Y. Zhang et al., STRUCTURAL CHARACTERIZATION OF LANGMUIR-BLODGETT-FILMS DERIVED FROM MULTISULFUR HETEROCYCLES, Journal of physical chemistry, 100(32), 1996, pp. 13804-13810
A novel multisulfur heterocyclic compound with alkyl chains, C3S5(C18H
37)(2) (4,5-bis(octadecylthio)-1,3-dithiole-2-thione), has been synthe
sized and fabricated into Langmuir-Blodgett (LB) films. The structure
of this film on SiO2 slides has been studied using X-ray photoelectron
spectroscopy (XPS) and SR and UV transmission linear dichroism (LD) m
easurements. From the isotherm, it is known that the Langmuir film at
the air-water interface is a bilayer. Angle-resolved XPS of films tran
sferred to SiO2 show that the alkyl chains of the molecule form the to
pmost layer of the film, with the C3S5 ring underneath the alkyl layer
. Electronic structure calculations indicate that the transition momen
t associated with the observed UV band lies coincident with the C-2 ax
is of the C3S5 ring group. In order to properly interpret the polarize
d absorption data, a simple model addressing The local field effect in
LD measurements was developed. Incorporating measured information on
the polarizability of the chromophore, UV and IR LD measurements showe
d the ring plane and the chains to be stacked at 69 degrees and 20 deg
rees, respectively, relative to the surface normal. These data coupled
with the XPS results permitted a structural model to be constructed w
hich accounts for the multilayer structure of the transferred film.