Synthesis, Structure, and Zero-Field SMM Behavior of Homometallic Dy2, Dy4, and Dy6 Complexes

Pawan Kumar; Abinash Swain; Joydev Acharya; Yanling Li; Vierandra Kumar; Gopalan Rajaraman; Enrique Colacio; Vadapalli Chandrasekhar

doi:10.1021/acs.inorgchem.2c01041

Synthesis, Structure, and Zero-Field SMM Behavior of Homometallic Dy2, Dy4, and Dy6 Complexes

Inorg Chem. 2022 Aug 1;61(30):11600-11621. doi: 10.1021/acs.inorgchem.2c01041. Epub 2022 Jul 18.

Authors

Pawan Kumar¹, Abinash Swain², Joydev Acharya¹, Yanling Li³, Vierandra Kumar¹, Gopalan Rajaraman², Enrique Colacio⁴, Vadapalli Chandrasekhar^{1

5}

Affiliations

¹ Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India.
² Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
³ Sorbonne Universit Institut Parisien de Chimie Molculaire, CNRS UMR 8232, 4 place Jussieu, 75252 Paris cedex 5, France.
⁴ Department of Inorganic Chemistry, University of Granada, 18071 Granada, Spain.
⁵ Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500 107, India.

PMID: 35849822
DOI: 10.1021/acs.inorgchem.2c01041

Abstract

The synthesis, structure, and magnetic properties of three Dy^III complexes 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 Dy^III salt, 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 (U_eff) of magnetization reversal equal to 87(1) K and a relaxation time of τ₀ = 6.4(3) × 10^-9 s. Under an applied magnetic field of 0.1 T, these parameters change to U_eff = 101(3) K, τ₀ = 2.5(1) × 10^-9 s. Complex 2 shows zero-field SMM behavior with U_eff = 31(2) K, τ₀ = 4.2(1) × 10^-7 s or τ₀₁ = 2(1) × 10^-7 s, U_eff1 = 37(8) K, τ₀₂ = 5(6) × 10^-5 s, and U_eff2 = 8(4) by considering two Orbach relaxation processes, while 3, also a zero-field SMM, shows a double relaxation of magnetization [U_eff1 = 62.4(3) K, τ₀₁ = 4.6(3) × 10^-8 s, and U_eff1 = 2(1) K, τ₀₂ = 4.6(2) × 10^-5 s]. 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 m_J = ±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 Dy^III centers 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.