The synthesis and photophysical characterization of nucleobase-substituted porphyrins designed to form rigid hydrogen-bonded ensembles, and to allow for energy transfer within the resulting complexes, is reported Watson-Crick nucleobase-pairing interactions between guanosine- and cytidine-bearing porphyrins are used to assemble the hydrogen-bonded ensembles. Likewise, zinc(II) and free-base porphyrins are used respectively as the donors and acceptors within these ensembles that, depending on design, contain either two or three total porphyrin subunits within the supramolecular assembly. The association constant for guanosine-to-cytidine association representing the primary interaction in each donor-acceptor assembly, is ca, 22 000 +- 200 Msup minus1 in CDsub 2Clsub 2 as determined from sup 1H NMR titration analyses. Both singlet and triplet energy transfer was observed within the various donor-acceptor assemblies. Whereas the singlet-state energy-transfer dynamics are consistent with a Foerster-type process, triplet energy transfer within the same complex is believed to occur through the hydrogen-bonded interface. The presently-described noncovalent approach to donor-acceptor ensemble generation is thus considered to provide a novel and useful approach to modeling aspects of the photon antennae that are part of the natural photosynthetic process. 31 refs., 8 figs., 2 tabs.