Site-Selective Orbital Interactions in an Ultrathin Iron-Carbene Photosensitizer Film

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 124; no. 8; pp. 1603 - 1609
• Main Authors: Temperton, Robert H, Rosemann, Nils W, Guo, Meiyuan, Johansson, Niclas, Fredin, Lisa A, Prakash, Om, Wärnmark, Kenneth, Handrup, Karsten, Uhlig, Jens, Schnadt, Joachim, Persson, Petter
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 27-02-2020
• Subjects: Atom and Molecular Physics and Optics; Atom- och molekylfysik och optik; Chemical Sciences; Fysik; Fysikalisk kemi; Inorganic Chemistry; Kemi; Natural Sciences; Naturvetenskap; Oorganisk kemi; Physical Chemistry; Physical Sciences
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/acs.jpca.0c00803

We present the first experimental study of the frontier orbitals in an ultrathin film of the novel hexa-carbene photosensitizer [Fe­(btz)3]3+, where btz is 3,3′-dimethyl-1,1′-bis­(p-tolyl)-4,4′-bis­(1,2,3-triazol-5-ylidene). Resonant photoelectron spectroscopy (RPES) was used to probe the electronic structure of films where the molecular and oxidative integrities had been confirmed with optical and X-ray spectroscopies. In combination with density functional theory calculations, RPES measurements provided direct and site-selective information about localization and interactions of occupied and unoccupied molecular orbitals. Fe 2p, N 1s, and C 1s measurements selectively probed the metal, carbene, and side-group contributions revealing strong metal–ligand orbital mixing of the frontier orbitals. This helps explain the remarkable photophysical properties of iron-carbenes in terms of unconventional electronic structure properties and favorable metal–ligand bonding interactionsimportant for the continued development of these type of complexes toward light-harvesting and light-emitting applications.