Diastereoselective methylation of bis(N-confused porphyrinatonickel(ii)): access to configurationally stable chiral bis(porphyrinoid) and non-symmetric dimers

Abstract

Bis- and tris(methylated) derivatives of 3,3'-bis(N-confused porphyrin) were obtained. Methylation of C21 stabilizes the geometry of the axially chiral system allowing separation of enantiomers and assignment of an absolute configuration by X-ray methods.

Towards Norcorrin: Hydrogenation Chemistry and the Heterodimerization of Nickel(II) Norcorrole

“…The observed splitting of the first oxidation (Ox1) as well as the first and second reduction waves (Red1 and Red2) may be caused,t os ome extent, by the nonsymmetric character of the bis(norcorrole), but, considering the structural similarity of the subunits,i tc ertainly indicates an electronic or electrostatic interaction between the subunits. [27][28][29][30] The HOMO-LUMO gap, expressed as the differenceb etween the first oxidation and first reduction potentials, observed for 4 (DE = 0.92 V) is less than that determined for the monomeric 1 (DE = 1.07 V). [14] Relativelyl ow potentials of the two oxidations assigned as Ox1 and the relatively high potentials of the two reductionsd enoted Red1 indicatet hat the process of removing two electrons from or injecting two electrons into 4 can be easily accomplished to yield relatively stable dicationic or dianionic bis(radicaloid)s. [15] The optical properties of the isomeric 2 and 3 are strikingly different and they also differ from the optical properties of the startings ystem 1 (Figure 5).…”

Supramolecular Chirality in Porphyrin Chemistry

“…Hence, the thermal self-cycloaddition of symmetrical (tetra-β,β'-sulfolenoporphyrinato)zinc with the subsequent extrusion of SO 2 yields the racemic chlorin-porphyrin complex, 8, the chiral property of which has not been explored yet, because the corresponding enantiomers have not been resolved [22]. However, in the case of β,β′-bonded chiral porphyrinoids, the corresponding enantiomers were successfully obtained [23]. In particular, the C21 methylation of 3,3′-bis(N-confused nickel porphyrin) resulted in the corresponding di-methylated derivative, 9.…”

Reversible Carbon–Carbon Bond Breaking and Spin Equilibria in Bis(pyrimidinenorcorrole)

“…Electrochemical measurements for 5 indicate an interaction between the subunits, which appears to be stronger than in singly‐bonded bis(porphyrinoids) ,. Two reversible oxidation couples ( E 1/2 =−0.10 and 0.11 V) and two reduction couples ( E 1/2 =−0.84 and −1.05 V), accompanied by the less accessible redox events at 1.02 V and −2.22 V were observed for 5 in CH 2 Cl 2 (potentials vs. the internal ferrocene standard).…”

“…The frequency of rotation around the C3‐C3′ bond can be estimated as about 340–370 Hz at the coalescence temperatures of individual signals reflecting flexibility of the molecular skeleton. That kind of structural flexibility prevents the chromatographic separation of atropisomers observed in the solid state by X‐ray diffraction ,. Unlike 3 , dimer 5 revealed only weak temperature dependence of its optical spectra (25–100 °C, toluene) with only a slight increase of absorption at 416 nm and a similar decrease at 950 nm (Figure S28).…”