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RECENTLY THERE HAS BEEN GROWING interest in the preparation and characterization of molecular/organic polymer-based materials that exhibit cooperative magnetic interactions (that is, ferro- and ferrimagnetic behavior) [1-6]. The electron-transfer salt [...]

The reaction of MnII(O2CMe)2 and NaCN or LiCN in water forms a light green insoluble material. Structural solution and Rietveld refinement of high‐resolution synchrotron powder diffraction data for this unprecedented, complicated compound of previously unknown composition revealed a new alkali‐free ordered structural motif with [MnII4(μ3‐OH)4]4+ cubes and octahedral [MnII(CN)6]4− ions interconnected in 3D by MnII‐N≡C‐MnII linkages. The composition is {[MnII(OH2)3][MnII(OH2)]3}(μ3‐OH)4][MnII(μ‐CN)2(CN)4]⋅H2O=[MnII4(μ3‐OH)4(OH2)6][MnII(μ‐CN)2(CN)4]⋅H2O, which is further simplified to [Mn4(OH)4][Mn(CN)6](OH2)7 (1). 1 has four high‐spin (S=5/2) MnII sites that are antiferromagnetically coupled within the cube and are antiferromagnetically coupled to six low‐spin (S=1/2) octahedral [MnII(CN)6]4− ions. Above 40 K the magnetic susceptibility, χ(T), can be fitted to the Curie–Weiss expression, χ ∝(T−θ)−1, with θ=−13.4 K, indicative of significant antiferromagnetic coupling and 1 orders as an antiferromagnet at Tc=7.8 K. Structural solution and Rietveld refinement of high‐resolution diffraction data for an unprecedented, complicated compound of previously unknown composition revealed a new alkali‐free ordered structural motif with [MnII4(μ3‐OH)4]4+ cubes and octahedral [MnII(CN)6]4− ions interconnected in 3D. [ABSTRACT FROM AUTHOR]

Mn(TCNE)[C4(CN)8]1/2 (TCNE=tetracyanoethylene) and [NEt4]MnII3(CN)7 have extended layers with nearest neighbor intralayer S=5/2 and S=1/2 spin sites that couple antiferromagnetically forming ferrimagnetic layers. These layers are uniformly connected via diamagnetic (nonmagnetic) bridging μ4-[(C4(CN)8]2− (8.77 Å) or μ-CN (5.48 Å) ligands, respectively, that antiferromagnetic couple the ferrimagnetic layers resulting in an antiferromagnet. The Jinter/kB is −1.0 and −1.8 K ( H=− JSi⋅Sj) for Mn(TCNE)[C4(CN)8]1/2 and [NEt4]MnII3(CN)7, respectively. Albeit intrinsically multilayered, these antiferromagnets have the same motif as that for artificial/synthetic antiferromagnets that exhibit giant magnetoresistance (GMR) and are commercially used in many magnetic memory applications. [ABSTRACT FROM AUTHOR]

An overview of recent progress in the optical control of magnetic properties of molecule-based magnets is given. In particular, we focus on the properties of cobalt iron Prussian blue magnets, in which we experimentally demonstrated coexistence of photoinduced magnetism and cluster glass-type magnetic order. These results will be contrasted with the recently discovered reversible photoinduced magnetic effects in the high-T C molecule-based magnet Mn(TCNE) x · y (CH 2 Cl 2 ). [ABSTRACT FROM AUTHOR]

Synchrotron-based infrared and Raman spectroscopies were brought together with diamond anvil cell techniques and an analysis of the magnetic properties to investigate the pressure-induced high → low spin transition in [Ru2(O2CMe)4]3[Cr(CN)6]. The extended nature of the diruthenium wave function combined with coupling to chromium-related local lattice distortions changes the relative energies of the π* and δ* orbitals and drives the high → low spin transition on the mixed-valence diruthenium complex. This is a rare example of an externally controlled metamagnetic transition in which both spin-orbit and spin-lattice interactions contribute to the mechanism. [ABSTRACT FROM AUTHOR]

