Now showing items 41-60 of 67

    • Protonation-Induced Hyperporphyrin Spectra of meso-Aminophenylcorroles 

      Thomassen, Ivar Kristian; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-06)
      UV–vis spectrophotometric titrations have been carried out on <i>meso-</i>tris(<i>o/m/p</i>-aminophenyl)corrole (H<sub>3</sub>[<i>o/m/p</i>-TAPC]) and <i>meso-</i>triphenylcorrole (H<sub>3</sub>[TPC]) in dimethyl sulfoxide with methanesulfonic acid (MSA). Monoprotonation was found to result in hyperporphyrin spectra characterized by new, red-shifted, and intense Q bands. The effect was particularly ...
    • Rare and Nonexistent Nitrosyls: Periodic Trends and Relativistic Effects in Ruthenium and Osmium Porphyrin-Based {MNO}7 Complexes 

      Demissie, Taye Beyene; Conradie, Jeanet; Vazquez-Lima, Hugo; Ruud, Kenneth; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-14)
      Relativistic and nonrelativistic density functional theory calculations were used to investigate rare or nonexistent ruthenium and osmium analogues of nitrosylhemes. Strong ligand field effects and, to a lesser degree, relativistic effects were found to destabilize {RuNO}<sup>7</sup> porphyrins relative to their {FeNO}<sup>7</sup> analogues. Substantially stronger relativistic effects account for ...
    • Regioselective formylation of rhenium-oxo and gold corroles: Substituent effects on optical spectra and redox potentials 

      Einrem, Rune F.; Jonsson, Einar Torfi; Teat, Simon J.; Settineri, Nicholas S.; Alemayehu, Abraham B.; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-28)
      Vilsmeier–Haack formylation of ReO and Au meso-triarylcorroles over 16–18 hours affords moderate to good yields (47–65%) of the ReO-3-formyl and Au-3,17-diformyl derivatives in a highly regioselective manner. Formylation was found to effect substantial upshifts for redox potentials (especially the reduction potentials) as well as significant to dramatic redshifts for both the Soret and Q bands.
    • Relativistic Effects on a Metal-Metal Bond: Osmium Corrole Dimers 

      Alemayehu, Abraham; McCormick, Laura J; Vazquez Lima, Hugo; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-07)
      A series of metal–metal bonded osmium corrole dimers, {Os[TpXPC]}2, were synthesized in reasonably good yields (35–46%) via the interaction of the corresponding free-base meso-tris(p-X-phenyl)corroles (H3[TpXPC], X = CF3, H, CH3, and OCH3), Os3(CO)12, and potassium carbonate in 1,2,4-trichlorobenzene under an inert atmosphere at 180 °C over several hours. The complexes are only the second class of ...
    • Relativity as a Synthesis Design Principle: A Comparative Study of [3 + 2] Cycloaddition of Technetium(VII) and Rhenium(VII) Trioxo Complexes with Olefins 

      Braband, Henrik; Benz, Michael; Spingler, Bernhard; Conradie, Jeanet; Roger, Alberto; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-13)
      The difference in [3 + 2] cycloaddition reactivity between fac- [MO<sub>3</sub>(tacn)]<sup>+</sup> (M = Re, <sup>99</sup>Tc; tacn = 1,4,7-triazacyclononane) complexes has been reexamined with a selection of unsaturated substrates including sodium 4- vinylbenzenesulfonate, norbornene, 2-butyne, and 2-methyl-3-butyn-2-ol (2MByOH). None of the substrates was found to react with the Re cation in water ...
    • Rhenium Biscorrole Sandwich Compounds: XAS Evidence for a New Coordination Motif 

      Alemayehu, Abraham; Abernathy, Macon Jedediah; Conradie, Jeanet; Sarangi, Ritimukta; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-23)
      The interaction of three free-base meso-tris(p-X-phenyl)corroles H3[TpXPC] (X = H, CH3, OCH3) with Re2(CO)10 at 235 °C in the presence of K2CO3 in o-dichlorobenzene has led to putative rhenium biscorrole sandwich compounds with the formula ReH[TpXPC]2. Density functional theory calculations and Re L3-edge extended X-ray absorption fine structure measurements suggest a seven-coordinate metal center, ...
    • Rhenium Corrole Dimers: Electrochemical Insights into the Nature of the Metal–Metal Quadruple Bond 

