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Results for “ALKYLATION”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Electronic States of 2,3-Diamino-1,4-naphthoquinone and Its N-Alkylated Derivatives

Diaminoquinones with a captodatively stabilized biradicaloid structure are options for singlet fission, but few such compounds are known. We report the solution spectroscopy and photophysics of 1,2,2,3-tetramethyl-2,3-dihydro-1H-naphtho[2,3-d]imidazole-4,9-dione (1): its steady-state and transient UV-visible absorption, linear dichroism in stretched poly(vinyl alcohol), and magnetic circular dichroism. We also describe the absorption spectra of the stable radical ions 1+ and 1- and of two parent structures, 2,3-diamino-1,4-naphthoquinone (2) and 2,3-bis(methylamino)-1,4-naphthoquinone (3). The spectra are interpreted and electronic transitions are assigned by comparison with the results of density functional theory and MS-CASPT2 calculations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Dinuclear Gold(I) Complexes Bearing Alkyl-Bridged Bis(N-heterocyclic carbene) Ligands as Catalysts for Carboxylative Cyclization of Propargylamine: Synthesis, Structure, and Kinetic and Mechanistic Comparison to the Mononuclear Complex [Au(IPr)Cl]

Eight new dinuclear gold(I) complexes, [Au 2 (L)X 2 ] (1–8), were synthesized using a straightforward synthetic procedure under very mild conditions. The complexes have been characterized by NMR spectroscopy, elemental analysis, and single-crystal X-ray structure analysis. Their catalytic activity was investigated in the carboxylative cyclization of propargylamine (PPA). A superior performance in comparison to [Au(IPr)Cl] (9) was obtained for complexes 1 and 2 having an eight-methylene bridge connecting two NHCs with an arene bearing an isopropyl substituent for X = Cl, Br. This prompted more detailed kinetic and mechanistic studies by FTIR comparing dinuclear complex 2 of X = Cl to complex 9. Fortuitously the FTIR studies allowed monitoring of the formation of the products carbamic acid (CA) and carbamate salt (CS), as well as a key cyclized intermediate first discovered by Ikariya. These data allow additional insight into the mechanism as well as the central role which may be played by Au(I) carbamate formation as a higher energy resting state present in the catalytic cycle. In conclusion, the crystal structures of four of the new complexes and a detailed computational study relevant to the role of carbamic acid (CA) and carbamates in the catalytic cycle are also reported.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Structural Stability of N -Alkyl-Functionalized Titanium Metal–Organic Frameworks in Aqueous and Humid Environments

Here, we show that the highly photoredox active metal–organic framework (MOF) MIL-125-NHCyp exhibits crystalline and porosity stability in humid environments for more than 30 days as well as increased hydrophobicity compared to the unfunctionalized framework. This improved stability, in synergy with its high photocatalytic activity, makes this MOF an enticing candidate for large-scale applications in CO 2 photoreduction.

36 MATERIALS SCIENCE↗