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A long-standing issue in topological insulator research has been to find a bulk single crystal material that provides a high-quality platform for characterizing topological surface states without interference from bulk electronic states. This material would ideally be a bulk insulator, have a surface state Dirac point energy well isolated from the bulk valence and conduction bands, display quantum oscillations from the surface state electrons and be growable as large, high-quality bulk single crystals. Here we show that this material obstacle is overcome by bulk crystals of lightly Sn-doped Bi1.1Sb0.9Te2S grown by the vertical Bridgman method. We characterize Sn-BSTS via angle-resolved photoemission spectroscopy, scanning tunnelling microscopy, transport studies, X-ray diffraction and Raman scattering. We present this material as a high-quality topological insulator that can be reliably grown as bulk single crystals and thus studied by many researchers interested in topological surface states., An ideal topological insulator possesses an insulating bulk and a unique conducting surface however such behaviour is typically inhibited by bulk conduction due to defects. Here, the authors show that Sn-doped Bi1.1Sb0.9Te2S grown by the vertical Bridgman technique might overcome this hurdle.

Using a mixed-ligand synthetic scheme, we create a family of quasi-two-dimensional antiferromagnets, namely, [Cu(HF$_2$)(pyz)$_2$]ClO$_4$ [pyz = pyrazine], [Cu$L_2$(pyz)$_2$](ClO$_4$)$_2$ [$L$ = pyO = pyridine-N-oxide and 4-phpyO = 4-phenylpyridine-N-oxide. These materials are shown to possess equivalent two-dimensional [Cu(pyz)$_2$]$^{2+}$ nearly square layers, but exhibit interlayer spacings that vary from 6.5713~\AA ~to 16.777~\AA, as dictated by the axial ligands. We present the structural and magnetic properties of this family as determined via x-ray diffraction, electron-spin resonance, pulsed- and quasistatic-field magnetometry and muon-spin rotation, and compare them to those of the prototypical two-dimensional magnetic polymer Cu(pyz)$_2$(ClO$_4$)$_2$. We find that, within the limits of the experimental error, the two-dimensional, {\it intralayer} exchange coupling in our family of materials remains largely unaffected by the axial ligand substitution, while the observed magnetic ordering temperature decreases slowly with increasing layer separation. Despite the structural motifs common to this family and Cu(pyz)$_2$(ClO$_4$)$_2$, the latter has significantly stronger two-dimensional exchange interactions and hence a higher ordering temperature. We discuss these results, as well as the mechanisms that might drive the long-range order in these materials, in terms of departures from the ideal $S=1/2$ two-dimensional square-lattice Heisenberg antiferromagnet. In particular, we find that both spin exchange anisotropy in the intralayer interaction and interlayer couplings (exchange, dipolar, or both) are needed to account for the observed ordering temperatures, with the intralayer anisotropy becoming more important as the layers are pulled further apart., Comment: 17 pages, 5 figures

As new uses for larger scale energy storage systems are realized, new chemistries that are less expensive or have higher energy density are needed. While lithium-ion systems have been well studied, the availability of new energy storage chemistries opens up the possibilities for more diverse strategies and uses. One potential path to achieving this goal is to explore chemistries where a multivalent ion such as Ca2+ or Mg2+ is the active species. Herein, we demonstrate this concept for a Ca-ion system utilizing manganese hexacyanoferrate (MFCN) as the cathode to intercalate Ca reversibly in a dry nonaqueous electrolyte. Through characterization via X-ray absorption near-edge spectroscopy, it is determined that only the manganese changes oxidation state during cycling with Ca. X-ray diffraction indicates the MFCN maintains its crystallinity during cycling, with only minor structural changes associated with expansion and contraction. Furthermore, we have demonstrated the first rechargeable Ca-ion battery uti...

