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27 results on '"Zafar, Hadiqa"'

5. Remolding and Deconstruction of Industrial Thermosets via Carboxylic Acid-Catalyzed Bifunctional Silyl Ether Exchange

Author

Husted, Keith E. L., primary, Brown, Christopher M., additional, Shieh, Peyton, additional, Kevlishvili, Ilia, additional, Kristufek, Samantha L., additional, Zafar, Hadiqa, additional, Accardo, Joseph V., additional, Cooper, Julian C., additional, Klausen, Rebekka S., additional, Kulik, Heather J., additional, Moore, Jeffrey S., additional, Sottos, Nancy R., additional, Kalow, Julia A., additional, and Johnson, Jeremiah A., additional

Published
2023
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8. UO22+-mediated ring contraction of pyrihexaphyrin: synthesis of a contracted expanded porphyrin-uranyl complex† †Electronic supplementary information (ESI) available: X-ray crystal structure for 1893382 (1) and 1893883 (4) (CIF); detailed experimental procedures and characterization data for all new compounds (PDF). CCDC 1893382 and 1893883. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c9sc01593k

Author

Brewster, James T., Root, Harrison D., Mangel, Daniel, Samia, Adam, Zafar, Hadiqa, Sedgwick, Adam C., Lynch, Vincent M., and Sessler, Jonathan L.

Subjects
Chemistry
Abstract

A new mixed hexaphyrin, pyrihexaphyrin (0.1.0.0.1.0) (1), was prepared via an acid catalyzed cyclization between 5,5′-(pyridine-2,6-diyl)bis(pyrrole-2-carbaldehyde) (2) and terpyrrole (3)., A new mixed hexaphyrin, pyrihexaphyrin (0.1.0.0.1.0) (1), was prepared via an acid catalyzed cyclization between 5,5′-(pyridine-2,6-diyl)bis(pyrrole-2-carbaldehyde) (2) and terpyrrole (3). This expanded porphyrin undergoes a ring contraction upon metallation with uranyl silylamide [UO2[N(SiMe3)2]2] under anaerobic conditions followed by purification over basic aluminum oxide exposed to air. The uranyl-contracted pyrihexaphyrin (0.0.0.0.1.0) complex (4) produced as a result contains a unique structural architecture and possesses a formally 22 π-electron globally aromatic periphery, as inferred from NMR spectroscopy, single crystal X-ray diffraction, and computational analyses. Support for the proposed contraction mechanism came from experimental data and DFT calculations. Proton NMR and mass spectroscopic analysis provided the first insight into expanded porphyrin-mediated activation of the uranyl dication (UO22+).

Published
2019

11. In-Plane Thorium(IV), Uranium(IV), and Neptunium(IV) Expanded Porphyrin Complexes

Author

Brewster, James T., primary, Mangel, Daniel N., additional, Gaunt, Andrew J., additional, Saunders, Douglas P., additional, Zafar, Hadiqa, additional, Lynch, Vincent M., additional, Boreen, Michael A., additional, Garner, Mary E., additional, Goodwin, Conrad A. P., additional, Settineri, Nicholas S., additional, Arnold, John, additional, and Sessler, Jonathan L., additional

Published
2019
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12. Porphyrinoid f-Element Complexes

Author

Brewster, James T., primary, Zafar, Hadiqa, additional, Root, Harrison D., additional, Thiabaud, Gregory D., additional, and Sessler, Jonathan L., additional

Published
2019
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15. Naphthylbipyrrole-Containing Amethyrin Analogue: A New Ligand for the Uranyl (UO22+) Cation

Author

Anguera, Gonzalo, Brewster, James T., Moore, Matthew D., Lee, Juhoon, Vargas-Zúñiga, Gabriela I., Zafar, Hadiqa, Lynch, Vincent M., and Sessler, Jonathan L.

Abstract

Using naphthobipyrrole as a functional building block, a new expanded porphyrin, naphthoisoamethyrin, was prepared in 85% yield under acid-catalyzed [4 + 2] MacDonald coupling conditions. Treatment of naphthoisoamethyrin with the nonaqueous uranyl silylamide salt [UO2[N(SiMe3)2]2·2THF] yielded the corresponding uranyl complex. Upon metalation, naphthoisoamethyrin undergoes a two-electron oxidation to yield a formal 22 π-electron aromatic species, as inferred from 1H NMR and UV–vis spectroscopy, as well as cyclic voltammetry.

Published
2024
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20. Porphyrinoid f-Element Complexes

Author

Brewster, James T., Zafar, Hadiqa, Root, Harrison D., Thiabaud, Gregory D., and Sessler, Jonathan L.

Abstract

Porphyrin and related pyrrole-containing macrocycles, collectively porphyrinoids, are versatile ligands that allow access to a multitude of coordination modes. Judicious modification of the porphyrin core as well as the pendant substituents has extended the coordination chemistry of porphyrinoids to include systems that are able to stabilize f-block element complexes with possible utility. This review focuses on our group’s efforts to prepare expanded porphyrin and porphyrinogen ligands that can serve as tools to study and apply f-element metal coordination chemistry: it covers the background of the topic, selected syntheses, and application of these species in the chemical and medical sciences.

