A Core‐Modified Rubyrin with <i>meso</i>‐Aryl Substituents and Phenanthrene‐Fused Pyrrole Rings: A Highly Conjugated Near‐Infrared Dye and Hg²⁺ Probe

Sending signals: The first core-modified, expanded porphyrin with polyaromatic units fused to the pyrrole rings absorbs far into the near-infrared and shows fluorescence that stretches into the second optical window of telecommunication. Doping a polyurethane membrane with the dye yields Hg2+-responsive optical test strips.