Anilato-Based Coordination Polymers with Slow Relaxation of the Magnetization: Role of the Synthetic Method and Anilato Ligand.

We have prepared and characterized three coordination polymers formulated as [Dy2(C6O4Cl2)3(fma)6] ⋅ 4.5fma (1) and [Dy2(C6O4X2)3(fma)6] ⋅ 4fma ⋅ 2H2O with X=Br (2) and Cl (3), where fma=formamide and C6O4X2 2-=3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone dianion with X=Cl (chloranilato) and Br (bromanilato). Compounds 1 and 3 are solvates obtained with slow and fast precipitation methods, respectively. Compounds 2 and 3 are isostructural and only differ in the X group of the anilato ligand. The three compounds present (6,3)-gon two-dimensional hexagonal honey-comb structures. Magnetic measurements indicate that the three compounds show slow relaxation of the magnetization at low temperatures when a continuous magnetic field is applied, although with different relaxation times and energy barriers depending on X and the crystallisation molecules. Compounds 1-3 represent the first examples of anilato-based lattices with formamide and field-induced slow relaxation of the magnetization.

Slow Relaxation of the Magnetization in Anilato-Based Dy(III) 2D Lattices.

The search for two- and three-dimensional materials with slow relaxation of the magnetization (single-ion magnets, SIM and single-molecule magnets, SMM) has become a very active area in recent years. Here we show how it is possible to prepare two-dimensional SIMs by combining Dy(III) with two different anilato-type ligands (dianions of the 3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone: C6O4X22-, with X = H and Cl) in dimethyl sulfoxide (dmso). The two compounds prepared, formulated as: [Dy2(C6O4H2)3(dmso)2(H2O)2]·2dmso·18H2O (1) and [Dy2(C6O4Cl2)3(dmso)4]·2dmso·2H2O (2) show distorted hexagonal honeycomb layers with the solvent molecules (dmso and H2O) located in the interlayer space and in the hexagonal channels that run perpendicular to the layers. The magnetic measurements of compounds 1, 2 and [Dy2(C6O4(CN)Cl)3(dmso)6] (3), a recently reported related compound, show that the three compounds present slow relaxation of the magnetization. In compound 1 the SIM behaviour does not need the application of a DC field whereas 2 and 3 are field-induced SIM (FI-SIM) since they show slow relaxation of the magnetization when a DC field is applied. We discuss the differences observed in the crystal structures and magnetic properties based on the X group of the anilato ligands (H, Cl and Cl/CN) in 1-3 and in the recently reported derivative [Dy2(C6O4Br2)3(dmso)4]·2dmso·2H2O (4) with X = Br, that is also a FI-SIM.

Multifunctional Ni(II)-Based Metamagnetic Coordination Polymers for Electronic Device Fabrication.

The combination of two 8-aminoquinoline-based Schiff base ligands (L1 and L2) with SCN- and Ni(II) has led to the synthesis of two new one-dimensional thiocyanato-bridged coordination polymers: [Ni(L1)(NCS)2]n (1) and [Ni(L2)(NCS)2]n (2). Both compounds are isostructural and consists of regular zigzag thiocyanato-bridged chains with very weak S···S interchain interactions. The measured room-temperature conductivities of compounds 1 and 2 (7.0 × 10-5 and 2.0 × 10-5 S m-1, respectively) are indicative of semiconductor behavior which increases in the presence of photoillumination (3.5 × 10-4 and 4.9 × 10-4 S m-1, respectively). The measured I-V characteristics of compound 1 and 2 based thin film metal-semiconductor (MS) junction devices under irradiation and nonirradiation conditions show a nonlinear rectifying behavior, typical of a Schottky diode (SD). The rectification ratios (Ion/Ioff) of the SDs in the dark at ±2 V (26.96 and 31.96 for 1- and 2-based devices, respectively) increase to 44.19 and 79.42, respectively, upon light irradiation. The photoinduced behavior has been analyzed by thermionic emission theory, and to determine the diode parameters, the Cheung's method has been employed. These diode parameters indicate that compound 2 has a better performance in comparison to compound 1 and that these materials are good candidates for applications in electrochemical devices. Magnetic measurements show that both compounds present ferromagnetic Ni-Ni intrachain and weak antiferromagnetic interchain interactions. The isothermal magnetizations at 2 K show that both compounds are metamagnets with critical fields of ca. 130 mT in 1 and 90 mT in 2 at 2 K. In the ferromagnetic phase (above the critical field), both compounds exhibit a long-range ferromagnetic order with critical temperatures of around 3.5 K in 1 and 3.0 K in 2. DC and AC measurements with different applied DC fields confirm the metamagnetic behaviors and have allowed the determination of the magnetic phase diagram in both compounds.

