Ab initio MO studies on disilane, germylsilane, and digermane radical anions as prototypes of polymer anions with silicon and germanium backbones

Tada, Tsukasa; Yoshimura, Reiko

doi:10.1021/j100107a008

Cited by 22 publications

(20 citation statements)

References 4 publications

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“…Our predicted adiabatic electron affinities for Ge 2 H 6 are negative, for instance −0.19 eV (or −0.02 eV after ZPVE correction) with B3LYP (Table 4), and the anion is thus unbound. Tada and Yoshimura earlier predicted that the adiabatic electron affinity40 is much more negative (−0.78 eV), but still in qualitative agreement with our results. No experimental electron affinity has been observed, as is the case for C 2 H 6 and Si 2 H 6 .…”

Section: Resultssupporting

confidence: 93%

“…Our theoretical GeH bond lengths fall in the range of 1.530–1.551 Å, which is in agreement with the experiment value (1.541 ± 0.006 Å) 39. For the Ge 2 H

_{6}^{−}

anion, Tada and Yoshimura40 theoretically explored seven structures, including minima and saddle points, in 1992. They found that a C 2h isomer has the lowest energy using the HF and MP2/DZPD methods.…”

Section: Resultssupporting

confidence: 87%

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Molecules for materials: Germanium hydride neutrals and anions. Molecular structures, electron affinities, and thermochemistry of GeH_n/GeH (n = 0–4) and Ge₂H_n/Ge₂H (n = 0–6)

Lü

Xie

et al. 2002

J Comput Chem

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The GeH(n) (n = 0-4) and Ge(2)H(n) (n = 0-6) systems have been studied systematically by five different density functional methods. The basis sets employed are of double-zeta plus polarization quality with additional s- and p-type diffuse functions, labeled DZP++. For each compound plausible energetically low-lying structures were optimized. The methods used have been calibrated against a comprehensive tabulation of experimental electron affinities (Chemical Reviews 102, 231, 2002). The geometries predicted in this work include yet unknown anionic species, such as Ge(2)H(-), Ge(2)H(2)(-), Ge(2)H(3)(-), Ge(2)H(4)(-), and Ge(2)H(5)(-). In general, the BHLYP method predicts the geometries closest to the few available experimental structures. A number of structures rather different from the analogous well-characterized hydrocarbon radicals and anions are predicted. For example, a vinylidene-like GeGeH(2) (-) structure is the global minimum of Ge(2)H(2) (-). For neutral Ge(2)H(4), a methylcarbene-like HGë-GeH(3) is neally degenerate with the trans-bent H(2)Ge=GeH(2) structure. For the Ge(2)H(4) (-) anion, the methylcarbene-like system is the global minimum. The three different neutral-anion energy differences reported in this research are: the adiabatic electron affinity (EA(ad)), the vertical electron affinity (EA(vert)), and the vertical detachment energy (VDE). For this family of molecules the B3LYP method appears to predict the most reliable electron affinities. The adiabatic electron affinities after the ZPVE correction are predicted to be 2.02 (Ge(2)), 2.05 (Ge(2)H), 1.25 (Ge(2)H(2)), 2.09 (Ge(2)H(3)), 1.71 (Ge(2)H(4)), 2.17 (Ge(2)H(5)), and -0.02 (Ge(2)H(6)) eV. We also reported the dissociation energies for the GeH(n) (n = 1-4) and Ge(2)H(n) (n = 1-6) systems, as well as those for their anionic counterparts. Our theoretical predictions provide strong motivation for the further experimental study of these important germanium hydrides.

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Section: Resultssupporting

confidence: 93%

“…Our theoretical GeH bond lengths fall in the range of 1.530–1.551 Å, which is in agreement with the experiment value (1.541 ± 0.006 Å) 39. For the Ge 2 H

_{6}^{−}

Section: Resultssupporting

confidence: 87%

Molecules for materials: Germanium hydride neutrals and anions. Molecular structures, electron affinities, and thermochemistry of GeH_n/GeH (n = 0–4) and Ge₂H_n/Ge₂H (n = 0–6)

Lü

Xie

et al. 2002

J Comput Chem

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“…The Hartree–Fock error is nonsystematic and always large, sometimes of the same order of magnitude as the bonding energy itself or even larger. Thus, most of the studies were performed at post-Hartree–Fock levels. ,− The MP2 level is satisfactory and provides geometries and bonding energies in good agreement with higher orders of perturbation theory. , …”