The pressure dependence of the magnetic properties of ferrimagnetic MaII (TCNE)I(OH2) up to 14.05 kbar and MnII(TCNE)3/2(I3)1/2 zTHF up to 14.32 kbar were studied. For MnII(TCNE)-I increases to the magnetic ordering temperature, T... bifurcation temperature, T..., coercive field, H..., and remnant magnetization, M..., were evident in the highpressure region. The T..., T... H..., M... and M (5 T) reversibly increased from ambient pressure values of 169 K, 169 K, 690 Oe, 620 emuOe/mol, and 13800 emuOe/mol to 257 K, 261 K, 1460 Oe, 2300 emuOe/mol, and 17100 emuOe/mol at 14.05 kbar, respectively. For Mn11(TCNE)3/2(I3) zTHF, the Tc and Tb were nearly coincident and increased linearly from 173 and 173 K, respectively, at ambient pressure to 273 and 272 K, respectively, at 14.32 kbar. Thus, the Tc increased at an average rate of 6.25 and 7.18 K/kbar for MnII(TCNE)I(OH2) and MnII(TCNE)3/2(I3)1/2 zTHF, respectively. For Mn(TCNE)1/2(I3)1/2 zTHF remnant magnetization and saturation magnetization did not significantly change with applied pressure. The H... exhibited a linear increase from ambient pressure to 5.00 kbar, reaching 860 Oe, but only achieving 880 Oe at 14.32 kbar. [ABSTRACT FROM AUTHOR]

Abstract: The 57Fe Mössbauer spectroscopy of mononuclear [Fe(II)(isoxazole)6](ClO4)2 has been studied to reveal the thermal spin crossover of Fe(II) between low-spin (S=0) and high-spin (S=2) states. Temperature-dependent spin transition curves have been constructed with the least-square fitted data obtained from the Mössbauer spectra measured at various temperatures between 84 and 270K during a cooling and heating cycle. This compound exhibits an unusual temperature-dependent spin transition behaviour with T C(↓)=223 and T C(↑)=213K occurring in the reverse order in comparison to those observed in SQUID observation and many other spin transition compounds. The compound has three high-spin Fe(II) sites at the highest temperature of study of which two undergo spin transitions. The compound seems to undergo a structural phase transition around the spin transition temperature, which plays a significant role in the spin crossover behaviour as well as the magnetic properties of the compound at temperatures below T C. The present study reveals an increase in high-spin fraction upon heating in the temperature range below T C, and an explanation is provided. [Copyright &y& Elsevier]

The bis-phenoxo-bridged dinuclear iron(III) compound Fe 2 (BBPA) 2 F 2 (H 2 BBPA =  N,N -bis(2-hydroxybenzyl)- N -(2-pyridylmethyl)amine) was structurally and magnetically characterized. It has distorted octahedral iron(III) centers with each iron(III) site having two cis -Fe(BBPA)F fragments that are bridged by two μ-phenoxo oxygen atoms. The dinuclear compound has a singlet ground state and thermally populated S  = 5 undecet excited state 114 cm −1 above the ground state as the magnetic susceptibility can be fit to the Van Vleck dimer equation ( H  = −2 J S a ·S b ) with g  = 2.02, J / k B  = −15 K (−10.4 cm −1 ), and a room temperature effective moment of 7.16 μ B /Fe III 2 in accord with weak antiferromagnetic coupling within the iron(III) dimer. [ABSTRACT FROM AUTHOR]

Several high spin ground-state compounds based upon ferromagnetic coupling between a metal ion and the chelating 3,5-di- tert -butyl-1,2-semiquinonate radical anion, [DTBSQ] − , as they possess unpaired electron spins in orthogonal d x 2 −y 2 /d z 2 and π ∗ orbitals, are described. [Cu II (DPyA)(DTBSQ)](ClO 4 ) (DPyA = 2,2′-dipyridylamine) was reinvestigated and its singlet excited state is 282 cm −1 [0.035 eV; J / k B = 406 K ( H = − J S a ·S b )] above the triplet ground state. [Cu II (bipy)(DBCat)(MeOH)] (bipy = 2,2-bipyridine; DBCat = 3,5-di- tert -butylcatecholate), [Cu II (bipy)(DTBSQ)](BF 4 ), [Cu II (DPyA)(DTBSQ)-(THF) 2 ](BF 4 ) and [Ni II (DPyA)(DTBSQ)(THF) 2 ](BF 4 ) have been structurally characterized and have high spin ground states whose low spin excited states lie 28 cm −1 (0.0034 eV), 382 cm −1 (0.047 eV), 335 cm −1 (0.042 eV), and 108 cm −1 (0.013 eV) higher, respectively. The triplet-singlet separation is 18% greater for [Cu II (DPyA)(DTBSQ)(THF) 2 ] + than [Cu II (DPyA)(DTBSQ)] + and is ascribed to greater orthogonality of the Cu II d x 2 −y 2 /d z 2 and [DTBSQ] − π ∗ orbitals for octahedral [Cu(DPyA)(DTBSQ)(THF) 2 ] + with respect to distorted square pyramidal structure of [Cu(DPyA)(DTBSQ)] + . This greater energy of the excited state correlates with the shorter than average M-O DTBSQ distance, i.e. [Cu(bipy)(DTBSQ)] + > [Cu II (DPyA)(DTBSQ)(THF) 2 ] + > [Ni(DPyA)(DTBSQ)(THF) 2 ] + . The order of magnitude lower value for [Cu II (bipy)(DBCat)(MeOH)] arises from a weak intradimer S = 1/2 Cu(II) interaction, not via ferromagnetic coupling between the S = 1/2 Cu(II) and [DTBSQ] − sites. [ABSTRACT FROM AUTHOR]