Alternating Ferro/Antiferromagnetic Copper(II) Chain Containing an Unprecedented Triple Formato/Hydroxido/Sulfato Bridge.

The first example of a triple formato/hydroxido/sulfato (FHS) bridge for any metal is reported in compound [Cu2(bpym)(OH)(HCO2)(SO4)(H2O)2]·3H2O (1). Its structure shows the presence of alternating triple FHS bridges and 2,2'-bipyrimidine (bpym) ones. Although in the initial synthesis the sulfate anions were introduced accidentally, here we report the rational synthesis and the magnetic properties of this compound. The magnetic properties show that 1 is an alternating ferro/antiferromagnetic (F/AF) chain compound with predominant antiferromagnetic interactions and were fit to an alternating F/AF S = (1)/2 chain with g = 2.103, JAF = -139 cm(-1), and JF = 116 cm(-1) (α = JF/|JAF| = 0.83). The JAF value found corresponds very well to those previously reported for Cu-bpym-Cu bridges (average value of ca. -150 cm(-1)). The JF value is also very close to the estimated one (ca. 100 cm(-1)) from magneto-structural correlations in triply Cu-Cu bridged compounds with both hydroxido and carboxylato bridges in equatorial positions.

Electrical Conductivity and Strong Luminescence in Copper Iodide Double Chains with Isonicotinato Derivatives.

Direct reactions between CuI and isonicotinic acid (HIN) or the corresponding esters, ethyl isonicotinate (EtIN) or methyl isonicotinate (MeIN), give rise to the formation of the coordination polymers [CuI(L)]n with L=EtIN (1), MeIN (2) and HIN (3). Polymers 1-3 show similar structures based on a CuI double chain in which ethyl-, methyl isonicotinate or isonicotinic acid are coordinated as terminal ligands. Albeit, their supramolecular architecture differs considerably, affecting the distances and angles of the central CuI double chains and thereby their physical properties. Hence, the photoluminescence shows remarkable differences; 1 and 2 show a strong yellow emission, whereas 3 displays a weak emission; and 1 and 2 are semiconductors with moderate room temperature conductivities, whereas 3 has increased electrical conductivity up to 3×10(-3)  S cm(-1) . Additionally, 1 and 2 present an irreversible transition to a highly conducting phase with a conductivity almost 4 orders of magnitude higher and a quasi-metallic behaviour. Thermogravimetric analysis (TGA) coupled to a mass spectrometer and magnetic measurements point to a partial thermally induced oxidation of the carboxylate groups of the ligands with Cu(I) to Cu(0) reduction. DFT calculations have been carried out to rationalise these observations.

Coordination polymers based on diiron tetrakis(dithiolato) bridged by alkali metals, electrical bistability around room temperature, and strong antiferromagnetic coupling.

