Polymorphic, Porous, and Host鈥揋uest Nanostructures Directed by Monolayer鈥揝ubstrate Interactions: Epitaxial Self-Assembly Study of Cyclic Trinuclear Au(I) Complexes on HOPG at the Solution鈥揝olid Interf

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• 作者：Bhaskar Chilukuri ; Roy N. McDougald Jr. ; Mukunda M. Ghimire ; Vladimir N. Nesterov ; Ursula Mazur ; Mohammad A. Omary ; K. W. Hipps
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：November 5, 2015
• 年：2015
• 卷：119
• 期：44
• 页码：24844-24858
• 全文大小：1074K
• ISSN：1932-7455

文摘

Synthesis, crystallographic characterization, and molecular self-assembly of two novel cyclotrimeric gold(I) complexes, Au<sub>3sub>[3,5-(COOEt)<sub>2sub>Pz]<sub>3sub> (Au<sub>3sub>Pz<sub>3sub>) and Au<sub>3sub>[(n-Pr鈥揙)C鈺怤(Me)]<sub>3sub> (Au<sub>3sub>Cb<sub>3sub>) was studied. Single crystal X-ray crystallography data reveal that both gold(I) complexes have one-dimensional stacking patterns caused by intermolecular Au(I)路路路Au(I) aurophilic interactions. The Au<sub>3sub>Pz<sub>3sub> trimer units stack with two alternate and symmetrical Au(I)路路路Au(I) interactions while the Au<sub>3sub>Cb<sub>3sub> units have three alternating and nonsymmetrical Au(I)路路路Au(I) interactions. Molecular self-assembly of the gold(I) complexes on the 1-phenyloctane/highly ordered pyrolytic graphite (HOPG) (0001) solution鈥搒olid interface is studied with scanning tunneling microscopy (STM). The gold(I) cyclotrimers form epitaxial nanostructures on the HOPG surface. At a concentration of 鈭? 脳 10<sup>鈥?sup> M, Au<sub>3sub>Pz<sub>3sub> complexes exhibit a single morphology, while Au<sub>3sub>Cb<sub>3sub> complexes exhibit polymorphology. Two polymorphs, one nonporous and the other porous, are observed at 22.0 卤 2.0 掳C for Au<sub>3sub>Cb<sub>3sub> complexes. A nonporous, low-surface-density (0.82 molecules/nm<sup>2sup>) Au<sub>3sub>Cb<sub>3sub> nanostructure forms first and then transforms into a high-density (1.43 molecules/nm<sup>2sup>) porous nanostructure. This is the first time any porous surface nanostructure is reported for an organometallic system. The porous structure is thought to be stabilized by a combination of hydrogen bonding and monolayer鈥搒ubstrate interactions. These pores are utilized to incorporate pyrene into the film, rendering this the first organometallic host鈥揼uest system imaged at the solid鈥搒olution interface. Molecular and periodic density functional theory (DFT) calculations shed light on the two-dimensional topography and polymorphic self-assembly revealed by STM; these calculations suggest significant electronic hybridization of the Au<sub>3sub> trimer orbitals and HOPG. The multiple-technique approach used herein provides insights concerning molecule鈥搒ubstrate and molecule鈥搈olecule interactions.