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The pyrolysis and combustion mechanism of the hydrocarbon fuel has important scientific and practical significance. However, it is difficult to detect the whole intermediates and products using traditional methods, which brings trouble to the analysis of the reaction process. In this paper, the microscopic reaction mechanism and the main products of n-eicosane (C20H42) were simulated based on the reactive force field molecular dynamics (ReaxFF-MD). The effects of temperature (2000–3500 K) and oxygen on the initial decomposition, the distribution of main products, and the reactive pathways of C20H42 fuel were studied to determine its reaction mechanism. The initial decomposition of C20H42 was mainly initiated by small alkyl radicals in pyrolysis, and by the oxygen-containing radicals in combustion. The participation of oxygen had a greater effect on accelerating the decomposition reaction. The reactions involving oxygen of C20H42 initial decomposition accounted for 87.5% of the total reactions at 2000 K. Moreover, the detailed distribution and formation pathways of the main products of H2, C2H4, CH4, H2O, CO, and CO2 were depicted to construct the overall reaction mechanism of C20H42. •H radical formed from the composition of C2H4 was exactly consistent with the •H radical consumed by the generation of CH4 and H2 in the pyrolysis stage. The feasibility of the simulation method was verified by the result of thermal analysis. The results are helpful for further research on the reaction mechanism of hydrocarbon fuels.

The first dinuclear and trinuclear chromium(III) and dinuclear vanadium(III) complexes of N$^{4}$-R-substituted-3,5-di(2-pyridyl)-1,2,4-triazole (Rdpt) ligands have been prepared by solvothermal complexations under inert atmospheres, and characterized. The reactions of Cr$^{III}$ and V$^{III}$ with adpt (R = amino) resulted in deamination of the ligand and yielded the dinuclear doubly-triazolate bridged complexes [V$_{2}^{III}$(dpt$^{-}$)$_{2}$Cl$_{4}$] (1) and [Cr$_{2}^{III}$(dpt$^{-}$)$_{2}$Cl$_{4}$] (2). In the case of the Cr$^{III}$ complex 2 this bridging results in a rare example of ferromagnetic coupling for a dinuclear Cr$^{III}$ compound. DFT studies confirm that in 2 the ferromagnetic coupling pathways dominate over the antiferromagnetic pathways, whereas in 1 the reverse occurs, consistent with the observed overall antiferromagnetic coupling in that case. It was also found that the use of different additives in the reaction allows the nuclearity of the Cr$^{III}$ product to be manipulated, giving either the dinuclear system, or the first example of a trinuclear circular helicate for a Rdpt complex, [Cr$_{3}^{III}$(dpt)$_{3}$Cl$_{6}$]·1¾MeCN·¼DCM (3). Reaction of N$^{4}$-pydpt (R = 4-pyridyl) with V$^{III}$ led to an unusual shift of the pyridyl substituent from N$^{4}$ to N$^{1}$ of the triazole, forming the ligand isomer N$^{1}$-pydpt, and giving a dinuclear doubly-triazole bridged complex, [V$_{2}^{III}$(N$^{1}$-pydpt)$_{2}$Cl$_{6}$]·2MeCN (4). Reaction with Cr$^{III}$ results in loss of the 4-pyridyl ring and a mixture of the di- and trinuclear complexes, 2 and 3. Interestingly, partial oxidation of the V$^{III}$ in dinuclear complex 4 to vanadyl V$^{IV}$=O was identified by crystallographic analysis of partially oxidized single crystals, [(V$^{IV}$O)$_{0.84}$(V$^{III}$)$_{1.16}$(N$^{1}$-pydpt)$_{2}$Cl$_{5.16}$] 0.84H$_{2}$O 1.16MeCN (5).

The synthesis and characterization of a family of compounds (pipzH2)[CrIII2LnIII4(µ4-O)2(µ3-OH)4(H2O)10(µ3-SO4)4(SO4)2]·2H2O [hereafter abbreviated as Cr2Ln4; Ln = Tb (1), Ho (2), Er (3), Yb (4), and Y (5); pipz = piperazine] are reported. The compounds were obtained from hydrothermal reactions of Ln(NO3)3·6H2O (Ln = Tb, Ho, Er, Yb, and Y), Cr(NO3)3·9H2O, Na2SO4, and pipz in a 2:1:3:4 molar ratio. Single-crystal X-ray diffraction studies revealed that 1–5 crystallize isomorphously in the space group P21/c with Z = 2. The metallic core is composed of a rare face-fused double-cubane [CrIII2LnIII4(µ4-O2–)2(µ3-OH–)4]10+ unit. The temperature dependence of bulk magnetic susceptibilities is indicative of antiferromagnetic interactions dominant in the Tb, Ho, and Er compounds. In fitting with the data of the diamagnetic YIII analogue, the interactions of Cr–Cr in this system are determined to be ferromagnetic with a coupling strength of 3.61(11) cm–1, but the type of Cr–Ln could be antiferromagnetic. The dynamic magnetic properties revealed the presence of slow magnetic relaxation in the Tb and Er analogues, which represent two rare examples of CrIII-containing clusters that exhibit single-molecule magnet (SMM) behavior.

TbPc2 single-molecule magnets adsorbed on a magnesium oxide tunnel barrier exhibit record magnetic remanence, record hysteresis opening, perfect out-of-plane alignment of the magnetic easy axes, and self-assembly into a well-ordered layer.

Herein we report the synthesis and characterization of a dinuclear TbIII single-molecule magnet (SMM) with two [TbPc2]0 units connected via a fused-phthalocyaninato ligand. The stable and robust complex [(obPc)Tb(Fused-Pc)Tb(obPc)] (1) was characterized by using synchrotron radiation measurements and other spectroscopic techniques (ESI-MS, FT-IR, UV). The magnetic couplings between the TbIII ions and the two π radicals present in 1 were explored by means of density functional theory (DFT). Direct and alternating current magnetic susceptibility measurements were conducted on magnetically diluted and nondiluted samples of 1, indicating this compound to be an SMM with improved properties compared to those of the well-known [TbPc2]−/0/+ and the axially symmetric dinuclear TbIII phthalocyaninato triple-decker complex (Tb2(obPc)3). Assuming that the probability of quantum tunneling of the magnetization (QTM) occurring in one TbPc2 unit is PQTM, the probability of QTM simultaneously occurring in 1 is PQTM2, mean...

Reactions of the N-substituted diethanolamine ligand N-n-butyldiethanolamine with chromium(II) and lanthanide(III)/rare earth salts (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) in the presence of coligands give access to three series of isostructural 1:1 3d(Cr(III))/4f(Ln(III)) coordination cluster compounds that can be designated in terms of octanuclear "square-in-square" (Ln = La-Tb), hexanuclear "triangle-in-triangle" (Ln = Dy, Ho, Y) and tetranuclear "butterfly" or defect dicubane core (Ln = Er-Lu) topologies as revealed by single-crystal X-ray crystallographic analysis. The bulk magnetic properties were also measured. The influences of the various components in the reaction system on the final topology and the role of the ionic radius are discussed.

