Synthesis and characterization of the most distorted 16π porphyrin: 16π octaisopropyltetraphenylporphyrin (OiPTPP)

Abstract

Previously unreported octaisopropyltetraphenylporphyrin (OiPTPP) was prepared from 3,4-diisopropylpyrrole, an unstable previously unisolated heterocyclic compound. Purification of the free-base 18π porphyrin required conversion to its 18π zinc(II) complex, chromatographic separation, and acid mediated demetalation. Oxidation of the 18π porphyrin with SbCl 5 furnished metal-free 16π octaisopropyltetraphenylporphyrin (OiPTPP). X-ray structural determination revealed that the novel species is the most distorted 16π porphyrin to date. The time course of decomposition of the oxidized species monitored by UV-vis spectra implied that the introduction of high steric repulsion was effective for enhancing stability of the 16π porphyrin. The reaction of metal-free 16π OiPTPP with LiBF 4 followed by Pd 2 (dba) 3 gave the corresponding 18π OiPTPP palladium(II) complex via reduction of the OiPTPP lithium(I) complex as previously reported for 16π octaisobutyltetraphenylporphyrin (OiBTPP). The new 18π porphyrin system could be characterized by the X-ray analysis of the 18π OiPTPP palladium(II) complex. The X-ray structure of the 18π metal complex also indicated that the distortion of the porphyrin ring had become larger than that of previously known 18π porphyrins.

Chemistry ofmeso-Aryl-Substituted Expanded Porphyrins: Aromaticity and Molecular Twist

“…In the opposite sense, an important question is how small of a ring can realize Möbius aromatic molecules. In this context, the tetrapyrrolic porphyrin skeleton has been demonstrated to be not large enough to implement a Möbius twisted topology within a molecule, because the reported [16]­porphyrins and [20]­porphyrins were largely distorted but not twisted and thus were nonaromatic or antiaromatic. − N -Fused [22]­pentaphyrins 5a,b′ were larger than porphyrins and might be a potential platform to realize a Möbius twisted topology Scheme ).…”

Synthesis and Characterization of Ultralow Fouling Poly(N-acryloyl-glycinamide) Brushes

“…Immobilization of hydrophilic or zwitterionic polymers − on different surfaces is a common strategy to create antifouling surfaces to prevent biofouling. It is generally accepted that polymer coatings offer a strong surface hydration barrier and steric repulsion to prevent the unwanted adsorption of foulants. − Hydrophilic polymer coatings (PEG, , polysaccharides, , polyacrylate, , and polyamide , ) achieve surface hydration via hydrogen bonding of polymers with water molecules, whereas zwitterionic polymer coatings (poly­(carboxybetaine methacrylate), poly­(sulfobetaine methacrylate), and poly­(3-(1-(4-vinylbenzyl)-1 H -imidazol-3-ium-3-yl)­propane-1-sulfonate)) achieve electrostatically induced surface hydration where water molecules bind to zwitterionic groups even stronger. The formation of a strong hydration layer at the polymer/water interface offers an energetic barrier to effectively inhibit unwanted foulant adsorption on polymer coatings.…”

Antiaromatic Character of 16 π Electron Octaethylporphyrins: Magnetically Induced Ring Currents from DFT-GIMIC Calculations

“…Measurements of the 1 H NMR and UV–vis spectra as well as calculations of nucleus-independent chemical shifts (NICS) suggested that the OEP-Zn(II) dication is antiaromatic, which is also expected when assuming that Hückel’s rule for aromaticity holds. The detected large blue shift of the UV–vis spectrum and the missing Q-band generally indicate that the porphyrinoid is antiaromatic. − For meso-unsubstituted porphyrinoids, the degree of aromaticity can also be estimated from the position of the 1 H NMR signal of the meso -hydrogens . Judging from those experimental data, Hiramatsu et al claimed that the OEP-Zn(II) dication is the strongest antiaromatic porphyrin that has been reported so far.…”