Changes in the unoccupied electronic structure of [Fe(H$_{2}$B(pz)$_{2})_{2}$(bipy)] thin films

We have investigated the unoccupied electronic structure of ultra thin films of the spin crossover [Fe(H$_{2}$B(pz)$_{2})_{2}$(bipy)] complex (with H$_{2}$B(pz)$_{2}=$bis(hydrido)bis(1H-pyrazol-1-yl)borate and bipy $=$ 2,2'-bipyridine) deposited on Au(111) by inverse photoemission (IPES) and X-ray absorption spectroscopy (XAS). The XAS clearly shows the changes of iron L edge spectra typically associated with thermal induced spin crossover and found to be very consistent with the changed of the lowest unoccupied molecular orbitals seen in inverse photoemission with temperature. A band gap of 2-3 eV is deduced from combined UPS and IPES measurements of the films on Au substrates. The shift of the unoccupied density of states seen in inverse photoemission and XAS, with temperature, differs little from the molecular powder suggesting little influence of the substrate. We suggested that the ordering of this spin-crossover molecule on the gold substrate, may lead to a small anisotropy energy, for the molecular high spin state.