A new family of pentadecanuclear coordination cluster compounds (from now on simply referred to as clusters) [{Ln15 (OH)20 (PepCO2 )10 (DBM)10 Cl}Cl4 ] (PepCO2 =2-[{3-(((tert-butoxycarbonyl)amino)methyl)benzyl}amino]acetate, DBM=dibenzoylmethanide) with Ln=Y and Dy was obtained by using the cell-penetrating peptoid (CPPo) monomer PepCO2 H and dibenzoylmethane (DBMH) as supporting ligands. The combination of an inorganic cluster core with an organic cell-penetrating peptoid in the coordination sphere resulted in a core component {Ln15 (μ3 -OH)20 Cl}(24+) (Ln=Y, Dy), which consists of five vertex-sharing heterocubane {Ln4 (μ3 -OH)4 }(8+) units that assemble to give a pentagonal cyclic structure with one Cl atom located in the middle of the pentagon. The solid-state structures of both clusters were established by single-crystal X-ray crystallography. MS (ESI) experiments suggest that the cluster core is robust and maintained in solution. Pulsed gradient spin echo (PGSE) NMR diffusion measurements were carried out on the diamagnetic yttrium compound and confirmed the stability of the cluster in its dicationic form [{Y15 (μ3 -OH)20 (PepCO2 )10 (DBM)10 Cl}Cl2 ](2+) . The investigation of both static (dc) and dynamic (ac) magnetic properties in the dysprosium cluster revealed a slow relaxation of magnetization, indicative of single-molecule magnet (SMM) behavior below 8 K. Furthermore, the χT product as a function of temperature for the dysprosium cluster gave evidence that this is a ferromagnetically coupled compound below 11 K.

We report three dinuclear cobalt(II) complexes, [Co(L)Cl2]2 (L = bpy, mbpy, and dmpbt), that are bridged solely by chloride ions. High-field electron paramagnetic resonance and magnetometric measurements were applied to investigate the magnetic intramolecular Co–Co interactions. Simulation results based on the multispin model reveal that the complexes are weakly ferromagnetically coupled and that the isotropic exchange coupling constants differ slightly for the three complexes. Moreover, the competing effects of zero-field splitting and magnetic coupling on the temperature-dependent magnetic susceptibility were analyzed.

Carbamate formation in green-plants through the RuBisCO enzyme continuously plays a pivotal role in the conversion of CO2 from the atmosphere into biomass. With this in mind, carbamate formation from CO2 by a lanthanide source in the presence of a secondary amine is herein explored leading to a lanthanide–carbamate cage with the formula [Dy4(O2CNiPr2)12]. Magnetic studies show slow relaxation leading to the observation of hysteresis loops; the tetranuclear cage being a single molecule magnet. Detailed interpretation of the data reveals: (i) the presence of two different exchange interactions, ferromagnetic and antiferromagnetic and (ii) the observation of exchange-bias quantum tunnelling with two distinct sets of loops, attributable to ferromagnetic interactions between dysprosium ions at longer distances and antiferromagnetic exchange between dysprosium ions at shorter distances. The results clearly demonstrate that the [Dy4(O2CNiPr2)12] cage acts as a quantum magnet which in turn could be at the heart of hybrid spintronic devices after having implemented CO2 as a feedstock.

The dinuclear doubly azole-bridged copper(II) complexes [Cu(II)2(L)2(MeCN)4](ClO4)4·3.73MeCN·0.80H2O and [Cu(II)2(L)6](ClO4)4·solvent (solvent = 2MeCN·H2O; 2MeCN·2H2O; 1.5MeOH·3.5H2O) were prepared [L = 3-(6-methyl-2-pyridyl)-[1,2,4]triazolo[4,3-a]pyridine]. Structural characterizations revealed very different local geometries about the copper(II) ions, being trigonal bipyramidal for the former (τ = 0.76) and square pyramidal for the latter (τ = 0.07, 0.15, 0.07) complex. Magnetic measurements of bulk material [Cu(II)2(L)2(H2O)4](ClO4)4 and [Cu(II)2(L)6](ClO4)4·2H2O revealed antiferromagnetic coupling in both complexes, however, of very different strengths. Electron paramagnetic resonance (EPR) spectroscopy was applied to investigate magnetic properties of the complexes in detail. These experimental findings were supported by broken-symmetry DFT calculations. Systematic magneto-structural correlations are discussed.

The reaction of Co(NO3)2·6H2O with N,N-diethanolamine (H2L1) in the presence of sodium acetate, using triethylamine as a base, leads to a tridecanuclear mixed-valent cobalt cluster [CoII9CoIII4(OH)6(H2O)2(L1)8(OAc)4](NO3)4·24H2O (1). Similar reaction with a newly designed hydroxy- and nitrogen-rich chelating ligand 2-[bis(pyridin-2-ylmethyl)amino]-2-(hydroxymethyl)propane-1,3-diol (H2L2) gives a mixed-valent Co13 cluster [CoII7CoIII6(OH)12(L2)6](NO3)8·10H2O (2). The cobalt ions in both 1 and 2 are nearly coplanar, forming a novel shieldlike configuration for 1 and a unique hexagram structure for 2, both of which have not been observed for the polynuclear cobalt clusters. The magnetic susceptibility investigation showed that complexes 1 and 2 exhibited ferromagnetic coupling between CoII ions. Further magnetic studies revealed a slight frequency dependence of 2, which suggests that 2 might be a single-molecule magnet.

The two Ni(2+)-containing heteropolytungstates [Ni14(OH)6(H2O)10(HPO4)4(P2W15O56)4](34-) (Ni14) and [Ni5(OH)4(H2O)4(β-GeW9O34)(β-GeW8O30(OH))](13-) (Ni5) have been successfully synthesized in aqueous, basic media under conventional reaction conditions, and they were characterized by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric and elemental analyses, electrochemistry, and magnetic studies. The cyclic voltammetry (CV) patterns of Ni14 and Ni5 showed chemically reversible multielectronic waves for slow scan time scales. For Ni14, an important acidity inversion effect between its reduced forms was observed. Magnetic studies revealed dominant ferromagnetic interactions among the nickel(II) ions in both polyanions.

Di-, tetra- and hexanuclear metallacycles of Zn2+, Co2+, and Ni2+ prepared by ring-opening reactions of 1,8-naphthalic anhydride with corresponding metal acetate in the presence of 2,2′-bipyridine or 1,10-phenanthroline, namely [Co4(bpy)4(naphDA)4(H2O)4]·12H2O (I), [Co6(phn)6(naphDA)6(H2O)12]·20H2O (II), [Ni6(phn)6(naphDA)6(H2O)12]·20H2O (III), [Zn4(bpy)4(naphDA)4(H2O)4]·2H2O (IV), and [Zn2(phn)2(naphDA)2(H2O)2]·H2O (V) (H2naphDA = 1,8-naphthalene dicarboxylic acid, bpy = 2,2′-bipyridine, phn = 1,10-phenanthroline) were structurally characterized. In the case of the reaction of nickel(II) acetate with 1,8-naphthalic anhydride in the presence of bpy a mononuclear complex [Ni(bpy)(naphDA)(H2O)3]·H2O (VI) was observed. Both the Co2+-metallacycles on heating to 420 °C resulted in the formation of CoO. The magnetic properties of the metallacycles containing Co2+ and Ni2+ ions were investigated. Dominant antiferromagnetic interactions in the tetra- and hexanuclear Co2+-metallacycles were observed. The hexanuclear Ni2+-metallacycle III with a spin state S = 3 showed intramolecular ferromagnetic interactions. For the metallacycle III, the magnetic susceptibility data above 50 K could be reproduced with the parameters of g = 2.26 and JNi–Ni = +1.2 cm–1 using single J-model based on Hamiltonian H = –2J (S1·S2 + S2·S3 + S3·S4 + S4·S5 + S5·S6 + S6·S1).

