Enantiopure Double ortho-Oligophenylethynylene-Based Helical Structures with Circularly Polarized Luminescence Activity

In this paper, we describe the optical and chiroptical properties of an enantiopure multipodal ortho-oligophenylethynylene (S,S,S,S)-1 presenting four chiral sulfoxide groups at the extremes. The presence of these groups together with alkynes allows the coordination with carbophilic Ag(I), and/or oxophilic Zn(II) cations, yielding double helical structures in an enantiopure way. In this sense, different behaviors in absorption, fluorescence, ECD and CPL spectra have been found depending on the stoichiometry and nature of the metal. We have observed that Zn(II) coordination favors an intensity increase of the electronic circular dichroism (ECD) spectra of compound (S,S,S,S)-1 yielding an M-helicity in the ortho-oligophenylene ethynylene (o-OPE) backbone. On the other hand, ECD spectra of final Ag(I) complex shows two different bands with an opposite sign to the free ligand, thus giving the P-helical isomer. In addition, circularly polarized luminescence (CPL) exhibit an enhanced intensity and negative sign in both complexes. Computational studies were also carried out, supporting the experimental results.

Automated summary

This paper describes the optical and chiroptical properties of a chiral multipodal ortho-oligophenylethynylene molecule with sulfoxide groups, which can coordinate with Ag(I) and Zn(II) cations to form double helical structures. The absorption, fluorescence, ECD, and CPL spectra show different behaviors depending on the metal stoichiometry and nature. Computational studies support the experimental results.