A series of expanded porphyrins, incorporating biimidazoles and bipyrroles within their macrocyclic framework, has been synthesized. Insights into the complex conformational characteristics of these ems were obtained from two-dimensional NMR spectroscopic studies. The relative energy values for the various asymmetric structures inferred from these analyses were compared using DFT molecular modeling calculations.Key words: macrocycles, expanded porphyrins, imidazoles, pyrroles, biimidazoles, supramolecular chemistry, heterocycles.