Pentanuclear spirocyclic Ni 4 Ln derivatives: field induced slow magnetic relaxation in the dysprosium and erbium analogues

Abstract

Five pentanuclear heterometallic isostructural complexes, [Ni 4 Ln(L) 2 (LH) 2 (CH 3 CN) 3 Cl]� xH 2 O�yCH 3 OH (Ln= Y III ( 1 ), Gd III ( 2 ), Tb III ( 3 ), Dy III ( 4 ) and Er III ( 5 )) [for 1 and 2 , x = 2, y = 1; for 3 , x = 6, y = 2; for 4 , x = 5, y = 1; for 5 , x = 2, y = 2)] were prepared by the reaction of (E)?2(hydroxymethyl)?6?(((2?hydroxyphenyl) imino) methyl)?4?methylphenol (LH 3 ) with LnCl 3 �6H 2 O and Ni(OAc) 2 �4H 2 O in the presence of Tetrabutylammonium hydroxide (TBA?OH) base. The structural characterization reveals compounds 1 ? 5 contains spirocyclic pentanuclear core [Ni 4 Ln(� 3 ?O) 4 (� 2 ?O) 4 ] 3+ where two triangular motifs [Ni 2 Ln(� 3 ?O) 2 (� 2 ?O) 2 ] 3+ that are fused together through a common vertex of Ln(III) ion. The central Ln(III) ion forms an eight?coordinated distorted triangular dodecahedron geometry while the Ni(II) ions forms a distorted octahedron geometry. Comprehensive dc magnetic studies reveal antiferromagnetic exchange interaction present between the Ni(II) centrs. The ac susceptibility measurement revels that dysprosium and erbium analogue shows field induced slow magnetic relaxation with an anisotropic barrier (U eff ) of 25.12 cm ?1 and 22.13 cm ?1 respectively.