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Volatile lanthanide complexes with fluorinated heptadentate ligands
Journal article   Open access   Peer reviewed

Volatile lanthanide complexes with fluorinated heptadentate ligands

Joshua C Zgrabik, Balaka Bhuniya, Thomas Branstad Phillips, Jorge Barroso, Bess Vlaisavljevich and Scott R Daly
Dalton transactions : an international journal of inorganic chemistry, Vol.53(7), pp.2998-3009
2024
DOI: 10.1039/d3dt04198k
PMID: 38265072
Appears in  UI Libraries Support Open Access
url
https://doi.org/10.1039/d3dt04198kView
Published (Version of record) Open Access

Abstract

Understanding factors that influence the volatility of lanthanide complexes remains an important goal for applications such as gas-phase f-metal separations and the synthesis of lanthanide-containing thin films. Lanthanide complexes often exhibit volatility differences that depend on the ability of ligands to saturate the lanthanide coordination sphere and attenuate intermolecular bonding in the solid state. This can make it difficult to assess how electronic factors associated with differing ligand substituents influence volatility. Here we describe the synthesis, structures, and thermal properties of a series of volatile lanthanide complexes (Ln = Nd, Er, and Yb) containing N4O3 ligands decorated with different alkyl and fluoroalkyl substituents (CF3, CF2CF2CF3, Me, and tBu). These ligands completely enveloped the tested lanthanides to form monomeric complexes with 7-coordinate distorted capped octahedral coordination geometries, as determined using single-crystal X-ray diffraction. Thermogravimetric analysis and bulk sublimation studies show how metal encapsulation affords complexes with the same volatility regardless of metal size, even with lanthanide ions with significantly different radii such as Nd3+ and Yb3+. Most notably, the results show that increasing ligand fluorination, a strategy often used to increase the volatility of metal complexes, is not always beneficial and can significantly attenuate the volatility of lanthanide complexes depending on location with respect to other substituents in the ligand framework. A pair-wise model based on density functional theory shows that the net intermolecular interactions in the unit cell can still be stronger when fluorination is present. In other words, even if individual interactions between neighboring molecules are weaker, the total number of interactions in the solid arising from the nature of crystal packing is equally important to consider.
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