We have computed the interaction energies for pyridine (C₅H₅N) and (CH₃)₃PO with H and F atoms on the surface of diamond(111) as a function of the type of neighboring surface atom. The pyridine-H and -F interaction energies differ by about 5 kcal/mol, which is only about one-third of that found for a one-dimensional model for the surface. The difference in the interaction energies for (CH₃)₃PO is larger. However, the (CH₃)₃PO-neighbor interaction energy is larger than for pyridine, so that the (CH₃)₃PO-H interaction becomes repulsive for six neighboring F atoms. Substituting CN for F dramatically increases the repulsion between the surface atoms and molecules. The repulsion is sufficiently large that H/CN does not appear to be better than H/F as a possible way to store data on a surface. While pyridine shows some potential as a possible probe to differentiate between H and F on a diamond surface, it is not ideal.