In the present work, we determined the electrical properties of octachlorinated
metallophthalocyanines with Co(II) and Cu(II) ions as metal centers. We engaged them in heterojunctions,
with lutetium bisphthalocyanine as a partner. Surprisingly, cobalt and copper complexes show opposite
behaviors, the first being an n-type material whereas the latter is a p-type material, as deduced from
the response of the heterojunctions towards ammonia; showing the unusual key role played by the
metal center. While the LuPc2/Cu(Cl8Pc) complex exhibits a negative response to ammonia, the LuPc2/
Co(Cl8Pc) complex exhibits a positive response to ammonia, with a sensitivity of 1.47% . ppm-1 at
concentrations lower than 10 ppm and a limit of detection of 250 ppb. All the devices operate at room
temperature and in real atmosphere.

molecular semiconductor, conductometric transducer, gas sensor, ammonia