Coordination polymer chains have been formed by the direct reaction between HSC6H2Cl2SH and FeCl3·6H2O in the presence of an aqueous solution of the corresponding alkali-metal hydroxide (M = Li, Na, and K) or carbonate (M = Rb and Cs). The structures consist of dimeric [Fe2(SC6H2Cl2S)4](2-) entities bridged by [M2(THF)4] [M = K (1), Rb (2), and Cs (3); THF = tetrahydrofuran] or {[Na2(µ-H2O)2(THF)2] (5 and 5') units. The smaller size of the lithium atom yields an anion/cation ion-pair molecule, [Li(THF)4]2[Fe2(SC6H2Cl2S)4] (4), in which the dianionic moieties are held together by Cl···Cl interactions. Electrical characterization of these compounds shows a general semiconductor behavior in which the conductivity and activation energies are mainly determined by the M-Cl and M-S bond distances. Compounds 1 and 5' are interesting examples of bistability showing reversible transitions centered at ca. 350 and 290 K with very large hysteresis of ca. 60 and 35 K, respectively. All of these compounds exhibit intradimer strong antiferromagnetic Fe···Fe interactions.

2D and 3D Anilato-Based Heterometallic M(I)M(III) Lattices: The Missing Link.

The similar bis-bidentate coordination mode of oxalato and anilato-based ligands is exploited here to create the first examples of 2D and 3D heterometallic lattices based on anilato ligands combining M(I) and a M(III) ions, phases already observed with oxalato but unknown with anilato-type ligands. These lattices are prepared with alkaline metal ions and magnetic chiral tris(anilato)metalate molecular building blocks: [M(III)(C6O4X2)3](3-) (M(III) = Fe and Cr; X = Cl and Br; (C6O4X2)(2-) = dianion of the 3,6-disubstituted derivatives of 2,5-dihydroxy-1,4-benzoquinone, H4C6O4). The new compounds include two very similar 2D lattices formulated as (PBu3Me)2[NaCr(C6O4Br2)3] (1) and (PPh3Et)2[KFe(C6O4Cl2)3](dmf)2 (2), both presenting hexagonal [M(I)M(III)(C6O4X2)3](2-) honeycomb layers with (PBu3Me)(+) in 1 or (PPh3Et)(+) and dmf in 2 inserted between them. Minor modifications in the synthetic conditions yield the novel 3D lattice (NEt3Me)[Na(dmf)][NaFe(C6O4Cl2)3] (3), in which hexagonal layers analogous to 1 and 2 are interconnected through Na(+) cations, and (NBu3Me)2[NaCr(C6O4Br2)3] (4), the first heterometallic 3D lattice based on anilato ligands. This compound presents two interlocked chiral 3D (10,3) lattices with opposite chiralities. Attempts to prepare 4 in larger quantities result in the 2D polymorph of compound 4 (4'). Magnetic properties of compounds 1, 3, and 4' are reported, and in all cases we observe, as expected, paramagnetic behaviors that can be satisfactorily reproduced with simple monomer models including a zero field splitting (ZFS) of the corresponding S = 3/2 for Cr(III) in 1 and 4' or S = 5/2 for Fe(III) in 3.

Supramolecular 2D/3D isomerism in a compound containing heterometallic Cu(II)2Co(II) nodes and dicyanamide bridges.

Three new heterometallic copper(II)-cobalt(II) complexes [(CuL(2))2Co{dca}2]·H2O(1), [(CuL(1))2Co{dca}2]n (2a), and [(CuL(1))2Co{dca}2]n (2b) [dca(-) = dicyanamide = N(CN)2(-)] have been synthesized by reacting the "metallo-ligand" [CuL(1)] or [CuL(2)] with cobalt(II) perchlorate and sodium dicyanamide in methanol-water medium (where H2L(1) = N,N'-bis(salicylidene)-1,3-propanediamine and H2L(2) = N,N'-bis(α-methylsalicylidene)-1,3-propanediamine). The three complexes have been structurally and magnetically characterized. Complex 1 is a discrete trinuclear species in which two metallo-ligands coordinate to a cobalt(II) ion through the phenoxido oxygen atoms along with two terminally coordinated dicyanamide ions. On the other hand, complexes 2a and 2b are one of the very scarce examples of supramolecular isomers since they present the same [(CuL(1))2Co{dca}2] trinuclear units (very similar to the trinuclear core in 1) and differ only in their superstructures. Thus, although each Cu2Co trimer in 2a and 2b is connected to four other Cu2Co trimers through four µ1,5-dca(-) bridges, 2a presents a square two-dimensional structure (each Cu2Co trimer is connected to four in-plane Cu2Co trimers); whereas, 2b shows a triangular three-dimensional lattice (each Cu2Co trimer is connected to three in-plane and one out-of-plane trimers). Variable-temperature magnetic susceptibility measurements show the presence of moderate antiferromagnetic exchange interactions (ferrimagnetic) in all the cases mediated through the double phenoxido bridges that have been fitted with an anisotropic model including spin-orbit coupling in the central Co(II) ion.