      Alemayehu, Abraham; Mccormick-Mcpherson, Laura J; Conradie, Jeanet; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-17)
      The interaction of free-base triarylcorroles with Re<sub>2</sub>(CO)<sub>10</sub> in 1,2- dichlorobenzene in the presence of 2,6-lutidine at 180 °C under strict anerobic conditions afforded approximately 10% yields of rhenium corrole dimers. The compounds exhibited diamagnetic <sup>1</sup> H NMR spectra consistent with a metal−metal quadruple bond with a σ<sup>2</sup> π<sup>4</sup> δ<sup>2</sup> ...
    • Rhenium-Imido Corroles 

      Alemayehu, Abraham; Teat, Simon J.; Borisov, Sergey M.; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-10)
      Metallocorroles involving 5d transition metals are currently of interest as near-IR phosphors and as photosensitizers for oxygen sensing and photodynamic therapy. Their syntheses, however, are often bedeviled by capricious and low-yielding protocols. Against this backdrop, we describe rhenium-imido corroles, a new class of 5d metallocorroles, synthesized simply and in respectable (∼30%) yields via ...
    • Simple, Axial Ligand-Mediated Route to Water-Soluble Iridium Corroles 

      Thomassen, Ivar K.; Rasmussen, Daniel; Einrem, Rune F.; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-15)
      The synthesis and purification of water-soluble porphyrin-type compounds for photodynamic therapy and other medical applications is often a tedious exercise. Here, we have investigated the simple stratagem of adding a water-soluble axial ligand to the standard protocol for iridium insertion into simple meso-triarylcorroles. Early results showed that six-coordinate Ir[TpXPC](dna)2 derivatives, in ...
    • Stable Platinum(IV) Corroles: Synthesis, Molecular Structure, and Room-Temperature Near-IR Phosphorescence 

      Alemayehu, Abraham; McCormick, Laura J; Gagnon, Kevin J.; Borisov, Sergey M.; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-17)
      A series of stable Pt(IV) corrole complexes with the general formula Pt<sup>IV</sup>[TpXPC](<i>m/p</i>-C<sub>6</sub>H<sub>4</sub>CN)(py), where TpXPC<sup>3–</sup> is the trianion of a tris(<i>p</i>-X-phenyl)corrole and X = CF<sub>3</sub>, H, and CH<sub>3</sub>, has been synthesized, affording key physicochemical data on a rare and elusive class of metallocorroles. Single-crystal X-ray structures of ...
    • Stepwise Deoxygenation of Nitrite as a Route to Two Families of Ruthenium Corroles: Group 8 Periodic Trends and Relativistic Effects 

      Alemayehu, Abraham; Vazquez Lima, Hugo; Gagnon, Kevin J.; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-19)
      Given the many applications of ruthenium porphyrins, the rarity of ruthenium corroles and the underdeveloped state of their chemistry are clearly indicative of an area ripe for significant breakthroughs. The tendency of ruthenium corroles to form unreactive metal–metal-bonded dimers has been recognized as a key impediment in this area. Herein, by exposing free-base meso-tris(p-X-phenyl)corroles, ...
    • Stereochemistry of Transition-Metal Dinitrosyl Complexes. A Molecular Orbital Rationale for the Attracto and Repulso Conformations 

      Ghosh, Abhik; Conradie, Jeanet (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-25)
      Transition-metal dinitrosyl complexes constitute a fairly large class of compounds, exemplified by some 500 structures in the Cambridge Structural Database. While many of the complexes exhibit a claw-like cis-attracto conformation, a handful of them exhibit a peculiar repulso conformation, in which the two NO groups are splayed outward and away from each other. Surprisingly, no computational study ...
    • The Story of 5d Metallocorroles: From Metal–Ligand Misfits to New Building Blocks for Cancer Phototherapeutics 

      Alemayehu, Abraham; Thomas, Kolle E.; Einrem, Rune Finsås; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-23)
      CONSPECTUS: Porphyrin chemistry is Shakespearean: over a century of study has not withered the field’s apparently infinite variety. Heme proteins continually astonish us with novel molecular mechanisms, while new porphyrin analogues bowl us over with unprecedented optical, electronic, and metal-binding properties. Within the latter domain, corroles occupy a special place, exhibiting a unique ...
    • Structure-sensitive marker bands of metallocorroles: A resonance Raman study of manganese and gold corrole derivatives 

