TY - UNPB
T1 - Photorearrangement of Bishypersilyl-1,2-dione: The Wavelength Matters
AU - Glotz, Gabriel
AU - Drusgala, Manfred
AU - Hamm, Florian
AU - Fischer, Roland C.
AU - Došlić, Nađa
AU - Kelterer, Anne-Marie
AU - Gescheidt-Demner, Georg
AU - Haas, Michael
PY - 2023
Y1 - 2023
N2 - We report on the synthesis, isolation and unique photoreactivity of a novel symmetric bissilyl-1,2-dione, 3. Its UV/Vis spectrum reveals two remarkable well-separated n→π* absorption bands at λmax = 637 nm (ε = 140 Lmol-1cm-1) and 317 nm (ε = 2460 Lmol-1cm-1). Irradiation at λ = 360/365 nm affords an isolable siloxyketene 4, whereas irradiation at λ = 590-630 nm leads to selective formation of siloxirane 5 by a 1,4-trimethylsilyl migration in high yield. These remarkable wavelength-dependent rearrangements are based on characteristic photochemical reaction pathways. Irradiation at 360/365 nm populates a second excited singlet state (S2) which triggers a hitherto unknown 1,3-hypersilyl migration yielding 4. At longer wavelengths (590/630 nm), the populated first excited singlet state (S1) undergoes intersystem crossing (ISC), and 5 emerges from a triplet (T1) precursor. We have established this reaction mechanism by spectroscopy (optical, in-situ IR, and NMR) and theoretical calculations. NMR and X-ray crystallography reveal the structural features of the products.
AB - We report on the synthesis, isolation and unique photoreactivity of a novel symmetric bissilyl-1,2-dione, 3. Its UV/Vis spectrum reveals two remarkable well-separated n→π* absorption bands at λmax = 637 nm (ε = 140 Lmol-1cm-1) and 317 nm (ε = 2460 Lmol-1cm-1). Irradiation at λ = 360/365 nm affords an isolable siloxyketene 4, whereas irradiation at λ = 590-630 nm leads to selective formation of siloxirane 5 by a 1,4-trimethylsilyl migration in high yield. These remarkable wavelength-dependent rearrangements are based on characteristic photochemical reaction pathways. Irradiation at 360/365 nm populates a second excited singlet state (S2) which triggers a hitherto unknown 1,3-hypersilyl migration yielding 4. At longer wavelengths (590/630 nm), the populated first excited singlet state (S1) undergoes intersystem crossing (ISC), and 5 emerges from a triplet (T1) precursor. We have established this reaction mechanism by spectroscopy (optical, in-situ IR, and NMR) and theoretical calculations. NMR and X-ray crystallography reveal the structural features of the products.
U2 - 10.26434/chemrxiv-2023-lpgq7
DO - 10.26434/chemrxiv-2023-lpgq7
M3 - Preprint
BT - Photorearrangement of Bishypersilyl-1,2-dione: The Wavelength Matters
ER -