A family of layered chiral porous magnets exhibiting tunable ordering temperatures.

A simple change of the substituents in the bridging ligand allows tuning of the ordering temperatures, Tc, in the new family of layered chiral magnets A[M(II)M(III)(X2An)3]·G (A = [(H3O)(phz)3](+) (phz = phenazine) or NBu4(+); X2An(2-) = C6O4X2(2-) = 2,5-dihydroxy-1,4-benzoquinone derivative dianion, with M(III) = Cr, Fe; M(II) = Mn, Fe, Co, etc.; X = Cl, Br, I, H; G = water or acetone). Depending on the nature of X, an increase in Tc from ca. 5.5 to 6.3, 8.2, and 11.0 K (for X = Cl, Br, I, and H, respectively) is observed in the MnCr derivative. Furthermore, the presence of the chiral cation [(H3O)(phz)3](+), formed by the association of a hydronium ion with three phenazine molecules, leads to a chiral structure where the Δ-[(H3O)(phz)3](+) cations are always located below the Δ-[Cr(Cl2An)3](3-) centers, leading to a very unusual localization of both kinds of metals (Cr and Mn) and to an eclipsed disposition of the layers. This eclipsed disposition generates hexagonal channels with a void volume of ca. 20% where guest molecules (acetone and water) can be reversibly absorbed. Here we present the structural and magnetic characterization of this new family of anilato-based molecular magnets.

The Versatility of Ethylene Glycol to Tune the Dimensionality and Magnetic Properties in DyIII-Anilato-Based Single-Ion Magnets.

We exploit the high versatility of the solvent ethylene glycol (eg = CH2OH-CH2OH) acting as a ligand with three different coordination modes: terminal (κO), chelate (κ2O,O'), and bridge (1κO,2κO') to prepare a novel family of six different coordination polymers with DyIII and three different anilato ligands (3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone dianion = C6O4X22-, with X = H, Cl, and Br). With the X = H derivative (dhbq2-), we have prepared [Dy2(dhbq)3(eg)2(µ-eg)]·4eg·2H2O (1), a 3D diamond-like network with a chelate and bridging eg molecules. With the X = Cl derivative (chloranilato), we have prepared [Dy2(C6O4Cl2)3(eg)4]·2eg·H2O (2) and [Dy2(C6O4Cl2)3(µ-eg)(H2O)4]·2eg·7H2O (3). Compound 2 has a 2D (6,3)-gon brick-wall lattice and contains a chelate and a terminal eg molecule. Compound 3 has a 3D diamond-like topology as 1, although now the chelate eg has been replaced by two water molecules. Finally, with the X = Br derivative (bromanilato), we have obtained [Dy2(C6O4Br2)3(eg)2(CH3OH)2]·2eg·4CH3OH (4), [Dy2(C6O4Br2)3(eg)4]·4eg (5), and [Dy2(C6O4Br2)3(eg)3(H2O)]·2eg·H2O (6). Compound 4 has a 2D (6,3)-gon herringbone topology and contains a chelate eg and a MeOH molecule. Compounds 5 and 6 have a 2D (6,3)-gon brick-wall topology with a chelate and a terminal eg molecules (in 5 and in one of the two independent Dy centers of 6). The other Dy center in 6 has a chelate eg and a water molecule. All the compounds show slow relaxation of the magnetization at low temperatures (in compounds 1, 2, and 5 with no applied DC field). The magnetization of compounds 1-6 relaxes through Orbach and direct mechanisms when a DC field is applied and through an Orbach and/or quantum tunneling mechanism when no DC field is applied.