      Terner, James; Kolle Ekaney, Thomas; Vazquez Lima, Hugo; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-03)
      Soret-excited resonance Raman spectra (λ<sub>ex</sub> 413.1 nm) were acquired for manganese(III) and gold(III) tris(pentafluorophenyl)corrole, each as four different isotopomeric samples: natural abundance, fully pyrrole-<sup>15</sup>N-substituted, fully meso<sup>13</sup>C-substituted, and fully pyrrole-<sup>15</sup>N-meso<sup>13</sup>C-substituted. The spectra were modeled with density functional ...
    • Synthesis and Molecular Structure of a Copper Octaiodocorrole 

      Thomassen, Ivar Kristian; McCormick, Laura J.; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-09)
      Although rather delicate on account of their propensity to undergo deiodination, β-octaiodoporphyrinoids are of considerable interest as potential precursors to novel β-octasubstituted macrocycles. Presented herein are early results of our efforts to synthesize β-octaiodocorrole derivatives. Oxidative condensation of 3,4-diiodopyrrole and aromatic aldehydes failed to yield free-base octaiodocorroles. ...
    • Synthesis and molecular structure of perhalogenated rhenium-oxo corroles 

      Alemayehu, Abraham B.; Einrem, Rune F.; McCormick‑McPherson, Laura J.; Settineri, Nicholas S.; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-12)
      As part of our efforts to develop rhenium-oxo corroles as photosensitizers for oxygen sensing and photodynamic therapy, we investigated the potential <i>β</i>-perhalogenation of five ReO <i>meso</i>-tris(<i>para</i>-X-phenyl)corroles, Re[T<i>p</i>XPC](O) (X = CF<sub>3</sub>, H, F, CH<sub>3</sub>, and OCH<sub>3</sub>), with elemental chlorine and bromine. With Cl<sub>2</sub>, <i>β</i>-octachlorinated ...
    • Theoretical Photoelectron Spectroscopy of Low-Valent Carbon Species: A ∼6 eV Range of Ionization Potentials among Carbenes, Ylides, and Carbodiphosphoranes 

      Ghosh, Abhik; Conradie, Jeanet (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-12-02)
      High-quality density functional theory calculations underscore a nearly 6 eV range for the ionization potentials (IPs) of neutral, low-valent carbon compounds, including carbenes, ylides, and zero-valent carbon compounds (carbones) such as carbodiphosphoranes (CDPs) and carbodicarbenes. Thus, adiabatic IPs as low as 5.5 ± 0.1 eV are predicted for CDPs, which are about 0.7–1.2 eV lower than those of ...
    • A Theoretical Search for Stable Terminal Carbides 

      Ghosh, Abhik; Conradie, Jeanet (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-20)
      xploratory scalar-relativistic density functional theory (B3LYP*-D3/ZORA-STO-TZ2P) calculations have been used to examine the stability and bonding of pseudotetrahedral Group 8 (Fe, Ru, and Os) and Group 9 (Co, Rh, and Ir) terminal carbide complexes with dδ4 ground states and tripodal tris(N-heterocyclic-carbene) supporting ligands. The calculations predict relatively low adiabatic ionization ...
    • A thermally stable {FeNO}(8) complex: properties and biological reactivity of reduced MNO systems 

      Patra, Ashis K.; Dube, Koustubh S.; Sanders, Brian C.; Papaefthymiou, Georgia C.; Conradie, Jeanet; Ghosh, Abhik; Harrop, Todd C. (Journal article; Tidsskriftartikkel; Peer reviewed, 2012-10-06)
      Reduced nitrogen oxide ligands such as NO<sup>−</sup>/HNO or nitroxyl participate in chemistry distinct from nitric oxide (NO). Nitroxyl has been proposed to form at heme centers to generate the Enemark–Feltham designated {FeNO}<sup>8</sup> system. The synthesis of a thermally stable {FeNO}<sup>8</sup> species namely, [Co(Cp<sup>*</sup>)<sub>2</sub>][Fe(LN<sub>4</sub>)(NO)] (3), housed in a heme-like ...
    • Transition-Metal Isocorroles as Singlet Oxygen Sensitizers 

      Larsen, Simon; Adewuyi, Joseph A.; Ung, Gaël; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-04)
      Building on a highly efficient synthesis of pyrrole-appended isocorroles, we have worked out conditions for manganese, palladium, and platinum insertion into free-base 5/10-(2-pyrrolyl)-5,10,15-tris(4-methylphenyl)isocorrole, H<sub>2</sub>[5/10-(2-py)- TpMePiC]. Platinum insertion proved exceedingly challenging but was finally accomplished with cis-Pt(PhCN)<sub>2</sub>Cl<sub>2</sub>. All the ...