The structure [MnIIITPP][Me2DCNQI] (TPP = tetraphenylporphinato; Me2DCNQI = 2,5-dimethyl-N,N′-dicyanoquinone-diimine) has been determined from X-ray powder diffraction data. The nonsolvated structure is composed of linear (1-D) chains of alternating [MnIIITPP]+ and μ-[Me2DCNQI]·− with intrachain Mn...Mn separations of 12.83 A, and a Mn-NDCNQI distance of 2.18 A. The dihedral angle between the mean Mn(N4)TPP and [Me2DCNQI]·− planes, and the Mn-(N-C)DCNQI angle are 84.18° and 143.6°, respectively. [MnIIITPP][Me2DCNQI] has a T c of 4.3 K from the 10 Hz χ″(T) data, 2-K coercivity of 5,600 Oe, and 6,300 emuOe/mol remnant magnetization that are reduced from that observed for related materials, and their inclusion extends the magnetostructural correlation between the intrachain coupling and both the dihedral angle between the mean Mn(N4)TPP and [TCNE]·− (TCNE = tetracyanoethylene) planes and Mn-(N-C)TCNE angles. This is in accord with the intrachain coupling arising from the overlap of the MnIII $$d_{z^2 }$$ -like singly occupied molecular orbital (SOMO) and the z component of the [TCNE]·− π* (πz*) SOMO, which increases with decreasing dihedral angle between the mean Mn(N4)TPP and [TCNE]·− planes and Mn-(N-C)TCNE angle.

The synthesis and characterization of a new family of magnetic materials based on the electron accepting cyanocarbon N,7,7-tricyanoquinomethanimine, TCQMI, its radical anion [TCQMI], and its σ-dimer, σ-[TCQMI]22−, are reported. [FeIIICp*2][TCQMI] (where Cp* is pentamethylcyclopentadienide) forms parallel chains of alternating [TCQMI]•− and [FeCp*2]•+ and magnetically orders at 3.4 K as a weak ferromagnet. M[TCQMI]2•zCH2Cl2 (M = V, Fe) are amorphous solids with [TCQMI]•− coordinated to metal centers through the nitrile groups. The Fe compound magnetically orders as a weak ferromagnet at ≈4 K, whereas the V compound shows no evidence of magnetic ordering. {[MnIIITPP]+}2[TCQMI]22− (TPP = tetraphenylporphyrin) results from the reaction of TCQMI with MnIITPP(py) due to the formation of the [TCQMI]22− σ-dimer in situ, and is a weak ferromagnet below 3.7 K. The lack of magnetic ordering in V[TCQMI]2•zCH2Cl2 is not currently understood, and is in strong contrast to V[TCNE]2•zCH2Cl2, which magnetically orders above room temperature.

The aqueous reaction of Mn(II) and NaCN leads to the isolation of the 3-D Prussian blue analogue (PBA) Na(2)Mn[Mn(CN)(6)]·2H(2)O (1·H(2)O), which under careful dehydration forms 1. 1·H(2)O is monoclinic [P2(1)/n, a = 10.66744(32) Å, b = 7.60223(23) Å, c = 7.40713(22) Å, β = 92.4379(28)°], while 1 is rhombohedral [R ̅3, a = 6.6166(2) Å, c = 19.2585(6) Å], and both structures are atypical for PBAs, which are typically face centered cubic. Most notably, the average ∠Mn-N-C angles are 165.3(3)° and 142.4(4)° for 1·H(2)O and 1, respectively, which are significantly reduced from linearity. This is attributed to the ionic nature of high-spin Mn(II) accommodating a reduced ∠Mn-N-C to minimize void space. Both 1 and 1·H(2)O magnetically order as ferrimagnets below their ordering temperature, T(c), of 58 and 30 K, respectively, as determined from the average of several independent methods. 1 and 1·H(2)O are hard magnets with 5 K coercive fields of 15,300 and 850 Oe, and remnant magnetizations of 9075 and 102 emu·Oe/mol, respectively. These data along with previous T(c)'s reported for related materials reveal that T(c) increases as the ∠Mn-N-C deviates further from linearity. Hence, the bent cyanide bridges play a crucial role in the superexchange mechanism by increasing the coupling via shorter Mn(II)···Mn(II) separations, and perhaps an enhanced overlap.

We demonstrate the effectiveness and accuracy of high resolution powder diffraction for determination of cocrystal structures through a double-blind study. Structures of 10 cocrystals of varying complexity were determined independently using single crystal and powder techniques. The two methodologies give identical molecular packing and hydrogen bond topology, and an rms difference in covalent bond lengths of 0.035 A. Powder techniques are clearly sufficient to establish a complete characterization of cocrystal geometry.

A modification to the usual least-squares analysis is implemented for the robust refinement of structural parameters from powder diffraction data in the presence of unmodeled impurities. This is accomplished in the programTOPAS-Academicby an iterative reweighting of the data as the model is refined. The method is tested and characterized using mixtures of known materials, acetaminophen and ibuprofen. The technique is also used to refine two previously unknown structures.

