| Abstract
| - Six group-14 metalloles were synthesized and characterized. The silicon, germanium, and tin metalloles compose two isostructural series determined by the substituent on the metal atoms: either methyl or phenyl groups. All have a broad UV/visible absorption maxima at 350 ± 10 nm leading to luminescence for five of the six metalloles. Electrochemical measurements, NMR spectroscopy, and molecular orbital calculations were employed to explain the differences in the luminescence properties of the compounds.
- A series of six group-14 dimethyl- or diphenyl−tetraphenylmetallacyclopentadienes were synthesized andcharacterized by their spectroscopic and electrochemical properties. The group-14 elements investigated weresilicon, germanium, and tin. (The compounds are designated according to the heteroatom and the substituent onthe heteroatom, i.e., SiMe, SiPh, ..., SnPh.) Five of the six compounds luminesce in both the solid state and insolution. The emission maxima of SiPh, GePh, and SnPh are invariant to a change in the heteroatom, while forSiMe, GeMe, and SnMe there is a strong dependence of the emission maxima on the identity of the heteroatom.SiMe emits at a longer wavelength than GeMe, while SnMe is not luminescent. The dramatic luminescencedifference between the two tin compounds was investigated. 13C NMR coupling to 119/117Sn, observed in bothSnMe and SnPh, was used to make 13C NMR resonance assignments. Qualitative results of semiempirical molecularorbital calculations support the 13C NMR assignments. The crystal structure data for SnPh was obtained at 20 °C: a = 10.353(2) Å, b = 16.679(2) Å, c = 9.482(1) Å, α = 99.91(1)°, β = 106.33(1)°, γ = 77.80(1)° with Z = 2in space group P1̄. It is proposed that the increased electron density at tin in SnMe is responsible for the deactivationof the emissive state. The presence of phenyl substituents in SnPh serves to stabilize the emissive state andluminescence is observed.
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