The reactivity of Co(II) phthalocyanine toward the oxidation of 2-mercaptoethanol was investigated using first principle theoretical methods. Calculations have been carried out using a hybrid Hartree-Fock/density functional approach (PBE0). Solvent effects have been included through a polarizable continuum model (C-PCM), while surface effects have been mimicked by a supramolecular (phthalocyanine + carbon cluster) approach. The influences of chemical environment and of the medium on reactivity were analyzed using two different reactivity descriptors, the donor acceptor intermolecular hardness and the electrophilicity index. Our results show that solvent and surface have a cooperative effect, both increasing the reactivity of the adsorbed complex. (C) 2003 Elsevier B.V. All rights reserved.