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SERS Spectroscopy and DFT Studies of Thionine and its Derivatives Adsorbed on Silver Colloids: Which N Atom is Used for Coordination of a Phenothiazine‐Based Natural Dye to Electron‐Deficient Metal Surface?
Author(s) -
Yu MalgEum,
Cheong ByeongSeo,
Cho HanGook
Publication year - 2017
Publication title -
bulletin of the korean chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.237
H-Index - 59
ISSN - 1229-5949
DOI - 10.1002/bkcs.11205
Subject(s) - phenothiazine , thionine , thiazine , chemistry , raman spectroscopy , stacking , crystallography , atom (system on chip) , photochemistry , ring (chemistry) , raman scattering , metal , moiety , stereochemistry , organic chemistry , optics , medicine , physics , electrode , electrochemistry , computer science , pharmacology , embedded system
A Surface‐enhanced Raman scattering ( SERS ) investigation has been carried out for thionine and its derivatives, well known blue‐based dyes sharing the phenothiazine core. The thionine SERS spectrum is similar to its Raman spectrum. This suggests that the strong Raman bands mostly arising from in‐plane ring modes are also enhanced on metal surface. Several originally weak Raman bands arising from the CNC moiety or H atoms on the thiazine N side also largely strengthen in the SERS spectrum. Density functional theory results for the plausible coordinated structures of thionine and the silver adatom reveal that coordination via the thiazine N atom to Ag + leads to the most stable structure, and its calculated spectrum also best reproduces the SERS spectrum. The thionine derivatives show surprisingly analogous spectra, reflecting that the derivatives coordinate in a similar fashion to the metal surface. The high preference of the thiazine N atom for coordination is traced to the positive charge on the S atom.