Field-Induced Single-Ion Magnet Behaviour in Two New Cobalt(II) Coordination Polymers with 2,4,6-Tris(4-pyridyl)-1,3,5-triazine

Abstract

Abstract:We herein reported the syntheses, crystal structures, and magnetic properties of a two-dimensional coordination polymer {[Co II (TPT) ]} n (2) based on the 2,4,6-Tris(4-pyridyl)-1,3,5-triazine (TPT) ligand. Structure analyses showed that complex 1 had a cationic hexagonal framework structure, while 2 was a neutral zig-zag chain structure with different distorted octahedral coordination environments. Magnetic measurements revealed that both complexes exhibit large easy-plane magnetic anisotropy with the zero-field splitting parameter D = 47.7 and 62.1 cm −1 for 1 and 2, respectively. This magnetic anisotropy leads to the field-induced slow magnetic relaxation behaviour. However, their magnetic dynamics are quite different; while complex 1 experienced a dominating thermally activated Orbach relaxation at the whole measured temperature region, 2 exhibited multiple relaxation pathways involving direct, Raman, and quantum tunneling (QTM) processes at low temperatures and Orbach relaxation at high temperatures. The present complexes enlarge the family of framework-based single-ion magnets (SIMs) and highlight the significance of the structural dimensionality to the final magnetic properties.

Field-Induced Slow Magnetic Relaxation and Anion/Solvent Dependent Proton Conduction in Cobalt(II) Coordination Polymers

“…The 2D coordination polymer, [Co­(L) 2 (SCN) 2 ·2CH 3 CN·2DMF] n (where L = 4′-(4-methoxyphenyl)-4,2′:6′,4″-terpyridine]) represents a particularly interesting example where the extended ligand-spacer prevents any magnetic interaction among the metal nodes thereby leading to isolated single-ion magnetic centers . Similar field-induced SIM behavior has been also explored by other research groups in 1D, − 2D, − and 3D − Co­(II) based coordination polymers where the metal centers remain magnetically isolated.…”

“…As mentioned earlier, Co II based MOFs with larger separation between the metal centers have gained interest recently due to their SIM-like behavior. − To study the slow relaxation of the magnetization dynamics, temperature dependent ac susceptibility measurements were done with 3.5 Oe ac field in the 2–10 K temperature range. At zero applied dc field the CPs show no peaks in the out of phase ac data, which can be due to fast resonant zero-field quantum tunneling of the magnetization (QTM) through the thermal relaxation barrier between the degenerate ground ±3/2 levels, which dominates other relaxation pathways in the absence of any applied field.…”

Field-Induced Single Molecule Magnetic Behavior of Mononuclear Cobalt(II) Schiff Base Complex Derived from 5-Bromo Vanillin

“…Single-molecule and single-ion magnets (SMMs, SIMs), realized in transition metal complexes showing slow magnetic relaxation, have gained much attention in molecular magnetism. These types of compounds are applicable in various technological areas such as switches, sensors, displays, low-temperature magnetic refrigerators, high-density information storage devices and quantum computing [1][2][3][4][5][6]. They show characteristic magnetic properties, such as slow relaxation of magnetization due to magnetic bistability of two ± MS levels at a molecular level [7,8].…”

Syntheses and Structural Investigations of Penta-Coordinated Co(II) Complexes with Bis-Pyrazolo-S-Triazine Pincer Ligands, and Evaluation of Their Antimicrobial and Antioxidant Activities

“…In this aspect, the triazine class [10][11][12][13][14][15][16][17][18][19] and their metal complexes [20][21][22][23][24] have been received a great deal of attention as they demonstrate wide range of therapeutic activities and a great array of biological applications including antimicrobial, antituberculosis, anticancer, antiviral, antibacterial, antifungal, anti-HIV, and antimalarial activities [9,25,26]. In addition, a number of metal complexes based on triazine derivatives have been studied for their interesting magnetic [27][28][29] and catalytic [30][31][32][33][34][35][36][37][38][39][40][41] applications. antibacterial, antifungal, anti-HIV, and antimalarial activities [9,25,26].…”

“…antibacterial, antifungal, anti-HIV, and antimalarial activities [9,25,26]. In ad number of metal complexes based on triazine derivatives have been studied interesting magnetic [27][28][29] and catalytic [30][31][32][33][34][35][36][37][38][39][40][41] applications.…”