Section: Introductionmentioning

confidence: 99%

Nature of the Three-Electron Bond

et al. 2018

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We analyze the properties of 15 3-electron bonds, which include σ-3-electron-bonds, such as dihalide radical anions and di-noble gas radical cations, π-3-electron-bonds as in hydrazine radical cations, and doubly-π-(3e)-bonded species such as O, FeO, S, etc. The primary analytical tool is the breathing-orbital valence-bond (BOVB) method, which enables us to quantify the charge shift resonance energy (RE) of the three electrons, and the bond dissociation energies (D). BOVB is tested reliable against MRCI calculations. Our findings show that in all 3-electron bonds, none of the VB structures have by themselves any bonding. In fact, in each VB structure, the three electrons maintain Pauli repulsion, while the entire bonding energy arises from resonance due to the charge shift between the two or more constituent VB structures. Hence, 3e-bonds are charge shift bonds (CSBs). The CSB character is probed by calculating the Laplacian (L) of the 3e-bond. Thus, much like the CSBs in electron-pair bonds, such as F or the central bond in [1.1.1]propellane, here too L is positive, thus showing the excess kinetic energy of the shared density due to the Pauli repulsion in the 3-electron VB structures. The RE values for 3-electron bonds are invariably larger than the corresponding bond energies. For the doubly-π-(3e)-bonded species, RE is very large, exceeding 100 kcal mol. As such, it is fitting to conclude that σ- and π-3-electron-bonds find their natural place in the CSB family along with two-electron CSBs, with which they share identical energetic and topological characteristics. Experimental manifestations/tests of 3e-CSBs are proposed.

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“…The results of a 29 Si ENDOR study were found to be hardly consistent with the ab inito π-type empty orbital model, suggesting a σ* Si-Si or Si 3d character of the SOMO in cyclopolysilane anion radicals, and ESR studies on analogous molecular systems lead to a representation of the SOMO as a linear combination of σ* Si-C and σ* Si-Si orbitals. According to recent ab initio studies at the MP4SDTQ level on the disilane and digermane radical anions, the SOMO is a heteroatom−heteroatom σ* antibonding orbital with a large heteroatom s diffuse orbital contribution, while the participation of Si 3d or Ge 4d orbitals is found to be negligibly small. We therefore have an uncertain picture of the low-energy unoccupied orbitals in such compounds.…”

Section: Introductionmentioning

confidence: 99%

Electron Attachment to the Lowest Unoccupied Orbitals in Linear and Branched Permethylated Polysilanes and Hexamethyldigermane and -distannane

et al. 1996

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The peculiar properties of polysilanes have stimulated many studies of their electronic structure. While the nature and ordering of the filled MOs have been studied in some detail, the theoretical predictions for the empty counterparts have never been tested experimentally. Here the electron transmission spectra of Me(SiMe2) n Me (with Me = CH3 and n = 1−4), MeSi(SiMe3)3, Si(SiMe3)4, Ge2Me6, and Sn2Me6 are presented and the energies of the observed resonances allow assignment of the lowest unoccupied levels. With the change from monomers to dimers, the presence of a heteroatom−heteroatom bond causes a large electron affinity increase; the LUMO is ascribed to a σ* MO essentially heteroatom in character, whereas the lowest σ*C-heteroatom MOs lie at about 1.5 eV higher energy. The spectra of the linear trimer and tetramer of silicon show that the energy separation between the lowest-lying empty orbitals is even larger than that observed in their filled counterparts. The lowest-lying empty MOs are thus well delocalized on the silicon skeleton but not on the substituents. The resonance energies are also compared with the unoccupied orbital energies calculated by means of ab initio 3-21G* and MNDO methods. The results presented here do not support the previously proposed π* model based upon ab initio calculations.

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Ab initio MO studies on disilane, germylsilane, and digermane radical anions as prototypes of polymer anions with silicon and germanium backbones

Cited by 22 publications

References 4 publications

Molecules for materials: Germanium hydride neutrals and anions. Molecular structures, electron affinities, and thermochemistry of GeH_n/GeH (n = 0–4) and Ge₂H_n/Ge₂H (n = 0–6)

Molecules for materials: Germanium hydride neutrals and anions. Molecular structures, electron affinities, and thermochemistry of GeH_n/GeH (n = 0–4) and Ge₂H_n/Ge₂H (n = 0–6)

Nature of the Three-Electron Bond

Electron Attachment to the Lowest Unoccupied Orbitals in Linear and Branched Permethylated Polysilanes and Hexamethyldigermane and -distannane

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Ab initio MO studies on disilane, germylsilane, and digermane radical anions as prototypes of polymer anions with silicon and germanium backbones

Cited by 22 publications

References 4 publications

Molecules for materials: Germanium hydride neutrals and anions. Molecular structures, electron affinities, and thermochemistry of GeHn/GeH (n = 0–4) and Ge2Hn/Ge2H (n = 0–6)

Molecules for materials: Germanium hydride neutrals and anions. Molecular structures, electron affinities, and thermochemistry of GeHn/GeH (n = 0–4) and Ge2Hn/Ge2H (n = 0–6)

Nature of the Three-Electron Bond

Electron Attachment to the Lowest Unoccupied Orbitals in Linear and Branched Permethylated Polysilanes and Hexamethyldigermane and -distannane

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Molecules for materials: Germanium hydride neutrals and anions. Molecular structures, electron affinities, and thermochemistry of GeH_n/GeH (n = 0–4) and Ge₂H_n/Ge₂H (n = 0–6)

Molecules for materials: Germanium hydride neutrals and anions. Molecular structures, electron affinities, and thermochemistry of GeH_n/GeH (n = 0–4) and Ge₂H_n/Ge₂H (n = 0–6)