This study investigates the influence of different metal centers in porphyrins and of different polyelectrolyte architectures on the formation of supramolecular metalloporphyrin-polyelectrolyte assemblies in aqueous solution via electrostatic self-assembly. Metal-analogues of the tetravalent anionic meso-tetrakis(4-sulfonatophenyl)-porphyrin (with Zn2+, Co2+, Ni2+, Mn3+, and Fe3+) are combined with the cationic dendrimer of generation 4 or with the linear polydiallyldimethyl-ammoniumchloride. Dynamic light scattering and atomic force microscopy reveal that the different molecular geometries of the metalloporphyrins resulting from axial ligands determine the size and the stability of the aggregates. A thermodynamic study elucidates the importance of the polymer architecture in controlling the size of the assembly and the role of the metal center. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 484-500