Structures and magnetic anisotropies of two seven-coordinate Co()-nitrate complexes showing slow magnetic relaxation

• Published in: New journal of chemistry 2023-08, Vol.47 (33), p.15553-1556
• Main Authors: Lv, Wei, Chen, Lei, Chen, Xue-Tai, Yan, Hong, Wang, Zhenxing, Ouyang, Zhong-Wen, Xue, Zi-Ling
• Format: Article
• Language: English
• Subjects: Anisotropy; Electron paramagnetic resonance; Ligands; Magnetic induction; Magnetic measurement; Magnetic permeability; Magnetic relaxation; Temperature dependence
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d3nj02160b

Two seven-coordinate Co( ii )-nitrate complexes, [Co(tmpdc)(NO 3 ) 2 ] ( 1 ) and [Co(tmpdt)(NO 3 ) 2 ]·CH 3 CN ( 2 ) (tmpdc = N , N , N ′, N ′-tetramethyl-2,6-pyridinedicarboxamide, tmpdt = N , N , N ′, N ′-tetramethyl-2,6-pyridinedithiocarboxamide) with tridentate neutral ligands tmpdc or tmpdt have been prepared. Their crystal structures by single X-ray diffraction show markedly different coordination geometries when two donor atoms of the tridentate ligand change from oxygen in 1 to sulfur in 2 . Complex 1 is a capped octahedral while complex 2 is a pentagonal bipyramid. Results of direct-current (dc) magnetic measurements and high-frequency electron paramagnetic resonance (HFEPR) indicate the anisotropic S = 3/2 spin ground state of the Co( ii ) ions with the easy-plane anisotropy for both 1 and 2 . Frequency- and temperature-dependent alternating-current (ac) magnetic susceptibility studies reveal slow magnetic relaxation for 1 and 2 under applied fields. Two seven-coordinate mononuclear Co( ii ) complexes are proved to have field-induced magnetic relaxation and one of them possesses capped octahedral geometry.