Synthesis and Surface
Investigations of N-Substituted
2,5-Dithio-7-azabicyclo[2.2.1]heptanes on Gold Surfaces
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Abstract
The reaction of various primary amines and 2,5-dihydroxy-1,4-dithiane
in the presence of a catalytic amount of Mg(II) in distilled water
provided a series of N-substituted 2,5-dithia-7-azabicyclo[2.2.1]heptanes.
The adsorption profiles of the sulfur-containing heterocycles on gold
surfaces have been explored by time-of-flight secondary ion mass spectrometry
(TOF-SIMS), X-ray photoelectron spectroscopy (XPS), and electrochemistry.
SIMS data indicated that these novel bicyclic sulfides interact with
gold surfaces favorably, independent of the N-substitution, with minimal
fragmentation. An XPS study revealed the three component core levels
of S 2p with binding energies at 161, 162, and 163 eV, indicating
a combination of the bound and unbound sulfur species. Using cyclic
voltammetry (CV) and electrochemical impedance spectroscopy (EIS),
we found the efficient adsorption of heterocycles onto gold and the
formation of densely packed films for alkyl and phenyl analogues.
However, the adsorption and film packing properties were greatly compromised
by an N<i>-</i>pyridyl substitution. The findings
indicate that the surface behavior of N-substituted 2,5-dithia-7-azabicyclo[2.2.1]heptanes
varies with respect to the N-substitution and the nature of the substituent,
suggesting that the adsorption profiles and the film packing of bicyclic
sulfides on gold surfaces are highly dependent on the binding interface
and the molecular orientation