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00925njm 22002777a 4500 dc Valdivia Mantas, Samuel author García-González, Francisco author Aranda Ruiz, Daniel author Ávila-Ferrer, Francisco José author López-Tocón, Isabel author Soto, Juan author Otero, Juan Carlos author 2024 Electrochemical SERS of pyridine adsorbed on a silver electrode has been analyzed by comparing the spectra to the calculated normal Raman and resonance Raman intensities of model systems of pyridine bonded to linear silver clusters with different densities of charge through the nitrogen (Ag-NPy) or flipped through the hydrogen in the para-position (Ag-HPy). The changes observed in the ν(CH) region of the SERS have been investigated for the first time and related to a molecular reorientation at negative surface excess of charge of the metal in such a way that the ν(CH) bands with the highest (mode 2) and lowest (mode 13) wavenumber dominate this spectral region at positive or negative electrode potentials, respectively. The calculations support that the ν(CH) region is dominated by a specific vibration depending on pyridine orientation and suggest that both species coexist in the SERS recorded at negative potentials. This conclusion is supported by the SERS of centrosymmetric pyrazine which do not show this behavior and remembers the predictions from the old propensity rules of the so-called electromagnetic mechanism of SERS. Valdivia, S.; García-González, F.; Aranda, D.; Ávila Ferrer, F. J.; López-Tocón, I.; Soto, J.; Otero, J. C. Remembering the Old Propensity Rules of the Electromagnetic Enhancement Mechanism of SERS: Reorientation of Pyridine on a Silver Electrode Induced by the Applied Potential. J. Phys. Chem. C 2024, 128 (30), 12566–12574. https://doi.org/10.1021/acs.jpcc.4c03084 https://hdl.handle.net/10630/32454 10.1021/acs.jpcc.4c03084 Espectroscopía Raman Efecto Raman de superficie intensificada Química física Remembering the old propensity rules of the electromagnetic enhancement mechanism of SERS: reorientation of pyridine on silver electrode induced by the applied potential