title: Multipoint anchoring of the [2.2.2.2]metacyclophane motif to a gold surface via self-assembly: coordination chemistry of a cyclic tetraisocyanide revisited.
abstract: A one-pot transformation of bis(2-isocyano-3-methylphenyl)ethane affords gram quantities of 8,16,24,32-tetraisocyano[2.2.2.2]metacyclophane ( 3). The solid state structure of 3 is remarkably close to the lowest energy conformation found on the potential energy landscape for 3 by DFT. In solution, the structure of metacyclophane 3 is mobile but can be locked in a rectangular gauche- anti- gauche- anti conformation by coordination of the isocyanide substituents to the [W(CO) 5] units to give [M] 4(mu 4-eta (1):eta (1):eta (1):eta (1)- 3) ( 5). The tetranuclear [M] 4(mu 4-eta (1):eta (1):eta (1):eta (1)- 3) motif featured in crystallographically characterized 5 may be present in several insoluble complexes of 3 previously described as mononuclear eta (4) species. A self-assembled monolayer of metacyclophane 3 is formed upon exposing a solution of 3 to the gold(111) surface with no precautions to exclude air or light. The monolayer nature of the film was confirmed by optical ellipsometry. The isocyanide stretching band for 3 shifts from 2119 cm (-1) in solution to 2175 cm (-1) upon chemisorption to metallic gold. The FTIR spectrum of the film indicates interaction of 3 with the gold surface via all four of its isocyanide anchors. No gold-facilitated oxidation of the -NC junctions was detected under ambient conditions. The energy cost associated with accessing the conformations of 3 suitable for mu 4-eta (1):eta (1):eta (1):eta (1) interaction of the molecule with the Au(111) surface is under 8 kcal/mol, a value that can be easily offset by formation of a gold-isocyanide bond. Two different mu 4-eta (1):eta (1):eta (1):eta (1) coordination arrangements of 3 with respect to gold atoms on the (111) face of the fcc Au lattice are suggested.
authors.affiliation: Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Toriyama
authors.forename: Tiffany R
authors.initials: TR
authors.lastname: Maher
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Holovics
authors.forename: Kumar
authors.initials: K
authors.lastname: Vanka
authors.forename: Victor W
authors.initials: VW
authors.lastname: Day
authors.forename: Cindy L
authors.initials: CL
authors.lastname: Berrie
authors.forename: Ward H
authors.initials: WH
authors.lastname: Thompson
authors.forename: Mikhail V
authors.initials: MV
authors.lastname: Barybin
mesh_terms: D003486:Cyanides / Q000737:chemistry*; D004988:Ethers, Cyclic; D006046:Gold; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010880:Piperidines; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
chemical_list: D003486:Cyanides; D004988:Ethers, Cyclic; D010880:Piperidines; D006046:Gold