Neue starre Calixaren-basierte Liganden für die Katalyse und Biomimetik

In the most thermodynamically stable cone conformation, the four phenolic oxygens of a calix[4]arene molecule are ideally situated to complex main group and transition metal ions. Depending on the number of the substituents at these oxygen atoms, the calixarene compounds can act as tetra-, tri-, di- or mono-anionic ligands in their metal complexes. Yet, few calixarenes were used in catalysis for organic transformations or in biomimetics. As the phenolic oxygens are hard donors, many transition metal complexes of calixarenes show high lability in solution, rendering them unsuitable for catalysis. Hard donors also hinder their use in biomimetic studies, even though similar multidentate binding motifs are often found in metalloenzymes. In this proposal, we describe the strategies toward the alternative calix[4]arene-based ligands, where some of the oxygen atoms are replaced with the better donating amines and imines. These strategies are based on the cross-coupling reactions at the lower rim of the calixarene molecule. The newly prepared ligands will be used in complexation with mid-row- and late-transition metal complexes for studies in catalysis and biomimetics. We believe that the chemistry described herein will have a significant impact on the further development of efficient catalytic systems and provide better understanding of metalloenzymes operation modes.