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.

Graphical abstractUnsymmetrical 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 full-size imageDownload as PowerPoint slide