Published
2020
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23. Thiol-triggered deconstruction of bifunctional silyl ether terpolymers via an S N Ar-triggered cascade.

Author

Brown CM, Husted KEL, Wang Y, Kilgallon LJ, Shieh P, Zafar H, Lundberg DJ, and Johnson JA

Abstract

While Si-containing polymers can often be deconstructed using chemical triggers such as fluoride, acids, and bases, they are resistant to cleavage by mild reagents such as biological nucleophiles, thus limiting their end-of-life options and potential environmental degradability. Here, using ring-opening metathesis polymerization, we synthesize terpolymers of (1) a "functional" monomer ( e.g. , a polyethylene glycol macromonomer or dicyclopentadiene); (2) a monomer containing an electrophilic pentafluorophenyl (PFP) substituent; and (3) a cleavable monomer based on a bifunctional silyl ether . Exposing these polymers to thiols under basic conditions triggers a cascade of nucleophilic aromatic substitution (S N Ar) at the PFP groups, which liberates fluoride ions, followed by cleavage of the backbone Si-O bonds, inducing polymer backbone deconstruction. This method is shown to be effective for deconstruction of polyethylene glycol (PEG) based graft terpolymers in organic or aqueous conditions as well as polydicyclopentadiene (pDCPD) thermosets, significantly expanding upon the versatility of bifunctional silyl ether based functional polymers., Competing Interests: CMB, PS and JAJ are named inventors on a patent application (US provisional application no. 63/195259) filed by the Massachusetts Institute of Technology on the monomers and copolymers in this work., (This journal is © The Royal Society of Chemistry.)

Published
2023
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24. Synthesis and Characterization of a Binuclear Copper(II)-dipyriamethyrin Complex: [Cu 2 (dipyriamethyrin)(μ 2 -1,1-acetato) 2 ].

Author

Brewster JT 2nd, Root HD, Zafar H, Thiabaud GD, Sedgwick AC, He J, Lynch VM, and Sessler JL

Subjects
Molecular Structure, Coordination Complexes chemical synthesis, Coordination Complexes chemistry, Copper chemistry, Models, Molecular
Abstract

The reaction between dipyriamethyrin and copper(II) acetate [Cu(OAc) 2 ] afforded what is, to our knowledge, the first transition metal-dipyriamethyrin complex. Molecular and electronic characterization of this binuclear Cu(II) complex via EPR, UV-vis, and single crystal X-ray diffraction analysis revealed marked differences between the present constructs and previously reported binuclear copper(II) hexaphyrin species. UV-vis titration analyses provided evidence for a homotropic positive allosteric effect, wherein the binuclear species is formed without significant intermediacy of a monomeric complex.

Published
2020
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26. UO 2 2+ -mediated ring contraction of pyrihexaphyrin: synthesis of a contracted expanded porphyrin-uranyl complex.

Author

Brewster JT 2nd, Root HD, Mangel D, Samia A, Zafar H, Sedgwick AC, Lynch VM, and Sessler JL

Abstract

A new mixed hexaphyrin, pyrihexaphyrin (0.1.0.0.1.0) ( 1 ), was prepared via an acid catalyzed cyclization between 5,5'-(pyridine-2,6-diyl)bis(pyrrole-2-carbaldehyde) ( 2 ) and terpyrrole ( 3 ). This expanded porphyrin undergoes a ring contraction upon metallation with uranyl silylamide [UO 2 [N(SiMe 3 ) 2 ] 2 ] under anaerobic conditions followed by purification over basic aluminum oxide exposed to air. The uranyl-contracted pyrihexaphyrin (0.0.0.0.1.0) complex ( 4 ) produced as a result contains a unique structural architecture and possesses a formally 22 π-electron globally aromatic periphery, as inferred from NMR spectroscopy, single crystal X-ray diffraction, and computational analyses. Support for the proposed contraction mechanism came from experimental data and DFT calculations. Proton NMR and mass spectroscopic analysis provided the first insight into expanded porphyrin-mediated activation of the uranyl dication (UO 2 2+ ).

Published
2019
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27. Naphthylbipyrrole-Containing Amethyrin Analogue: A New Ligand for the Uranyl (UO 2 2+ ) Cation.

Author

Anguera G, Brewster JT 2nd, Moore MD, Lee J, Vargas-Zúñiga GI, Zafar H, Lynch VM, and Sessler JL

Abstract

Using naphthobipyrrole as a functional building block, a new expanded porphyrin, naphthoisoamethyrin, was prepared in 85% yield under acid-catalyzed [4 + 2] MacDonald coupling conditions. Treatment of naphthoisoamethyrin with the nonaqueous uranyl silylamide salt [UO 2 [N(SiMe 3 ) 2 ] 2 ·2THF] yielded the corresponding uranyl complex. Upon metalation, naphthoisoamethyrin undergoes a two-electron oxidation to yield a formal 22 π-electron aromatic species, as inferred from 1 H NMR and UV-vis spectroscopy, as well as cyclic voltammetry.

Published
2017
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