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

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.