Synthesis of Helically π‐Extended N‐Confused Porphyrin Dimer via <i>meso</i>‐Bipyrrole‐Bridge with Near‐Infrared‐II Absorption Capability
Kazuhisa Yamasumi, Yusuke Notsuka, Yoshihisa Yamaoka, Shigeki Mori, Masatoshi Ishida, Hiroyuki Furuta
Abstract
Quinoidal dimeric porphyrin dye synthesis exhibiting second near-infrared (NIR-II) absorbability is described herein. A precisely designed meso-pyrrolyl-substituted N-confused porphyrin possesses a distinct metal coordination site at the periphery. Nickel metalation of this compound led to the oxidative C-H coupling between adjacent α-pyrrole rings, affording two dimeric complexes, which exhibited intense NIR-II absorptions ranging from 1000 to 1400 nm. As was evidenced by decreased aromaticity, the quinoidal resonant structures contributed to the emergence of photoacoustic spectral capabilities in the NIR-II window. Thus, the potential of these compounds as prototypical contrast agents in various bioimaging applications has been demonstrated.