NIR Absorbing Aromatic E‑Ethylene Bridged Hexaphyrins (2.1.1.2.1.1): Synthesis, Characterization, and Protonation Studies

Judicious syntheses, spectroscopic analyses, and
solid state structural evidence of two structural variants (with
planar geometry) of strongly aromatic hybrid [30] E-ethylene
bridged hexaphyrins (2.1.1.2.1.1) exhibiting strong NIR absorption
are reported. The induced correspondence of fused phenanthrene
on the pyrrole moieties has led to a further red-shift of up to ∼45
nm in the neutral and protonated form of the macrocycles. The
electronic nature and aromaticity of both hexaphyrins are fully
supported by DFT calculations.