Synthesis and computational and experimental investigations of a para-nicotinic acid-bridged dirhenium(I) dimer complex

dc.contributor.authorStoyanov, Stanislav R.
dc.contributor.authorKomreddy, Venugopal R.
dc.contributor.authorRillema, D. Paul
dc.contributor.authorMoore, Curtis E.
dc.contributor.authorNguyen, Huy A.
dc.description© Authors. Open access license, 100 percent of their research articles upon acceptance and publication by a peer-reviewed ACS journal.en_US
dc.description.abstractThe 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.en_US
dc.description.sponsorshipWichita State University Office of Research Administration, Kansas, NSF EPSCoR, and the Department of Energy for support. S.R.S. acknowledges the support of the Program for Energy Research and Development of the Government of Canada. S.R.S. thanks Dr. John M. Villegas for the helpful comments on the presentation of the results.en_US
dc.identifier.citationStanislav R. Stoyanov, Venugopal Komreddy, D. Paul Rillema, Curtis E. Moore, and Huy Nguyen ACS Omega 2020 5 (22), 12944-12954en_US
dc.publisherAmerican Chemical Societyen_US
dc.relation.ispartofseriesACS Omega;v.5:no.22
dc.rights.holder© 2020 American Chemical Societyen_US
dc.subjectMetal to ligand charge transferen_US
dc.subjectQuantum mechanicsen_US
dc.subjectExcited statesen_US
dc.titleSynthesis and computational and experimental investigations of a para-nicotinic acid-bridged dirhenium(I) dimer complexen_US
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