Synthesis and Functionalization of Triply Fused Porphyrin Dimers

Abstract

AbstractCurrent applications of porphyrins in medicine and optics, such as photodynamic therapy or nonlinear absorption, increasingly require the use of far‐red absorbing dyes. Modification of the porphyrin structure to accommodate these conditions can be achieved by extending the conjugation of the porphyrin π system, which causes a bathochromic shift in the absorption spectrum. Thus, conjugated porphyrin oligomers have found widespread use. However, past synthetic strategies have mainly targeted symmetric porphyrin dimers, trimers, and oligomers which limit the practical use of such chromophores. To further extend the absorption profile, a series of symmetric and unsymmetric dimeric and oligomeric porphyrin β–β, meso–meso, β′–β′ triply fused systems were synthesized by oxidative coupling methods. This required an analysis and optimization of the various synthetic strategies. These arrays exhibit a dramatic bathochromic shift into the near‐infrared region and many display absorption at wavelengths greater than 1050 nm. Additionally, post‐fusing chemical transformations, namely, organolithium, cycloaddition, and transition‐metal‐catalyzed reactions, at the meso and β positions enable the fine‐tuning of such arrays to enhance the bathochromic shift and their potential optical applications.