Conformation-selective coordination-driven self-assembly of a ditopic donor with Pd(II) acceptors

Area of Science:

• Coordination Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Investigating coordination-driven self-assembly for creating complex supramolecular structures.
• Exploring the versatility of pyridine-triazole ligands in metal-organic framework construction.

Purpose of the Study:

• To investigate the self-assembly behavior of a specific pyridine-triazole ligand (L) with different palladium(II) acceptors.
• To characterize the resulting supramolecular architectures, including macrocycles and molecular cages.
• To evaluate the catalytic potential of the synthesized cage structures.

Main Methods:

• Synthesis and characterization of coordination complexes using X-ray crystallography.
• Density Functional Theory (DFT) calculations (B3LYP) to corroborate experimental findings.
• Catalytic testing of the molecular cage in Knoevenagel condensation reactions.

Main Results:

• The ligand selectively forms [2+2] macrocycles with 90°cis-blocked Pd(II) acceptors.
• A molecular cubic cage ([6+12] Pd6L12) is formed with tetratopic Pd(NO3)2.
• The cage exhibits Lewis basicity due to sp2 hybridized nitrogen atoms and catalyzes Knoevenagel condensations.

Conclusions:

• The conformation of the pyridine-triazole ligand is dictated by the geometry of the palladium acceptor.
• Self-assembly leads to distinct supramolecular structures (macrocycles and cages) based on metal coordination environment.
• The synthesized molecular cage demonstrates utility as a recyclable catalyst for organic transformations.