We studied the properties of the monolayers and deposition behaviour of a new member of the group of bis-porphyrin complexes of rare earth metals, namely the newly fabricated lutetium(III) bis-2,3,7,8,12,13,17,18-octakis-(butylthio)tetraazaporphyrinato, as a pure compound and in mixture with cadmium stearate, in the light of their magnetic, semiconducting and gas sensing properties. In both cases the molecules assumed a tilted edge-on orientation at the liquid-air interface, with the molecular rings perpendicular to the water surface, as deduced from pi-A isotherms. Multilayer Langmuir-Blodgett (LB) films were successfully built up only when the bis-porphyrin molecules were mixed with cadmium stearate. Electronic absorption spectra using plane-polarized light indicated isotropy in the plane of the film, i.e. the axes of the molecules were randomly oriented in this plane. The peak width at half-height for the Q band increased on passing from the chloroform solution to the LB films of pure and mixed compounds, indicating different degrees of molecular packing. A single electron spin resonance line was given by the chloroform solution of the molecule and it was also maintained in the mixed LB film.