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Symmetry-Selective Ultrafast Charge Transfer via Cyano End Groups at the PDIF-CN 2 –Au(111) Interface

Year: 2026

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide 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 π* orbitals aligned toward Au(111). Although the overall electronic structure remains largely molecular, the nearly degenerate cyano σ*(π)/π*(π) 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 ∼0.43 e – from Au into the cyano π*(π) orbital and the transfer of ∼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.

Source: Nano Letters

DOI: 10.1021/acs.nanolett.6c01061