Charge transfer states appear in the π-conjugated pure hydrocarbon molecule on Cu(111)

Abstract

We report on the results of experimental and theoretical studies on the electronic structure of gas-phase diindenoperylene (DIP) and DIP-monolayer (ML) on Cu(111). Vapor-phase ultraviolet photoelectron spectroscopy (UPS) was realized for 11.3 mg of DIP, giving reference orbital energies of isolated DIP, and UPS and inverse photoemission spectroscopy of DIP-ML/graphite were performed to obtain DIP-ML electronic states at a weak interfacial interaction. Furthermore, first-principles calculation clearly demonstrates the interfacial rearrangement. These results provide evidence that the rearrangement of orbital energies, which is realized in HOMO–LUMO and HOMO–HOMO−1 gaps, brings partially occupied LUMO through the surface-induced aromatic stabilization of DIP, a pure hydrocarbon molecule, on Cu(111).

Orientation-Dependent Work-Function Modification Using Substituted Pyrene-Based Acceptors

“…All three features show their maximum intensity between 3 and 6 Å coverage, which indicates that they originate from molecules in the interfacial region. The occurrence of the new peaks is reminiscent of what was observed for related acceptors on metal surfaces, e.g., F4-TCNQ, 12 HATCN, 59 3,4,9,10-perylenetetracarboxylic-dianhydride (PTCDA), 17 , 60 perylene-3,4,9,10-tetracarboxylic diimide, 61 6,13-pentacenequinone (P2O), 5,7,12,14-pentacenetetrone (P4O), 16 and diindenoperylene (DIP), 62 , 63 where substantial negative charge is transferred from the substrate to the molecule upon chemisorption. In analogy, we assign the feature close to the Fermi level to hybrid orbital(s) formed by metal states and the molecular LUMO now being partially filled.…”

Metal-organic interface functionalization via acceptor end groups: PTCDI on coinage metals

“…We expect that the results presented will provide reliable data to further test available adsorption models [1,2], especially regarding the role of functional groups and intermolecular interactions on the interface electronics and multilayer properties. Moreover, comparing the adsorption distances of chemisorbed PTCDI, PTCDA [25], and DIP [33] on Cu(111) and physisorbed perylene [34] on the same substrate shows that the functional groups are crucial for the existence of CT, but not for a short adsorption distance. Thus, using the bonding distance as exclusive indicator for organic-metal interaction strength can be misleading without a proper VB characterization.…”

“…For comparison, unsubstituted perylene adsorbs at shorter distances, which is especially striking on Cu(111) as often a decreased bonding distance is associated with increased adsorbate/substrate interaction [1,2,5]. However, in contrast to PTCDI (and also PTCDA [25] and DIP [33]), for perylene, no (partially) filled LUMO in the monolayer on Cu(111) could be evidenced by UPS [34].…”

Nitrogen substitution impacts organic-metal interface energetics

“…However, in contrast to these well-established bulk properties, the chemical and structural properties of its interface with metals have not yet been explored in detail. The (111)-surfaces of the coinage metals Au, Ag, and Cu cover a wide range of reactivity and, therefore, emerged as model systems to study the contact formation with OSCs such as pentacene [26][27][28][29], perylene [30][31][32], coronene [33][34][35][36], diindenoperylene (DIP) [37][38][39][40], perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) [35,[41][42][43][44], or 6,13-pentacenequinone (P2O) and 5,7,12,14-pentacenetetrone (P4O) [45][46][47]. In the present paper, we performed a systematic study of the ELA and molecular surface structure of TAT adsorbed on Au(111), Ag(111), and Cu(111) by combining inverse photoelectron spectroscopy (IPES), ultraviolet photoelectron spectroscopy (UPS), and x-ray photoelectron spectroscopy (XPS) with low energy electron diffraction (LEED) and the x-ray standing wave (XSW) technique.…”