Tris(trifluoromethyl)germylethynyl derivatives of biphenyl and anthracene: Synthesis, structure, and evidence of the intramolecular charge transfer on the germanium center

• Some model of tris(trifluoromethyl)germyl derivatives have been prepared.
• Unusually intramolecular energy and electron-transfer have been found.
• Vacant Ge 4d atomic orbitals play a key role in this phenomenon.

Symmetrical and unsymmetrical 4,4′-biphenyl, and 9,10-anthracene derivatives with tris(trifluoromethyl)germylethynyl –CC–Ge(CF3)3 substitutes have been prepared, their properties have been studied and compared with those of dimethyl(phenyl)silylethynyl –CC–Si(Ph)Me2 compounds. UV–visible absorption, steady-state, and time-resolved fluorescence spectra in solution for this germanium and silicon compounds have been investigated. The process of photoinduced electron-transfer from the aromatic group to the germanium center has been found in the unsymmetrical 4-biphenyl –CC–Ge(CF3)3 molecule. Anthracene derivatives with –CC–Ge(CF3)3 substitutes have been characterized crystallographically.

Unsymmetrical 4-[tris(trifluoromethyl)germylethynyl]biphenyl shows the energy and charge transfer from the aromatic ligand on the germyl perfluoromethyl group at a laser pulse excitation in solution at room temperature. The rate constant of the charge transfer is 2.7 × 109 s−1. It is assumed that the key role in the mechanism of charge transfer and stabilization of radical ion pairs in the excited state of play the germanium 4d AO.Figure optionsDownload as PowerPoint slide