A series of homonuclear lanthanide complexes incorporating isonicotinic based carboxylate tectonic and oxalate coligand: structures, luminescent and magnetic properties

Abstract

A new family of five new lanthanide–organic frameworks incorporating both substituted isonicotinic acid and an oxalate coligand, have been fabricated successfully through a solvo-thermal reaction, namely, {[Ln(μ₂-H₂minca)](μ₂-C₂O₄)·2H₂O]·mH₂O}_n, (Ln = Sm (1), m = 0; Eu (2), m = 1; Gd (3), m = 1; Tb (4), m = 0; Ho (5), m = 0), (H₃minca = 2-(hydroxyl)-6-methyl-isonicotinic acid, H₂C₂O₄ = oxalate acid). Complexes 1–5 are isomorphous and isostructural, and they all exhibit two dimensional (2-D) corrugated networks with 6³ topology, in which {LnO₈} polyhedra are linked through carboxylate and oxalate groups into a net-like sheet. The luminescence emission spectra of the complexes vary depending on which lanthanide(III) ion is present. The H₂minca ligand provides efficient energy transfer for sensitization of the Eu(III) and Tb(III) complexes. Variable temperature magnetic susceptibility measurements show that compound 3 displays weak anti-ferromagnetic interactions. The magnetic behaviors of 1, 2, 4 and 5 are ascribed to the depopulation of the Stark levels and weak antiferromagnetic interactions within the lanthanide(III) complexes.