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Quantum-chemical analyses of aromaticity, UV spectra, and NMR chemical shifts in plumbacyclopentadienylidenes stabilized by Lewis bases

Authors

  • Toshiaki Kawamura,

    1. Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachi-Oji, Tokyo, Japan
    2. JST, CREST, Kawaguchi, Saitama, Japan
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  • Minori Abe,

    1. Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachi-Oji, Tokyo, Japan
    2. JST, CREST, Kawaguchi, Saitama, Japan
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  • Masaichi Saito,

    1. Department of Chemistry, Graduate School of Science and Engineering, Saitama University, Shimo-okubo, Sakura-ku, Saitama, Japan
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  • Masahiko Hada

    Corresponding author
    1. Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachi-Oji, Tokyo, Japan
    2. JST, CREST, Kawaguchi, Saitama, Japan
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Abstract

We carried out a series of zeroth-order regular approximation (ZORA)-density functional theory (DFT) and ZORA-time-dependent (TD)-DFT calculations for molecular geometries, NMR chemical shifts, nucleus-independent chemical shifts (NICS), and electronic transition energies of plumbacyclopentadienylidenes stabilized by several Lewis bases, (Ph)2(tBuMe2Si)2C4PbL1L2 (L1, L2 = tetrahydrofuran, Pyridine, N-heterocyclic carbene), and their model molecules. We mainly discussed the Lewis-base effect on the aromaticity of these complexes. The NICS was used to examine the aromaticity. The NICS values showed that the aromaticity of these complexes increases when the donation from the Lewis bases to Pb becomes large. This trend seems to be reasonable when the 4n-Huckel rule is applied to the fractional π-electron number. The calculated 13C- and 207Pb-NMR chemical shifts and the calculated UV transition energies reasonably reproduced the experimental trends. We found a specific relationship between the 13C-NMR chemical shifts and the transition energies. As we expected, the relativistic effect was essential to reproduce a trend not only in the 207Pb-NMR chemical shifts and J[Pb-C] but also in the 13C-NMR chemical shifts of carbons adjacent to the lead atom. © 2014 Wiley Periodicals, Inc.

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