Soft-Landing of Co^III(salen)⁺ and Mn^III(salen)⁺ on Self-Assembled Monolayer Surfaces

Abstract

Soft-landing of mass-selected CoIII(salen)+ and MnIII(salen)+ complexes [salen = N,N′-ethylenebis(salicylideneaminato)] was performed using self-assembled monolayer surfaces of alkanethiol (HSAM) and fluorinated alkanethiol (FSAM) on gold as targets. Physical processes associated with ion deposition were studied using time-resolved in situ secondary ion mass spectrometry (SIMS) in a specially designed Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). We demonstrate charge retention by a significant fraction of precursor ions on the FSAM and complete neutralization on the HSAM surface. Our results indicate efficient electron transfer from gold to the deposited species for the HSAM surface and inefficient, if any, electron transfer on the FSAM surface. Formation of abundant cluster ions observed in SIMS spectra is attributed to gas-phase reactions in the SIMS plume. Detailed analysis allowed us to extract the kinetics of both ionic and neutral complexes trapped on the FSAM surface. The results indicate that neutralization on this surface most likely takes place on the defect sites.