Mixed-valence trinuclear manganese compounds [Mn3O(O2CTh)6(L)x(H2O)y]·n(solvent) (Th = thiophene, 1·CH3CN: L = pyridine (py), x = 3, y = 0, n = 1, solvent = CH3CN; 1·∼H2O: L = py, x = 3, y = 0, n = ∼1, solvent = H2O; 2: L = py, x = 2, y = 1, n = 0.25, solvent = CH3CN; 3: L = 3-Mepy, x = 2, y = 1, n = 0) containing a [MnIIMn2III(μ3-O)]6+ core have been prepared. Homo-valence tetranuclear manganese complexes (NBun4)[Mn4O2(O2CAr)9(L)] (4·ThCO2H·CH2Cl2: Ar = –Th, L = EtOH; 6: Ar = –Ph, L = H2O; 7: Ar = –Ph-p-Me, L = H2O; 8·CH2Cl2: –Ph-3,5-Me2, no L) with a [MnIII4(μ3-O)2]8+ core and [MnIIMnIII3O2(O2CTh)7(bpy)2] (5) were synthesized, structurally and magnetically characterized. Compounds 1–3 were obtained by comproportionation of MnII(O2CMe)2·4H2O with (NBun4)MnVIIO4 in aprotic pyridine (1) or aprotic/protic py/EtOH (2) or Mepy/EtOH (3) solvent mixtures. Clusters 4–8 were synthesized by comproportionation of MnII(O2CAr)2·xH2O/ArCOOH with (NBun4)MnVIIO4 in EtOH/CH3CN. X-ray structural characterization of the 2-thiophenecarboxylate (ThCO2−) containing compounds 1·CH3CN, 1·∼2H2O and 4·ThCO2H·CH2Cl2 revealed a thiophene ring disorder about the (O2)C–C(Th) bond so that the S atom and opposite (5–)CH group are distributed over two ring positions each. The MnII atom in the approximately isosceles triangular [MnIIMn2III(μ3-O)]6+ cores in 1 could be clearly assigned from bond valence sum calculations and bond distances. The [Mn4(μ3-O)2]8+ core in the anionic complexes in the structures of 4·ThCO2H·CH2Cl2 and 8·CH2Cl2 has an all MnIII oxidation level and “butterfly-like” arrangement. The magnetic properties of 4–8 were investigated by variable temperature magnetic susceptibility and magnetization measurements. Similar magnetic behavior was observed for the [MnIII4(μ3-O)2]8+ butterfly-core compounds 4, 6–8, with antiferromagnetic interactions between pairs of manganese ions with amplitude of ∼14.5 cm−1 and ∼4.6 cm−1 for the Mnb⋯Mnb and Mnb⋯Mnw coupling, respectively (b = body, w = wing). Changing the Ar-ligand size in [Mn4O2(O2CAr)9(L)]− does not have a significant effect on the magnetic properties of these butterfly clusters.

Reaction of [MnIII8MnIV4O12(CH3COO)16(H2O)4] with [A-α-PW9O34]9− in a 1:2 molar ratio in aqueous, acidic medium resulted in the manganese(III)-containing, sandwich-type tungstophosphate [MnIII3(H2O)5(A-α-PW9O34)2]9− (1). Polyanion 1 crystallizes as a mixed potassium/cesium/guanidinium salt in the triclinic space group P 1 ¯ , with cell parameters a = 13.1718(19) A, b = 16.505(2) A, c = 22.842(4) A, α = 104.141(7)°, β = 106.267(8)°, γ = 101.369(6)°, V = 4430.6(12) A3, and Z = 2. The title polyanion comprises two [A-α-PW9O34]9− Keggin fragments linked via three MnIII ions, two of which are 6-coordinated and one is 5-coordinated. Polyanion 1 was further characterized by IR, TGA, elemental analysis, magnetic measurements, and electrochemistry.

The structural aspects and magnetic properties of a novel five-coordinated copper(II) coordination polymer derived from a carboxylate tethered naphthalimide ligand, namely 5-(1,3-dioxo-1H, 3H-benzo[de]isoquinolin-2-yl)-isophthalic acid are presented. The coordination polymer having monodentate carboxylate groups connecting the copper ions to form a spiral duplex structure shows anti-ferromagnetic property.

By heating of FeCl2 and MnCl2 in the ionic liquid [BMIm][OTf] (BMIm: 1-butyl-3- methylimidazolium, OTf: trifluoromethanesulfonate), the compounds [BMIm][M(OTf)3] (M: Fe+II, Mn+II) have been obtained as colorless crystals. Similarly, [BMIm][Li(OTf)2] was synthesized by heating of LiCl in [BMIm][OTf]. While the crystal quality of the [BMIm][M(OTf)3] (M: Fe+II, Mn+II) products thus obtained is low, mild oxidation of Fe(CO)5 or Mn2(CO)10 with GeI4 applied as an alternative in the same ionic liquid allowed a slow growth of well-formed, needle-shaped crystals. According to X-ray structure analysis based on single crystals, [BMIm][M(OTf)3] (M: Fe+II, Mn+II) crystals are monoclinic, and [BMIm][Li(OTf)2] crystals are triclinic. All compounds form infinite 1 ∞[M(OTf)3] (M=Fe, Mn) and 1 ∞[Li(OTf)2] chains. The compounds have further been characterized by FT-IR spectroscopy, energy-dispersive X-ray analysis (EDX), differential thermal analysis (DTA), thermogravimetry (TG), and magnetic measurements.

A family of mononuclear tetrahedral cobalt(II) thiourea complexes, [Co(L-1)(4)](NO3)(2) (1) and [Co(L-x)(4)](ClO4)(2) where x = 2 (2), 3 (3), 4 (4) (where L-1 = thiourea, L-2 = 1,3-dibutylthiourea, L-3 = 1,3-phenylethylthiourea, and L-4 = 1,1,3,3-tetramethylthiourea), has been synthesized using a rationally designed synthetic approach, with the aim of stabilizing an Ising-type magnetic anisotropy (-D). On the basis of direct-current, alternating-current, and hysteresis magnetic measurements and theoretical calculations, we have identified the factors that govern the sign and magnitude of D and ultimately the ability to design a single-ion magnet for a tetrahedral cobalt(II) ion. To better understand the magnetization relaxation dynamics, particularly for complexes 1 and 2, dilution experiments were performed using their diamagnetic analogues, which are characterized by single-crystal X-ray diffraction with the general molecular formulas of [Zn(L-1)(4)](NO3)(2) (5) and [Zn(L-2)(4)]-(ClO4)(2) (6). Interestingly, intermolecular interactions are shown to play a role in quenching the quantum tunneling of magnetization in zero field, as evidenced in the hysteresis loop of 1. Complex 2 exhibits the largest U-eff value of 62 cm(1) and reveals open hysteresis loops below 4 K. Furthermore, the influence of the hyperfine interaction on the magnetization relaxation dynamics is witnessed in the hysteresis loops, allowing us to determine the electron/nuclear spin S(Co) = 3/2/I(Co) = 7/2 hyperfine coupling constant of 550 MHz, a method ideally suited to determine the hyperfine coupling constant of highly anisotropic metal ions stabilized with large D value, which are otherwise hard to determine by conventional methods such as electron paramagnetic resonance.

