Four cyano-bridged 1D bimetallic polymers have been prepared by using the paramagnetic building block trans-[Ru(acac)(2)(CN)(2)](-) (Hacac=acetylacetone): {[{Ni(tren)}{Ru(acac)(2)(CN)(2)}][ClO(4)].CH(3)OH}(n) (1) (tren=tris(2-aminoethyl)amine), {[{Ni(cyclen)}{Ru(acac)(2)(CN)(2)}][ClO(4)].CH(3)OH}(n) (2) (cyclen=1,4,7,10-tetraazacyclododecane), {[{Fe(salen)}{Ru(acac)(2)(CN)(2)}]}(n) (3) (salen(2-)=N,N'-bis(salicylidene)-o-ethyldiamine dianion) and [{Mn(5,5'-Me(2)salen)}(2){Ru(acac)(2)(CN)(2)}][Ru(acac)(2)(CN)(2)].2CH(3)OH (4) (5,5'-Me(2)salen=N,N'-bis(5,5'-dimethylsalicylidene)-o-ethylenediimine). Compounds 1 and 2 are 1D, zigzagged NiRu chains that exhibit ferromagnetic coupling between Ni(II) and Ru(III) ions through cyano bridges with J=+1.92 cm(-1), zJ'=-1.37 cm(-1), g=2.20 for 1 and J=+0.85 cm(-1), zJ'=-0.16 cm(-1), g=2.24 for 2. Compound 3 has a 1D linear chain structure that exhibits intrachain ferromagnetic coupling (J=+0.62 cm(-1), zJ'=-0.09 cm(-1), g=2.08), but antiferromagnetic coupling occurs between FeRu chains, leading to metamagnetic behavior with T(N)=2.6 K. In compound 4, two Mn(III) ions are coordinated to trans-[Ru(acac)(2)(CN)(2)](-) to form trinuclear Mn(2)Ru units, which are linked together by pi-pi stacking and weak Mn...O* interactions to form a 1D chain. Compound 4 shows slow magnetic relaxation below 3.0 K with phi=0.25, characteristic of superparamagnetic behavior. The Mn(III)...Ru(III) coupling constant (through cyano bridges) and the Mn(III)...Mn(III) coupling constant (between the trimers) are +0.87 and +0.24 cm(-1), respectively. Compound 4 is a novel single-chain magnet built from Mn(2)Ru trimers through noncovalent interactions. Density functional theory (DFT) combined with the broken symmetry state method was used to calculate the molecular magnetic orbitals and the magnetic exchange interactions between Ru(III) and M (M=Ni(II), Fe(III), and Mn(III)) ions. To explain the somewhat unexpected ferromagnetic coupling between low-spin Ru(III) and high-spin Fe(III) and Mn(III) ions in compounds 3 and 4, respectively, it is proposed that apart from the relative symmetries, the relative energies of the magnetic orbitals may also be important in determining the overall magnetic coupling in these bimetallic assemblies.
In the crystal structure, an eight-coordinated calcium center is connected to adjacent seven-coordinated calcium ions by a pair of µ-aqua bridging ligands, leading to the formation of a chain, which is linked via benzenetricarboxylate ligands to neighboring chains to furnish a two-dimensional layer structure. Layers are connected into a three-dimensional structure facilitated by hydrogen bonding interactions. Copyright 2004 John Wiley & Sons, Ltd.KEYWORDS: 1,3,5-benzenetricarboxylic acid; calcium; coordination polymer; crystal structure COMMENTConstruction of inorganic-organic hybrid coordination polymers with multidentate carboxylic acids is of current Figure 1. ORTEP plot showing the coordinating environment of Ca atoms and btc ligand. Selected geometric parameters: Ca1-O1 2.308(1), Ca1-O7 2.422(1), Ca1-O8 2.730(1), Ca1-O9 2.457(1), Ca1-O10 2.407(1), Ca1-O11 2.349(1), Ca1-O5A 2.380(1), Ca2-O8 2.508(1), Ca2-O12 2.367(1), Ca2-O3D 2.528(1), Ca2-O4D 2.583(1)Å. All O-Ca-O angles are in the range of 49.88(3) to 180• . Symmetry codes: A = −x, −y, −z; B = x, y − 1, z; C = −x + 1/2, −y + 3/2, −z; D = x, y + 1, z; E = −x + 1/2, −y + 1/2, −z. 1 -3 Most documented 1,3,5-benzenetricarboxylicacid-based (H 3 btc) coordination polymers have been constructed using transition metals.4,5 Herein, we report the crystal structure of a two-dimensional calcium-btc coordination polymer, [Ca 3 (btc) 2 (H 2 O) 12 ] n (1). In the crystal structure, there are two types of calcium ion center; Fig. 1. The Ca1 atom is seven-coordinated by two carboxylate oxygen atoms and five water molecules, and the Ca2 atom, which sits on a center of inversion, is eight-coordinated by four carboxylate oxygen atoms and four water molecules. Two Ca1 atoms are linked to a Ca2 atom via a pair of µ-aqua bridges, forming a linear trinuclear metal aggregate, that is further linked by six btc ligands at two mutually plumb directions to furnish a two-dimensional layer; Fig. 2. All btc ligands link three trinuclear Ca aggregates employing all three carboxylate groups. Finally, all coordinating water molecules, as well as the carboxylic groups, engage in hydrogen bonding interactions that serve to connect the coordination layers into a three-dimensional network structure. EXPERIMENTALA mixture of H 3 btc (20 mg) and triethylamine (50 mg) was dissolved in isopropanol (5 ml), layered on a 5 ml aqua solution of CaAc 2 (20 mg) in a long tube that was sealed with a wooden stopper. Colorless block crystals deposited after 1 month. Intensity data were collected at 298 K on a Bruker AXS SMART CCD diffractometer using a colorless crystal of size 0.22 × 0.23 × 0.25 mm 3 . C 18 H 30 Ca 3 O 24 , M = 750.66, monoclinic, C2/c, a = 19.337(4), b = 11.491(2), c =
A series of cyano-bridged Ln(III)Ru(III)2 coordination polymers, Ph4P{Ln(NO3)2[Ru(acac)2(CN)2]2} [Ln = Tb (1), Dy (2), Er (3), Gd (4); Hacac = acetylacetone] have been synthesized by the reaction of Ln(NO3)3 with trans-Ph4P[Ru(acac)2(CN)2] in methanol. X-ray crystallographic determination reveals that these compounds are isostructural and have a wavy (4,4) layer structure with the Ln3+ ions bridged by trans-[Ru(acac)2(CN)2]-. Magnetic studies shows that the magnetic coupling between the Ln(III) and Ru(III) ions through the cyano bridges in 1-4 is negligibly weak.
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