| Title | Synthesis and computational and experimental investigations of a para-nicotinic acid-bridged dirhenium(I) dimer complex |
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| Author | Stoyanov, S R ;
Komreddy, V; Rillema, D P; Moore, C E; Nguyen, H |
| Source | ACS Omega vol. 5, issue 22, 2020 p. 12944-12954, https://doi.org/10.1021/acsomega.0c00704  Open Access |
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| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20200088 |
| Publisher | American Chemical Society |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf; html |
| Subjects | Science and Technology; solar energy; energy; energy resources; Energy technology |
| Illustrations | 3-D diagrams; tables; spectra; schematic representations |
| Released | 2020 05 22 |
| Abstract | The Re(I) dimer complex, [fac(CO)3(phen)Re1-N(py)COORe2(phen)fac(CO)3]+ (py = pyridine; phen = 1,10-phenanthroline), contains two different Re(I) centers 9.3 Å apart, one with a nitrogen donor and the
other with an acetate donor from the bridging isonicotinate ligand. The complexes were characterized by 1H NMR, UV-vis, fluorescence, and IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The absorption and emission
properties of the dimer dominated by charge transfer transitions are analyzed with respect to those of the monomers, [fac(CO)3(phen)Re-N(pyCOOCH3)]+ and [fac(CO)3(phen)ReOOCCH3]. Spectral comparison of these three complexes results in the unexpected
finding that the dimer emission (575 nm) occurs near that of the nicotinate-containing monomer (580 nm) rather than near the lower energy-emitting state (650 nm) of the acetate-containing monomer. Density functional theory (DFT) calculations
elucidate this unusual emission behavior. The geometries of the dimer and two monomers are optimized in the singlet ground and lowest-energy triplet excited states (LLTS's) to interpret absorption and emission behaviors, respectively. The singlet
excited states calculated using time-dependent DFT correlate well with the absorption spectra in the lowest-energy and other major electronic transitions. The energy gaps and low-lying singlet excited states of the dimer are close to those of the
acetate-containing monomer. The lowest-energy Franck-Condon triplet excited state of the dimer arising from electronic transitions localized on the acetate moiety is unstable. The next higher Franck-Condon triplet excited state arises from long-range
charge transfer transition, and its energy is close to that of the nicotinate-containing monomer. Optimization of the dimer LLTS yields a stable state based on a long-range charge transfer transition involving occupied orbitals partially localized on
the bridging nicotinate moiety. The LLTS energies of the dimer and nicotinate-containing monomer are in very good agreement as are the emission energies of these complexes. The correlated spectroscopic and computational results corroborate to the
understanding of charge transfer states and transitions toward the development of photosensitive compounds for photoelectrochemical solar energy conversion cells. |
| GEOSCAN ID | 326170 |
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