It is shown that the noncovalent donor-spacer-acceptor (DSA) motif is useful in constructing an electron-transfer assembly. As a representative example, the equilibrium and structure of one of the DSA assemblies, consisting of Zn-tetraphenylporphyrin, a spacer unit bearing pyridine and amidinium moieties, and 3,4-dinitrobenzoic acid, were studied in detail by the extensive use of UV-vis titration, fluorescence spectroscopy, and H-1 NMR, with the help of a three-component equilibrium model. Complex formation and fluorescence quenching in 20 different DSA complexes constructed from a library of five donors, two spacers, and two acceptors were investigated. It has been experimentally shown that supramolecular modular approach is useful for a systematic and quick search for a functionally optimized assembly.