Several high spin ground-state compounds based upon ferromagnetic coupling between a metal ion and the chelating 3,5-di- tert -butyl-1,2-semiquinonate radical anion, [DTBSQ] − , as they possess unpaired electron spins in orthogonal d x 2 −y 2 /d z 2 and π ∗ orbitals, are described. [Cu II (DPyA)(DTBSQ)](ClO 4 ) (DPyA = 2,2′-dipyridylamine) was reinvestigated and its singlet excited state is 282 cm −1 [0.035 eV; J / k B = 406 K ( H = − J S a ·S b )] above the triplet ground state. [Cu II (bipy)(DBCat)(MeOH)] (bipy = 2,2-bipyridine; DBCat = 3,5-di- tert -butylcatecholate), [Cu II (bipy)(DTBSQ)](BF 4 ), [Cu II (DPyA)(DTBSQ)-(THF) 2 ](BF 4 ) and [Ni II (DPyA)(DTBSQ)(THF) 2 ](BF 4 ) have been structurally characterized and have high spin ground states whose low spin excited states lie 28 cm −1 (0.0034 eV), 382 cm −1 (0.047 eV), 335 cm −1 (0.042 eV), and 108 cm −1 (0.013 eV) higher, respectively. The triplet-singlet separation is 18% greater for [Cu II (DPyA)(DTBSQ)(THF) 2 ] + than [Cu II (DPyA)(DTBSQ)] + and is ascribed to greater orthogonality of the Cu II d x 2 −y 2 /d z 2 and [DTBSQ] − π ∗ orbitals for octahedral [Cu(DPyA)(DTBSQ)(THF) 2 ] + with respect to distorted square pyramidal structure of [Cu(DPyA)(DTBSQ)] + . This greater energy of the excited state correlates with the shorter than average M-O DTBSQ distance, i.e. [Cu(bipy)(DTBSQ)] + > [Cu II (DPyA)(DTBSQ)(THF) 2 ] + > [Ni(DPyA)(DTBSQ)(THF) 2 ] + . The order of magnitude lower value for [Cu II (bipy)(DBCat)(MeOH)] arises from a weak intradimer S = 1/2 Cu(II) interaction, not via ferromagnetic coupling between the S = 1/2 Cu(II) and [DTBSQ] − sites. [ABSTRACT FROM AUTHOR]

Reaction of [Ru 2 (O 2 CMe) 4 ]Cl and Na[Co III Pc(CN) 2 ] (H 2 Pc = phthalocyanine) forms [Ru 2 (O 2 CMe) 4 ][Co III Pc(CN) 2 ] with the targeted linear structure possessing linear ⋯Ru–N C–Co⋯ linkages. The magnetic properties of [Ru 2 (O 2 CMe) 4 ][Co III Pc(CN) 2 ] can be fit to a zero field splitting model with D /k B = 95 K (66 cm −1 ). Attempts to prepare the Cr(III) analogue were unsuccessful due to cyanide abstraction by the ruthenium site. [ABSTRACT FROM AUTHOR]