A family of thirteen tetranuclear heterometallic zinc(II)-lanthanide(III) complexes of the hexa-imine macrocycle (L(Pr))(6-), with general formula Zn(II)(3)Ln(III)(L(Pr))(NO(3))(3)·xsolvents (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm or Yb), were prepared in a one-pot synthesis using a 3:1:3:3 reaction of zinc(II) acetate, the appropriate lanthanide(III) nitrate, the dialdehyde 1,4-diformyl-2,3-dihydroxybenzene (H(2)L(1)) and 1,3-diaminopropane. A hexanuclear homometallic zinc(II) macrocyclic complex [Zn(6)(L(Pr))(OAc)(5)(OH)(H(2)O)]·3H(2)O was obtained using a 2:0:1:1 ratio of the same reagents. A control experiment using a 1:0:1:1 ratio failed to generate the lanthanide-free [Zn(3)(L(Pr))] macrocyclic complex. The reaction of H(2)L(1) and zinc(II) acetate in a 1:1 ratio yielded the pentanuclear homometallic complex of the dialdehyde H(2)L(1), [Zn(5)(L(1))(5)(H(2)O)(6)]·3H(2)O. An X-ray crystal structure determination revealed [Zn(3)(II)Pr(III)(L(Pr))(NO(3))(2)(DMF)(3)](NO(3))·0.9DMF has the large ten-coordinate lanthanide(III) ion bound in the central O(6) site with two bidentate nitrate anions completing the O(10) coordination sphere. The three square pyramidal zinc(II) ions are in the outer N(2)O(2) sites with a fifth donor from DMF. Measurement of the magnetic properties of [Zn(II)(3)Dy(III)(L(Pr))(NO(3))(3)(MeOH)(3)]·4H(2)O with a weak external dc field showed that it has a frequency-dependent out-of-phase component of ac susceptibility, indicative of slow relaxation of the magnetization (SMM behaviour). Likewise, the Er and Yb analogues are field-induced SMMs; the latter is only the second example of a Yb-based SMM. The neodymium, ytterbium and erbium complexes are luminescent in the solid phase, but only the ytterbium and neodymium complexes show strong lanthanide-centred luminescence in DMF solution.

The synthesis and characterization of a family of compounds (pipzH2)[CrIII2LnIII4(µ4-O)2(µ3-OH)4(H2O)10(µ3-SO4)4(SO4)2]·2H2O [hereafter abbreviated as Cr2Ln4; Ln = Tb (1), Ho (2), Er (3), Yb (4), and Y (5); pipz = piperazine] are reported. The compounds were obtained from hydrothermal reactions of Ln(NO3)3·6H2O (Ln = Tb, Ho, Er, Yb, and Y), Cr(NO3)3·9H2O, Na2SO4, and pipz in a 2:1:3:4 molar ratio. Single-crystal X-ray diffraction studies revealed that 1–5 crystallize isomorphously in the space group P21/c with Z = 2. The metallic core is composed of a rare face-fused double-cubane [CrIII2LnIII4(µ4-O2–)2(µ3-OH–)4]10+ unit. The temperature dependence of bulk magnetic susceptibilities is indicative of antiferromagnetic interactions dominant in the Tb, Ho, and Er compounds. In fitting with the data of the diamagnetic YIII analogue, the interactions of Cr–Cr in this system are determined to be ferromagnetic with a coupling strength of 3.61(11) cm–1, but the type of Cr–Ln could be antiferromagnetic. The dynamic magnetic properties revealed the presence of slow magnetic relaxation in the Tb and Er analogues, which represent two rare examples of CrIII-containing clusters that exhibit single-molecule magnet (SMM) behavior.

New chiral Schiff-base ligand l-H2vap, derived from the condensation of o-vanillin and l-2-amino-3-phenyl-1-propanol, reacts with Cu(Ac)2·H2O and Gd(NO3)3·6H2O in the presence of triethylamine to produce a chiral tetranuclear complex l-[Cu4(Hvap)2(vap)2(MeOH)2](NO3)2·MeOH (1). The single-crystal X-ray diffraction analyses reveal that complex 1 crystallizes in the chiral monoclinic space group P21 with Z = 2. Four copper(II) atoms are held together by two alkoxide μ3-O2 − atoms and two phenoxide μ2-O2 − atoms from four individual ligands to form a boat-shaped {Cu4O4} unit. The solid-state CD spectra confirm the chiral nature of complex 1. Magnetic studies indicate that there are strong antiferromagnetic interactions between the adjacent copper(II) ions in complex 1.

A series of seven isostructural homodinuclear lanthanide complexes are reported. The magnetic properties (ac and dc SQUID measurements) are discussed on the basis of the X-ray structural properties which show that the two lanthanide sites are structurally different. MCD spectroscopy of the dysprosium(III) and neodymium(III) complexes ([Dy(III)2(L)(OAc)4](+) and [Nd(III)2(L)(OAc)4](+)) allowed us to thoroughly analyze the ligand field, and high-frequency EPR spectroscopy of the gadolinium(III) species ([Gd(III)2(L)(OAc)4](+)) showed the importance of dipolar coupling in these systems. An extensive quantum-chemical analysis of the dysprosium(III) complex ([Dy(III)2(L)(OAc)4](+)), involving an ab initio (CASSCF) wave function, explicit spin-orbit coupling (RASSI-SO), and a ligand field analysis (Lines model and Stevens operators), is in full agreement with all experimental data (SQUID, HF-EPR, MCD) and specifically allowed us to accurately simulate the experimental χT versus T data, which therefore allowed us to establish a qualitative model for all relaxation pathways.

The first use of methyl 2-pyridyl ketone oxime (mpkoH) in zinc(II)/lanthanide(III) chemistry leads to the [ZnLn(mpko)3(mpkoH)3](ClO4)2 and [ZnLn(NO3)2(mpko)3(mpkoH)] families of dinuclear Zn(II)Ln(III) complexes displaying blue-green, ligand-based photoluminescence; the Zn(II)Dy(III) compound shows field-induced relaxation of magnetization.