Linkage isomerism in coordination polymers.

The use of the recently prepared polynitrile ligand tcnopr3OH(-) ([(NC)(2)CC(OCH(2)CH(2)CH(2)OH)C(CN)(2)](-)) with different salts of Fe(II), Co(II), and Ni(II) has led to a very rare example of linkage isomerism in a coordination chain. These pairs of linkage isomers can be formulated as [M(tcnopr3OH-κN,κO)(2)(H(2)O)(2)]; M = Fe (1), Co (3), and Ni(5) and [M(tcnopr3OH-κN,κN')(2)(H(2)O)(2)]; M = Fe (2), Co (4), and Ni (6). Compounds 1-2, 3-4, and 5-6 are three pairs of linkage isomers since they present the same formula and chain structure and they only differ in the connectivity of the polynitrile ligand bridging the metal ions in the chain: through a N and an O atom (1κN:2κO-isomer) or through two N atoms (1κN:2κN'-isomer). The magnetic properties show, as expected, very similar behaviors for both isomers.

A rare example of a double metamagnetic transition leading to 2D and 3D long-range order in the two-dimensional pyrazine- and azido-bridged cobalt(II) compound [Co(pyz)(N3)2].

The synthesis, characterization, crystal structure and detailed magnetic properties of a pyrazine (pyz) and azido (N3) bridged cobalt(II) compound of formula [Co(N3)2(pyz)] (1) are reported. Compound 1 shows a layered structure formed by Co(II) chains with double µ-N3(κN1,N1) bridges that are further connected by µ-(pyrazine-κN1,N4) bridges. The layers present weak van der Waals interactions between azido terminal groups. The magnetic properties show the presence of a metamagnetic behaviour in 1 with two critical fields of 200 and 400 mT at low temperatures. AC magnetic measurements show the presence of a long-range 2D ferromagnetic order at Tc ≈ 8.0-7.0 K for dc fields above 200 mT and a long-range 3D ferromagnetic order at Tc ≈ 4.5 K for dc fields above 400 mT.

Slow Magnetic Relaxation in a Co2 Dy Trimer and a Co2 Dy2 Tetramer.

The combination of Co(III) and Dy(III) with a compartmental Schiff base ligand (H3 L=3-[(2-Hydroxy-3-methoxy-benzylidene)-amino]-propane-1,2-diol), presenting three different coordinating pockets, has allowed the synthesis of two novel Co(III)-Dy(III) complexes: [Co2 Dy(HL)4 ]NO3 ⋅ 2CH3 CN (1), a rare example of trinuclear linear CoIII 2 DyIII complex (and the first with slow relaxation of magnetization in absence of a DC field) and [Co2 Dy2 (µ3 -OH)2 (HL)2 (OAc)6 ] ⋅ 4.6H2 O (2), the first tetranuclear CoIII 2 DyIII 2 cluster with a rhomb-like structure where the Co(III) ions are connected along the short diagonal of the rhomb. 1 presents two different relaxation processes: a fast relaxation dominated by Quantum tunnelling (QT) and a slow relaxation with an energy barrier of 40 K. 2 shows two close relaxation processes without applied DC fields that follow QT and Orbach mechanisms whereas for HDC =500 Oe, the QT is cancelled and a direct term appears. Here we present the synthesis, X-ray structure and magnetic characterization of these two Co(III)-Dy(III) single-ion/molecule magnets.

Solvent-tuned ultrasonic synthesis of 2D coordination polymer nanostructures and flakes.

