Complexation Behavior of Pinene–Bipyridine Ligands towards Lanthanides: The Influence of the Carboxylic Arm

Atena B Solea,Katharina M Fromm,Olimpia Mamula,Liangru Yang,Aurelien Crochet,Christophe Allemann

doi:10.3390/chemistry4010002

Abstract

The complexation behavior of two novel, chiral pinene–bipyridine-type ligands ((–)-HL1 and (–)-HL2) containing a carboxylic arm towards lanthanide Ln(III) (Ln = La, Eu, Lu) ions was investigated through spectroscopic methods. The association constants of the mononuclear complexes determined from the UV-Vis titrations indicated that the ligand (–)-HL1 possessing a shorter carboxylic arm formed more stable complexes compared with (–)-HL2, whose carboxylic arm had one more methylene unit. This is due to the formation of more stable seven-member metal chelate rings in the first case as compared with the eight-member metal chelate rings in the second. IR and fluorescence spectroscopy provided additional information about the structure of these complexes.

Highlights

Haute Ecole d’Ingénierie et d’Architecture Fribourg, HEIA-FR, HES-SO, University of Applied Sciences of Department of Chemistry, University of Fribourg, Chemin du Musée 9, CH-1700 Fribourg, Switzerland; School of Chemistry & Chemical Engineering, Henan University of Technology, Zhengzhou 450001, China; Abstract: The complexation behavior of two novel, chiral pinene–bipyridine-type ligands ((–)-HL1 and (–)-HL2) containing a carboxylic arm towards lanthanide Ln(III) (Ln = La, Eu, Lu) ions was investigated through spectroscopic methods
The complexity of the self-assembled species increases with the coordination number of the metal ions. Such a behavior can be expected for the lanthanide ions Ln(III)
The lability and the lack of directionality typical for the dative bonds formed by Ln(III) ions render the diastereoselective synthesis of enantiopure, self-assembled polynuclear structures quite challenging

Summary

Introduction

Due to their large ionic radii and high coordination numbers Their interesting features such as large Stokes shifts, emission [7], and magnetic properties [8] can lead to the formation of self-assembled architectures with interesting functionalities [9]. Such Ln(III) complexes have found many applications in lanthanide–actinide extraction processes [10,11], bioimaging [12], sensing [13], lighting and displays [14,15,16,17,18], or as singlemolecular magnets [8,19].

Methods

Results

Conclusion