This work reports the design and synthesis of a sterically protected triphenylamine scaffold which undergoes one‐electron oxidation to form an amine‐centered radical cation of remarkable stability. ...Several structural adjustments were made to tame the inherent reactivity of the radical cation. First, the parent propeller‐shaped triphenylamine was planarized with sterically demanding bridging units and, second, protecting groups were deployed to block the reactive positions. The efficiently shielded triphenylamine core can be reversibly oxidized at moderate potentials (+0.38 V, vs. Fc/Fc+ in CH2Cl2). Spectroelectrochemistry and chemical oxidation studies were employed to monitor the evolution of characteristic photophysical features. To obtain a better understanding of the impact of one‐electron oxidation on structural and electronic properties, joint experimental and computational studies were conducted, including X‐ray structural analysis, electron paramagnetic resonance (EPR), and density functional theory (DFT) calculations. The sterically shielded radical cation combines various desirable attributes: A characteristic and unobstructed absorption in the visible region, high stability which enables storage for weeks without spectroscopically traceable degradation, and a reliable oxidation/re‐reduction process due to effective screening of the planarized triphenylamine core from its environment.
Single and happy: Extensive steric shielding of a bridged triphenylamine enabled the generation of a persistent N‐centered radical cation with an intense absorption band in the visible region and a reliable oxidation/re‐reduction process. X‐ray structural analysis, electron paramagnetic resonance (EPR), spectroelectrochemistry, and density functional theory (DFT) calculations were used to disclose the impact of one electron oxidation on the structural and electronic attributes.
The palladium(II)-catalysed addition of arylboronic acids to vinylaziridines has been developed. This reaction proceeds via an insertion/ring-opening process to provide (Z)-allylsulfonamides ...preferentially. This stereoselectivity is complimentary to existing methods that typically proceed via a SN2' mechanism to yield (E)-allylsulfonamides. Electron-deficient arylboronic acids were the optimum substrates for this reaction, while electron-donating groups on the aromatic ring of the boronic acids resulted in moderate yields.
The palladium(
ii
)-catalysed addition of arylboronic acids to vinylaziridines has been developed. This reaction proceeds
via
an insertion/ring-opening process to provide (
Z
)-allylsulfonamides ...preferentially. This stereoselectivity is complimentary to existing methods that typically proceed
via
a S
N
2′ mechanism to yield (
E
)-allylsulfonamides. Electron-deficient arylboronic acids were the optimum substrates for this reaction, while electron-donating groups on the aromatic ring of the boronic acids resulted in moderate yields.
The palladium(
ii
)-catalysed addition of arylboronic acids to vinylaziridines has been developed. This reaction proceeds
via
an insertion/ring-opening process to provide (
E
)-allylsulfonamides. This stereoselectivity is complimentary to existing methods that typically proceed
via
an S
N
2′ mechanism to yield (
Z
)-allylic systems.
This paper describes the research and development of a cavity-structure-based 30 GHz transmitting antenna for a portable satellite communication terminal, with focus on minimizing grating lobe levels ...in far-field amplitude radiation patterns. A hexagonal array architecture was found to offer the best performance in terms of grating lobe level suppression.
This thesis describes, based on certain design specifications, the research and development of a cavity array antenna that improves the performance of the existing EHF active phased array of cavity ...elements presented in (1). The best array lattice candidate was found to be an offset gridded hexagonal array lattice with a simulated directivity of D$\sb{\rm o}$ = 34.60 dB, a symmetrical beamwidth of $\Theta\sb{\rm 3dB}$ 2.3$\sp\circ$, and all sidelobes and grating lobes approximately 15 dB down from the main beam peak in all $\phi$ planes. A new cavity element architecture design was proposed to include vias to provide for a continuous, common ground plane for the antenna. A study to determine the appropriate number of vias to use for optimal cavity element performance was inconclusive due to manufacturing problems and a study to determine the repeatability of the manufacturing process suggested that the manufacturing process is not repeatable. As a means of improving the radiation performance of the elements, a brief study of the grounding of a cavity element was carried out. The cavity element was found to suffer from improper grounding. The final array lattice and feed network represent an improvement over the original antenna of (1) in terms of an increased directivity and simplified feed network complexity with approximately the same symmetrical beamwidth and sidelobe/grating lobe levels. (Abstract shortened by UMI.)
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