Ho WKH, Bao ZY, Gan X, Wong KY, Dai J, Lei D. Probing Conformation Change and Binding Mode of Metal Ion-Carboxyl Coordination Complex through Resonant Surface-Enhanced Raman Spectroscopy and Density Functional Theory.
J Phys Chem Lett 2019;
10:4692-4698. [PMID:
31368709 DOI:
10.1021/acs.jpclett.9b01435]
[Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Understanding carboxyl-metal ligand interaction has great significance in analytical chemistry. Herein, we use resonant surface-enhanced Raman scattering (SERS) to probe the physiochemical interaction and conformation change in several metal ion-carboxyl coordination complex systems adsorbed on the surface of plasmonically resonant metal nanostructures. Our SERS results and density function theory calculations jointly reveal that low-valence metal ions (such as K+ and Pb2+) tend to bind to the carboxyl active site of a Raman tag molecule, 4-mercaptobenzoic acid (4-MBA), in a unidentate binding mode of low binding energy whereas high-valence metal ions (such as Fe3+) favor a bidentate binding mode of relatively high binding energy. Particularly, Pb2+-ion concentration-dependent SERS suggests a repulsive interaction among the coordination complex leading to a tilted configuration of 4-MBA on the metal surface. This work indicates the resonant SERS approach is suitable not only for studying the carboxyl-metal ligand interaction but also for detecting various types of heavy metal ions at low concentrations.
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