Porphyrins and metalloporphyrins: Versatile circular dichroic reporter groups for structural studies

During the last few years, porphyrins and metalloporphyrins have attracted widespread attention as chromophores for studies in circular dichroism (CD) , an indispensable chiroptical tool for monitoring chiral interactions. Thi s review summarizes the multifaceted properties of porphyrins and metallopo rphyrins, powerful CD chromophores that are characterized by their intense and red-shifted Soret band, propensity to undergo pi-pi stacking, facile in corporation of metals, and ease in varying solubility. Such attributes make porphyrins one of the most attractive and sensitive chromophores used in C D studies. They offer possibilities for studying the stereochemistry of chi ral porphyrin assemblies, large organic molecules, biopolymers, and compoun ds available in miniscule quantities. The tendency of porphyrins to undergo pi-pi stacking and zinc porphyrins to coordinate with amines enable the CD exciton chirality method to be extended to configurational assignments of flexible compounds containing only one stereogenic center. Various artifici al porphyrin receptors have been synthesized for the recognition of biologi cally important chiral guests such as carbohydrates, amino acids, and their derivatives. The induced CD of the host porphyrin Soret band reflects the identity of guests and binding modes of host/guest complexation with high s ensitivity. (C) 2000 Wiley-Liss, Inc.