• Triplet state CPL active helicene-dithiolene platinum bipyridine complexes
    T. Biet, T. Cauchy, Q. Sun, J. Ding, A. Hauser, P. Oulevey, T. Bürgi, D. Jacquemin, N. Vanthuyne, J. Crassous and N. Avarvari
    Chemical Communications, 53 (66) (2017), p9210-9213
    DOI:10.1039/C7CC05198K | unige:96312 | Abstract | Article HTML | Article PDF | Supporting Info
Chiral metal dithiolene complexes represent a family of chiral precursors, which can give rise to molecular materials with properties resulting from the interplay of chirality with conductivity, magnetism, and photophysics. We describe herein the first examples of chiral metal diimine dithiolene complexes, by the use of a platinum(II) centre coordinated by 2,2’-bipyridine and helicene-dithiolene ligands. Straightforward synthesis of racemic and enantiopure complexes allows the preparation of luminescent Pt(bipy) [4] and [6]helicene compounds for which the solid-state structure was determined as well. TD-DFT calculations support the assignment of the low energy bands observed in the UV-vis absorption spectra as mixed metal-ligand-to-ligand charge transfer transitions and confirm that the emission band results from the T1 excited state. Interestingly the enantiopure [6]helicene complexes show CPL activity at room temperature in acetonitrile solutions with anisotropy factors of 3×10-4.
  • Where does the Raman optical activity of [Rh(en)3]3+ come from? Insight from a combined experimental and theoretical approach
    M. Humbert-Droz, P. Oulevey, L.M. Lawson Daku, S. Luber, H. Hagemann and T. Bürgi
    Phys. Chem. Chem. Phys., 16 (42) (2014), p23260-23273
    DOI:10.1039/C4CP02145B | unige:40863 | Abstract | Article HTML | Article PDF
Backscattered Raman optical activity (ROA) spectra are measured for Δ- and Λ-tris-(ethylenediamine)rhodium(III) chloride in aqueous solution. In addition, the spectra of the four possible conformers in the Λ configuration are investigated by ab initio calculations. The Λ(δδδ) conformer is in best agreement with experimental spectra and examined in more details. The two most stable conformers according to the calculations are not compatible with the experimental ROA spectrum. Insights into the origin of observed band intensities are obtained by means of group coupling matrices. The influence of the first solvation shell is explored via an ab initio molecular dynamics simulation. Taking explicit solvent molecules into account further improves the agreement between calculation and experiment. Analysis of selected normal modes using group coupling matrices shows that solvent molecules lead to normal mode rotation and thus contribute to the ROA intensity, whereas the contribution of the Rh can be neglected.



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