LB multilayers of highly conjugated porphyrin dimers: differentiation of properties and behaviour between the free base and the metallated derivatives

Meso,meso′-buta-1,3-diyne-bridged Ni(II), Cu(II) and free base and meso,meso′-ethene-bridged Ni(II) and free base have been deposited in mixture with arachidic acid as thin films by the Langmuir–Blodgett technique. The floating layers and the film so fabricated have been characterised. Moreover, interesting gas sensing properties have been manifested by the two metallated butadiyne derivatives, evidencing high stability, reversibility, selectivity and sensitivity to nitric oxide. On the contrary, the free bases and the metallated ethene-bridged derivative do not exhibit such behaviour. A rationale of these different characteristics has been proposed on the basis of the existence of different bisporphyrin conformers in the films that reverberates also on the multilayer order and structure.