Heterodinuclear [Co-Ln] complexes of semicarbazide-arm bearing ligand: synthesis from the cleavage of starting [Co-Co] complex, structures and magnetic properties

Abstract

The heterometallic bridging potential of the anion of 1-(2-hydroxy-3-methoxybenzylidene)-semicarbazide (HL) to CoIIand four 4f ions was examined during a 4f ion coordination-driven cleavageof [Co2(m-OH2)(O2CCMe3)4(HO2CCMe3)4](Co2-Piv) and scrambling of pivalate anions from the startingmaterial. Room-temperature reactions with four different lanthanide nitrate salts yielded [CoLnL(m2-OOCCMe3)4(CH3OH)].3CH3OH [Ln = Gd (1), Tb (2), Dy (3) and Ho (4)]. The formation in solution and thecrystallization in the solid state indicated that the reactions inhibit any further aggregation ofCo-Lncores to higher order aggregates. After scrambling, the pivalate ions in [Co-Ln] show three types ofcoordination modes to sustain the dinuclear aggregates with varying degrees of distortion in thedinuclear entities bound to a single L ion. Atom economy was maintained with respect to the pivalateions as no external addition of these anions was made. The dc magnetic measurements revealed thepresence of weak ferromagnetic interactions in complexes1and2and weak antiferromagneticinteractions in complexes3and4.