Interplay of Magnetic Exchange Interactions and Ni S Ni Bond Angles in Polynuclear Nickel (II) Complexes
Y Krupskaya, A Alfonsov, A Parameswaran… - …, 2010 - Wiley Online Library
ChemPhysChem, 2010•Wiley Online Library
The ability of bridging thiophenolate groups (RS−) to transmit magnetic exchange
interactions between paramagnetic NiII ions is examined. Specific attention is paid to
complexes with large Ni SR Ni angles. For this purpose, dinuclear [Ni2L1 (μ‐OAc)⋅
I2][I5](2) and trinuclear [Ni3L2 (OAc) 2][BPh4] 2 (3), where H2L1 and H2L2 represent 24‐
membered macrocyclic amino‐thiophenol ligands, are prepared and fully characterized by
IR‐and UV/Vis spectroscopy, X‐ray crystallography, static magnetization M measurements …
interactions between paramagnetic NiII ions is examined. Specific attention is paid to
complexes with large Ni SR Ni angles. For this purpose, dinuclear [Ni2L1 (μ‐OAc)⋅
I2][I5](2) and trinuclear [Ni3L2 (OAc) 2][BPh4] 2 (3), where H2L1 and H2L2 represent 24‐
membered macrocyclic amino‐thiophenol ligands, are prepared and fully characterized by
IR‐and UV/Vis spectroscopy, X‐ray crystallography, static magnetization M measurements …
Abstract
The ability of bridging thiophenolate groups (RS−) to transmit magnetic exchange interactions between paramagnetic NiII ions is examined. Specific attention is paid to complexes with large NiSRNi angles. For this purpose, dinuclear [Ni2L1(μ‐OAc)⋅I2][I5] (2) and trinuclear [Ni3L2(OAc)2][BPh4]2 (3), where H2L1 and H2L2 represent 24‐membered macrocyclic amino‐thiophenol ligands, are prepared and fully characterized by IR‐ and UV/Vis spectroscopy, X‐ray crystallography, static magnetization M measurements and high‐field electron spin resonance (HF‐ESR). The dinuclear complex 2 has a central N3Ni2(μ‐S)2(μ‐OAc)Ni2N3 core with a mean NiSNi angle of 92°. The macrocycle L2 supports a trinuclear complex 3, with distorted octahedral N2O2S2 and N2O3S coordination environments for one central and two terminal NiII ions, respectively. The NiSNi angles are at 132.8° and 133.5°. We find that the variation of the bond angles has a very strong impact on the magnetic properties of the Ni complexes. In the case of the Ni2‐complex, temperature T and magnetic field B dependencies of M reveal a ferromagnetic coupling J=−29 cm−1 between two NiII ions (H=JS1S2). HF‐ESR measurements yield a negative axial magnetic anisotropy (D<0) which implies a bistable (easy axis) magnetic ground state. In contrast, for the Ni3‐complex we find an appreciable antiferromagnetic coupling J′=97 cm−1 between the NiII ions and a positive axial magnetic anisotropy (D>0) which implies an easy plane situation.
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