The Influence of the Molecular Dipole on the Electronic Structure of Isomeric Icosahedral Dicarbadodecaborane and Phosphacarbadodecaborane Molecular Films

We compare the molecular films of three different isomers of closo-dicarbadodecaborane (orthocarborane (1,2-C₂B₁₀H₁₂), metacarborane (1,7-C₂B₁₀H₁₂), paracarborane (1,12-C₂B₁₀H₁₂)) and two related icosahedral cage molecules, 1-phospha-2-carbadodecaborane (1,2-PCB₁₀H₁₁) and 1-phospha-7-carbadodecaborane (1,7-PCB₁₀H₁₁) adsorbed on a variety of substrates. While the experimental electronic structure from combined photoemission and inverse photoemission studies of the molecular films are in good agreement with semiempirical calculations for the isolated molecule, there is a shift in the chemical potential for each molecule. The experimental position of the molecular chemical potential implicates an influence of both interface and adsorbate dipole.