Herein, a new 2-dimensional coordination polymer based on copper (II), {Cu2(L)(DMF)2}n, where L stands for 1,2,4,5-benzenetetracarboxylate (complex 1) is synthesized. Interestingly, we demonstrate that both solvent and sonication are relevant in the top-down fabrication of nanostructures. Water molecules are intercalated in suspended crystals of complex 1 modifying not only the coordination sphere of Cu(II) ions but also the final chemical formula and crystalline structure obtaining {[Cu(L)(H2O)3]·H2O}n (complex 2). On the other hand, ultrasound is required to induce the nanostructuration. Remarkably, different morphologies are obtained using different solvents and interconversion from one morphology to another seems to occur upon solvent exchange. Both complexes 1 and 2, as well as the corresponding nanostructures, have been fully characterized by different means such as infrared spectroscopy, x-ray diffraction and microscopy.

Field-induced single molecule magnet behavior of a dinuclear cobalt(II) complex: a combined experimental and theoretical study.

Two dinuclear cobalt(ii) complexes, [(dmso)CoIIL1(µ-(m-NO2)C6H4COO)CoII(NCS)] (1) and [(dmso)CoIIL2(µ-(m-NO2)C6H4COO)CoII(NCS)] (2) [dmso = dimethylsulfoxide, H2L1 = (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-methoxyphenol) and H2L2 = (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-ethoxyphenol)] have been synthesized and structurally characterized by single-crystal X-ray diffraction, magnetic-susceptibility measurements and various spectroscopic techniques. Each complex contains a cobalt(ii) center with a slightly distorted octahedral geometry and a second cobalt(ii) center with a distorted trigonal prismatic one. To obtain insight into the physical nature of weak non-covalent interactions, we have extensively used the Bader's quantum theory of atoms-in-molecules (QTAIM). In addition, the non-covalent interaction reduced density gradient (NCI-RDG) methods established the presence of such non-covalent intermolecular interactions. Variable temperature magnetic susceptibility measurements show that both cobalt centers in each complex are in the high spin state (S = 3/2) and both complexes show weak ferromagnetic couplings through the double phenoxido bridges (J = 3.36(3) cm-1 in 1 and 4.56(2) cm-1 in 2). The magnetic properties of both complexes can be fitted to a Co(ii) dimer model including similar orbital reduction factors (α = -0.94(1) for 1 and -0.85(1) for 2) although different zero field splitting parameters D(1) = 11.0(4) cm-1 and D(2) = 19.5(4) cm-1 in 1 and D(1) = 8.2(4) cm-1 and D(2) = -1.3(4) cm-1 in 2. AC magnetic measurements reveal that the CoII2 unit in complex 2 exhibits field-induced slow relaxation of the magnetization at low temperatures and high frequencies.

Slow relaxation of the magnetization, reversible solvent exchange and luminescence in 2D anilato-based frameworks.

A series of multifunctional 2D frameworks prepared with Dy(iii) and the bromanilato ligand, formulated as: [Dy2(C6O4Br2)3(G)n]·nG with G = H2O, dimethylformamide (dmf) and dimethylsulfoxide (dmso), can exchange the coordinated and non-coordinated solvent molecules (G) in a reversible way. These multifunctional frameworks show field induced slow relaxation of the magnetization and luminescence that can be easily and reversibly modified by solvent exchange.

Magnetic bistability and thermochromism in a molecular Cu(II) chain.

An original magnetic bistability and a thermochromic transition are observed in a new Cu(II) molecular chain. Thermal structural studies reveal changes in the Cu(II) coordination sphere, driven by a more pronounced Jahn-Teller effect at low temperature. These distortions provoke a gradual color change. The structural study at 10 K shows a dimerization of the molecular chain, in agreement with the abrupt magnetic transition observed at 30 K.

Magnetic Properties of End-to-End Azide-Bridged Tetranuclear Mixed-Valence Cobalt(III)/Cobalt(II) Complexes with Reduced Schiff Base Blocking Ligands and DFT Study.

