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Gas-phase synthesized transition metal-benzene sandwich complexes of M(benzene) 2 (M ) Ti, V, and Cr) are soft-landed onto a self-assembled monolayer of n-octadecanethiol (C 18 -SAM) at a collision energy of 10-20 eV. The resulting adsorption states and thermal desorption kinetics of the soft-landed complexes are studied with infrared reflection absorption spectroscopy and temperature-programmed desorption. The complexes keep their native sandwich structure intact on the SAM substrate even after the "hyperthermal" deposition event. The soft-landed complexes are oriented with their molecular axes largely tilted off the surface normal of the SAM substrate and exhibit unusually large desorption activation energies (E d ) ∼130 kJ/mol). For comparison, thermal deposition (∼25 meV) of Cr(benzene) 2 vapor onto the C 18 -SAM, carried out using a physical vapor deposition technique, showed that the complexes are weakly physisorbed (E d ) ∼70 kJ/mol) on the SAM with a random orientation. Only a hyperthermal collision event allows the incident complexes to penetrate into the SAM matrix. The desorption of the embedded complexes in the SAM is then suppressed to around room temperature and may be associated with the crystal-rotator phase transitions of the SAM matrix.

Gas-phase-synthesized chromium−benzene 1:2 sandwich cation complexes [Cr+(benzene)2] were soft-landed on a self-assembled monolayer (SAM) of fluorinated alkanethiol (C10F-SAM) at a hyperthermal collision energy of ∼20 eV. The adsorption properties and thermal stability of the soft-landed complexes were studied with infrared reflection absorption spectroscopy (IRAS) and temperature-programmed desorption (TPD). The landed complexes were neutralized due to charge transfer from the SAM substrate, but their native sandwich structure remained intact. The hyperthermal collision event resulted in the penetration of the incoming complexes into the C10F-SAM matrix. The embedded complexes then tended to orient their molecular axes approximately along the surface normal. This orientational preference is measurably different from that of complexes isolated in alkanethiol SAM matrices, a discrepancy that might be caused by a repulsive interaction between the π cloud of the capping benzene rings of the complex and the side-chain CF2 groups of the fluorocarbon chains in the C10F-SAM matrix. The thermal desorption study showed that the complexes supported inside the C10F-SAM could resist thermal desorption until the high-temperature region of ∼320 K, a persistence revealing a large desorption activation energy (∼190 kJ/mol).