Long aliphatic chain derivatives of trigonal lanthanide complexes

Area of Science:

• Coordination Chemistry
• Lanthanide Complexes
• Organometallic Chemistry

Background:

• Trigonal lanthanide complexes (LnL) with pendant aldehyde groups are known to react with primary amines.
• Modification of LnL with primary amines yields novel aliphatic lanthanide complexes.

Purpose of the Study:

• To synthesize and characterize novel aliphatic lanthanide complexes, LnL¹⁸.
• To investigate the structural and magnetic properties of these new complexes.
• To compare the properties of LnL¹⁸ with the parent LnL complexes.

Main Methods:

• Synthesis of LnL¹⁸ complexes by reacting LnL (Ln = Yb, Lu) with 1-octadecylamine.
• Structural characterization using X-ray crystallography (for YbL¹⁸).
• Magnetic property measurements including static magnetic susceptibility and A.C. magnetic susceptibility.
• Emission spectroscopy to determine energy level splitting.

Main Results:

• The crystal structure of YbL¹⁸ shows subtle perturbations in the Yb(III) coordination sphere, retaining heptacoordination.
• Octadecyl chains direct crystal packing into lipophilic arrays via van der Waals interactions.
• Energy level splitting of the ²F_7/2 ground multiplet is similar between YbL¹⁸ and YbL.
• Spin-lattice relaxation in diluted samples is governed by direct and Raman processes, with faster relaxation in YbL¹⁸ at high temperatures.

Conclusions:

• The derivatization of LnL with 1-octadecylamine to form LnL¹⁸ preserves the core coordination environment of the lanthanide ion.
• The long aliphatic chains influence solid-state packing and dynamics.
• The octadecyl chains contribute to faster spin-lattice relaxation in the derivatized complexes at higher temperatures, likely due to increased phonon interactions.