Polyoxometalates (POMs) are a remarkable class of inorganic compounds with enormous structural and compositional diversity and potential applications in various fields, such as catalysis, analytical chemistry, magnetism, nanotechnology, and medicine. In particular lacunary heteropolytungstates of the Keggin and Wells–Dawson type are useful inorganic, diamagnetic ligands allowing for encapsulation of various multinuclear metal-oxo assemblies. Examples of such kinds of structurally, catalytically, and magnetically interesting POMs are the manganese-containing derivative {Mn14W36}, [2a] the iron-containing derivatives {Fe9W12}, [3a] {Fe13W36}, [3b,c] {Fe16W48}, [3d] {Fe28W48}, [3e] the nickel-containing derivatives {Ni9W27}, [4a] {Ni8/Ni9W18}, [4b] {Ni12W35}, [4c] and {Ni20W34}, [4d] and the copper-containing derivatives {Cu14W36} [5a] and {Cu20W48X} (X=Cl, Br, I). [5b,c] Some transition-metal-containing polyoxomolybdates are also known, such as {Fe30Mo72}, [6a] {V30Mo72}, [6b] as well as {Co16Mo16} (two types of structures containing 16 cobalt centers, in the form of four tetramers). The class of cobalt-containing POMs was pioneered by Baker and Pope. Meanwhile a large number of POMbased Co complexes with nuclearities ranging from 2 to 16 has been reported. Our group has reported a nona-cobaltcontaining polyanion capped by six antenna-like Co ions in the solid state, as well as several polytungstates containing smaller numbers of cobalt ions. Very recently it was shown that [Co4(H2O)2(PW9O34)2] 10 [9a] is a hydrolytically and oxidatively stable homogeneous water-oxidation catalyst. During the past decade many high-nuclearity transitionmetal-based coordination complexes with interesting electronic and magnetic properties have been prepared. Some cobalt derivatives with nuclearities ranging from 2 to 32 are also known. It is a challenge to encapsulate high-nuclearity magnetic cores in diamagnetic POM shells, in particular by using conventional, soft synthesis methods. We have now succeeded in preparing the tetrameric 36-tungsto-8-phosphate [{Co4(OH)3PO4}4(PW9O34)4] 28 (1), containing 16 cobalt(II) centers (Figure 1).

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An unprecedented dodecanuclear CoIII3CoII9 and a dinuclear CoII2 cluster were synthesized facilely from reactions of different coblt(II) salts with the ligand (1H-benzimidazol-2-yl)methanol. The cobalt ions in the Co12 supercluster are linked into a disclike structures through μ3-OL, μ-OL, μ3-O2–, μ1,1-N3– and μ1,1,1-N3– bridges. Magnetic studies reveal that strong ferromagnetic coupling through double end-on (EO) azido bridges exists in 1, while both ferromagnetic coupling through the μ3-OL and μ-OL pathways and antiferromagnetc coupling through the μ1,1,1-N3– pathway exist in 2, which results in a ferrimagnetic behaviour of 2.

The dinickel(II) compound [Ni2(μ-OAc)2(OAc)2(μ-H2O)(asy·dmen)2]·2.5H2O, 1; undergoes facile reaction in a 1:2 molar ratio with benzohydroxamic acid (BHA) in ethanol to give the novel nickel(II) tetranuclear hydroxamate complex [Ni4(μ-OAc)3(μ-BA)3(asy·dmen)3][OTf]2·H2O, 2, in which the bridging acetates, bridging two nickel atoms in 1, undergo a carboxylate shift from the μ2-η1:η1 bridging mode of binding to the μ3-η1:η2 bridging three nickel atoms in the tetramer. The structure of complex 2 was determined by single-crystal X-ray crystallography. The two monodentate acetates, water and two bidentate bridging acetates of two moles of complex 1 are replaced by three monodentate bridging acetates and three benzohydroxamates. Three nickel atoms in the tetramer, Ni(2), Ni(3) and Ni(4) are in a N2O4 octahedral environment, while the fourth nickel atom Ni(1) is in an O(6) octahedral environment. The Ni–Ni separations are Ni(1)–Ni(2) = 3.108 A, Ni(1)–Ni(3) = 3.104 A and Ni(1)–Ni(4) = 3.110 A, which are longer than previously studied in dinuclear urease inhibited models but shorter than in the nickel(II) tetrameric glutarohydroxamate complex [Ni4(μ-OAc)2(μ-gluA2)2(tmen)4][OTf]2, isolated and characterized previously in this laboratory. Magnetic studies of the tetrameric complex show that the four Ni(II) ions are ferromagnetically coupled, leading to a total ground spin state ST = 4. Three analogous tetranuclear nickel hydroxamates were prepared from AHA and BHA and the appropriate dinuclear complex with either sy·dmen or asy·dmen as capping ligands.

Pillared clays (PILCs) with magnetic properties are materials with potential for wide application in industry and the environment, but only a few studies of these types of materials have been carried out. The purpose of this study was to advance knowledge of the preparation and magnetic properties of pillared clays by examining in detail a series of magnetic Ti-pillared clays (Ti-M-PILCs). Samples were synthesized at ambient temperature by sodium borohydride reduction of ferrous ions added by ion-exchange to Ti-pillared montmorillonite (Ti-PILCs). The properties of the Ti-M-PILCs were investigated using a superconducting quantum interference device (SQUID) and Mossbauer spectroscopy. Hysteresis, zero-field-cooled (ZFC), and field-cooled (FC) regimes were measured on different precursor materials prepared by calcination of Ti-PILCs at temperatures between 200 and 600°C. Hysteresis loops, recorded between -7 and 7 T in the temperature range 200—300 K, were observed in most samples depending on the preparation of clays. The ZFC/FC measurements were made after heating from 2 to 300 K under an applied magnetic field of 39.8 kA m -1 . The influence of the calcination temperature of the starting Ti-PILCs on the structural and magnetic properties of the Ti-M-PILCs was examined. The presence of two different Fe-alloy distributions was found; a dispersed one for the less-calcined Ti-PILCs and clusters for the more-calcined ones.

By reaction of MIICl2·x H2O (M = Fe (x = 4), Co, Ni (x = 6)) and LiOH·H2O in diethylene glycol (DEG) rod-like crystals of the composition MII4Cl4(OCH2CH2OCH2CH2OH)4 are formed. According to X-ray diffraction data obtained by both, single crystals and powders, the CoII and NiII compounds crystallize monoclinic with C2/c (CoII4Cl4(OCH2CH2OCH2CH2OH)4 (1): a = 2084.1(4), b = 919.0(2), c = 1754.0(4) pm, β = 124.3(1)°, Z = 4; NiII4Cl4(OCH2CH2OCH2CH2OH)4 (2): a = 2055.2(4), b = 932.1(2), c = 1727.4(4) pm, β = 125.2(1)°, Z = 4), whereas FeII4Cl4(OCH2CH2OCH2CH2OH)4 (3) crystallizes tetragonal with (a = 1251.4(2), c = 915.3(2) pm, Z = 2). All compounds exhibit analogous molecular structures which are built of a heterocubane-type core consisting of four metal ions and four deprotonated oxygen atoms of four coordinated diethylene glycol molecules. Neutrality of charge is realized by additional coordination of four chloride anions. In addition to the structural characterization, the thermal and magnetical properties of the title compounds are investigated in detail.

