Yu Fei, Cao Zi-Heng, Ge Jing-Yuan, Sun Yi-Chen, Ouyang Zhong-Wen, Zuo Jing-Lin, Wang Zhenxing, Kurmoo Mohamedally
State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210023, P. R. China.
Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China.
Dalton Trans. 2017 Mar 27;46(13):4317-4324. doi: 10.1039/c7dt00110j.
Three Fe(iii) dimers, [Fe(L-H)]·2CHCN (1), [Fe(L-OCH)] (2) and [Fe(L-OCH)]·2CHCN (3), containing the pentadentate O,N,N,O,O-donor Schiff-base ligands with variable size pendants, were synthesized and structurally characterized. The three ligands were generated in situ from 2-(iminomethyl)phenol, 2-methoxy-6-(iminomethyl)phenol and 2-ethoxy-6-(iminomethyl)phenol, respectively. All three crystal structures contain centrosymmetric dimers of edge-sharing octahedra of Fe(iii) ions through a pair of μ-phenoxido bridges. The exchange coupling is ferromagnetic for 1 (J = +0.47(1) cm, ∠Fe-O-Fe = 98.02°) and 2 (J = +0.86(1) cm, ∠Fe-O-Fe = 97.17°), but antiferromagnetic for 3 (J = -0.72(1) cm, ∠Fe-O-Fe = 98.53°), which are correlated by high-field electron paramagnetic resonance revealing moderate magneto-anisotropy of D = -0.24(3) cm, E = 0.08(1) cm for 1, D = -0.38(1) cm, E = 0.11(1) cm for 2, and D = 0.30(3) cm, E = 0.02(1) cm for 3. The exchange couplings were further estimated by DFT calculations, which gave the finest Fe-O-Fe angle of 97.83° for the ferromagnetic-antiferromagnetic crossover.
合成并表征了三种含有不同大小侧链的五齿O,N,N,O,O-供体席夫碱配体的Fe(iii)二聚体，即[Fe(L-H)]·2CHCN (1)、[Fe(L-OCH)] (2)和[Fe(L-OCH)]·2CHCN (3)。这三种配体分别由2-(亚氨基甲基)苯酚、2-甲氧基-6-(亚氨基甲基)苯酚和2-乙氧基-6-(亚氨基甲基)苯酚原位生成。所有三种晶体结构均包含通过一对μ-苯氧基桥连接的Fe(iii)离子的中心对称边共享八面体二聚体。对于1（J = +0.47(1) cm，∠Fe-O-Fe = 98.02°）和2（J = +0.86(1) cm，∠Fe-O-Fe = 97.17°），交换耦合是铁磁性的，但对于3（J = -0.72(1) cm，∠Fe-O-Fe = 98.53°）是反铁磁性的，通过高场电子顺磁共振揭示了它们的相关性，其中1的磁各向异性适中，D = -0.24(3) cm，E = 0.08(1) cm；2的D = -0.38(1) cm，E = 0.11(1) cm；3的D = 0.30(3) cm，E = 0.02(1) cm。通过DFT计算进一步估计了交换耦合，对于铁磁-反铁磁转变，得到了最佳的Fe-O-Fe角为97.83°。
