Syntheses, crystal structures and magnetic properties of four cyano-bridged bimetallic alternating chain complexes based on [CrIII(salen)(CN)2]− and [CrIII(bipy)(CN)4]− building blocks

Abstract

Four cyano-bridged bimetallic alternating chain complexes, [Mn(salen)]₃[Cr(salen)(CN)₂]₃·4H₂O (1) (salen = N,N′-ethylenebis(salicylideneiminato)dianion), [Mn(salpn)]₃[Cr(salen)(CN)₂]₃·4H₂O (2) (salpn = N,N′-1,2-propylenebis(salicylideneiminato)dianion), [Mn(salen)][Cr(bipy)(CN)₄] (3) and [Mn(salpn)][Cr(bipy)(CN)₄] (4), have been synthesized and characterized. The single crystal X-ray analysis reveals the 1-D alternating chain structure for all the four complexes. Noteworthily, complexes 1 and 2 exhibit crystallographic disordering of the Mn^III and Cr^III, as well as the bridged C and N atoms from cyano groups, due to the difficulty in identifying these atoms using the X-ray diffraction technique. All the four assemblies show significant interchain π–π interactions and thus, further extend to high dimensional supramolecular networks. The magnetic measurement reveals the expected dominant intrachain antiferromagnetic interactions in complexes 1–4. However, the weak intrachain antiparallely aligned spins seem to be overcome by external fields, which lead to the higher magnetization values than expected.