Fused porphyrinoids as promising near-infrared absorbing dyes

Various aromatic segments have been fused onto the porphyrin periphery to create porphyrinoids that have expanded π-conjugated networks and thus exhibit red-shifted absorption spectra. Fused coplanar porphyrin oligomers, represented by meso–meso, β–β, β–β triply linked porphyrin arrays (porphyrin tapes), are endued with more red-shifted absorption spectra and better nonlinear optical properties. These fused porphyrinoids have emerged as promising near-infrared (NIR) absorbing dyes, pointing to future applications such as conducting wire, NIR emitter, photovoltaics, and nonlinear optical materials. Developments of the fused porphyrinoid chemistry are reviewed in this feature article with focus on the synthesis, the relationships between their absorption spectra and molecular structures, and the applications in materials science.