Synthesis and characterization of two self-assembled [Cu 6 Gd 3 ] and [Cu 5 Dy 2 ] complexes exhibiting the magnetocaloric effect, slow relaxation of magnetization, and anticancer activity.

Two new paths for coordination driven self-assembly reactions under the binding support of 2-((1-hydroxy-2-methylpropan-2-ylimino)methyl)-6-methoxyphenol (H ₂ L) have been discovered from the reactions of Cu(ClO ₄ ) ₂ ·6H ₂ O, NEt ₃ and GdCl ₃ /DyCl ₃ ·6H ₂ O in MeOH/CHCl ₃ (2 : 1) medium. A similar synthetic protocol is useful to provide two different types of self-aggregated molecular clusters [Cu ₆ Gd ₃ (L) ₃ (HL) ₃ (μ ₃ -Cl) ₃ (μ ₃ -OH) ₆ (OH) ₂ ]ClO ₄ ·4H ₂ O (1) and [Cu ₅ Dy ₂ (L) ₂ (HL) ₂ (μ-Cl) ₂ (μ ₃ -OH) ₄ (ClO ₄ ) ₂ (H ₂ O) ₆ ](ClO ₄ ) ₂ ·2NHEt ₃ Cl·21H ₂ O (2). The adopted reaction procedure established the importance of the HO ^- and Cl ^- ions in the mineral-like growth of the complexes, derived from solvents and metal ion salts. In the case of complex 1, one Gd ^III center has been trapped at the central position of the core upheld by six μ ₃ -OH and three μ ₃ -Cl groups, whereas for complex 2 one Cu ^II center was trapped using four μ ₃ -hydroxo and two μ-chlorido groups. The magnetothermal behavior of 1 has been examined for a magnetocaloric effect of -Δ S _m = 11.3 J kg ^-1 K ^-1 at 2 K for Δ H = 7 T, whereas the magnetic susceptibility measurements of 2 showed slow magnetic relaxation with U _eff = 15.8 K and τ ₀ = 9.8 × 10 ^-7 s in zero external dc field. Cancer cell growth inhibition studies proved the potential of both the complexes with interestingly high activity for the Cu ₆ Gd ₃ complex against human lung cancer cells. Both complexes 1 and 2 also exhibited DNA and human serum albumin (HSA) binding abilities in relation to the involved binding sites and thermodynamics.