Time dependent density functional theory and polarizable continuum model have been used to describe tetra-phenyl-porphyrin derivatives in different solvents and at different pH values. Our results show that last generation functionals are able to describe with good accuracy the photophysics of the title compounds, including different physical-chemical properties of excited electronic states. In particular, the strong modification of polarizabilities induced in some cases by electron excitation could explain a recent hypothesis about NLO characteristics of specific porphyrin adducts.