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.