Unique nanoscale {Cu36IILn24III} (Ln = Dy and Gd) metallo-rings

Two unprecedented 3d-4f hexagonal metallo-rings {Ln(24)Cu(36)} (Ln = Dy and Gd) with a diagonal dimension of about 4.6 nm were facilely synthesized by self-assembly of Cu-II, Ln(III) nitrates and benzoate in the presence of triethylamine. Magnetic studies show slow relaxation behaviour for the dysprosium analogue and a large magnetocaloric effect (MCE) for the gadolinium analogue.