Oxalato-Bridged Neutral Octanuclear Heterometallic Complexes [Ln4K4(L)4(μ-H2O)4(NO3)2(μ-Ox)] (Ln = Dy(III), Gd(III), Tb(III), Ho(III); LH3 = N[CH2CH2N═CH-C6H3-2-OH-3-OMe]3; Ox = (C2O4)2–): Synthesis, Structure, Magnetic and Luminescent Properties

Stepwise reaction of LH3 (LH3 = N[CH2CH2N═CH-C6H3-2-OH-3-OMe]3) with Ln(NO3)3·nH2O and potassium oxalate [K2Ox] afforded discrete heterometallic neutral octanuclear complexes [Ln4K4(L)4(μ-H2O)4(NO3)2(μ-Ox)] (Ln = Dy(III), Gd(III), Tb(III), Ho(III); LH3 = N[CH2CH2N═CH-C6H3-2-OH-3-OMe]3; Ox = (C2O4)2–). The molecular structures of 1–4 were confirmed by single-crystal X-ray crystallography. The asymmetric unit of these compounds contains two lanthanide(III) ions and two potassium cations present in the opposite corners of a distorted rectangle. Such a motif is further bridged by an oxalate anion to generate the octanuclear heterometallic complex. The lanthanides are eight-coordinate in a distorted trigonal dodecahedron geometry. On the other hand, the potassium ions adopt a nine-coordinate coordination sphere in a distorted tricapped trigonal prism geometry. Magnetic studies on 1–4 reveal the absence of significant magnetic interactions between the magnetic centers present in these complexes.