Constructing Robust Channel Structures by Packing Metallacalixarenes: Reversible Single-Crystal-to-Single-Crystal Dehydration

The self-assembly process involving the dianion of trimesic acid (Htrim2−) and {Cu(tmen)}2+ templating cations (tmen = N,N,N′,N′-tetramethylethylenediamine) affords a new metallacalixarene, [Cu4(tmen)4(Htrim)4]·nH2O. The packing of the cyclic molecules in the crystal generates channels that are filled by water molecules. The dehydration−rehydration process of the crystals was found to be reversible

New heterometallic coordination polymers constructed from 3d–3d′ binuclear nodes

Heterobinuclear [CuIIMnII] and [CuIICoII] cationic complexes can efficiently act as nodes for designing coordination polymers. The crystal structures of two binuclear precursors, [LCuCo(NO3)2] (1) and [LCuMn(NO3)2] (2), have been solved (L2− is the dianion of the Schiff base resulting from the 2 : 1 condensation of 3-methoxysalicyladehyde with 1,3-propanediamine). The nitrato ligands, coordinated to CoII and, respectively, the MnII ions from the precursors, are easily replaced by exo-dentate ligands, resulting in 1-D coordination polymers: 1∞[L(H2O)CuCo(oxy-bbz)]·CH3CN·C2H5OH (3), 1∞[L(H2O)CuCo(2,5-dhtp)]·CH3CN (5) and ∞[L(H2O)CuMn(ox)]·3H2O (6) (oxy-bbz2− = the dianion of 4,4′-oxy-bis(benzoic) acid; 2,5-dhtp2− = the dianion of 2,5-dihydroxy-terephthalic acid; ox2− = the dianion of the oxalic acid). In the case of the [CuMn] node, the interaction with oxy-bbz2− affords a binuclear complex, [LCuMn(oxy-bbz)(H2O)2] (4)

Conducting mixed-valence salt of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with the paramagnetic heteroleptic anion [CrIII(oxalate)2(2,2′-bipyridine)](-)

The synthesis and crystal structure of the first tetrathiafulvalene (TTF) based radical cation salt containing the heteroleptic paramagnetic anion [CrIII(2,2′-bipy)(C2O4)2]− are reported. In the salt formulated as α′-(BEDT-TTF)2[Cr(C2O4)2(2,2′-bipy)]·CHCl2CH2Cl according to the single-crystal X-ray structure, the BEDT-TTF (bis(ethylenedithio)tetrathiafulvalene) donors are in a mixed valence state and form two types of uniform chains within organic layers. Two overlap modes are observed in these chains, which are canted with respect to the stacking direction, leading to a peculiar α′ packing mode. The anions organize in supramolecular chains sustained by π–π interactions between the bipyridine units. The magnetic behavior of the compound follows a Curie–Weiss law, with a magnetic contribution arising from both cationic and anionic counterparts. Single-crystal electrical transport measurements are in agreement with a semiconductor behavior and have been correlated with extended Hückel tight-binding calculations

Slow Relaxation of Magnetization in an Isostructural Series of Zinc–Lanthanide Complexes: An Integrated EPR and AC Susceptibility Study

We report the synthesis, structure, and spectroscopic and dynamic magnetic properties of a series of heterodinuclear complexes, [ZnLn(LH4 )2 ](NO3 )3 ⋅6 H2 O (Ln=Nd, Tb, Dy, Ho, Er, and Yb), with the singly deprotonated form of a new compartmentalized Schiff-base ligand, LH5 . The Ln(III) ions in these systems show a distorted square-antiprism geometry with an LnO8 coordination sphere. EPR spectroscopy and DC magnetic studies have shown that the anisotropic nature of the complexes is far more complicated than predicted on the basis of a simple electrostatic model. Among the investigated systems, only the Dy(III) derivative showed single-ion magnet behavior, in zero and an applied magnetic field, both in pure polycrystalline samples and in a series of polycrystalline samples with different degrees of dilution at the single-crystal level in the isostructural Y(III) derivative. The rich dynamics observed as functions of frequency, field, and temperature reveals that multiple relaxation mechanisms are at play, resulting in a barrier of 189 cm(-1) , which is among the highest reported for a dinuclear Zn-Dy system. Analysis of the dynamic behavior as a function of dilution degree further evidenced the persistence of non-negligible intermolecular interactions, even at the lowest concentration of 1 %