In this contribution, the synthesis and characterisation of a series of complexes of the type [Ru(L–L 0 )(CO) 2 Cl 2 ] are reported,where L–L 0 are the chelating ligands L1–L8, 2-(4H-[1,2,4]triazol-3 0 -yl)-pyridine (L1); 2-(4H-[1,2,4]triazol-3 0 -yl)-pyrazine; (L2); 2-(1-methyl-4H-[1,2,4]-triazol-3-yl)pyridine (L3); 2-(5-pyridin-2-yl-4H-[1,2,4]-triazole-3-yl)phenol (L4); 3-(5-methylphenyl)-pyridin-2-yl-1,2,4-triazole (L5); 3-(4-methylphenyl)-pyridin-2-yl-1,2,4-triazole (L6); 3-(4-methoxyphenyl)-pyridin-2-yl-1,2,4-triazole (L7);3,6-bis[(4-methoxyphenyl)iminomethyl]pyridazine (L8). L1–L7 are triazole-based ligands, which provide two distinct bidentatecoordinate modes (via N2 or N4 of the triazole) whereas L8 is pyridazine-based and contains two identical bidentate binding pock-ets. The products obtained are analysed using infrared and NMR spectroscopy. The X-ray and molecular structures of the com-plexes with the ligands L2, L6, L7 and L8 are reported. These structures are the first to be reported for triazole basedruthenium chloro and ruthenium pyridazine imine complexes. The data show that the triazole ring in L2, L6 and L7 is coordinatedvia the N2 atom, and that the pyridazine-based ligand L8 uses only one binding pocket hence accommodating only one ruthe-nium(II) centre. For all compounds the cis(CO)transCl conformation is obtained. The results obtained are compared with thoseobtained for other similar compounds. 2005 Elsevier B.V. All rights reserved.

The synthesis and characterisation of a pyridazine-containing two-armed grid ligand L2 (prepared from one equivalent of 3,6-diformylpyridazine and two equivalents of p-anisidine) and the resulting transition metal (Zn. Cu, Ni, Co, Fe, Mn) complexes (1-9) are reported. Single-crystal X-ray structure determinations revealed that the copper(i) complex had self-assembled as a [2 × 2] grid, [Cu 1 4(L2) 4 ][PF 6 ] 4 . (CH 3 CN)(H 2 O)(CH 3 CH 2 OCH 2 CH 3 ) 0 . 2 5 (2(CH 3 CN)(H 2 O)(CH 3 CH 2 OCH 2 -CH 3 ) 0 . 2 5 ), whereas the [Zn 2 (L2) 2 (CH 3 -CN) 2 (H 2 O) 2 ][ClO 4 ] 4 .CH 3 CN(1.CH 3 CN), [Ni I I 2(L2) 2 (CH 3 CN) 4 ][BF 4 ] 4 .(CH 3 CH 2 -OCH 2 CH 3 ) 0 . 2 5 (5a.(CH 3 CH 2 OCH 2 -CH 3 ) 0 . 2 5 ) and [Co I I 2(L2) 2 (H 2 O) 2 -(CH 3 CN) 2 ][ClO 4 ] 4 . (H 2 O)(CH 3 CN) 0 . 5 (6a.(H 2 O)(CH 3 CN) 0 . 5 ) complexes adopt a side-by-side architecture; iron(II) forms a monometallic cation binding three L2 ligands, [Fe I I (L2) 3 ]-[Fe I I I Cl 3 OCl 3 Fe I I I ].CH 3 CN (7 . CH 3 CN). A more soluble salt of the cation of 7, the diamagnetic complex [Fe I I (L2) 3 ][BF 4 ] 2 . 2H 2 O (8), was prepared, as well as two derivatives of 2, [Cu 1 2(L2) 2 (NCS) 2 ].H 2 O (3) and [Cu 1 2(L2)(NCS) 2 ] (4). The manganese complex, [Mn H 2(L2) 2 Cl 4 ].3H 2 O (9), was not structurally characterised, but is proposed to adopt a side-by-side architecture. Variable temperature magnetic susceptibility studies yielded small negative J values for the side-by-side complexes: J = -- 21.6 cm and g = 2.17 for S = 1 dinickel(II) complex [Ni I I 2(L2) 2 (H 2 O) 4 ][BF 4 ] 4 (5b) (friction monomer 0.02); J = - 7.6 cm - 1 and g = 2.44 for S = dicobalt(II) complex [Co I I 2(L2) 2 (H 2 O) 4 ][ClO 4 ] 4 (6b) (fraction monomer 0.02): J = - 3.2 cm - 1 and g = 1.95 for S = dimanganese(II) complex 9 (fraction monomer 0.02). The double salt, mixed valent iron complex 7.H 2 O gave J = -75 cm ' and g = 1.81 for the S= diiron(III) anion (fraction monomer = 0.025). These parameters are lower than normal for Fe I I I OFe I I I species because of fitting of superimposed monomer and dimer susceptibilities arising from trace impurities. The iron(II) centre in 7.H 2 O is low spin and hence diamagnetic, a fact confirmed by the preparation and characterisation of the simple diamagnetic iron(II) complex 8. Mossbauer measurements at 77 K confirmed that there are two iron sites in 7.H 2 O, a low-spin iron(II) site and a high-spin diiron(III) site. A full electrochemical investigation was undertaken for complexes 1, 2, 5b, 6b and 8 and this showed that multiple redox processes are a feature of all of them.

Eleven new mononuclear manganese(III) complexes prepared from two hexadentate ligands, L1 and L2, with different degrees of steric bulk in the substituents are reported. L1 and L2 are Schiff bases resulting from condensation of N,N'-bis(3-aminopropyl)ethylenediamine with 3-methoxy-2-hydroxybenzaldehyde and 3-ethoxy-2-hydroxybenzaldehyde respectively, and are members of a ligand series we have abbreviated as R-Sal2323 to indicate the 323 alkyl connectivity in the starting tetraamine and the substitution (R) on the phenolate ring. L1 hosts a methoxy substituent on both phenolate rings, while L2 bears a larger ethoxy group in the same position. Structural and magnetic properties are reported in comparison with those of a previously reported analogue with L1, namely, [MnL1]NO3, (1e). The BPh4(-) and PF6(-) complexes [MnL1]BPh4, (1a), [MnL2]BPh4, (2a), [MnL1]PF6, (1b'), and [MnL2]PF6, (2b), with both ligands L1 and L2, remain high-spin (HS) over the measured temperature range. However, the monohydrate of (1b') [MnL1]PF6·H2O, (1b), shows gradual spin-crossover (SCO), as do the ClO4(-), BF4(-), and NO3(-) complexes [MnL1]ClO4·H2O, (1c), [MnL2]ClO4, (2c), [MnL1]BF4·H2O, (1d), [MnL2]BF4·0.4H2O, (2d), [MnL1]NO3, (1e), and [MnL2]NO3·EtOH, (2e). The three complexes formed with ethoxy-substituted ligand L2 all show a higher T1/2 than the analogous complexes with methoxy-substituted ligand L1. Analysis of distortion parameters shows that complexes formed with the bulkier ligand L2 exhibit more deformation from perfect octahedral geometry, leading to a higher T1/2 in the SCO examples, where T1/2 is the temperature where the spin state is 50% high spin and 50% low spin. Spin state assignment in the solid state is shown to be solvate-dependent for complexes (1b) and (2e), and room temperature UV-visible and NMR spectra indicate a solution-state spin assignment intermediate between fully HS and fully low spin in 10 complexes, (1a)-(1e) and (2a)-(2e).

