STM studies on monolayers of wCo L/ xA metallogrids on 4 8 graphite

Self-assembled tetranuclear complexes of metallogrid type wCo4 L4.x PF6., R1sCH3, R2sH compound 1. and wCo4 L4.x AsF6., R1sH, R2sCH3 compound 2., Ls4,6-bis 611R1-21,21-bipyrid-6-yl.-2-R2-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 mm2 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 Ds5.2=10y16 cm2rs. The free energy of the diffusion activation were found to be DFds730 meV. q1999 Published by Elsevier Science B.V. All rights reserved.