| Autor: |
Xia CC; State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China. wangxy66@nju.edu.cn., Zhang XY; State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China. wangxy66@nju.edu.cn., Zhang CC; State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China. wangxy66@nju.edu.cn., Li G; State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China. wangxy66@nju.edu.cn., Wei HY; Jiangsu Key Laboratory of Biofunctional Materials, School of Chemistry and Materials Science, Nanjing Normal University, Nanjing, 210023, China. weihaiyan@njnu.edu.cn., Wang XY; State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China. wangxy66@nju.edu.cn. |
| Abstrakt: |
A novel bis-bidentate nitronyl nitroxide radical based on triazolopyrimidine, NIT-2-TrzPm (NIT-2-TrzPm = (2-(2'-triazolopyrimidine)-4,4,5,5-tetramethyl-4,5-dihydro-1 H -imidazol-1-oxy-3-oxide)) and six new transition metal complexes of this ligand, namely [M(hfac) 2 (NIT-2-TrzPm)]·CH 2 Cl 2 (M = Mn (1Mn) and Co (2Co)), [M(hfac) 2 ] 2 (NIT-2-TrzPm) (M = Mn (3Mn) and Co (4Co)), [Mn(NIT-2-TrzPm) 2 (MeOH) 2 ](ClO 4 ) 2 ·MeOH (5Mn), and [Co(NIT-2-TrzPm) 2 (MeOH) 2 ] 2 (ClO 4 ) 4 ·4MeOH (6Co) were prepared and characterized structurally and magnetically. These complexes can be selectively synthesized by controlling the reaction ratio of M(hfac) 2 ·2H 2 O to the radical ligand (for 1Mn to 4Co) or using metal perchlorates as the starting materials (for 5Mn and 6Co). Single crystal X-ray crystallographic analyses confirmed that 1Mn and 2Co are isostructural 3d-2p M II -radical complexes, in which the NIT-2-TrzPm radical acts as a terminal bidentate ligand chelating to one 3d ion, while 3Mn and 4Co are isostructural 3d-2p-3d M II -radical-M II complexes with the NIT-2-TrzPm radical acting as a bridging ligand between two 3d ions. For complexes 5Mn and 6Co, two NIT-2-TrzPm ligands from the equatorial positions coordinate with the metal center to form the 2p-3d-2p structures with the axial positions occupied by two methanol molecules. Magnetic analysis on the Mn II complexes revealed the existence of a strong antiferromagnetic interaction between the Mn II and the NIT radical spin, while weak ferromagnetic coupling for Mn⋯Mn and Rad⋯Rad in the Mn-NIT-Mn and Rad-Mn-Rad spins was confirmed. Interestingly, although the NIT-bridged complexes 3Mn and 4Co possess significantly different magnetic anisotropy, field-induced slow magnetic relaxation can be observed in both complexes, which was assigned to the phonon bottleneck effect for 3Mn and field-induced SMM behavior for 4Co. To the best of our knowledge, 3Mn is the first example of the NIT-bridged binuclear Mn II complex undergoing slow magnetic relaxation. |
