2 research outputs found

    Effect of Fluorine Substitution on the Aromaticity of Polycyclic Hydrocarbons

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    The effect of fluorine substitution on the aromaticity of polycyclic hydrocarbons (PAH) is investigated. Magnetically induced current densities, current pathways, and current strengths, which can be used to assess molecular aromaticity, are calculated using the gauge-including magnetically induced current method (GIMIC). The degree of aromaticity of the individual rings is compared to those obtained using calculated nucleus-independent chemical shifts at the ring centers (NICS(0) and NICS(0)<sub><i>zz</i></sub>). Calculations of explicitly integrated current strengths for selected bonds show that the aromatic character of the investigated polycyclic hydrocarbons is weakened upon fluorination. In contrast, the NICS(0) values for the fluorinated benzenes increase noteworthy upon fluorination, predicting a strong strengthening of the aromatic character of the arene rings. The integrated current strengths also yield explicit current pathways for the studied molecules. The current pathways of the investigated linear polyacenes, pyrene, anthanthrene, coronene, ovalene, and phenanthro-ovalene are not significantly affected by fluorination. NISC(0) and NICS(0)<sub><i>zz</i></sub> calculations provide contradictory degrees of aromaticity of the fused individual ring. Obtained NICS values do not correlate with the current strengths circling around the individual rings

    Heteroleptic Cyclopentadienyl-Amidinate Precursors for Atomic Layer Deposition (ALD) of Y, Pr, Gd, and Dy Oxide Thin Films

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    Thin films of rare-earth (RE) oxides (Y<sub>2</sub>O<sub>3</sub>, PrO<sub><i>x</i></sub>, Gd<sub>2</sub>O<sub>3</sub>, and Dy<sub>2</sub>O<sub>3</sub>) were deposited by atomic layer deposition from liquid heteroleptic RE­(<i><sup>i</sup></i>PrCp)<sub>2</sub>(<i><sup>i</sup></i>Pr-amd) precursors with either water or ozone as the oxygen source. Film thickness, crystallinity, morphology, and composition were studied. Saturation was achieved with Gd<sub>2</sub>O<sub>3</sub> when O<sub>3</sub> was used as the oxygen source at 225 °C and with Y<sub>2</sub>O<sub>3</sub> with both oxygen sources at as high temperature as 350 °C. The growth rates were 0.90–1.3 Å/cycle for these processes. PrO<sub><i>x</i></sub> was challenging to deposit with both oxygen sources but with long, 20 s purges after the water pulses uniform films could be deposited. However, saturation was not achieved. With Dy<sub>2</sub>O<sub>3</sub>, uniform films could be deposited and the Dy­(<i><sup>i</sup></i>PrCp)<sub>2</sub>(<i><sup>i</sup></i>Pr-amd)/O<sub>3</sub> process was close to saturation at 300 °C. The different oxygen sources had an effect on the crystallinity and impurity contents of the films in all the studied processes. Whether ozone or water was better choice for oxygen source depended on the metal oxide material that was deposited
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