Interaction of the trilacunary Keggin polyanions [A-α-XW9O34](10-) (X = Si(IV), Ge(IV)) with Co(II) and phosphate ions in aqueous, basic media and under mild heating leads to the formation of the tetrameric, Co16-containing heteropolytungstates [{Co4(OH)3PO4}4(A-α-XW9O34)4](32-) (X = Si(IV), Ge(IV)). Both polyanions were characterized in the solid state by single-crystal X-ray diffraction, IR spectroscopy, and thermogravimetric and elemental analyses. Furthermore, the electrochemical and magnetic properties of these isostructural polyanions were investigated.

Two planar tetranuclear dysprosium(III) complexes, [Dy(4)(mu(3)-OH)(2)(hmmpH)(2)(hmmp)(2)(Cl)(4)].3MeCN.MeOH (1) and [Dy(4)(mu(3)-OH)(2)(hmmpH)(2)(hmmp)(2)(N(3))(4)].4MeOH (2) {hmmpH(2) = 2-[(2-hydroxyethylimino)methyl]-6-methoxyphenol}, which exhibit an anion-dependent magnetic slow relaxation behavior, have been synthesized by in situ condensation of o-vanillin and 2-aminoethanol. The higher energy barrier observed in 2 could be the result of a more favorable crystal field and/or orientations of single-ion easy axes of magnetization of the Dy(III) ions.

The reaction of N-methydiethanolamine (mdeaH2), benzoic acid, FeCl3, and Ln(NO3)3·6H2O or LnCl3·xH2O yields a series of decanuclear coordination clusters, [Ln3Fe7(μ4-O)2(μ3-OH)2(mdea)7(μ-benzoate)4(N3)6]·4MeCN·H2O, where Ln = Gd(III) (1) or Tb(III) (2), and [Er3Fe7(μ4-O)2(μ3-OH)2(mdea)7(μ-benzoate)4(N3)5(MeOH)]Cl·7.5H2O·11.5MeOH (3). The isostructural compounds 1-3 all crystallize isotypically in the triclinic space group P1̅ with Z = 2, as does the previously reported dysprosium analogue 4. Six of the Fe(III) ions are pseudooctahedrally coordinated, whereas the seventh has a trigonal-bipyramidal coordination geometry. Temperature-dependent direct-current magnetic susceptibility studies indicate that intracluster antiferromagnetic interactions are dominant in 1-3. The frequency-dependent out-of-phase (χ″) alternating-current susceptibility reveals that 2 undergoes a slow relaxation of its magnetization, presumably resulting from anisotropy of the Tb(III) ions. Between 30 and 295 K, the (57)Fe Mössbauer spectra reveal paramagnetic behavior with six partially resolved quadrupole doublets, one for the trigonal-bipyramidal Fe(III) site and five for the six pseudooctahedral Fe(III) sites. The Mössbauer spectra of 2 and 3 obtained between 3 and 30 K are consistent with the presence of Fe(III) intracluster antiferromagnetic coupling with slow magnetic relaxation relative to the Larmor precession time. Further, the observed changes in the effective magnetic field values in the spectra measured at 3 K with increasing applied field are consistent with the effect of the local spin polarization along the applied magnetic field direction, a behavior reminiscent of antiparallel spin-coupled iron molecular paramagnetic systems.

Dysprosium based ionic liquids displaying slow relaxation of magnetization at low temperatures are reported.

The synthesis and characterization of three chiral and one achiral amino acid anion ligated dysprosium hydroxo clusters [Dy5(OH)5(α-AA)4(Ph2acac)6] (α-AA = D-PhGly, L-Pro, L-Trp, Ph2Gly; Ph2acac = dibenzoylmethanide) are reported. The solid state structures were determined using single crystal X-ray diffraction and show that five Dy(III) ions are arranged in a square-based pyramidal geometry with NO7-donor-sets for the basal and O8-donor-sets for the apical Dy atom. Both static (dc) and dynamic (ac) magnetic properties were investigated for all four compounds and show a slow relaxation of magnetization, indicative of single molecule magnet (SMM) behaviour below 10 K in all cases. The similar SMM behaviour observed for all four compounds suggests that the very similar coordination geometries seen for the dysprosium atoms in all members of this family, which are independent of the amino acid ligand used, play a decisive role in steering the contribution of the single ion anisotropies to the observed magnetic relaxation.

Two homoleptic phosphanylamido dysprosium complexes [Li(THF)4][(Ph2PNPh)4Dy] and [Dy{N(PPh2)2}3] have been synthesized. Both have a highly symmetric arrangement of the ligand which is only slightly broken in the solid state by steric and packing effects as a result of the weak coordination of phosphorus atoms to the metal centre. Magnetic properties of these two compounds are similar with both showing slow magnetic relaxation.

X-ray crystallography of the title complexes indicates a discrete mixed valence (Co2(II)-Co2(III)) defect dicubane molecular unit where each cobalt nucleus attains a distorted octahedral geometry. The α-diimine (L-L) chelator coordinated to each cobalt ion stops further polymerization or nuclearization. The water molecules in the lattice play a crucial role in the formation of the supramolecular architectures. Magnetic data were analyzed using the effective spin-1/2 Hamiltonian approach and the parameters are, J = 115(6) K, ΔJ = -57.0(1.2) K, g(xy) = 3.001(25), and g(z) = 7.214(7) for 1 and J = 115(12) K, ΔJ = -58.5(2.5) K, g(xy) = 3.34(5), and g(z) = 6.599(12) for 2 suggesting that only the g matrices are prone to the change of α-diimine chelator.

The synthesis, structural characterization, magnetic and catalytic properties of a new class of lanthanide-containing cationic heteropolyoxovanadium clusters with a nanochocolate-like structure are reported. The title compounds were characterized by single-crystal and powder X-ray diffraction, IR and 51V-NMR spectroscopies and magnetic susceptibility measurements.

By using Mössbauer spectroscopy in combination with susceptibility measurements it was possible to identify the supertransferred hyperfine field through the oxygen bridges between DyIII and FeIII in a {Fe4Dy2} coordination cluster. The presence of the dysprosium ions provides enough magnetic anisotropy to “block” the hyperfine field that is experienced by the iron nuclei. This has resulted in magnetic spectra with internal hyperfine fields of the iron nuclei of about 23 T. The set of data permitted us to conclude that the direction of the anisotropy in lanthanide nanosize molecular clusters is associated with the single ion and crystal field contributions and 57Fe Mössbauer spectroscopy may be informative with regard to the the anisotropy not only of the studied isotope, but also of elements interacting with this isotope.