Three-dimensional Dirac semimetals (DSMs) are materials that have massless Dirac electrons and exhibit exotic physical properties. It has been suggested that structurally distorting a DSM can create a topological insulator but this has not yet been experimentally verified. Furthermore, Majorana fermions have been theoretically proposed to exist in materials that exhibit both superconductivity and topological surface states. Here we show that the cubic Laves phase ${\mathrm{Au}}_{2}\mathrm{Pb}$ has a bulk Dirac cone that is predicted to gap on cooling through a structural phase transition at 100 K. The low temperature phase can be assigned a ${\mathrm{Z}}_{2}=\ensuremath{-}1$ topological index, and this phase becomes superconducting below 1.2 K. These characteristics make ${\mathrm{Au}}_{2}\mathrm{Pb}$ a unique platform for studying the transition between bulk Dirac electrons and topological surface states as well as studying the interaction of superconductivity with topological surface states, combining many different properties of emergent materials---superconductivity, bulk Dirac electrons, and a topologically nontrivial ${\mathrm{Z}}_{2}$ invariant.

Elucidating the nature of the magnetic ground state of iron-based superconductors is of paramount importance in unveiling the mechanism behind their high temperature superconductivity. Until recently, it was thought that superconductivity emerges only from an orthorhombic antiferromagnetic stripe phase, which can in principle be described in terms of either localized or itinerant spins. However, we recently reported that tetragonal symmetry is restored inside the magnetically ordered state of a hole-doped BaFe2As2. This observation was interpreted as indirect evidence of a new double-Q magnetic structure, but alternative models of orbital order could not be ruled out. Here, we present Mossbauer data that show unambiguously that half of the iron sites in this tetragonal phase are non-magnetic, establishing conclusively the existence of a novel magnetic ground state with a non-uniform magnetization that is inconsistent with localized spins. We show that this state is naturally explained as the interference between two spin-density waves, demonstrating the itinerant character of the magnetism of these materials and the primary role played by magnetic over orbital degrees of freedom., Comment: 7 pages, 3 figures

By analysing X-ray pair distribution function data using a multivariate statistical approach, we isolate the cation solvation structure for monovalent (Li+/Na+/K+) and multivalent (Mg2+/Ca2+/Zn2+) electrolytes based on TFSI salts in diglyme. Parallel molecular dynamics simulations provide enhanced structural details. The data suggest that contact ion-pairs are a common feature in multivalent electrolytes. © the Partner Organisations 2014.

Tetrathiafulvalene-chloranil (TTF-CA) was synthesized by two methods, liquid assisted grinding (LAG) and vapor digestion (VD), which largely reduce the use of reaction solvents. The effects of the small quantities of LAG solvent and solvent vapors in VD toward the formation of a particular TTF-CA product polymorph were studied from both tetrathiafulvalene forms (orange and brown) as reactants. It was concluded that a high solvent polarity index favors the formation of the ionic black polymorph of TTF-CA vs the quasineutral green form, whereas the crystal structure and crystal habit of the orange tetrathiafulvalene polymorph also favors the formation of the black TTF-CA. The crystal structure of the black TTF-CA was determined from synchrotron X-ray powder diffraction (XRPD), and it consists of dimerized TTF+• and CA−• radical ions, in agreement with room temperature magnetic susceptibility measurements indicating the material is diamagnetic. FT-IR showed that the compound is a semiconductor with a small band gap of ∼0.198 eV and it remains ionic at low temperatures. The latter was confirmed by XRPD showing the black TTF-CA does not undergo a phase transition in the range 298−20 K. Band structure calculations are in good agreement with the measured band gap. Fil: Lapidus, Saul H.. Stony Brook University; Estados Unidos Fil: Naik, Amit. Thomas Nelson Community College; Estados Unidos Fil: Wixtrom, Alex. Christopher Newport University; Estados Unidos Fil: Massa, Nestor Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina Fil: Ta Phuoc, Vinh. UniversitéFrancois Rabelais Tours; Francia Fil: del Campo, Leire. Université d’Orleans; Francia Fil: Lebegue, Sebestien. Université de Lorraine; Francia Fil: Aygyayn, Jaynos G.. Université de Lorraine; Francia Fil: Abdel Fattah, Tarek. Christopher Newport University; Estados Unidos Fil: Pagola, Silvina. College of William and Mary; Estados Unidos

