Compartmentalization of Alkaline-Earth Metals in Salen-Type Cu- and Ni-Complexes in Solution and in the Solid State

Alba Finelli; Nelly Hérault; Aurélien Crochet; Katharina M Fromm

doi:10.1021/acsomega.9b00365

Compartmentalization of Alkaline-Earth Metals in Salen-Type Cu- and Ni-Complexes in Solution and in the Solid State

ACS Omega. 2019 Jun 13;4(6):10231-10242. doi: 10.1021/acsomega.9b00365. eCollection 2019 Jun 30.

Authors

Alba Finelli¹, Nelly Hérault¹, Aurélien Crochet¹, Katharina M Fromm¹

Affiliation

¹ Department of Chemistry and FriMat, Department of Chemistry, University of Fribourg, Ch. du Musée 9, 1700 Fribourg, Switzerland.

Abstract

The precise arrangement of metal ions in type and number by a ligand represents an important challenge in biology as well as in materials science. The preorganization of different metal ions such as alkaline-earth and transition-metal ions is of particular interest for the design of catalysts or precursors of oxides. This study is based on a Ω-shaped salen-derived ligand comprising N₂O₂ and O₂O₂ coordination sites. The selective binding of Cu(II) and Ni(II) and alkaline-earth-metal ions is influenced by many factors such as the size of the cation, the solvent, or the counterion. UV-vis and ¹H NMR titrations and single-crystal X-ray structures reveal that the obtained complexes tend to adopt different structures in solution compared to the solid state. Mainly discrete motifs with a stoichiometry 1:1 (LM₁ to alkaline-earth-metal ions) have been shown to form in the solid state, whereas in solution, the 2:1 complexes are predominant.