Helical Porphyrinoids: Incorporation of Ferrocene Subunits into Macrocyclic Structures

Abstract

Ferrocene‐containing porphyrinoids have been synthesized in which ferrocene‐1,1′‐diyl units are linked to a dipyrrin or thiatripyrrin to form macrocyclic structures. NMR spectroscopic evidence shows that these new systems adopt helical conformations that undergo an inversion process in solution. In addition, small amounts of unexpected scrambling products have been isolated and characterized, namely a dipyrrin‐bisferrocenophane and two expanded bis(ferrocene) macrocycles. The formation of these systems, which contain macrocyclic rings of different sizes, is a consequence of the structural flexibility of the ferrocene unit. Cyclic voltammetry shows that ferrocene oxidation is reversible in all the systems reported here, and that it is finely tuned by the properties of the ring system. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Deltoid versus Rhomboid: Controlling the Shape of Bis-ferrocene Macrocycles by the Bulkiness of the Substituents

“…It is noteworthy that similar dangling motions of ferrocene subunits heteroannularly integrated in macrocycles have already been reported, like e.g. the helical ferrocene porphyrinoids reported by Stępień et al 29 DFT calculations. DFT calculations.…”

A Chiral Macrocyclic Oligothiophene with Broken Conjugation – Rapid Racemization through Internal Rotation

“…The barrier for racemization is considerably lower than the barrier for similar ferrocene-based macrocycles with smaller ring sizes. [55] Further cooling of the sample to 183 K revealed a second dynamic process that is most likely related to rotational restrictions in the di-tert-butylphenyl units.…”

Ruthenocenoporphyrinoids: Conformation Determines Macrocyclic π Conjugation Transmitted Across a d‐Electron Metallocene

“…The range of ruthenocene chemical shifts observed for 5 ( δ =10–3 ppm), 5 ‐H + ( δ =13–3 ppm), and 5 ‐H 2 2+ ( δ =14–3 ppm) are consistent with a macrocyclic paratropic ring current creating considerable magnetic anisotropy. This paratropic current influences the shifts of pyrrole and thiophene β‐hydrogen atoms, which experience upfield shifts (relative to the nonaromatic reference molecules) 11. Significantly, in the dihydro derivative 6 ‐H 2 , the sign of the anisotropy is reversed and is consistent with the presence of a diatropic current in the macrocycle.…”