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Query: EC:2.4.1.14 (
SPS
)
813
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
The lithium salt of the anionic
SPS
pincer ligand composed of a central hypervalent lambda4-phosphinine ring bearing two ortho-positioned diphenylphosphine sulfide side arms reacts with [Mn(CO)5Br] to give fac-[Mn(
SPS
)(CO)3]. This isomer can be converted photochemically to
mer
-[Mn(
SPS
)(CO)3], with a very high quantum yield (0.80+/-0.05). The thermal backreaction is slow (taking ca. 8 h at room temperature), in contrast to rapid electrode-catalyzed
mer
-to-fac isomerization triggered by electrochemical reduction of
mer
-[Mn(
SPS
)(CO)3]. Both geometric isomers of [Mn(
SPS
)(CO)3] have been characterized by X-ray crystallography. Both isomers show luminescence from a low-lying 3IL (
SPS
-based) excited state. The light emission of fac-[Mn(
SPS
)(CO)3] is largely quenched by the efficient photoisomerization occurring probably from a low-lying Mn-CO dissociative excited state. Density functional theory (DFT) and time-dependent DFT calculations describe the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of fac- and
mer
-[Mn(CO)3(
SPS
)] as ligand-centered orbitals, largely localized on the phosphinine ring of the
SPS
pincer ligand. In line with the ligand nature of its frontier orbitals, fac-[Mn(
SPS
)(CO)3] is electrochemically reversibly oxidized and reduced to the corresponding radical cation and anion, respectively. The spectroscopic (electron paramagnetic resonance, IR, and UV-vis) characterization of the radical species provides other evidence for the localization of the redox steps on the
SPS
ligand. The smaller HOMO-LUMO energy difference in the case of
mer
-[Mn(CO)3(
SPS
)], reflected in the electronic absorption and emission spectra, corresponds with its lower oxidation potential compared to that of the fac isomer. The thermodynamic instability of
mer
-[Mn(CO)3(
SPS
)], confirmed by the DFT calculations, increases upon one-electron reduction and oxidation of the complex.
...
PMID:Syntheses, X-ray structures, photochemistry, redox properties, and DFT calculations of interconvertible fac- and mer-[Mn(SPS)(CO)3] isomers containing a flexible SPS-based pincer ligand. 1632 2
