Magnetic characteristics of new cyano-bridged two-dimensional honeycomb-like bimetallic assemblies containing Ni(II)-N[triple bond]C-Cr(III) or Ni(II)-N[triple bond]C-Cr(I) linkages.

Three cyano-bridged bimetallic assemblies, [NiL(1)](3)[Cr(CN)(6)](2).7H(2)O (1), [NiL(2)](3)[Cr(CN)(6)](2).9H(2)O (2), and [NiL(2)](3)[Cr(CN)(5)(NO)](2).9H(2)O (3) (L(1) = 3,10-dimethyl-1,3,5,8,10,12-hexaazacycloctadecane and L(2) = 3,10-diethyl-1,3,5,8,10,12-hexaazacycloctadecane), have been prepared and characterized structurally and magnetically. Complex 1 crystallizes in the monoclinic space group of C2/c with a = 25.929 A, b = 15.442(3) A, c = 19.553(4) A, beta = 106.21(3) degrees, and Z = 4, while 2 and 3 are in the trigonal space group P3 with a = b = 14.919(2) A, c = 9.5246(19) A, gamma = 120 degrees, and Z = 1 for 2 and a = b = 14.863(2) A, c = 9.3134(19) A, gamma = 120 degrees, and Z = 1 for 3. The structures of 1-3 are similar and consist of cyano-bridged two-dimensional (2D) honeycomb-like neutral Ni(3)Cr(2) layers. In each complex, [Cr(CN)(6)](3-) or [Cr(CN)(5)(NO)](3-) coordinates to three trans-[Ni(macrocycle)](2+) groups using three fac-CN(-) ligands, providing a 2D layered network. The NO group in [Cr(CN)(5)(NO)](3-) remains monodentate. Magnetic studies show the existence of a short-range ferromagnetic interaction in all of the complexes. Complexes 1 and 2 exhibit long-range antiferromagnetic ordering at 13.0 and 11.9 K, respectively, and a metamagnetic transition with critical field of ca. 1.6 kOe for 1 and 1.5 kOe for 2 at 1.8 K. Complex 3 exhibits long-range ferromagnetic ordering below 4.3 K.