Browsing by Author "Zeller, Matthias"

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    Design, Synthesis, and Structure of Copper Dithione Complexes: Redox‐Dependent Charge Transfer
    (Wiley, 2019-12) Colston, Kyle J.; Dille, Sara A.; Mogesa, Benjamin; Astashkin, Andrei V.; Brant, Jacilynn A.; Zeller, Matthias; Basu, Partha; Chemistry and Chemical Biology, School of Science
    Redox‐active ligands impart versatility in transition metal complexes, which are attractive for photosensitizers, dye sensitized solar cells, photothermal therapy, etc. Dithiolene (Dt) ligands can transition between fully reduced and fully oxidized states. Herein, we report the syntheses, characterization, crystal structures and electronic properties of four [Cu(R2Dt0)2]+/2+ (R = Me, iPr) complexes, [Cu(iPr2Dt0)2][PF6] (1a), [Cu(iPr2Dt0)2][PF6]2 (1b), and [Cu(Me2Dt0)2][PF6] (2a), [Cu(Me2Dt0)2][PF6]2 (2b), where iPr2Dt0 = N,N′‐diisopropyl‐1,2‐piperazine dithione and Me2Dt0 = N,N′‐dimethyl‐1,2‐piperazine dithione. In addition, the molecular structure of [Cu(iPr2Dt0)2][BF4]2(1c) is also reported. Complexes 1a and 2a crystallized in the triclinic, P1 space group, and 1c crystallized in the monoclinic crystal system, space group C2/c. The single‐crystal X‐ray diffraction measurements show that the Cu(I) complexes have a distorted tetrahedral geometry, whereas the Cu(II) complex exhibits a true square‐planar geometry. Cu(I) complexes exhibit a low energy charge‐transfer band (450–650 nm), which are not observed in Cu(II) complexes. Electrochemical studies of these complexes show both ligand‐ and metal‐based redox couples.
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    Organic Photoredox Catalyzed Direct Hydroamination of Ynamides with Azoles
    (Wiley, 2022-03-15) Wang, Ban; Mccabe, Gavin E.; Parrish, Mitchell J.; Singh, Jujhar; Zeller, Matthias; Deng, Yongming; Chemistry and Chemical Biology, School of Science
    Disclosed herein is a photoinduced selective hydroamination of ynamides with nitrogen heteroaromatic nucleophiles. By using an organocatalytic photoredox system, a direct method to construct a diverse of (Z)-α-azole enamides from ynamides and pyrazoles, as well as triazoles, benzotriazoles, indazoles, and tetrazoles, is developed, thus providing a photocatalytically synthetic route to heterocyclic motifs common in medicinal agents. Based on the mechanistic studies, the hydroamination is postulated to operate via a mechanism in which the single-electron oxidation of ynamide and the intermediacy of an alkyne radical cation, is responsible for the observed reactivity.
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    Photoinduced oxidative cyclopropanation of ene-ynamides: synthesis of 3-aza[n.1.0]bicycles via vinyl radicals
    (Royal Society of Chemistry, 2021-05) Deng, Yongming; Zhang, Jason; Bankhead, Bradley; Markham, Jonathan P.; Zeller, Matthias; Chemistry and Chemical Biology, School of Science
    The first photoinduced synthesis of polyfunctionalized 3-aza[n.1.0]bicycles from readily available ene-ynamides and 2,6-lutidine N-oxide using an organic acridinium photocatalyst is reported. Applying a photocatalytic strategy to the reactive distonic cation vinyl radical intermediate from ynamide, a series of bio-valuable 3-azabicycles, including diverse 3-azabicyclio[4.1.0]heptanes and 3-azabicyclo[5.1.0]octanes that are challenging to accomplish using traditional methods, have been successfully synthesized in good to high yields under mild and metal-free conditions. Mechanistic studies are consistent with the photocatalyzed single-electron oxidation of ene-ynamide and the intermediacy of a putative cationic vinyl radical in this transformation. Importantly, this strategy provides new access to the development of photocatalytic vinyl radical cascades for the synthesis of structurally sophisticated substrates.
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    Syntheses, spectroscopic, redox, and structural properties of homoleptic Iron(III/II) dithione complexes
    (Royal Society of Chemistry, 2020-10-16) Colston, Kyle J.; Dille, Sara A.; Mogesa, Benjamin; Brant, Jacilynn; Nemykin, Victor N.; Zeller, Matthias; Basu, Partha; Chemistry and Chemical Biology, School of Science
    Two sets of FeIII/II dithione complexes [FeII( i Pr2Dt0)3][PF6]2 ([1][PF6]2), [FeII(Me2Dt0)3][PF6]2 ([2][PF6]2), and [FeIII( i Pr2Dt0)3][PF6]3 ([3][PF6]3), [FeIII(Me2Dt0)3][PF6]3 ([4][PF6]3), and compound [FeIII( i Pr2Dt0)3][FeCl4][PF]2 ([3][FeCl4][PF6]2) were synthesized from N,N'-diisopropyl piperazine-2,3-dithione ( i Pr2Dt0) and N,N'-dimethyl piperazine-2,3-dithione (Me2Dt0) ligands. Complexes [1][PF6]2-[4][PF6]3 have been characterized by NMR, IR, and UV-visible spectroscopies, and by electrochemistry. The molecular structures of [2][PF6]2 and [3][FeCl4][PF6]2 have been determined by X-ray crystallography. Complexes [2][PF6]2 and [3][FeCl4][PF6]2 both crystallized in the monoclinic space group P21/n. Both complexes exhibit distorted octahedral geometry and the three coordinated ligands in each complex exhibit different dithione folding. Complexes [1][PF6]2-[4][PF6]3 exhibit a single FeIII/II based couple and three quasi-reversible ligand-based redox couples. The electronic spectra of [1][PF6]2-[4][PF6]3 show intense MLCT bands that indicate strong mixing between metal and ligand orbitals. DFT calculations were used to provide a framework for understanding the electronic origin of their redox chemistry and spectroscopic features.