Understanding stability trends along the lanthanide series.

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Lanthanide Chemistry

Background:

• Lanthanide complexes exhibit varying stability across the series.
• Polyaminocarboxylate ligands like TETA(4-), BCAED(4-), and BP18C6(2-) are crucial for complex formation.
• Understanding these stability trends is vital for applications in various fields.

Purpose of the Study:

• To investigate the stability trends of lanthanide complexes with TETA(4-), BCAED(4-), and BP18C6(2-) ligands.
• To rationalize observed stability trends using computational methods.
• To correlate computational findings with experimental data.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Geometry optimizations were performed using the TPSSh/6-31G(d,p) level with a 46+4f(n) ECP for lanthanides.
• Free energies of complex formation and hydration free energies were calculated.

Main Results:

• DFT calculations accurately reproduced experimental bond lengths for lanthanide coordination spheres.
• Coordination sphere contractions followed quadratic trends across the lanthanide series.
• Calculated stability trends aligned with experimental data, showing ligand-dependent variations.

Conclusions:

• The study successfully rationalized lanthanide complex stability trends using DFT.
• Stability is governed by a balance between ligand binding energies and hydration energies.
• Ligand structure critically influences the stability trends across the lanthanide series.