Solvent induced optimization of energy transfer properties in a series of Zn(II)-porphyrin-appended dendrimers has been studied by means of exciton-exciton annihilation. Upon changing from a polar solvent (tetrahydrofuran) to a non-polar solvent (3-methyl-pentane), the annihilation energy transfer rates increase by 28-44%. This is related to a decrease of the hydrodynamic radius, which enhances the communication between the Zn(II)-porphyrin chromophores. As a consequence, the overall energy transfer efficiency is increased, thereby yielding complete annihilation between all the chromophores in the smallest generation dendrimer. (c) 2006 Elsevier B.V. All rights reserved.