Visualizing the frontier orbitals of a conformationally adapted metalloporphyrin

We present a molecular-level study of the geometric and electronic properties of Co-II tetraphenylporphyrin molecules adsorbed on the Cu(111) surface. A combination of low-temperature scanning tunneling microscopy and neor-edge X-ray absorption fine structure observations reveals how the metal substrate induces a conformationol adaptation into a distorted saddle-shaped geometry. By scanning tunneling spectroscopy we identified the discrete energy levels of the molecule and mapped their spatial electron-density distributions. These results, along with a simple theoretical description, provide a direct correlation between the shape of frontier molecular orbitals and intramoleculor structural features.