Crystal structure of tetra-aqua-[2-(pyridin-2-yl)-1H-imidazole-κ(2) N (2),N (3)]iron(II) sulfate

In the title compound, [Fe(C8H7N3)(H2O)4]SO4, the central Fe(II) ion is octa-hedrally coordinated by two N atoms from the bidentate 2-(pyridin-2-yl)-1H-imidazole ligand and by four O atoms of the aqua ligands. The largest deviation from the ideal octa-hedral geometry is reflected by the small N-Fe-N bite angle of 76.0 (1)°. The Fe-N coordination bonds have markedly different lengths [2.1361 (17) and 2.243 (2) Å], with the shorter one to the pyrimidine N atom. The four Fe-O coordination bond lengths vary from 2.1191 (18) to 2.1340 (17) Å. In the crystal, the cations and anions are arranged by means of medium-strength O-H⋯O hydrogen bonds into layers parallel to the ab plane. Neighbouring layers further inter-connect by N-H⋯O hydrogen bonds involving the imidazole fragment as donor group to one sulfate O atom as an acceptor. The resulting three-dimensional network is consolidated by C-H⋯O, C-H⋯π and π-π inter-actions.

Antiferromagnetic or canted antiferromagnetic orderings of Fe(III) d spins of FeX4- ions in BEDT-TTFVO(S).FeX4 (X = Cl, Br) [BEDT-TTFVO(S) = bis(ethylenedithio)tetrathiafulvalenoquinone(-thioquinone)-1,3-dithiolemethide]

By the reaction of new donor molecules, bis(ethylenedithio)tetrathiafulvalenoquinone(-thioquinone)-1,3-dithiolemethides [BEDT-TTFVO (1) and BEDT-TTFVS (2)] with FeX3 (X = Cl, Br) in CS2/CH3CN, 1:1 salts of 1 or 2 with an FeX4- ion (1.FeX4 and 2.FeX4) were obtained as black needle crystals. Their crystal structures are very similar to each other, in which the donor molecules are strongly dimerized and the dimers construct a one-dimensional uniform chain along the a axis, while the FeX4- ions are located at an open space surrounded by the neighboring donor molecules and also construct a one-dimensional uniform chain along the a axis. There are close contacts between the donor molecules and the FeX4- ions and significant differences in the contact distances among the four salts. All of the salts are semiconductors with room-temperature electrical conductivities of 10-4-10-2 S cm-1. The Fe(III) d spins of the FeX4- ions are subject to dominant ferromagnetic interaction through the participation of one of the singlet pi spins to form a short-range ferromagnetic d-spin chain. Such neighboring chains interact antiferromagnetically with each other through the singlet pi spins and are ordered at 1.0, 2.4, and 0.8 K for 1.FeCl4, 1.FeBr4, and 2.FeCl4, respectively. On the other hand, the antiferromagnetic ordering occurred with some canted angle at 1.9 K to leave a small magnetization for 2.FeBr4.

Ferromagnetic Anomaly Associated with the Antiferromagnetic Transitions in (Donor)[Ni(mnt)2]-Type Charge-Transfer Salts

Three newly prepared [Ni(mnt)2] complexes, (HMTTF)[Ni(mnt)2], (ChSTF)[Ni(mnt)2], and (DBTTF)2[Ni(mnt)2], are reported (DBTTF = dibenzotetrathiafulvalene, ChSTF = 2,3-cyclohexylenedithio-1,4-dithia-5,8-diselanafulvalene, HMTTF = bis(trimethylene)-tetrathiafulvalene, and mnt = maleonitrile dithiolate). The former two compounds have usual DA-type (D = donor, A = acceptor) mixed stacks, whereas the DBTTF complex has DDDDAA-type 6-fold columns. These compounds are electrical insulators, but the HMTTF and ChSTF complexes exhibit chiT minima at 16 and 55 K, respectively, followed by chiT peaks at 8 and 16 K. Below these temperatures the ESR signal disappears, indicating antiferromagnetic transitions. The origin of the ferromagnetic interaction is explained either from the difference of the g values between the donor and the anion or from the intrinsic ferromagnetic interaction of the [Ni(mnt)2] anions.

Bulk Spontaneous Magnetization in the New Radical Cation Salt TM-TTF[Cr(NCS)4(isoquinoline)2] (TM-TTF = Tetramethyltetrathiafulvalene)

A new organic-inorganic hybrid salt [TM-TTF][Cr(NCS)(4)(isoquinoline)(2)] (1) (TM-TTF = Tetramethyltetrathiafulvalene) has been synthesized. Compound 1 crystallizes in the triclinic P space group with a = 8.269(1), b = 10.211(2), and c = 11.176(2) A, alpha = 89.244(9), beta = 88.114(6), and gamma = 74.277(7) degrees, V = 907.6(3) A(3), and Z = 1. The crystal structure was resolved in the temperature range between 223 and 123 K, showing that changes in the crystal structure at low temperature result in stronger interactions between anions and cations. The packing of 1 consists of mixed anion-cation layers in the bc plane containing S.S and pi-pi anion-cation interactions, the layers being connected by very short S.S contacts between anions and cations. Magnetic measurements in a small external field show bulk spontaneous magnetization with a T(c) of 6.6 K consistent with the presence of weakly coupled ferrimagnetic order in compound 1. The EPR measurements also demonstrate the interaction between the d and pi electrons and the presence of an internal magnetic field brought about by the magnetic ordering.

