Solute-solvent electronic interaction is responsible for initial charge separation in ruthenium complexes [Ru(bpy)3]2+ and [Ru(phen)3]2+
| Autor: | Charles W. Stark, Juri Pahapill, Matt Rammo, Aleksander Trummal, Meelis-Mait Sildoja, Katrin Petritsenko, Merle Uudsemaa, Aleksander Rebane |
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| Rok vydání: | 2019 |
| Předmět: |
Materials science
chemistry.chemical_element 02 engineering and technology General Chemistry Dielectric 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Biochemistry 0104 chemical sciences Ruthenium lcsh:Chemistry Electron transfer Electric dipole moment Dipole lcsh:QD1-999 chemistry Polarizability Excited state Materials Chemistry Environmental Chemistry Physical chemistry Molecule 0210 nano-technology |
| Zdroj: | Communications Chemistry, Vol 2, Iss 1, Pp 1-6 (2019) |
| ISSN: | 2399-3669 |
| DOI: | 10.1038/s42004-019-0213-5 |
| Popis: | Origin of the initial charge separation in optically-excited Ruthenium(II) tris(bidentate) complexes of intrinsic D3 symmetry has remained a disputed issue for decades. Here we measure the femtosecond two-photon absorption (2PA) cross section spectra of [Ru(2,2′-bipyridine)3]2 and [Ru(1,10-phenanthroline)3]2 in a series of solvents with varying polarity and show that for vertical transitions to the lower-energy 1MLCT excited state, the permanent electric dipole moment change is nearly solvent-independent, Δμ = 5.1–6.3 D and 5.3–5.9 D, respectively. Comparison of experimental results with quantum-chemical calculations of complexes in the gas phase, in a polarizable dielectric continuum and in solute-solvent clusters containing up to 18 explicit solvent molecules indicate that the non-vanishing permanent dipole moment change in the nominally double-degenerate E-symmetry state is caused by the solute-solvent interaction twisting the two constituent dipoles out of their original opposite orientation, with average angles matching the experimental two-photon polarization ratio. Ruthenium(II) complexes are widely used as photosensitisers for electron transfer, but given their high intrinsic symmetry, the origin of the excited state dipole moment is unclear. Here two-photon absorption experiments supported by theoretical calculations suggest this arises from solvent-solute electronic interactions. |
| Databáze: | OpenAIRE |
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