Tris(1,10-phenanthrolin-1-ium) hexa­cyanidoferrate(III) ethanol monosolvate trihydrate

The asymmetric unit of the title complex, (C12H9N2)3[Fe(CN)6]·C2H5OH·3H2O, consists of two half [Fe(CN)6]3− anions located on inversion centers, three 1,10-phenanthrolin-1-ium cations, [Hphen]+, an ethanol and three water solvent mol­ecules. The average Fe—C and C—N bond lengths are 1.942 (6) and 1.154 (3) Å, respectively, while the Fe—C—N angles deviate slightly from linearity with values ranging from 177.8 (2) to 179.7 (2)°. The FeIII atoms adopt a distorted octa­hedral geometry. All the species are linked through O—H⋯N, N—H⋯O and O—H⋯O hydrogen-bonding inter­actions, resulting in a three-dimensional supra­molecular network

Poly[[diaqua­hexa-μ-cyanido-cerium(III)ferrate(III)] dihydrate]

In the structure of the title complex, {[CeFe(CN)6(H2O)2]·2H2O}n, the CeIII and FeIII atoms exhibit square anti­prismatic [CeN6(H2O)2] (site symmetry m2m) and octahedral [FeC6] (site symmetry 2/m) coordination geometries, respectively. The metal atoms are linked alternately through the cyanide groups, forming a three-dimensional framework in which the {Ce2Fe2(CN)4} puckered square unit is the basic building block. The crystal packing is enforced by O—H⋯O and O—H⋯N hydrogen bonds, including the uncoordinated water molecule which is located on a mirror plane

Magnetic properties and spin dynamics in single molecule paramagnets Cu6Fe and Cu6Co

The magnetic properties and the spin dynamics of two molecular magnets have been investigated by magnetization and d.c. susceptibility measurements, Electron Paramagnetic Resonance (EPR) and proton Nuclear Magnetic Resonance (NMR) over a wide range of temperature (1.6-300K) at applied magnetic fields, H=0.5 and 1.5 Tesla. The two molecular magnets consist of CuII(saldmen)(H2O)}6{FeIII(CN)6}](ClO4)38H2O in short Cu6Fe and the analog compound with cobalt, Cu6Co. It is found that in Cu6Fe whose magnetic core is constituted by six Cu2+ ions and one Fe3+ ion all with s=1/2, a weak ferromagnetic interaction between Cu2+ moments through the central Fe3+ ion with J = 0.14 K is present, while in Cu6Co the Co3+ ion is diamagnetic and the weak interaction is antiferromagnetic with J = -1.12 K. The NMR spectra show the presence of non equivalent groups of protons with a measurable contact hyperfine interaction consistent with a small admixture of s-wave function with the d-function of the magnetic ion. The NMR relaxation results are explained in terms of a single ion (Cu2+, Fe3+, Co3+) uncorrelated spin dynamics with an almost temperature independent correlation time due to the weak magnetic exchange interaction. We conclude that the two molecular magnets studied here behave as single molecule paramagnets with a very weak intramolecular interaction, almost of the order of the dipolar intermolecular interaction. Thus they represent a new class of molecular magnets which differ from the single molecule magnets investigated up to now, where the intramolecular interaction is much larger than the intermolecular one

Cyanomethylene-bis(phosphonate) as ditopical ligand: stepwise formation of a 2-D heterometallic Fe(III)-Ag(I) coordination network

A new heteroditopic ligand, cyanomethylene-bis(5,5-dimethyl-2-oxo-1,3,2 lambda(5)-dioxa-phosphorinane) 1 (bphosCN), has been reacted with Fe(ClO4)(3) to afford the mononuclear complex Fe(bphosCN)(3) 2 which crystallized in the cubic system, space group Pa (3) over bar. The iron center, chelated by the oxygen atoms of the ligand, shows an almost perfect octahedral geometry, with the CN groups disposed at 120 degrees each other. Further reaction with AgClO4 provided the heterometallic coordination polymer (infinity)(2) {[(Fe (bphosCN)(3))(3)Ag-3(H2O)(2)]center dot(ClO4)(3)} 3 as the unique crystalline polymorph, in the monoclinic space group P21/a. The targeted 2D honeycomb type structure has been achieved through an interplay between coordinative CN-Ag bonds and CN center dot center dot center dot H2O bonds. The magnetic measurements demonstrate the existence of isolated paramagnetic Fe(III) centers in both complexes