Systematic exploration of the molecular framework material Zn(CN)2 at high pressure has revealed several distinct series of transitions leading to five new phases: four crystalline and one amorphous. The structures of the new crystalline phases have been resolved through ab initio structural determination, combining charge flipping and direct space methods, based on synchrotron powder diffraction data. The specific transition activated under pressure depends principally on the pressure-transmitting fluid used. Without fluid or in large molecule fluids (e.g., isopropanol, ethanol, or fluorinert), the high-pressure behavior intrinsic to Zn(CN)2 is observed; the doubly interpenetrated diamondoid framework structure transforms to a distorted, orthorhombic polymorph, Zn(CN)2-II (Pbca) at ∼1.50–1.58 GPa with asymmetric displacement of the bridging CN ligand and reorientation of the Zn(C/N)4 tetrahedra. In small molecule fluids (e.g., water, methanol, methanol–ethanol–water), the nonporous interpenetrated Zn(CN)...

Systematic exploration of the molecular framework material Zn(CN)2 at high pressure has revealed several distinct series of transitions leading to five new phases: four crystalline and one amorphous. The structures of the new crystalline phases have been resolved through ab initio structural determination, combining charge flipping and direct space methods, based on synchrotron powder diffraction data. The specific transition activated under pressure depends principally on the pressure-transmitting fluid used. Without fluid or in large molecule fluids (e.g., isopropanol, ethanol, or fluorinert), the high-pressure behavior intrinsic to Zn(CN)2 is observed; the doubly interpenetrated diamondoid framework structure transforms to a distorted, orthorhombic polymorph, Zn(CN)2-II (Pbca) at ~1.50-1.58 GPa with asymmetric displacement of the bridging CN ligand and reorientation of the Zn(C/N)4 tetrahedra. In small molecule fluids (e.g., water, methanol, methanol-ethanol-water), the nonporous interpenetrated Zn(CN)2 framework can undergo reconstructive transitions to porous, non-interpenetrated polymorphs with different topologies: diamondoid (dia-Zn(CN)2, Fd3m, P(trans) ~ 1.2 GPa), londaleite (lon-Zn(CN)2, P6(3)/mmc, P(trans) ~ 0.9 GPa), and pyrite-like (pyr-Zn(CN)2, Pa3, P(trans) ~ 1.8 GPa). Remarkably, these pressure-induced transitions are associated with near 2-fold volume expansions. While an increase in volume with pressure is counterintuitive, the resulting new phases contain large fluid-filled pores, such that the combined solid + fluid volume is reduced and the inefficiencies in space filling by the interpenetrated parent phase are eliminated. That both dia-Zn(CN)2 and lon-Zn(CN)2 phases were retained upon release to ambient pressure demonstrates the potential for application of hydrostatic pressures to interpenetrated framework systems as a novel means to generate new porous materials.

CuF(2)(H(2)O)(2)(3-chloropyridine) possesses a five-coordinate Cu(2+) center with a slightly distorted trigonal bypyramidal coordination geometry. Strong intermolecular F···H-O hydrogen bonds enable the formation of 2D layers and provide the primary magnetic exchange path that leads to the stabilization of long-range antiferromagnetic (AFM) order below T(N) = 2.1 K.

Linear chain thiocyanate complexes of M(NCS)(2)(OCMe(2))(2) (M = Fe, Mn, Cr) composition have been prepared and structurally, chemically, and magnetically characterized. Fe(NCS)(2)(OCMe(2))(2) exhibits metamagnetic-like behavior, and orders as an antiferromagnet at 6 K. The Mn and Cr compounds are antiferromagnets with T(c) of 30 and 50 K, respectively, with J/k(B) = -3.5 (-2.4 cm(-1)) and -9.9 K (-6.9 cm(-1)), respectively, when fit to one-dimensional (1-D) Fisher chain model (H = -2JS(i)·S(j)). Co(NCS)(2) was prepared by a new synthetic route, and powder diffraction was used to determine its structure to be a two-dimensional (2-D) layer with μ(N,S,S)-NCS motif, and it is an antiferromagnet (T(c) = 22 K; θ = -33 K for T25 K). M(NCS)(2)(OCMe(2))(2) (M = Fe, Mn) and Co(NCS)(2) react with (NBu(4))(TCNE) in dichloromethane to form M(TCNE)[C(4)(CN)(8)](1/2), and in acetone to form M[C(4)(CN)(8)](OCMe(2))(2) (M = Fe, Mn, Co). These materials possess μ(4)-[C(4)(CN)(8)](2-) that form 2-D layered structural motifs, which exhibit weak antiferromagnetic coupling. Co(TCNE)[C(4)(CN)(8)](1/2) behaves as a paramagnet with strong antiferromagnetic coupling (θ = -50 K).

