Crystal engineering of monometallic lanthanide(iii) supramolecular systems within the N3-tridentate hydrazone Schiff-base ligand

Abstract

A comprehensive series of mononuclear Ln(III) complexes based on N₃-tridentate Schiff-base ligand L have been synthesized using triflate or nitrate lanthanide(III) metal salts. X-ray structural characterization shows that the obtained complexes exhibit a variety of coordination modes around the Ln(III) centers tuned through appropriate counterions and reaction conditions. Examination of the above-mentioned factors reveals that, in the case of all lanthanide assemblies, we observe anion-driven structural diversity. Tuning of the crystal structure of the formed supramolecular systems is also highly influenced by the lanthanide contraction phenomenon, directly resulting in a series of isostructural groups, with general formulae of [ML₂(OTf)_nX_3−n](OTf)_3−n, if n = 2, X = MeCN (except for Yb), and if n = 1, X = MeOH in the triflate series, and [ML(NO₃)₃(X)](Y), where X and Y represent MeOH, MeCN or H₂O, respectively, in the nitrate series. The present study gives insight into the lanthanide contraction phenomenon within the tridentate N-heterocyclic coordination architectures of Ln(III) systems and can serve for targeted manipulation of properties through molecular tectonics and crystal engineering aspects in the domains, where subtle changes of the Ln(III) coordination spheres are important like molecular magnetism or catalysis.