3-n-Propylpyridiniumsilsesquioxane chloride polymer, abbreviated as SiPy+Cl-, was used to coat a porous silica gel, SiO2, surface to form the chemically modified solid SiO2/SiPy+Cl-. The resulting polymer film was well adhered to the surface and presented an ion exchange capacity of 0.74 mmol g(-1). Metal halides, MClz [M = Fe(III), Cu(II), and Zn(II)], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes described by the equation: mSiO(2)/SiPy+Cl- + MClz reversible arrow (SiO2/SiPy+)(m)[MClz+m](m-), where the [MClz+m](m-) species adsorbed on the surface are FeCl4-, ZnCl42-, and CuCl42-. Accurate estimates of the specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures. (C) 2003 Elsevier Inc. All rights reserved.