Antiferro- to ferromagnetic crossover in diphenoxido bridged NiII2MnII complexes derived from N2O2 donor Schiff base ligands

Three new trinuclear NiII–MnII complexes have been synthesized using three different “metalloligands” [NiL1], [NiL2] and [NiL3] derived from the Schiff bases H2L1 = N,N′-bis(salicylidene)-1,3-pentanediamine, H2L2 = N,N′-bis(salicylidene)-1,3-propanediamine and H2L3 = N,N′-bis(salicylidene)-1,3,-diaminopropan-2-ol), respectively. In all three complexes, [(NiL1)2Mn(OOCPh)2(H2O)2]·CH3OH (1), [(NiL2)2Mn(OOCPh)2(CH3OH)2]·CH3OH (2) and [(NiL3)2Mn(OOCPh)2(H2O)2]·CH3OH (3), in addition to the double phenoxido bridge, the two terminal NiII atoms are linked to the central MnII by means of a syn–syn bridging benzoate, giving rise to a linear structure. Complex 1 with Ni–O–Mn angle of 97.35° exhibits antiferromagnetic interactions (JNi–Mn = −0.60 cm−1) whereas ferromagnetic exchange is observed in 2 and 3 (JNi–Mn = +2.00 and +1.10 cm−1 respectively) having Ni–O–Mn angle 97.34° (in 2), 97.27° (in 3). Theoretical calculations have been performed in order to understand the effect of structural parameters that can tune the magnetic properties of this type of complexes such as small differences in the Ni–O–Mn angle and/or slight variations in intermolecular contacts within the crystal.

Three new Ni(II)–Mn(II) complexes, derived from different Schiff base ligands, having very slight variations in average phenoxido bridging angles (97.27–97.35°) have been synthesized in order to analyze that small difference in structural parameters can be responsible for ferro- to antiferromagnetic crossover in this type of complexes.Figure optionsDownload as PowerPoint slide