Based on the electrochemical properties of a series of metallophthalocyanines this article shows that the
phthalocyanine bearing four alkoxy groups and twelve fluorine atoms behaves approximately as those
with eight fluorine atoms. This indicates that the electron-donating effect of one alkoxy group balances the
electro-withdrawing effect of one fluorine atom. We engaged three metallophthalocyanines, namely the
octafluoro copper phthalocyanine, Cu(F8Pc), an octaester metallophthalocyanine and a phthalocyanine
bearing four alkoxy groups and twelve fluorine atoms, Zn(T4F12Pc), in building original conductometric
transducers that are Molecular Semiconductor – Doped Insulator heterojunctions (MSDIs) in association
with the highly conductive lutetium bisphthalocyanine, LuPc2. Whereas the octaester derivative
and Zn(T4F12Pc) exhibited a negative response to ammonia, as expected for p-type materials, Cu(F8Pc)
exhibited a particular behavior. At low humidity levels, 30 and 10% rh, the current of the Cu(F8Pc)/LuPc2
MSDI decreases, similarly to p-type devices, but at higher relative humidity values, 70% rh, the current
increases under ammonia, which is the signature of a n-type behavior. This ambipolar behavior is unique
amongst semiconducting sensing materials. This work opens the way to the study of ambipolar materials
as sensing materials for the development of a new type of conductometric gas sensors.