Exploring the Effect of Ligand Structural Isomerism in Langmuir-Blodgett Films of Chiral Luminescent Eu(III) Self-Assemblies

Here we have investigated the influence of the antenna group position on both the formation of chiral amphiphilic Eu-III-based self-assemblies in CH3CN solution and, on the ability to form monolayers on the surface of quartz substrates using the Langmuir-Blodgett technique, by changing from the 1-naphthyl (2(R), 2(S)) to the 2-naphthyl (1(R), 1(S)) position. The evaluation of binding constants of the self-assemblies in CH3CN solution was achieved using conventional techniques such as UV/Visible and luminescence spectroscopies along with more specific circular dichroism (CD) spectroscopy. The binding constants obtained for EuL, EuL2 and EuL3 species in the case of 2-naphthyl derivatives were comparable to those obtained for 1-naphthyl derivatives. The analysis of the changes in the CD spectra of 1(R) and 1(S) upon addition of Eu-III not only allowed us to evaluate the values of the binding constants but the resulting recalculated spectra may also be used as fingerprints for assignment of the chiral self-assembly species formed in solution. The obtained monolayers were predominantly formed from EuL3 (approximate to 85%) with the minor species present in. 15% EuL2.