Synthesis of ligands for self-assembly of discrete metallo-supramolecular complexes

Abstract

Different aspects of self-assembly and self-sorting of metallo-supramolecular have been investigated in this thesis. Starting with self-sorting, four different 9,9'-spirobifluorene derivatives substituted with pyridine were synthesized as racemates as well as in enatiomerically pure form and used to investigate self-discrimination and self-recognition during the assembly of two different rhombic systems consisting of two ligands and two metal ions; Pd- or Pt-corner (M₂L₂). The two systems differ in the lengths of the spacer between the spirobifluorene and the metal-binding pyridine, the smaller one having no spacer and the long one having an ethynylspacer. <br /> For the ligand with the shorter spacer a crystal structure of the homochiral complex was obtained, confirming the preference for self-recognition of the system, which was also observed in the NMR- and mass spectra. In the case of the larger ligand no self-sorting behavior was observed. The ability of the larger ligand to form a catenane was established by mass, ¹H-NMR-spectroscopy and crystallography.<br /> The small spirobifluorene based ligand was used with Pd(II)to form a M6L12-sphere, and several attempts were made to confirm the presence of the M₆L₁₂-species. A smaller M₂L₄- cage was formed with a third synthesized spirobifluorene derivative and confirmed by mass spectroscopy. <br /> Two ligands with both a soft and a hard metal-binding site were synthesized and used in complexation experiments with Ti(IV), Pd(II) and Pt(II) in order to obtain a self-assembled supramolecular multicomponent complex. We succeeded in performing the first complexation steps with both ligands, preparing for the final complexation event. <br /> Lastly, a ligand based on a thiophene core with bipyridine as the metal binding unit was synthesized and tested for its ability to form a triple helix with Fe(II) and undergo spin crossover.