Interaction of 4-imidazolemethanol with a copper electrode revealed by isotope-edited SERS and theoretical modelingElectronic supplementary information (ESI) available: Comparison of solution Raman and SERS spectra at different concentrations (Fig. S1); SERS spectra of phosphate anions (Fig. S2); structures of Cu6-ImMeOH-H2O complexes (Fig. S3); calculated Mulliken atom charges (Table S1); and calculated bond lengths of complexes Cu6-ImMeOH-H2O (Table S2). See DOI: 10.1039/c5cp01290b

• Main Authors: Matulaitien, Ieva, Poci t, Egl, Kuodis, Zenonas, Eicher-Lorka, Olegas, Niaura, Gediminas
• Format: Journal Article
• Language: English
• Published: 17.06.2015
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c5cp01290b

Adsorption of 4-imidazolemethanol (ImMeOH) on a copper electrode has been investigated by in situ isotope-edited (H/D and 63 Cu/ 65 Cu) surface enhanced Raman spectroscopy (SERS) in aqueous solutions at physiological pH (7.0) in a potential window from −0.500 to −1.100 V. Theoretical modeling by DFT calculations at the B3LYP/6-311++G(d,p) level for light atoms and LANL2DZ with ECP for copper atoms have been employed for the interpretation of experimental data. The copper surface was modeled by a cluster of 6 atoms. It was found that the imidazole ring adopts Tautomer-I form in the adsorbed state and coordinates with the Cu surface through the N3 atom. Linear potential-dependence of ν (C4&z.dbd;C5) mode with the slope of (15 ± 1) cm −1 V −1 was experimentally observed. The imidazole ring mode near 1492 cm −1 primarily due to ν (C2-N3) + β (C2H) vibration has also showed a considerable decrease in frequency at more negative electrode potentials with the slope of (9 ± 2) cm −1 V −1 . Both modes can be used as sensitive probes for analysis of interaction of the imidazole ring with the metal surface. In agreement with experimental data theoretical modeling has predicted higher stability of surface bound Tautomer-I compared with Tautomer-II. The formation of a covalent bond between the metal and adsorbate was experimentally evidenced by metal isotopic ( 63 Cu/ 65 Cu) frequency shift of ν (Cu-N) mode at 222 cm −1 , combined with theoretical modeling of the surface complex. The formation of a covalent bond between the copper electrode and the adsorbate bearing an imidazole ring is experimentally and theoretically evidenced by an isotopic 63 Cu/ 65 Cu frequency shift of Cu-N stretching mode at 222 cm −1 .