Qin Yuanyuan, Wu Yuewei, Luo Shuchang, Xi Jing, Guo Yan, Ding Yi, Zhang Jun, Liu Xiangyu
State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan 750021, China.
College of Chemical Engineering, Guizhou University of Engineering Science, Bijie 551700, China.
Dalton Trans. 2022 Nov 15;51(44):17089-17096. doi: 10.1039/d2dt02345h.
Four air-stable mononuclear Co(II) complexes, with the formulas [Co(dapbh)(HO)(CHOH)] (1), [Co(Hdapbh)(N)(CHOH)]·(CHOH) (2), [Co(Haapbh)(CHOH)]·(NO) (3) and [Co(Hbapbh)(HO)(NO)]·(NO) (4), have been synthesized and structurally characterized by single crystal X-ray diffraction. In all of the complexes, the Co(II) centers constrained by the rigid pentadentate ligand HL with two protonable hydrogens adopt a heptacoordinated pentagonal-bipyramidal geometry. The combined analyses of magnetic data and calculations unveil large easy-plane magnetic anisotropies for these complexes ( = +37.338, +37.273, +41.138 and +41.139 cm for 1-4, respectively), which indicate that the chemical alterations of the equatorial ligand and the ligand field strength in the axial positions synergistically fine-tune the magnitude of the values. Magnetic investigations demonstrate the field-induced single-ion magnetic behavior in complexes 1, 2 and 4 with diverse energy barriers () of 12.25 for 1, 44.15 for 2 and 48.72 K for 4, corresponding to the geometrical distortion of the heptacoordinated Co(II) ion. That is, the greatest deviation from the ideal symmetry in 4 is responsible for the highest barrier.
