New, Multi‐Dimensional Cu(tn)‐[M(CN)₆]^n– Cyano‐Bridged, Bimetallic Coordination Materials (M = Fe^II, Co^III, Cr^III and tn = 1,3‐Diaminopropane)

Abstract

International audienceReaction of the [FeIII(CN)6]3– anion with [CuII(tn)(H2O)n]2+ (tn = 1,3-diaminopropane) affords the compounds [{CuII(tn)}2{FeII(CN)6}]·KCl·5H2O (1), [{CuII(tn)}2{FeII(CN)6}]·4H2O (2), and [{CuII(tnH)2(H2O)2}{FeII(CN)6}]·2H2O (3). Each iron center in 1 and 2 is linked to six copper(II) ions by six cyanide bridges, while each copper ion is linked to three equivalent iron(II) ions. Despite these resemblances, the two compounds present large structural differences caused by two different orientations of the Cu–NC–Fe bridges: compound 1 has a 2D structure which can be described as successions of “Cu4Fe3” defective cubane units, while compound 2 displays a 3D arrangement. Compound 3, in which only two trans-CN groups are bridging, displays a 1D structure. The tn ligand is chelating in 1, as is usually observed in several parent compounds, but is unexpectedly a bridging ligand in 2 and a terminal protonated tnH+ ligand in 3. Thus, the dimension of the three compounds seems to depend on the tn coordination modes. For the three iron compounds 1–3, the synthetic processes involve the spontaneous reduction of the paramagnetic [FeIII(CN)6]3– anion into the diamagnetic [FeII(CN)6]4– anion. In order to avoid such diamagnetic building blocks, the paramagnetic [Cr(CN)6]3– anion was used instead of the iron(III) analog, leading to [{CuII(tn)}3{CrIII(CN)6}2]·3H2O (4), which is the first 2D ferromagnet containing “-Cu–NC–Cr-” linkages. A similar study was performed using the diamagnetic [Co(CN)6]3– anion, leading to [{CuII(tn)}3{CoIII(CN)6}2]·3H2O (5), which is the Co analog of 4. The magnetic properties of compounds 1–3 and 5 show the presence of isolated CuII ions with weak ferromagnetic (1) or antiferromagnetic (2, 3, and 5) interactions. Compound 4 presents a long-range ferromagnetic ordering below Tc = 9.5 K

Structure and magnetism of heptanuclear complex constructed by the encapsulation of octacyanotungstate(IV) with copper(II) cations of tripodal ligands

“…In the IR spectra ( Fig. S1), complex 1 displays a band at the position of 2165 cm − 1 due to the bridging υ CN stretch of the heptanuclear cation, and a second band at 2112 cm − 1 assigned to the terminal υ CN stretch of the heptanuclear cation [8], which is consistent with the un-saturated coordination mode of [W(CN) 8 …”

Syntheses, Crystal Structures, and Magnetic Properties of Two Cyano‐Bridged CrIIIMII (M = Cu, Ni) Bimetallic Assemblies with Macrocyclic Ligands

“…This can be rationalized from the strict orthogonality of the magnetic orbitals of Cu II and Cr III ions 16. The decrease of χ M T below 26 K may result from the magnetic saturation effect 12l. Although the structure of 1 features a 1D alternate bimetallic chain, different Cu–N cyanide bond lengths produce the Cr–Cu–Cr ··· Cu ··· Cr–Cu–Cr ··· Cu ··· spin arrangement, and thus neither the 1D infinite chain model17a nor the uniform chain model12i are suitable for fitting the magnetic data.…”

Transformation of a Chiral Nanoporous Bimetallic Cyano-Bridged Framework Triggered by Dehydration/Rehydration

“…74 The existence of extremely long Cu-N bonds has been attributed to the coexistence of pseudoJahn-Teller elongation and electrostatic interactions. 75 Here the Jahn-Teller distortion indices, T, vary from 0.718 to 0.878 ( Table 2 Cu-NtC angles vary from 94.2(9) to 120.2(9)°( 47 The nonlinearity in the M′-OtC-fragment has been explained on the basis of two valence bond structures, 77 and since Cu-NtC-is an isoelectronic system, a similar explanation can be applied here, as a first approximation ( Figure S3 in the Supporting Information).…”

“…In this respect, cyanometalate complexes have been widely studied in many fields, mainly because of their rich and interesting structures and magnetic, catalytic, and adsorption properties. [45][46][47] They also have the potential to form dynamic porous materials as they can adapt to changes caused by external stimuli, either within the layer or in between the layers. Such unique and novel dynamic processes in single crystals of cyano-bridged frameworks have been described.…”