A new series of relatively flexible cofacial donor-acceptor dyads for singlet-singlet energy transfer with the corrole or etio-porphyrin free base and zinc porphyrin as the acceptor and donor, respectively, were synthesized and characterized (represented as (PMes(2)COx)ZnH3 (13), (PMes(2)CO)ZnH3 (14), and (PMes(2)CX)ZnH3 (15)) where (PMes(2)COx = [2-[5-(5,15-dimesitylcorrol-10-yl)-diphenylether-2'-yl]-13,17-diethyl-2, 3,7,8,12,18-hexamethylporphyrin]), (PMes(2)CO = [5-[5-(5,15-dimesitylcorrol-10-yl)-dibenzofuran-4-yl]-13,17-diethyl-2,3, 7,8,12,18-hexamethylporphyrin]), and (PMes(2)CX = [5-[5-(5,15-dimesitylcorrol-10-yl)-9,9-dimethylxanthen-4-yl)]-13,17-diet hyl-2,3,7,8,12,18-hexamethylporphyrin]), respectively) along with the homobismacrocycles (DPOx)ZnH2 (17) and (DPOx)Zn-2 (18) (where (DPOx = 2,2'-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]diphe nylether) as comparison standards. The rate for energy transfer (k(ET)) extracted by the measurements of fluorescence lifetimes are of the same order of magnitude as those recently reported for the rigidly held face-to-face dyads ((DPB)ZnH2 (1), (DPX)ZnH2 (2), (DPA)ZnH2 (3), (DPO)ZnH2 (4), and (DPS)ZnH2 (5) where (DPB = 1,8-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]biphen ylene), (DPX = 4,5-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]-9,9-d imethylxanthene), (DPA = 1,8-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]anthra cene), (DPO = 4,6-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]dibenz ofuran), and (DPS = 4,6-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]dibenz othiophene), respectively), but for the first time, it is shown that the presence of a bulky group located between the acceptor and the donor moiety influences the transfer rate. The presence of perpendicular mesityl groups on the acceptor macrocycle prevents the two macrorings from interacting strongly; therefore, k(ET) is slower. On the other hand, by rendering the rigid spacer flexible (i.e., changing the dibenzofuran rigid spacer to the flexible diphenylether assembling fragment), k(ET) increases due to stronger intermacrocycle interactions. This study is complemented by DFT computations (B3LYP/3-21G*) as a molecular modeling tool where subtle structural features explain the changes in k(ET). During the course of this study, X-ray structures of 17 and 18 were investigated and exhibit a linear stacking of the bismacrocycles where intermolecular porphyrin-porphyrin interactions are observed (d(inter(Zn center dot center dot center dot Zn)) = 4.66 and 4.57 angstrom, for 17 and 18, respectively).