A tetragonal polymorph of [Ni(HF(2))(pyz)(2)]PF(6) (designated β) is isomorphic to its SbF(6)-congener at 295 K and features linear Ni-FHF-Ni pillars. Enhancements in the spin exchange (J(FHF) = 7.7 K), Néel temperature (T(N) = 7 K), and critical field (B(c) = 24 T) were found relative to monoclinic α-PF(6). DFT reveals that the HF(2)(-) bridges are significantly better mediators of magnetic exchange than pyz (J(pyz)), where J(FHF) ≈ 3J(pyz), thus leading to quasi-1D behavior. Spin density resides on all atoms of the HF(2)(-) bridge whereas N-donor atoms of the pyz ring bear most of the density.

Mn(CN)2 is prepared by thermolysis of either (NEt4)Mn3(CN)7 or (NEt4)2Mn3(CN)8 (380 °C, 1 h, 90% yield) and characterized by high-resolution synchrotron powder XRD and magnetic susceptibility measurements.

Na2Mn[Mn(CN)6]·2H2O (I) is prepared from aqueous solutions of Mn(OAc)2 and NaCN (80% yield).

A further example of using a covalent-bond-forming reaction to alter supramolecular assembly by modification of hydrogen-bonding possibilities is presented. This concept was introduced by Lemmerer, Bernstein & Kahlenberg [CrystEngComm(2011),13, 55–59]. The title structure, C9H11N3O·C7H6O4, which consists of a reacted niazid molecule,viz.N′-(propan-2-ylidene)nicotinohydrazide, and 2,4-dihydroxybenzoic acid, was solved from powder diffraction data using simulated annealing. The results further demonstrate the relevance and utility of powder diffraction as an analytical tool in the study of cocrystals and their hydrogen-bond interactions.

Grinding of a one-dimensional (1-D) ladder coordination polymer (CP), [Zn(μ-CH(3)CO(2))(CF(3)CO(2))bpe] (1), and a hydrogen-bonded 1-D CP, [Cd(CH(3)CO(2))(2)bpe(H(2)O)] (2), with KBr resulted in the exchange of carboxylate by bromide ions and the formation of 1-D zigzag and 2-D CPs respectively.

Square-planar S = 1/2 Ag(II) ions in polymeric Ag(nic)(2) are linked by bridging nic monoanions to yield 2D corrugated sheets. Long-range magnetic order occurs below T(N) = 11.8(2) K due to interlayer couplings that are estimated to be about 30 times weaker than the intralayer exchange interaction.

The M-[TCNE] (M = 3d metal; TCNE = tetracyanoethylene) system is one of the most interesting classes of molecule-based magnets, exhibiting a plethora of compositions and structures (inorganic polymer chains, 2D layers, 3D networks, and amorphous solids) with a wide range of magnetic ordering temperatures (up to 400 K). A systematic study of vibrational (both infrared and, for the first time, Raman) properties of the family of new TCNE-based magnets of M(II)(TCNE) (NCMe)(2)[SbF(6)] [M = Mn, Fe, Ni] composition is discussed in conjunction with their magnetic behavior and newly reso-lved crystal structures. The vibrational properties of the isolated TCNE(●-) anion in the paramagnetic Bu(4)N [TCNE(●-)] salt and recently characterized 2D layered magnet Fe(II)(TCNE)(NCMe)(2)[FeCl(4)] are also reported for comparison. Additionally, a linear correlation between ν(C=C) (a(g)) frequency of the TCNE ligand and its formal charge Z (the spin density on the π* orbital), Z = [1571 - ν(C=C) (a(g))]/154.5 [e], is presented. It is shown that monitoring Z by Raman spectroscopy is of great use in providing information that allows understanding the peculiarity of the superexchange interaction in M-[TCNE] magnets and establishing the structure-magnetic properties correlations in this class of magnetic material.

