Fingerprint of Fractional Charge Transfer at the Metal/Organic Interface

Abstract

Although physisorption is a widely occurring mechanism of bonding at the organic/metal interface, contradictory interpretations of this phenomenon are often reported. Photoemission and X-ray absorption spectroscopy investigations of nanorods of a substituted pentacene, 2,3,9,10-tetrafluoropentacene, deposited on gold single crystals reveal to be fundamental to identify the bonding mechanisms. We find fingerprints of a fractional charge transfer from the clean metal substrate to the physisorbed molecules. This phenomenon is unambiguously recognizable by a non-rigid shift of the core-level main lines while the occupied states at the interface stay mostly unperturbed, and the unoccupied states experience pronounced changes.The experimental results are corroborated by first-principles calculations.

Island shape and electronic structure in diindenoperylene thin films deposited on Au(110) single crystals

“…Additionally, XPS and NEXAFS do not show any fingerprint of fractional charge transfer from the substrate to the molecule. 69 Contrary to what we observe in the present case, the fractional charge transfer in physisorption is characterized by unperturbed occupied states and strongly perturbed unoccupied states, accompanied by a non-rigid shift of the photoemission lines. 69 Therefore, we can conclude that DIP is physisorbed on Au(110) single crystals with image-charge screening as the mechanism playing the major role.…”

Resolving intramolecular-distortion changes induced by the partial fluorination of pentacene adsorbed on Cu(111)

“…The adsorption distances in bold are taken from XSW measurements [18], whereas those in italics correspond to the calculated values [9]. on this molecule [15,16] and PFP [18,20,21]. In addition, at the low-BE edge, there is a small tail that is attributed to a low portion of carbon atoms bound to the substrate (C-Cu), probably belonging to molecules adsorbed close to step edges [20][21][22].…”

“…However, the distortion of a hydrocarbon core has not been experimentally probed with the same success [7,8] and, in most cases, it has only been accessible through state-of-the-art density-functionaltheory (DFT) calculations [8][9][10]. In this work, we directly quantify, using the x-ray standing wave (XSW) technique [11][12][13], the distortion of the hydrocarbon backbone of a partially fluorinated pentacene (PEN) derivative, namely 2,3,9,10tetrafluoropentacene (F4PEN, C 22 F 4 H 10 ) [14][15][16], vacuumsublimated on Cu(111). Our measurements (see Ref.…”

Modulating the Electronic and Solid‐State Structure of Organic Semiconductors by Site‐Specific Substitution: The Case of Tetrafluoropentacenes

“…For 2,3,9,10‐tetrafluoropentacene, no OFET data are available, but its interfacial properties on metal surfaces were studied extensively . The compound shows pronounced nanorod morphology on Au(110) and charge transfer from the surface, indicating that the chemical modification has impact on the morphology and electronic properties at the molecular and thin‐film levels . An X‐ray standing‐wave investigation could quantify the substantial molecular distortion that 2,3,9,10‐tetrafluoropentacene is undergoing upon interaction with a Cu(111) surface on an atomic level …”

“…[35][36][37] The compound shows pronounced nanorod morphology on Au(110) and charge transfer from the surface, indicating that the chemical modificationh as impact on the morphology and electronic properties at the molecular and thin-film levels. [35,36] An X-ray standing-wave investigation could quantify the substantial molecular distortion that 2,3,9,10-tetrafluoropentacene is undergoing upon interaction with aCu(111)s urface on an atomiclevel. [37] In this work, we describe the synthesis of two new isomers of peripherally substituted tetrafluoropentacenes with a 1,4,8,11-(for which computational predictions were made by Lukeš et al) [23] and 1,4,9,10-substitution pattern (Scheme 1c) using the 1,2,4,5-tetrazine-induced elimination of the 6,13ethenob ridge.…”