Herein,
we studied the behavior of TcO4
– in trifluoroacetic
anhydride (TFAA) under visible light irradiation
in situ by UV–vis spectroscopy. One carboxylate of Tc(VII)
C2F3O5Tc (1) and two
wheel-like carboxylate clusters of Tc(IV) Tc8(μ-O)8(CF3COO)16 (2, 3) and Tc8(μ-O)8(C6H5COO)16 (4) were synthesized and analyzed
using pXRD, TGA, UV–vis spectroscopy, and SCXRD techniques.
According to SCXRD, it was found that Tc(IV) trifluoroacetate exists
in two crystalline modifications. By UV–vis spectroscopy and
DFT calculations, it was shown that the primary compound in the reaction
system is trifluoroacetate Tc(VII). A technetium trifluoroacetate(VII)
and Tc intermediates of unidentified nature both show photosensitivity.
The influence of intermolecular noncovalent interactions on the volatility
of trifluoroacetate and benzoate Tc(IV) is shown. The main regularities
of chemical transformations of technetium in nonaqueous solutions
of carboxylates have been revealed. The obtained data on the kinetics
of the process suggest that technetium in trifluoroacetic anhydride
can simultaneously exist in the form of Tc(VII), Tc(VI), Tc(V), and
Tc(IV). Under laser ionization or prolonged heating, the formation
of the Tc(II,III)-cluster is observed.