Two tetranuclear mixed-valence cobalt(III/II) complexes having the general formula [(µ1,3-N3){CoII(L n )(µ-O2CC6H4NO2)CoIII(N3)}2]PF6 (where H2L1 and H2L2 are two reduced Schiff base ligands) have been synthesized and characterized. The structures of both complexes show cobalt(II) and cobalt(III) centers with a distorted octahedral geometry with cobalt(III) and cobalt(II) centers located at the inner N2O2 and outer O4 cavities of the reduced Schiff base ligands, respectively. The oxidation states of both cobalt centers have been confirmed by bond valence sum (BVS) calculations. The magnetic properties show that both compounds behave as cobalt(II) dimers connected through an end-to-end azido bridging ligand and show moderate antiferromagnetic Co(II)-Co(II) couplings of -11.0 and -14.4 cm-1 for 1 and 2, respectively, as also corroborated by DFT calculations, J theo = -13.07 cm-1 for 1 and -12.49 cm-1 for 2. The calculated spin densities of both complexes at the cobalt(II) centers are -2.75 and +2.75, respectively, clearly supporting that they are the magnetic centers.

Trinuclear Lanthanide Coordination Clusters: Single-Molecule-Magnet Behavior and Catalytic Activity in the Friedel-Crafts Alkylation Reaction.

A new multidentate ligand (H3 L) was synthesized by the condensation reaction of 4-tert-butyl-2,6-diformylphenol and 2-amino-4-nitrophenol. The reaction of the ligand with hydrated lanthanide nitrate produced two isostructural trinuclear coordination clusters: [DyLn3 L3 (DMF)3 (H2 O)2 ] ⋅ 3.8DMFLn=Dy (1) and Nd (2) (DMF=N, N-dimethylformamide). Single-crystal X-ray diffraction analysis revealed that there are three lanthanide ions arranged in an almost perfect linear fashion in both complexes. Magnetic studies show single-molecule-magnet (SMM) behavior in the Dy derivative with τ0 =1.7×10-6 s and a thermal energy barrier of 7.0 cm-1 . Both complexes were used as catalysts towards the Friedel-Crafts alkylation reaction of indole with different aldehydes with yields varying from 59-98 %. Complex 1 showed better catalytic efficiency than complex 2. This is the first report of using trinuclear lanthanide coordination clusters as catalysts for the Friedel-Crafts alkylation reaction.

Pre- and post-synthetic modulation of the ordering temperatures in a family of anilato-based magnets.

We report the synthesis and characterization of six novel heterometallic molecule-based 2D magnets with the bromanilato ligand (C6O4Br22- = 1,3-dibromo-2,5-dihydroxy-1,4-benzoquinone dianion) and six different benzene derivative molecules. The compounds, formulated as (NBu4)[MnCr(C6O4Br2)3]·1.75C6H5Br (1), (NBu4)[MnCr(C6O4Br2)3]·C6H5X with X = Cl (2), I (3) and CH3 (4) and (NBu4)[MnCr(C6O4Br2)3]·2C6H5X with X = CN (5) and NO2 (6), present the classical hexagonal honeycomb-(6,3) lattice with alternating Mn(ii) and Cr(iii) ions. The layers are packed in an eclipsed way along the a direction giving rise to hexagonal channels where the benzene derivative molecules are located with π-π interactions between the benzene and anilato rings. The interlayer space contains the NBu4+ cations needed to compensate the anionic charge of the [MnIICrIII(C6O4Br2)3]- layers. The Mn-Cr exchange coupling through the bromanilato ligands is antiferromagnetic, leading to a long range ferrimagnetic order in the six compounds with ordering temperatures around 10 K. These ordering temperatures can be slightly modified in the range 9.5-11.4 K by simply changing the benzene-derivative solvent molecule. Here we discuss the possible structural and electronic reasons for this tuning effect of the solvent molecule and the important structural role played by the solvent molecules. We also show that it is possible to exchange the solvent molecules inside the hexagonal channels post-synthetically causing a tiny change in the ordering temperature and coercive field. Furthermore, we also show that it is possible to further change the ordering temperatures by simply removing the solvent molecules by heating the sample at low pressures to obtain a de-solvated phase.