Pendant Macrocyclic Metallic Building Blocks for the Design of Cyano-Bridged Heterometallic Complexes with 1D Chain and 2D Layer Structures

A series of cyano-bridged Ni(II)−Cr(I/III) complexes have been synthesized by the reactions of hexaazacyclic NiII complexes with [Cr(CN)6]3- or [Cr(CN)5(NO)]3-. Using the tetravalent NiII complex [Ni(H2L2)]4+ (L2 = 3,10-bis(2-aminoethyl)-1,3,6,8,10,12-hexaazacyclotetradecane), one-dimensional chainlike complexes were produced and subject to magnetic studies, affording the intermetallic magnetic exchange constants of J 1 = +0.23 cm-1 and J 2 = +8.4 cm-1 for the complex [Ni(H2L2)][Cr(CN)5(NO)]ClO4·5H2O (1) and of J = +5.9 cm-1 for the complex [Ni(H2L2)]4[Cr(CN)6]5OH·15H2O (2). X-ray diffraction analysis shows that complex 1 has a zigzag chain structure, whereas complex 2 consists of a branched chain structure. Complex 2 exhibits antiferromagnetic ordering at 8.0 K (T N). When an octahedral NiII complex cis-[NiL3(en)]2+ (en = 1,2-ethylenediamine, L3 = 3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane) was used for the synthesis, the common 2D honeycomb-layered complex [NiL3]3[Cr(CN)5(NO)]2·8H2O (3) was obtained, which has a T N value of 3.3 K. Below T N, a metamagnetic behavior was observed in complexes 2 and 3.