Probing diffusivity and configurational flexibility of a tetrabenzoporphyrin on metal surfaces by tip-enhanced Raman spectroscopy

Identification of functional molecular configurations sets forth towards a complete understanding of different metal surface-supported nano-scale phenomena such as catalysis, diffusion, and chemical or photovoltaic reactions. Tetrabenzoporphyrin molecules have been of interest in this field as they are thermally and chemically stable porphyrin derivatives with robust applications in the field of photoelectronics, such as organic field-effect transistors, organic light-emitting diodes, organic photovoltaic cells, and related devices due to their high hole mobility and strong absorption in the visible region. Here, ultrahigh vacuum (UHV) high-resolution scanning tunneling microscopy (STM) combined with tip-enhanced Raman spectroscopy (TERS) has been employed to characterize the diffusing domains of 5,10,15,20-tetraphenyltetrabenzoporphyrin (TPTBP) on the Au(100) surface and self-assembled condensed phases on the Ag(100) surface. The intermolecular interactions and the surface adsorbed configurations in the self-assembled condensed phases were identified with STM analysis. Plasmonic field-enhanced Raman spectroscopic features were used for the chemical identification of the diffusive phase and the condensed phases in a comparative manner. • Configurational flexibility in 2D molecular assembly • Molecular surface diffusivity control on the Au surface • Vibrational fingerprinting by Raman spectroscopy for configuration recognition