The Schiff base compound 2,2'-{[(2-aminoethyl)imino]bis[2,1-ethanediyl-nitriloethylidyne]}bis-2-hydroxy-benzoic acid (H(4)L) as a proligand was prepared in situ from 3-formylsalicylic acid with tris(2-aminoethyl)amine (tren). The trinuclear 3d-4f metal complexes of this ligand {[Ln{Ni(H(2)L)(tren)}(2)](NO(3))(3)} (Ln = Gd, Dy, Er, Lu) could be obtained as single crystalline material by synthesizing the proligand in the presence of the metal salts [Ni(NO(3))(2)·(H(2)O)(6)] and [Ln(NO(3))(3)·(H(2)O)(m)] (Ln = Gd, Dy, Er, Lu). In the solid state, the complexes adapt a new V shaped structure. Mass spectrometric ion signals related to the trinuclear complexes were detected both in positive and negative ion mode via electrospray ionization mass spectrometry supporting the single crystal X-ray analysis. Hydrogen/deuterium exchange (HDX) experiments in solution support the fragmentation scheme. The magnetic studies on all these compounds suggest the presence of weak antiferromagnetic interactions between neighboring metal centers.

In Tb(Pc)2 single-molecule magnets, where Pc is phthalocyanine, adsorbed on magnesium oxide, the fluctuations of the terbium magnetic moment are strongly suppressed in contrast to the adsorption on silver. On page 5195, J. Dreiser and co-workers investigate that the molecules are perfectly organized by self-assembly, as seen in the scanning tunnelling microscopy image (top part of the design). The molecules are probed by circularly polarized X-rays depicted as green spirals.

The reaction between CuSO(4)·5H(2)O and [NMe(2)H(2)]Cl in N,N'-dimethylformamide (DMF) at 95 °C yielded green crystals of (NMe(2)H(2))(4)[Cu(6)O(2)(SO(4))(6)(DMF)(4)] 1. The discrete [Cu(6)(μ(4)-O)(2)(μ(3)-SO(4))(4)(μ(2)-SO(4))(2)(DMF)(4)](4-) anions present in 1 contain two edge-sharing Cu(4)(μ(4)-O) tetrahedra, with the copper(II) centers bridged by sulfato ligands. These anions are linked into a two-dimensional network through hydrogen bonds involving the dimethylammonium cations. When the reaction was carried out in the absence of [NMe(2)H(2)]Cl, yellow-green crystals of (NMe(2)H(2))(4)[Cu(6)O(2)(SO(4))(6)(DMF)(2)] 2 were obtained. The anions in 2 contain similar Cu(6)O(2)(SO(4))(6) aggregates to those in 1, though these differ in terms of the copper(II) coordination geometries. In addition, the anions in 2 are linked into chains through bridging sulfato ligands. The Cu(6)O(2)(SO(4))(6) aggregates observed in 1 and 2 are related to those present in the rare copper sulfate mineral fedotovite, K(2)Cu(3)O(SO(4))(3), and in common with this mineral both 1 and 2 decompose in the presence of moisture. The reaction between CuSO(4)·5H(2)O and [NMe(2)H(2)]Cl in DMF at room temperature gave (NMe(2)H(2))[Cu(2)(OH)(SO(4))(2)(H(2)O)(2)] 3, the structure of which contains triangular Cu(3)(OH)(SO(4)) units that share vertices to form tapes. Magnetic measurements revealed that 1 and 3 are both spin-canting metamagnetic systems. Field-induced responses were observed below 5 K, with the critical field indicating metamagnetic behavior from antiferromagnetic to ferromagnetic equal to 110 Oe for both compounds.

International audience; A series of four isostructural dodecanuclear complexes [Mn(III)9Mn(II)2Ln(III)(0)(8)(OH)(Piv)(16) (NO3)(CH3CN)]center dot xCH(3)CN center dot yC(7)H(16) (piv = pivalate; x = 1/2, y = Ln = Tb (1); x = 2, y = 1/2, Ln = Dy (2), Ho (3), and Y (4)) has been prepared for which the structural motif described as 'a lanthanide ion nested in a large manganese shell' is observed. All compounds show out-ofphase signals in their ac susceptibilities, and their single-molecule magnet behaviour was confirmed by single-crystal micro-SQUID studies of 1-3 which show hysteresis loops of molecular origin at T < 1.0 K. The SMM behaviour observed in compounds 1-3 is more pronounced than that for 4, which contains the diamagnetic Yu(III) ion. This is principally the result of ferromagnetic coupling between the paramagnetic anisotropic Le(III) ions (Tb-III. Dy-III and Hot(III)) and the manganese shell, which enhances the total spin ground state of the complexes. (C) 2012 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

International audience; Two types of structurally related one-dimensional coordination polymers were prepared by reacting lanthanide trichloride hydrates [LnCl(3) center dot (H2O)(m)] with dibenzoyl-methane (Ph(2)acacH) and a base. Using cesium carbonate (Cs2CO3) and praseodymium, neodymium, samarium, or dysprosium salts yielded [Cs{Ln(Ph(2)acac)(4)}) (Ln = Pr (1), Nd (2), Sm (3), Dy (4)) in considerable yields. Reaction of potassium tert-butoxide (KOtBu) and the neodymium salt [NdCl3 center dot (H2O)(6)] with Ph(2)acacH resulted in [K{Nd(Ph(2)acac)(4)}](n) (5). All polymers exhibit a heterobimetallic backbone composed of alternating lanthanide and alkali metal atoms which are bridged by the Ph(2)acac ligands in a linear fashion. ESI-MS investigations on DMF solutions of 1-5 revealed a dissociation of all the five compounds upon dissolution, irrespective of the individual lanthanide and alkali metal present. Temporal profiles of changes in optical density were acquired performing pump/probe experiments with DMF solutions of 1-5 via femtosecond laser spectroscopy, highlighting a lanthanide-specific relaxation dynamic. The corresponding relaxation times ranging from seven picoseconds to a few hundred picoseconds are strongly dependent on the central lanthanide atom, indicating an intramolecular energy transfer from ligands to lanthanides. This interpretation also demands efficient intersystem crossing within one to two picoseconds from the SI to T, level of the ligands. Magnetic studies show that [Cs{Dy(Ph(2)acac)(4)}}(n) (4) has slow relaxation of the magnetization arising from the single Dy3+ ions and can be described as a single-ion single molecule magnet (SMM). Below 0.5 K, hysteresis loops of the magnetization are observed, which show weak single chain magnet (SCM) behavior.

A well defined salen–nickel complex was introduced as “metalloligand” in lanthanide-based MOFs. By using this strategy unique structures, in which the salen–nickel unit acts as flexible strut, were obtained. The shape of the network is strongly influenced by the ion radius of the lanthanide element.

We present zero field muon spin lattice relaxation measurements of a Dysprosium triangle molecular magnet. The local magnetic fields sensed by the implanted muons indicate the coexistence of static and dynamic internal magnetic fields below ${T}^{\ensuremath{\ast}}\ensuremath{\sim}35\text{ }\text{K}$. Bulk magnetization and heat capacity measurements show no indication of magnetic ordering below this temperature. We attribute the static fields to the slow relaxation of the magnetization in the ground state of ${\text{Dy}}_{3}$. The fluctuation time of the dynamic part of the field is estimated to be $\ensuremath{\sim}0.55\text{ }\ensuremath{\mu}\text{s}$ at low temperatures.