Polynuclear Ni(II)/Co(II)/Mn(II) Complexes Based on Terphenyl–Tetracarboxylic Acid Ligand: Crystal Structures and Research of Magnetic Properties

Abstract

By the solvothermal reactions of a [1,1':3',1''-terphenyl]-3,3'',5,5''-tetracar -boxylic acid (H 4 tpta) with transition metal ions, three novel polymeric complexes, namely,(3) have been isolated. The heterometallic clusters of these polymeric complexes are dimeric and tetrameric, respectively. 1 is comprised of dimeric paddle wheel Ni(II) units to generate a 2D structure.In complexes 2 and 3, metal ions form tetrameric units that extend via all dimensions to give 3D structures with the Schläfli symbol of (4 3 )(4 3 )(4 6 ·6 18 ·8 4 ) and (4 6 )(4 12 ·5 3 ·6 9 ·7 4 ), respectively. The results of variable temperature magnetization measurements (χ M T-T and χ M −1 -T) show that complexes 1 and 2 display unusual ferromagnetic coupling via the M-O-C-O-M bridges, while complex 3 shows predominantly antiferromagnetic behavior. The M(H) curve of 1 does not saturate until the highest field of 80 kOe, indicating the significant magnetic anisotropy in this complex system, whereas the final saturation value of 2.79 Nβ for 2 manifests the existence of typically paramagnetic property and the absence of long-range magnetic ordering. The dynamic magnetization experiments have been also carried out to further explore the magnetic behaviors of 1 and 2. There are no frequency dependences in the dynamic magnetization experiments, suggesting the absence of slow magnetic relaxation of these two complexes.

Crystal structure of tetraqua-bis(4-(hydroxymethyl)benzoato-κO)nickel(II), C16H22O10Ni

“…It can be also self-assembled into a multinuclear secondary structural unit with metal ions to further construct coordination polymer networks of various structures. The carboxyl-and carboxylate rich coordination mode and diverse coordination chemistry are favored by coordination chemists and crystal engineering scholars [4,5]. And the carboxyl oxygen atoms can form hydrogen bonds with a solvent molecule such as water, thereby assembling a supramolecular structure to form a supramolecular compound having a special property [6].…”

Single-Crystal-to-Single-Crystal Breathing and Guest Exchange in CoII Metal–Organic Frameworks

“…Previous studies on the carboxylate bridged dinuclear metal complexes show that the syn – syn bridging pattern triggers antiferromagnetic exchange interactions between the metal ions, whereas anti – anti and syn – anti bridging modes often lead to weak ferromagnetic or antiferromagnetic couplings. − Moreover, it is also well-known that the metal···metal distances as well the coordination geometry around the metal centers affect the extent of magnetic coupling between the adjacent metal atoms. In this present case, from the structural analysis of 1 and 1a (Figure ), it is observed that two syn – syn carboxylate bridges are present between two neighboring magnetically interacting Co II centers for both 1 and 1a .…”

Post-Synthetic Functionalization of Ni-MOF by Eu3+ Ions: Luminescent Probe for Aspartic Acid and Magnetic Property

“…The χ M T value at 300 K (2.4 cm 3 K mol −1 ) exceeds the desired value (2.0 cm 3 K mol −1 ) slightly for two magnetically isolated Ni(II) ions (Figure 9), reflecting the existence of orbital contribution arising from the high-spin octahedral Ni(II) ions. 53,54 Upon cooling, χ M T declines slowly to reach a rock bottom of 2.2 cm 3 K mol −1 at 35 K, suggesting an antiferromagnetic interaction in the range of 35−300 K. The further temperature decrease results in χ M T rising to the maximum value of 2.43 cm 3 K mol −1 at 6.0 K, indicating a ferromagnetic character. Finally, below 6.0 K, the χ M T decreased again, caused by the zero-field splitting of Ni(II) and/or some kinds of intramolecular antiferromagnetic interactions.…”