- Anisotropic Synthetic Allomelanin Materials via Solid-State Polymerization of Self-Assembled 1,8-Dihydroxynaphthalene Dimers
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Melanosomes in nature have diverse morphologies, including spheres, rods, and platelets. By contrast, shapes of synthetic melanins have been almost entirely limited to spherical nanoparticles with few exceptions produced by complex templated synthetic methods. Here, we report a non-templated method to access synthetic melanins with a variety of architectures including spheres, sheets, and platelets. Three 1,8-dihydroxynaphthalene dimers (4-4′, 2-4′ and 2-2′) were used as self-assembling synthons. These dimers pack to form well-defined structures of varying morphologies depending on the isomer. Specifically, distinctive ellipsoidal platelets can be obtained using 4-4′ dimers. Solid-state polymerization of the preorganized dimers generates polymeric synthetic melanins while maintaining the initial particle morphologies. This work provides a new route to anisotropic synthetic melanins, where the building blocks are preorganized into specific shapes, followed by solid-state polymerization.
- Cao, Wei,D'Alba, Liliana,Farha, Omar K.,Forman, Christopher J.,Gianneschi, Nathan C.,Gong, Xinyi,Hu, Ziying,Jayaraman, Arthi,Kapoor, Utkarsh,Malliakas, Christos D.,McCallum, Naneki C.,Oktawiec, Julia,Shawkey, Matthew D.,Sun, Hao,Thompson, Matthew P.,Zhou, Xuhao
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- Investigation of the hydrogen bond donating ability of 1,8-naphthalenediol by NMR spectroscopy and its use as a hydrogen bonding catalyst
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The hydrogen bond donating ability of 1,8-naphthalenediol was investigated via a series of 1H, 13C, and 31P NMR experiments. Complexation studies using triphenylphosphine oxide and cyclohexanone as hydrogen bond acceptors
- Turkmen, Yunus Emre
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- Influence of Backbone Substituents on the Ethylene (Co)polymerization Properties of α-diimine Pd(II) and Ni(II) Catalysts
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A series of α-diimine ligands with different substituents on the acenaphthyl backbone were synthesized and characterized. The corresponding Ni(II) and Pd(II) complexes were prepared and used in ethylene polymerization and copolymerization with methyl acrylate. In ethylene polymerization, these Ni(II) complexes showed activities of up to 1.6 × 107 g/((mol of Ni) h), generating polyethylene with a molecular weight (Mn) of up to 4.2 × 105. Interestingly, these Ni(II) complexes behave very similarly in ethylene polymerization except for the complex with two methoxy substituents on the ortho position of the acenaphthyl backbone, in which case about 3 times higher polyethylene molecular weight and much lower branching density were observed. The ligand substituent effect is much more dramatic for the Pd(II) complexes. In ethylene polymerization, activities of up to 1.7 × 105 g/((mol of Pd) h) and a polyethylene molecular weight (Mn) of up to 4.7 × 104 could be obtained. The Pd(II) complex with two methoxy substituents on the ortho position of the acenaphthyl backbone demonstrated much higher activity and generated polyethylene with about 3 times higher molecular weight than that for the classic Pd(II) complex. A similar trend was maintained in ethylene-methyl acrylate copolymerization.
- Zou, Wenping,Chen, Changle
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- Total synthesis of the natural product benzo[j]fluoranthene-4,9-diol: An approach to the synthesis of oxygenated benzo[j]fluoranthenes
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A synthetic sequence to the benzo[j]fluoranthene nucleus is described. Crucial steps of the procedure include a Suzuki coupling between appropriately substituted 2-bromo-acenaphthylene-1-carbaldehydes and 2-formylbenzeneboronates followed by McMurry ring closure. The synthesis represents a new approach to the benzo[j]fluoranthene ring system and specifically provides a method for the rapid preparation of differently substituted derivatives. Following this strategy, the first total synthesis of the recently isolated natural product benzo[j]fluoranthene-4,9-diol was carried out.
- Lahore, Santosh,Narkhede, Umesh,Merlini, Lucio,Dallavalle, Sabrina
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