Perimeter Coordinated Diastereomeric Rh(I) Complex of Helically Twisted Weakly Aromatic Hybrid Singly N‑Confused β−β Fused Ferrocenoporphyrinoids.

Expedient synthesis, spectroscopic, solid state structural proof,
and theoretical study of helically twisted weakly aromatic hybrid singly Nconfused
ferrocenoporphyrinoids and the peripheral coordinated Rh(I)
complex are reported. The X-ray crystal structure of the macrocycles reveals
an ambiguously inverted pyrrole ring reinforcing regioselective β,β-linkage
with the spatially adjacent N-confused N-methyl pyrrole ring leading to
endocyclic extension of macrocyclic π-conjugation via tricyclic [5.5.5] moiety.
The three-dimensional structure with built-in fused tricyclic [5.5.5] moiety has
paved way to three-dimensional weak diatropicity with vis−NIR absorptions.
The peripheral coordinated Rh(I) complex owing to helical chirality about the
macrocyclic ring and planar chirality about the square planar Rh coordination
site exists as a mixture of diastereomers (5:3) with well resolved 1H NMR spectra anticipating weak aromaticity. The experimental
spectroscopic measurements are in agreement with theoretically determined electronic structure and properties strongly elucidating
sustained weak diatropic ring currents in twisted macrocycles both in neutral form and in the metalated complex. Further fragment
molecular orbital approach and molecular orbital theory gave insights on the stability of N-confused β−β fused oxoferrocenoporphyrinoids
and formation of the selective peripheral coordinated Rh(I) complex.