Insight into the electronic structure of the supramolecular “rods-in-belt” AuICuI and AuIAgI self-assembled complexes from X-ray photoelectron and absorption spectroscopy

Herein, we report a comprehensive characterization of the electronic structure of two families of alkynyl-diphosphine supramolecular complexes with the heterometallic AuCu and AuAg cores. Using X-ray photoemission and absorption spectroscopy we disentangled the structure of their occupied and unoccupied electronic states close to the Fermi level. The results obtained suggest that the major contribution to the highest occupied molecular orbitals is made by the triple bonded carbons hosted in the dialkynyl-gold “rods” and the copper (silver) atoms from the central cluster core of the heterometallic AuCu (AuAg) molecules. The lowest unoccupied molecular orbitals are located on the carbon skeleton of the complexes and include π*-CC and π*-CCaromatic orbitals. The onset of the valence band in the AuAg systems starts at about 0.3 eV lower than that in the AuCu complexes, implying a slightly larger energy gap for the silver-based systems. It was also established that with increasing size of the complexes, the molecule becomes more and more sensitive to X-ray damage effects.