ABSTRACT
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.
ABSTRACT
The design, synthesis, and structural and magnetic properties of the two new bimetallic complexes [Sm(DMF)(4)(H(2)O)(2)Cr(CN)(6)].H(2)O and [Sm(DMF)(2)(H(2)O)(3)Cr(CN)(6)].H(2)O (DMF = N,N-dimethylformamide) are presented. [Sm(DMF)(4)(H(2)O)(2)Cr(CN)(6)].H(2)O was prepared by the reaction between Sm(3+) and [Cr(CN)(6)](3-) in a methanol-DMF solution, while [Sm(DMF)(2)(H(2)O)(3)Cr(CN)(6)].H(2)O was prepared by the reaction between Sm(3+), DMF, and [Cr(CN)(6)](3-) in the molar ratio of 1:2:1 in H(2)O. [Sm(DMF)(4)(H(2)O)(2)Cr(CN)(6)].H(2)O crystallizes in the monoclinic space group of P2(1)/c with a = 13.161(3) A, b = 12.928(3) A, c = 19.174(4) A, beta = 109.82(3) degrees, and Z = 4, while [Sm(DMF)(2)(H(2)O)(3)Cr(CN)(6)].H(2)O is in the triclinic space group P1 with a = 7.7535(1) A, b = 9.4307(3) A, c = 16.2905(5) A, alpha = 94.1590(14) degrees, beta = 100.0597(18) degrees, gamma = 100.9154(18) degrees, and Z = 2. The structure of [Sm(DMF)(4)(H(2)O)(2)Cr(CN)(6)].H(2)O possesses a cyano-bridged one-dimensional (1D) zigzag chain structure with alternating Sm(DMF)(4)(H(2)O)(2) and Cr(CN)(6) moieties. [Sm(DMF)(2)(H(2)O)(3)Cr(CN)(6)].H(2)O consists of cyano-bridged neutral brick wall-like layers in which each [Cr(CN)(6)](3-) unit uses three cyanide groups in the meridional arrangement to connect with three [Sm(DMF)(2)(H(2)O)(3)](3+) units. Each [Sm(DMF)(2)(H(2)O)(3)](3+) unit, in turn, links three [Cr(CN)(6)](3-), generating a flat brick wall-like structure. Magnetic studies on [Sm(DMF)(2)(H(2)O)(3)Cr(CN)(6)].H(2)O showed a magnetic-phase transition temperature below 4.2 K and a coercive field of 100 Oe at 1.85 K, while no long-range magnetic ordering was observed in the 1D complex [Sm(DMF)(4)(H(2)O)(2)Cr(CN)(6)].H(2)O.
ABSTRACT
Two bimetallic assemblies, [Ni(tn)(2)](2)[Cr(CN)(5)(NO)]OH.H(2)O (1) and [Ni(tn)(2)](2)[Co(CN)(6)]NO(3).2H(2)O (2) (tn = 1,3-diaminopropane), have been prepared and structurally and magnetically characterized. Crystal data for 1 (2): space group P1 (P1), a = 8.698(3) (8.937(2)) A, b = 10.001(2) (9.863(1)) A, c = 10.158(2) (10.064(1)) A, alpha = 87.40(2) (86.064(10)) degrees, beta = 65.10(2) (65.489(10)) degrees, gamma = 81.63(2) (81.572(12)) degrees and Z = 1 (1). Both structures consist of two-dimensional grid-like polycations containing Ni-N triple bond C-M linkages (M = Cr or Co) and counteranions (OH, NO(3)). Magnetic studies of 1 showed that the complex displays a metamagnetic behavior originating from intralayer ferromagnetic and interlayer antiferromagnetic interactions. Long-range antiferromagnetic ordering was observed at T(N) = 3.3 K. Complex 2 exhibits intramolecular ferromagnetic interactions through the diamagnetic N triple bond C-Co-N triple bond C bridges, owing to superexchange involving the empty d(sigma) orbital of the diamagnetic Co(III) ion.
ABSTRACT
2,2'-Biphenanthroline (2,2'-biphen) formed from 1,10-phenanthroline when a new two-dimensional layered vanadium oxide metal coordination complex, [(2,2'-biphen)Co]V3O8.5, which contains novel 4,8,10-net sheets, was hydrothermally synthesized.