The reaction of MnII and KCN in aqueous and non-aqueous media leads to the isolation of three-dimensional (3-D) Prussian blue analogues, K2Mn[Mn(CN)6] (1a-d, 1e, respectively). Use of RbCN forms Rb2Mn[Mn(CN)6] (2). 1 and 2 are isomorphic (monoclinic, P21/n: 1 [a = 10.1786(1) Å, b = 7.4124(1) Å, Ca 6.9758(1) Å, β = 90.206(1)°]; 2 [a= 10.4101(1)Å, b = 7.4492(1) Å, c = 7.2132(1) Å, β=90.072(1)°]),with a small monoclinic distortion from the face centered cubic (fcc) structure that is typical of Prussian blue structured materials that was previously reported for K2Mn[Mn(CN)6]. Most notably the average Mn-N-C angles are 148.8° and 1 53,3° for 1 and 2, respectively, which are significantly reduced from linearity. This is attributed to the ionic nature of high spin MnII accommodating a reduced M -CN-M' angle and minimizing void space. Compounds 1a,b have a sharp, strong vOH band at 3628 cm-1,while 1e lacks a vOH absorption. The vOH absorption in 1a,b is attributed to surface water, as use of D2O shifts the absorption to 2677 cm-1, and that 1a-e are isostructural. Also, fcc Prussian blue-structured Cs2Mn[Mn(CN)6] (3) has been structurally [Fm3m: a = 10.6061(1) Å] and magnetically characterized. The magnetic ordering temperature, T, increases as K+ (41 K)> Rb+ (34.6 K) > Cs+ (21 K) for A2Mn[Mn(CN)6] in accord with the increasing deviation for linearity of the Mn-N-C linkages [148.8 (K+) > 153.3 (Rb+) > 180 (Cs+], decreasing Mn(ll)…Mn(ll) separations [5.09 (K+) <5.19 (Rb+) < 5.30 A (Cs+), and decreasing size of the cation (increasing electrostatic interactions). Hence, the bent cyanide bridges play a crucial role in the superexchange mechanism by increasing the coupling via shorter Mn(ll)…Mn(ll) separations, and perhaps enhanced overlap. In addition, the temperature dependent magnetic behavior of K4[MnII(CN)6]·3H2O is reported. [ABSTRACT FROM AUTHOR]

Abstract: This work presents a systematic investigation on coordination chemistry of a novel pyridine-2,6-dicarboxylic acid N-oxide (pydco), and also reveals the significant function of supramolecular interactions in dominating the resultant crystalline nets. Assemblies of pydco with transition-metal ions under similar conditions yield a series of polymers in the absence/presence of the organonitrogen ligands {[Cu(pydco)(L)0.5(H2O)]·2H2O} n (L=bipy (1), bpa (2) and bpe (3)), {[M(pydco)(bpp)(H2O)]·2H2O} n (M=Cu (4) and Ni (5)), [Ag2(pydco)] n (6) and [Ag2Cu(pydco)2] n (7) (bipy=4,4′-bipyridine, bpa=1,2-bis(4-pyridyl)ethane, bpe=1,2-bis(4-pyridyl)ethene, bpp=1,3–bis(4-pyridyl)propane). 1–5 feature different structural characteristics, although they exhibit analogous chain networks. Remarkably, extended architectures are further constructed with the aid of weak interactions. Reaction of pydco with AgAc yields a 2-D polymer 6, which was reported in our recent Communication. A mixed-metal coordination polymer 7 was obtained by the self-assembly of AgAc, Cu(Ac)2 ·H2O and pydco. In 7, two left- and right-hand helical chains are constructed by carboxylic groups of pydco and Cu centers, which are further connected by [AgCO2]2 cores into a 2-D network. Structural evolution under the co-ligand intervention in this series of compounds, as well as the general coordination rule of pydco, has been further discussed. Furthermore, variable temperature magnetic properties of 1, 3 and 7 are also studied. The magnetic measurements of 1 and 3 reveal the existence of weak antiferromagnetic interactions with J 1 =−4.59cm−1 and J 2 =−4.63cm−1, respectively. Whereas 7 displays weak ferromagnetic interactions with J 3 =1.81cm−1. [Copyright &y& Elsevier]

