More Like this

1. On the Preparation of Nickel Porphyrins Bearing Two to Four Nitro Groups at β ‐Positions

   https://doi.org/10.1002/ejoc.202500420  

   Tatar, Ameneh; Havlík, Martin; Navrátilová, Tereza; Uhlíková, Tereza; Drozdová, Michaela; Hricková, Karolína; Hajduch, Jan; Anzenbacher, Pavel; Dolenský, Bohumil (June 2025, European Journal of Organic Chemistry)

   The preparation, isolation, and identification of dinitro, trinitro, and tetranitro metalloporphyrins bearing nitro groups on pyrrole rings—desirable intermediates that enable fundamental changes in the chemico‐physical properties of the porphyrin core—are studied. All six possible dinitro‐Ni‐TPP isomers are formed; three are isolated as pure substances using column chromatography, while the remaining three are inseparable. All possible trinitro‐Ni‐TPP isomers are prepared and isolated, except for the 2,7,13 isomer. Attempts to synthesize tetranitro‐Ni‐TPP either through direct nitration of metalloporphyrin or via direct condensation of the nitropyrrole building blocks are unsuccessful. The molecular structures are unambiguously identified using 2D NMR experiments. Some experimental observations, though not all, are consistent with quantum chemical calculations performed on the geometry, energy, Fukui indices, dipole moments of nitroporphyrins, and the energy of nitration intermediates. 

   more » « less
2. Cyclophane-Sustained Ultrastable Porphyrins

   https://doi.org/10.1021/jacs.0c02311  

   Liu, Wenqi; Lin, Chenjian; Weber, Jacob A.; Stern, Charlotte L.; Young, Ryan M.; Wasielewski, Michael R.; Stoddart, J. Fraser (May 2020, Journal of the American Chemical Society)
3. Meso -tetra(dioxanyl)porphyrins: Neutral, low molecular weight, and chiral porphyrins with solubility in aqueous solutions

   https://doi.org/10.1142/S108842462150070X  

   Jiang, Xu-Liang; Damunupola, Dinusha; Bruckner, Christian (July 2021, Journal of Porphyrins and Phthalocyanines)

   null (Ed.)

   The synthesis of a low-molecular weight, neutral, porphyrin meso-tetra(dioxan-2-yl)porphyrin of significant solubility in aqueous solution is described using 4 × 1 or 2 + 2-type approaches. The key intermediate dioxan-2-carbaldehyde is accessible in either racemic or in stereo-pure forms from commercially available starting materials in three steps, allowing also the preparation of chiral porphyrins. 

   more » « less
4. Synthesis of 2-bromo- and 2-phenyl-neo-confused porphyrins

   https://doi.org/10.1039/d0ob01642j  

   Almejbel, Arwa S.; Lash, Timothy D. (September 2020, Organic & Biomolecular Chemistry)

   null (Ed.)

   Neo-confused porphyrins (neo-CPs), porphyrin isomers with a 1,3-connected pyrrolic subunit, are aromatic structures with a CNNN coordination core. Previously, examples of neo-CPs with fused benzo units or electron-withdrawing ester substituents have been described. In this paper, two new examples of neo-CPs are reported that lack a fused aromatic unit or an ester moiety, but instead have a bromo or phenyl substituent on the neo-confused ring. Acid-catalyzed condensation of suitably substituted 1,2′-dipyrrylmethane dialdehydes with a 2,2′-dipyrrylmethane, followed by oxidation with aqueous ferric chloride solutions, afforded the neo-CPs in 40–45% yield. These porphyrin analogues had slightly reduced diatropic ring currents and slowly decomposed in solution. The related palladium( ii ) and nickel( ii ) complexes proved to be very unstable, even though the diatropicity of the macrocycle was enhanced. This study shows that stabilizing substituents are necessary for investigations into this class of porphyrinoids. Attempts to prepare imidazole versions of neo-CPs were unsuccessful. 

   more » « less
5. Solutions of ϕ (n) = ϕ (n + k) and σ (n) = σ (n + k)

   https://doi.org/10.1093/imrn/rnaa218  

   Ford, Kevin (August 2020, International Mathematics Research Notices)

   null (Ed.)

   Abstract We show that for some even $$k\leqslant 3570$$ and all  $$k$$ with $442720643463713815200|k$, the equation $$\phi (n)=\phi (n+k)$$ has infinitely many solutions $$n$$, where $$\phi $$ is Euler’s totient function. We also show that for a positive proportion of all $$k$$, the equation $$\sigma (n)=\sigma (n+k)$$ has infinitely many solutions $$n$$. The proofs rely on recent progress on the prime $$k$$-tuples conjecture by Zhang, Maynard, Tao, and PolyMath. 

   more » « less