Crystal structures of three anionic lanthanide-aluminium [3.3.1] metallacryptate complexes

Area of Science:

• Coordination Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Metallacryptate complexes represent advanced supramolecular structures with potential applications in catalysis and materials science.
• The synthesis of isomorphous complexes allows for systematic studies of structural and electronic properties.
• Lanthanide ions (Ln) and aluminum ions (Al) offer unique coordination preferences and electronic characteristics.

Purpose of the Study:

• To synthesize and characterize novel isomorphous [3.3.1] metallacryptate complexes incorporating lanthanide ions.
• To investigate the structural features, including coordination geometry, stereochemistry, and disorder within these complexes.
• To explore the role of pyridine ligands in the structural dynamics of the metallacryptand framework.

Main Methods:

• Synthesis of three isomorphous metallacryptate complexes: [GdAl6], [DyAl6], and [YbAl6].
• Single-crystal X-ray diffraction analysis to determine precise molecular structures and coordination environments.
• Analysis of structural disorder arising from the presence or absence of coordinated pyridine ligands.

Main Results:

• The complexes feature an aluminum-based metallacryptand encapsulating a central Ln(III) ion.
• The encapsulated Ln(III) ions exhibit nine-coordinate, capped-square-anti-prism geometry, while Al(III) ions are octahedral.
• Structural disorder was observed, involving the rearrangement of salicyl-hydroximato ligands upon pyridine dissociation.

Conclusions:

• The synthesized [3.3.1] metallacryptates are three-dimensional metallacrowns capable of encapsulating Ln(III) ions.
• The study elucidates the intricate structural interplay between the metallacryptand framework, encapsulated ion, and guest ligands.
• The observed disorder provides insights into the dynamic nature and flexibility of these complex supramolecular architectures.