First radical cation salt of paramagnetic transition metal complex containing TTF as ligand, [Cu(II)(hfac)2(TTF-py)2](PF6) x 2CH2Cl2 (hfac = hexafluoroacetylacetonate and TTF-py = 4-(2-tetrathiafulvalenyl-ethenyl)pyridine)

The preparation, X-ray crystal structure, EPR data, and magnetic measurement of [Cu(II)(hfac)(2)(TTF-py)(2)](PF(6)).2CH(2)Cl(2), a novel material where the conducting and the localized spin systems are covalently linked through conjugated bridges, are reported. The partial oxidation of the TTF-type organic donor ligand yielded the first radical cation salt of a paramagnetic transition metal complex. Moreover, this compound shows a mixed valence state at the unimolecular level, and additionally, the arrangement of the molecules in the crystal structure revealed the presence of isolated mixed valence TTF dimers.

New tetrathiapentalene-derived charge transfer salts with paramagnetic transition metal complex anion: kappa-(EDDH-TTP)(3)[Cr(phen)(NCS)(4)] x 2CH(2)Cl(2) and kappa(21)-(BDH-TTP)(5)[Cr(phen)(NCS)(4)](2) x 2CH(2)Cl(2)

The preparation, crystal structures, and optical and magnetic properties of two new charge-transfer salts kappa-(EDDH-TTP)(3)[Cr(phen)(NCS)(4)] x 2CH(2)Cl(2) (1) and kappa(21)-(BDH-TTP)(5)[Cr(phen)(NCS)(4)](2) x 2CH(2)Cl(2) (2), where phen = 1,10- phenanthroline, EDDH-TTP = 2-(4,5-ethylenedithio-1,3-dithiol-2-ylidene)-5-(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene, and BDH-TTP = 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene, are reported. Crystal data: (1) monoclinic P2(1)/a, a = 25.0752(5) A, b = 10.6732(3) A, c = 28.1601(6) A, beta = 95.195(2) degrees, Z = 4, R = 0.0585 for 6741 independent reflections with I > 3 sigma(I); (2) monoclinic P2(1)/a, a = 23.8275(4) A, b = 9.1015 (2) A, c = 27.0420(1) A, beta = 99.9297(8) degrees, Z = 4, R = 0.0530 for 4565 independent reflections with I > 2 sigma(I). The crystal structures for both compounds consist of alternating organic and inorganic layers. The organic layer in compound 1 is characterized as kappa-type, while the organic layer in 2 resembles the kappa-type but it contains orthogonal dimers and monomers, and it is therefore called kappa(21). Compound 1 shows metallic behavior down to low temperature. Salt 2 shows semiconductive behavior, which is explained as the result of either charge ordering owing to the kappa(21)-type structure or Peierls distortion due to the one-dimensional electronic nature. However, weak metallic behavior could be observed at 10 kbar above ca. 150 K and at 15 kbar above 170 K. The magnetic susceptibilities for both compounds show Curie-Weiss behavior, showing that the exchange interactions between the magnetic anions are weak. Polarized reflectance spectra of single crystals were measured over the spectral range from 650 to 7000 cm(-1). Moreover, absorption and diffusion reflectance spectra of powdered crystals dispersed in KBr (from 400 to 7000 cm(-1)) were recorded. Vibrational and electronic features are discussed.

Bulk weak ferromagnet in ferrimagnetic chains of organic-inorganic hybrid materials based on BDH-TTP and paramagnetic thiocyanato complex anions: (BDH-TTP)[M(isoq)(2)(NCS)(4)], M = Cr(III), Fe(III)

The preparation, X-ray crystal structures, and magnetic properties of two new isostructural charge transfer salts, (BDH-TTP)M(isoq)(2)(NCS)(4) (M = Cr(III) (1), Fe(III) (2), BDH-TTP = 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene, isoq = isoquinoline), are reported. Crystal data for 1: monoclinic, space group C2/c (#15), a = 16.1363(9) A, b = 19.0874(12) A, c = 12.5075(6) A, beta = 95.70(4) degrees, V = 3833.2(4) A(3), Z = 4, R = 0.0516 for 2844 reflections with I > 2 sigma(I); for 2: monoclinic, C2/c (#15), a = 16.1938(8) A, b = 19.1117(11) A, c = 12.5100(10) A, beta = 94.265(3) degrees, V = 3861.0(4) A(3), Z = 4, R = 0.0479 for 2969 reflections with I > 2 sigma(I). The crystal structure consists of zigzag mixed organic and inorganic layers, and each layer is formed by mixed columns of BDH-TTP radical cations and paramagnetic metal complex anions. Short intermolecular atomic contacts between donor and anion are observed within the column in the c-direction. The two compounds have weak room-temperature electrical conductivities. ESR measurements show a single signal without separating the donor and anion spins, suggesting a pi interaction between the d and pi electrons. For both compounds ferrimagnetic interactions are observed between the nonequivalent donor and anion spins. These materials exhibit bulk canted weak ferromagnetism below 7.6 K for both 1 and 2.