The kinetic inertness of the hexaaquachromium(III) (kH2O= 2.4 × 10-6 s-1) has led to challenges with respect to incorporating CrIII ions into Prussian blue-type materials; however, hexakis(acetonitrile)chromium(III) was shown to be substantially more labile (∼104 times) and enables a new synthetic route for the synthesis of these materials via nonaqueous solvents. The synthesis, spectroscopic, and physical properties of Cr[M(CN)6] (M = V, Cr, Mn, Fe) Prussian blue analogues synthesized from [CrIII(NCMe)6]3+ and the corresponding [MIIICN)6]3- are described. All these compounds {(NEt4)0.02CrIII[VIII(CN)6]0.98(BF4)0.08·0.10MeCN (1), CrIII[CrIII(CN)6]·0.16MeCN (2), CrIII[MnIII(CN)6]·0.10MeCN (3), and (NEt4)0.04CrIII0.64CrIV0.40 [FeII(CN)6]0.40[FeIII(CN)6]0.60(BF4)0.16·1.02MeCN (4)} are ferrimagnets exhibiting cluster-glass behavior. Strong antiferromagnetic coupling was observed for M = V, Cr, and Mn with Weiss constants (θ) ranging from -132 to -524 K; and in 2, where the strongest coupling is observed (θ = -524 K), the highest Tc (110 K) value was observed. Weak antiferromagnetic coupling was observed for M = Fe (θ = -12 K) leading to the lowest Tc (3 K) value in this series. Weak coupling and the low Tc value observed in 4 were additionally contributed by the presence of both [FeIII(CN)6]4- and [FeIII(CN)6]3- as confirmed by 57Fe-Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]

MIICl2 (M = Mn, Fe, Co) as their acetonitrile solvates were isolated, and their structural, spectroscopic, and magnetic properties were studied. MCl2(NCMe)2 (M = Fe, Mn) form 1-D chains of octahedral MII ions with four bridging chlorides and two axial MeCN's. The presence of an axial distortion for MFe causes a significant magnetic anisotropy that increases significantly below 150 K; however, χav [=(χ‖ + 2χ⊥)/3] almost coincides with the value obtained on a polycrystalline sample. MnCl2(NCMe)2 is a paramagnet with a weak antiferromagnetic coupling. Annealing FeCl2-(NCMe)2 at 55 °C forms the monosolvate of FeCl2(NCMe) composition in which two chains collapse into a double chain with formation of Fe-Cl bonding such that half of the μ-Cl's becomes μ3-Cl's. This material orders magnetically below Tc = 4.3 K. For M = Co, paramagnetic tetrahedral [CoCl3(NCMe)]- anions are isolated. [ABSTRACT FROM AUTHOR]

Dinuclear [(TPyA)MII(CA2-)MII(TPyA)]2+ [TPyA = tris(2-pyridylmethyl)amine; CA2- = chloranilate dianion; M = Co (12+), Fe (22+)] complexes have been prepared by the reaction of M(BF4)2•6H2O, TPyA, H2CA, and triethylamine in MeOH solution. Their reduced forms [(TPyA)MII(CA•3-)MII(TPyA)]+ [M = Co(1+), Fe (2+)] have been synthesized by using cobaltocene, and oxidized forms of 1, [(TPyA)CoIII(CAn)-CoIII(TPyA)]z+ [z= 3, n = 3- (13+); z = 4, n = 2- (14+)], have been obtained by using FcBF4 and ThianBF4 (Fc = ferrocenium; Thian = thianthrinium), respectively. The dinuclear compound bridged chloranilates (CA2- or CA•3-) were isolated and characterized by X-ray crystallography, electrochemistry, magnetism, and EPR spectroscopy. Unlike the other redox products, valence ambiguous 13+ forms via a complex redox-induced valence electron rearrangement whereby the one-electron oxidation of the [CoIICA2-CoIII]2+ core forms [CoIIICA•3-CoIII]3+, not the expected simple 1-e- transfer mixed-valent [CoIICA2-CoIII]3+ core. The M ions in 1 and 2 have a distorted octahedral geometry by coordination with four nitrogens of a TPyA, two oxygens of a chloranilate. Due to the interdimer offset face-to-face π-π and/or herringbone interactions, all complexes show extended 1-D and/or 2-D supramolecular structures. The existence of CA•3- in 13+ is confirmed from both solid-state magnetic and solution EPR data. Co-based 1n+ exhibit antiferromagnetic interactions [12+: g = 2.24, J/kB = -0.65 K (-0.45 cm-1); 1+: g = 2.36, J/kB = -75 K (52 cm-1)], while Fe-based 2n+ exhibit ferromagnetic interactions [22+: g = 2.08, J/kB = 1.0 K (0.70 cm-1); 2+: g = 2.03, J/kB = 28 K (19 cm-1)] [H = -2JS1•S2 for 12+ and 22+; H = -2J(S1•S2 + S2•S3) for 1+ and 2+]. Thus, due to direct spin exchange CA•3- is a much strong spin coupling linkage than the superexchange spin-coupling pathway provided by CA2-. [ABSTRACT FROM AUTHOR]

