Y. Gorbunova et al., Langmuir-Blodgett films of bis(octakispropyloxy) samarium bisphthalocyanine. Spectroscopic and gas-sensing properties, LANGMUIR, 17(16), 2001, pp. 5004-5010
In this work, the synthesis of a novel substituted bisphthalocyanine, the b
is[octakis(propyloxy)-phthalocyaninato] samarium(III) complex, is reported.
Langmuir-Blodgett (LB) films of this compound have been prepared. The infl
uence of the propyloxy groups in the structure of the LB films and in their
spectroscopic, chemical, electrochromic, and gas-sensing properties has be
en evaluated. Ther-A isotherms exhibit greater monolayer stability than tha
t observed in the unsubstituted analogue. The compressed monolayers are eas
ily transferred by Y-type deposition resulting in red films instead of the
expected green monolayers. The LB films have been characterized spectroscop
ically using UV-vis, near-IR, and FTIR techniques. The UV-vis spectra show
that the Q-band splits into two peaks on passing from the chloroform soluti
on to the LB films. This is the first example of a Davydov splitting in a b
isphthalocyanine compound. The Davydov splitting, which is responsible for
the red color of the LB films, is characteristic of crystalline order. The
FTIR spectra also indicate the presence of long-range order in the LB films
. Electrochromism. is clearly observed in cast films but appears attenuated
in LB films due to the coincidence of the electronic absorption bands of t
he blue and red forms with the bands corresponding to the Davydov splitting
. Finally, LB films deposited onto ITO microelectrodes (spacing of 75 micro
ns) show an appreciable conductivity. The resistance of the devices varies
reversibly when they are exposed to several volatile organic compounds. Alt
hough the resistance of the LB films is higher than that observed in simila
r gas sensors prepared from unsubstituted or tertbutyl-substituted bisphtha
locyanines, the response toward the vapors is more intense.