  Using first principles calculations in the framework of Density Functional
Theory, we investigated the electronic and transport properties of
metal(II)-phthalocyanine (M(II)Pc) systems, both in a single molecule
configuration and in a model-device geometry. In particular, using the
Copper(II)- and Manganese(II)-Pc as prototypical examples, we studied how
electronic correlations on the central metal-ion influence the analysis of the
electronic structure of the system and we demonstrated that the choice of the
exchange-correlation functional, also beyond the standard local or gradient
corrected level, is of crucial importance for a correct interpretation of the
data. Finally, our electronic transport simulations have shown that
M(II)Pc-based devices can act selectively as molecular conductors, as in the
case of Copper, or as spin valves, as in the case of Manganese, demonstrating
once more the great potential of these systems for molecular nanoelectronics
applications.
