Symmetry-selective ultrafast charge transfer via cyano end groups at the PDIF-CN▫$_2$▫–Au(111) interface

Kladnik, Gregor (author), Cassinese, Antonio (author), Schio, Luca (author), Goldoni, Andrea (author), Morgante, Alberto (author), Floreano, Luca (author), Cvetko, Dean (author)

Cyano-functionalized perylene diimides provide a platform for engineering orbital-specific electronic transparency at organic‒metal interfaces. Here we resolve the adsorption geometry, orbital symmetry, and ultrafast charge-transfer dynamics of PDIF-CN▫$_2$▫ on Au(111) using polarization-dependent NEXAFS, XPS, resonant Auger spectroscopy with core-hole-clock analysis, and STM. Molecules in the monolayer lie flat with out-of-molecular plane polarized cyano-derived ▫$\pi^*$▫ orbitals aligned toward Au(111). Although the overall electronic structure remains largely molecular, the nearly degenerate cyano ▫$\sigma^*(\pi)/\pi^*(\pi)$▫ doublet becomes distinctly split at the interface, enabling symmetry-selective coupling of cyano orbitals. We use Auger spectator shifts to quantify bidirectional charge exchange within the N 1s core-hole lifetime, yielding injection of ▫$\sim$▫0.43 e▫$^-$▫ from Au into cyano ▫$\pi^*(\pi)$▫ orbital and the transfer of ▫$\sim$▫0.17 e▫$^-$▫ in the opposite direction. These findings establish cyano end groups as symmetry-selective gateways for femtosecond charge transfer at molecule‒metal interfaces.

• Language: English
• Keywords: thin films, interfaces, charge transfer, Auger spectroscopy
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: Str. 6983-6990
• Numbering: Vol. 26, iss. 21
• PID: 20.500.12556/RUL-183097
• UDC: 544
• ISSN on article: 1530-6984
• DOI: 10.1021/acs.nanolett.6c01061
• COBISS.SI-ID: 278874883
• Publication date in RUL: 04.06.2026

Record is a part of a journal

• Title: Nano letters
• Shortened title: Nano lett.
• Publisher: American Chemical Society
• ISSN: 1530-6984
• COBISS.SI-ID: 18341927

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: tanki filmi, površine, prenos naboja, Augerjeva spektroskopija