A co-crystal of two polymorphic active pharmaceutical ingredients (APIs), first reported and patented in 1937, has been prepared and thoroughly characterised, including crystal structure analysis. The existence of four crystal forms of one of the APIs, the sedative and hypnotic active pharmaceutical ingredient 3,3-diethyl-2,4(1H,3H)-pyridinedione, pyrithyldione (PYR), and of three crystal forms of the co-crystal-forming second API, the non-steroidal anti-inflammatory drug 1,2-dihydro-1,5-dimethyl-4-(1-methylethyl)-2-phenyl-3H-pyrazol-3-one, propyphenazone (PROP), has been reported previously, but they have only been partly characterised. For both compounds, none of the metastable forms exist at room temperature. DSC, hot-stage microscopy, X-ray diffraction and powder synchrotron X-ray diffraction were employed to characterise the polymorphic forms and to determine the crystal structures of forms I-III of PYR and forms I and II of PROP.

We develop a probabilistic method for analyzing global features of a cellular network under intrinsic statistical fluctuations, which is important when there are finite numbers of molecules. By making a self-consistent mean field approximation of splitting the variables in order to reduce the large number of degrees of freedom, which is reasonable for a not very strongly interacting network, we discovered that the underlying energy landscape of the mitogen-activated protein kinases (MAPKs) signal transduction network (with experimentally measured or inferred parameters such as chemical reaction rate coefficients in the network) is funneled toward a global minimum characterized by the nonequilibrium steady-state fixed point of the system at the end of the signal transduction process. For this system, we also show that the energy landscape is robust against intrinsic fluctuations and random perturbation to the inherent chemical reaction rates. The ratio of the slope versus the roughness of the energy landscape becomes a quantitative measure of robustness and stability of the network. Furthermore, we quantify the dissipation cost of this nonequilibrium system through entropy production, caused by the nonequilibrium flux in the system. We found that a lower dissipation cost corresponds to a more robust network. This least dissipation property might provide a design principle for robust and functional networks. Finally, we find the possibility of bistable and oscillatory-like solutions, which are important for cell fate decisions, upon perturbations. The method described here can be used in a variety of biological networks.

The structural, spectroscopic and magnetic properties of the two-dimensional (2D) molecule-based magnets of [Mn(II)(TCNE)(NCMe)2]X (X = PF6, AsF6, SbF6; TCNE = tetracyanoethylene, NCMe = acetonitrile) composition are reported. It is shown that the alteration of the interlayer distance by increasing the anion size has little effect on the critical magnetic ordering temperature, Tc, suggesting that it depends predominantly on the intra-plane magnetic exchange. The observed field-induced irreversibility in static magnetization, a slow decay of isothermal remanence below Tc, and the dynamic susceptibility data are in accord with a re-entrant spin-glass nature of the ground state of all materials. In contrast to the isostructural Fe-based magnets, in which strong magnetocrystalline anisotropy facilitates the finite temperature magnetic ordering with the magnetization easy axis perpendicular to the μ4-TCNE(•-) plane, in the studied Mn-based magnets the easy axis is canted away from the normal direction, due to a small magnetocrystalline anisotropy. The two magnetic transitions observed on cooling are assigned to the ferrimagnetic long-range ordering of the normal magnetization component followed by the re-entrant spin-glass type transition resulting from a random freezing of the in-plane magnetization component.

Solid state techniques involving pressure and temperature have been used to synthesize the fluoride member of the CuX(2)(pyrazine) (X = F, Cl, Br) family of coordination polymers that cannot be crystallized by solution methods. CuF(2)(pyrazine) exhibits unique trans doubly-bridged Cu-F(2)-Cu chains that provide an opportunity to quantify magnetic superexchange in an isostructural Cu-X(2)-Cu series.

Mn(II)(TCNE)I(OH(2)) was isolated from the reaction of tetracyanoethylene (TCNE) and MnI(2)(THF)(3), and has a 2-D structure possessing an unusual, asymmetric bonded μ(4)-[TCNE]˙(-). Direct antiferromagnetic coupling between the S = 5/2 Mn(II) and S = 1/2 [TCNE]˙(-) leads to magnetic ordering as a canted antiferrimagnet at a T(c) of 171 K.