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Synthesis, Structure, and Zero-Field SMM Behavior of Homometallic Dy2, Dy4, and Dy6 Complexes
Journal
Inorganic Chemistry
ISSN
00201669
Date Issued
2022-08-01
Author(s)
Kumar, Pawan
Swain, Abinash
Acharya, Joydev
Li, Yanling
Kumar, Vierandra
Rajaraman, Gopalan
Colacio, Enrique
Chandrasekhar, Vadapalli
Abstract
The synthesis, structure, and magnetic properties of three DyIIIcomplexes of different nuclearity, [Dy2(H2L)2(NO3)] [NO3]·2H2O·CH3OH (1), [Dy4(HL)2(piv)4(OH)2] (2), and [Dy6(H2L)3(μ3-OH)(μ3-CO3)3(CH3OH)4(H2O)8] 5Cl·3H2O (3) [(H4L) = 6-((bis(2-hydroxyethyl)amino)-N′-(2-hydroxybenzylidene)picolinohydrazide)], are described. This variety of complexes with the same ligand could be obtained by playing with the metal-to-ligand molar ratio, the type of DyIIIsalt, the kind of base, and the presence/absence of coligand. 1 is a dinuclear complex, while 2 is a tetranuclear assembly with a butterfly-shaped topology. 3 is a homometallic hexanuclear complex that exhibits a propeller-shaped topology. Interestingly, in this complex 3, three atmospheric carbon dioxide molecules are trapped in the form of carbonate ions, which assist in holding the hexanuclear complex together. All of the complexes reveal a slow relaxation of magnetization even in zero applied field. Complex 1 is a zero-field SMM with an effective energy barrier (Ueff) of magnetization reversal equal to 87(1) K and a relaxation time of τ0= 6.4(3) × 10-9s. Under an applied magnetic field of 0.1 T, these parameters change to Ueff= 101(3) K, τ0= 2.5(1) × 10-9s. Complex 2 shows zero-field SMM behavior with Ueff= 31(2) K, τ0= 4.2(1) × 10-7s or τ01= 2(1) × 10-7s, Ueff1= 37(8) K, τ02= 5(6) × 10-5s, and Ueff2= 8(4) by considering two Orbach relaxation processes, while 3, also a zero-field SMM, shows a double relaxation of magnetization [Ueff1= 62.4(3) K, τ01= 4.6(3) × 10-8s, and Ueff1= 2(1) K, τ02= 4.6(2) × 10-5s]. The ab initio calculations indicated that in these complexes, the Kramer's ground doublet is characterized by an axial g-tensor with the prevalence of the mJ= ±15/2 component, as well as that due to the weak magnetic coupling between the metal centers, the magnetic relaxation, which is dominated by the single DyIIIcenters rather than by the exchange-coupled states, takes place via Raman/Orbach or TA-QTM. Moreover, theoretical calculations support a toroidal magnetic state for complex 2.
Volume
61
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