The structure and spin-crossover magnetic behavior of [Fe[sup II]1[sub 6]][BF[sub 4]][sub 2] (1 = isoxazole) and [Fe[sup II]1[sub 6]][CIO[sub 4]][sub 2] have been studied. [Fe[sup II]1[sub 6]][BF[sub 4]][sub 2] undergoes two reversible spin-crossover transitions at 91 and 192 K, and is the first two-step spin transition to undergo a simultaneous crystallographic phase transition, but does not exhibit thermal hysteresis. The single-crystal structure determinations at 260 [space group P&3macr;, a = 17.4387(4) Å, c = 7.6847(2) Å] and at 130 K [space group P&1macr;, a = 17.0901(2) Å, b = 16.7481(2) Å, c = 7.5413(1) Å, α = 90.5309(6)°, β = 91.5231(6)°, γ = 117.8195(8)°] reveal two different iron sites, Fe1 and Fe2, in a 1:2 ratio. The room-temperature magnetic moment of 5.0 µ[sub B] is consistent with high-spin Fe(ll). A plateau in µ(T) having a moment of 3.3 µ[sub B] centered at 130 K suggests a mixed spin system of some high-spin and some Iow-spin Fe(ll) molecules. On the basis of the Fe-N bond distances at the two temperatures, and the molar fraction of high-spin molecules at the transition plateau, Fe1 and Fe2 can be assigned to the 91 and 192 K transitions, respectively. [Fe[sup II]1[sub 6]][CIO[sub 4]][sub 2] [space group P&3macr;, a = 17.5829(3) Å, c = 7.8043(2) Å, β = 109.820 (3)°, T = 295 K] also possesses Fe1:Fe2 in a 1:2 ratio, and magnetic measurements show a single spin transition at 213 K, indicating that both Fe1 and Fe2 undergo a simultaneous spin transition. [Fe[sup II]1[sub 6]][CIO[sub 4]][sub 2] slowly decomposes in solutions containing acetic anhydride to form [Fe[sup III, sub 3]O(OAc)[sub 6]1[sub 3]][CIO[sub 4]] [space group /2, a = 10.1547(7) Å, b = 16.5497(11) Å, c = 10.3205(9) Å, β@ = 109.820 (3)°, T = 200 K]. The isosceles Fe[sub 3] unit contains two Fe···Fe distances of 3.2844(1) Å and a third Fe···Fe distance of 3.2857(1) Å. The magnetic data can be fit to a trinuclear model with H = -2J(S[sub 1]·S[sub 2] + S[sub 2]·S[sub 3]) 2J[sub 13](S[sub 1]·S[sub 3]), where J = 27.1 and J[sub 13] = 32.5 cm[sup -1]. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of dinuclear [CoII(NCMe)5CoII(NCS)4]·MeCN have been investigated. The structure consists of an octahedral CoII(NCMe)5 center connected to a tetrahedral CoII(NCS)4 center bridged by a μ1,3-NCS- ligand. The bridging NCS- weakly couples the pair of S = 3/2 CoII spin sites, as evidenced by the magnetic data being best fit by the Curie-Weiss expression with θ = -15.5 K. [ABSTRACT FROM AUTHOR]

Abstract: LnIII[Ru2(CO3)4]·8H2O (Ln=Gd, Nd, Ho, Yb) is formed from the reaction of LnIII and [Ru2(CO3)4]3− in water. These LnIII materials have a 3D network structure composed of linked chains and μ n -CO3 linkages to both Ru and LnIII sites, and are best described as LnIII(OH2)4[Ru2(CO3)4]1/2[Ru2(CO3)4(OH2)2]1/2 ·3H2O. Complete characterization of the GdIII species is presented, as the other LnIII are isostructural and exhibit large spin–orbit coupling leading to complex magnetic behavior. Magnetic ordering is not observed above 2K. [Copyright &y& Elsevier]

Tetranuclear [CuII4(OH)4(aib)4)](hfac)4 (1; aib = 2-methyl-2-amino-4-iminopentane; hfac = hexafluoroacetylacetonate) forms from the reaction of aqueous ammonia and Cu(hfac)2·2H2O in acetone. The structure of 1 reveals that four noncoordinating hfac- counterions stabilize the distorted cubane complex via multiple H-bonding contacts. Magnetic susceptibility studies reveal that cubane-like 1 is best described as a pair of independent antiferromagnetically coupled dimers with g = 2.10 and J/kB = -298 K (207 cm-1) (H = -2JS1·S2). [ABSTRACT FROM AUTHOR]