM spectroscopy would allow for filtering out special features of the species if they arise at energies well separated from the other states of the molecule.…”

Self‐Assembly of a Mononuclear [FeIII(L)(EtOH)2] Complex Bearing an n‐Dodecyl Chain on Solid Highly Oriented Pyrolytic Graphite Surfaces

“…[10,13] Single-crystal X-ray structural analysis revealed that 1 is a Figure 2). [10,13] Single-crystal X-ray structural analysis revealed that 1 is a Figure 2).…”

“…[5][6][7][8][9] Earlier studies by us showed that ferric wheels derived from poly-alcoholato ligands substituted with octadecyl alkyl side arms form well-ordered arrays upon adsorption on highly oriented pyrolytic graphite (HOPG) surfaces. [10] Long-alkyl-chain-substituted complexes were employed to increase van der Waals interactions between molecules and the substrate to stabilize molecular aggregates on the surface. We also have a long-running interest in designing methods for obtaining nanostructured materials from precursor coordination complexes of transition-metal cations.…”

“…www.chemeurj.org hydrocarbon chains (CH 2 ) n exceeding n = 10 have been successfully crystallized. [10,13] Single-crystal X-ray structural analysis revealed that 1 is a mononuclear complex [Fe(L)A C H T U N G T R E N N U N G (EtOH) 2 ] ( Figure 2). The iron center in 1 exhibits the expected distorted octahedral O 5 N coordination environment, with FeÀN 2.154(9) , FeÀO phenol 1.877(10) , FeÀO carboxylate 1.990(8) and 2.021 (8) , and Fe À O ethanol 2.011(7) and 2.075 (8) .…”