Porphyrins are heterocyclic macrocycles that consist of four pyrrole subunits connected via their carbons through methine bridges. These structures are widely distributed in nature fulfilling many roles ranging from oxygen transportation (hemoglobin), electron transfer (cytochromes), enzyme catalysis involving oxidations and reductions (peroxidase, catalase, cytochrome oxidase) to light harvesting and photosynthesis (chlorophylls). Their widespread occurrence has attracted the interest of organic chemists for over 100 years. Replacing one or more pyrrole subunits in the porphyrin framework with a carbocyclic ring, such as cyclopentadiene, generates carbaporphyrinoids. This book describes the preparation and characterization of tropone-fused carbaporphyrinoids using the '3 + 1' modification of the MacDonald strategy. Additionally, investigations into the reactivity of these systems are presented.