STM studies on monolayers of [Co(L) 4]A 8 metallogrids on graphite

Abstract

Self-assembled tetranuclear complexes of metallogrid type [Co 4(L 4)](PF 6), R 1=CH 3, R 2=H (compound 1) and [Co 4(L 4)](AsF 6), R 1=H, R 2=CH 3 (compound 2), L=4,6-bis(6 11R 1-2 1,2 1-bipyrid-6-yl)-2-R 2-pyrimidine were adsorbed onto highly oriented pyrolitic graphite and studied by STM. Monodomains of a regularly packed layer of adsorbed molecules with areas up to 0.5 μm 2 were observed. Sample 1 showed a molecular pattern with nearly orthogonal periodicities of 1.35 nm×2.6 nm consisted with the size of the 2×2 Co-grid oriented normally to the surface. A periodicity of 2.5 nm×2.4 nm was found for complex 2 consistent with orientation of the grid parallel to the surface. Holes in the monolayer, which were formed by removal of a particular complex by STM, were observed to diffuse along the surface with a diffusion coefficient of D=5.2×10 −16 cm 2/s. The free energy of the diffusion activation were found to be Δ F d=730 meV.