Soft-Landing Isolation of Vanadium−Benzene Sandwich Clusters on a Room-Temperature Substrate Using n-Alkanethiolate Self-Assembled Monolayer Matrixes

Abstract

Gas-phase synthesized vanadium-benzene 1:2 (VBz(2)) sandwich clusters were size-selectively deposited onto bare gold and long-chain n-alkanethiolate [-S-(CH(2))(n-1)-CH(3); n = 16, 18, and 22] self-assembled monolayer (SAM)-coated gold substrates under ultrahigh vacuum (UHV) conditions. Investigation of the resulting deposited clusters was performed by infrared reflection absorption spectroscopy (IRAS) and thermal desorption spectroscopy (TDS). The IR frequencies of the soft-landed VBz(2) clusters show excellent agreement with the fundamentals reported in IR data of VBz(2) in an argon matrix. The analysis of IRAS spectra reveals that while there was no orientational preference of the VBz(2) clusters on a bare gold substrate, the VBz(2) clusters deposited onto the SAM substrates were highly oriented with the molecular axis 70-80 degrees tilted off the surface normal. In addition, analysis of TDS spectra revealed unusually large adsorption heats of the physisorbed VBz(2) clusters. The present results are explained by cluster penetration into the long-chain alkanethiolate SAM and for the first time demonstrate the matrix isolation of gas-phase organometallic clusters around room temperature.

Preparation of Surface Organometallic Catalysts by Gas‐Phase Ligand Stripping and Reactive Landing of Mass‐Selected Ions

“…[12][13][14] For instance, a recent study by Nakajima and co-workers demonstrated facile matrix isolation of vanadium-benzene sandwich clusters through ion soft landing. [15] In addition, a previous publication from our group describes an investigation of the charge retention and neutralization behavior of organometallic metal-salen complexes soft landed onto 1H,1H,2H,2H-perfluorododecane-1-thiol (FSAM) and 1-dodecanethiol self-assembled monolayer (HSAM) surfaces on gold. [16] More recently, in a collaborative study, we demonstrated that acid-mediated redox chemistry may be observed in thin films of organometallic complexes prepared by ion soft landing.…”

Understanding ligand effects in gold clusters using mass spectrometry

“…For instance, peptides and proteins are typically ionized by protonation and lose charge by releasing protons to the SAM. In contrast, native cations such as organometallic complexes undergo charge reduction through electron transfer from the underlying metal surface 200,201. In the case of multiply charged cationic gold clusters, we demonstrated that the charge may be controlled by changing the terminal functionality of the monolayer as well as the coverage of ions 152,153.…”

<em>In Situ</em> SIMS and IR Spectroscopy of Well-defined Surfaces Prepared by Soft Landing of Mass-selected Ions

“…To date, a multitude of techniques have been applied for this purpose including secondary ion mass spectrometry (SIMS) 19,[97][98][99][100] , temperature programmed desorption and reaction 50,52 , laser desorption and ionization 101 , pulsed molecular beam reaction 102 , infrared spectroscopy (FTIR and Raman) 98,103,104 , surface enhanced Raman spectroscopy 103,105 , cavity ringdown spectroscopy 106 , xray photoelectron spectroscopy 35,107 , scanning tunneling microscopy 33,[108][109][110][111] , atomic force microscopy [112][113][114] , and transmission electron microscopy 39 . However, to most accurately characterize surfaces prepared or modified by ion soft landing, it is crucial that the analysis be performed in situ without exposure of the substrate to the environment in the laboratory.…”