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Stannylenes: Structures, Electron Affinities, Ionization Energies, and Singlet–Triplet Gaps of SnX2/SnXY and XSnR/SnR2/RSnR′ Species (X; Y = H, F, Cl, Br, I, and R; R′ = CH3, SiH3, GeH3, SnH3)

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journal contribution
posted on 16.01.2012, 00:00 by Ashwini Bundhun, Ponnadurai Ramasami, Peter P. Gaspar, Henry F. Schaefer
Systematic computational studies of stannylene derivatives SnX2/SnXY and XSnR/SnR2/RSnR′ were carried out using density functional theory. The basis sets used for H, F, Cl, Br, C, Si, and Ge atoms are of double-ζ plus polarization quality with additional s- and p-type diffuse functions, denoted DZP++. For the iodine and tin atoms, the Stuttgart-Dresden basis sets, with relativistic small-core effective core potentials (ECP), are used. All geometries are fully optimized with three functionals (BHLYP, BLYP, and B3LYP). Harmonic vibrational wavenumber analyses are performed to evaluate zero-point energy corrections and to determine the nature of the stationary points located. Predicted are four types of neutral-anion separations, plus adiabatic ionization energies (EIE) and singlet–triplet energy gaps (ΔES‑T). The dependence of all three energetic properties upon choice of substituent is remarkably strong. The EAad(ZPVE) values (eV) obtained with the B3LYP functional range from 0.70 eV [Sn­(CH3)2] to 2.36 eV [SnI2]. The computed EIE values lie between 7.33 eV [Sn­(SnH3)2] and 11.15 eV [SnF2], while the singlet–triplet splittings range from 0.60 eV [Sn­(SnH3)2] to 3.40 eV [SnF2]. The geometries and energetics compare satisfactorily with the few available experiments, while most of these species are investigated for the first time. Some unusual structures are encountered for the SnXI+ (X = F, Cl, and Br) cations. The structural parameters and energetics are discussed and compared with the carbene, silylene, and germylene analogues.