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Using Na-encapsulated benzo[18]crown-6 (Na)(B18C6) as a counter cation, we successfully magnetically isolated a fluoride-bridging Dy dinuclear complex {[(PW11O39)Dy(H2O)(2)](2)F} (Dy2POM) with lacunary Keggin ligands. (Na)(B18C6) formed two types of tetramers through C-HMIDLINE HORIZONTAL ELLIPSISO, pi MIDLINE HORIZONTAL ELLIPSIS pi and C-HMIDLINE HORIZONTAL ELLIPSIS pi interactions, and each tetramer aligned in one dimension along the c-axis to form two types of channels. One channel was partially penetrated by a supramolecular cation from the +/- a-axis direction, dividing the channel in the form of a bamboo node. Dy2POM was spatially divided by this bamboo node, which magnetically isolated one portion from the other. The temperature dependence of the magnetic susceptibility indicated a weak ferromagnetic interaction between the Dy ions bridged by fluoride. Dy2POM exhibited the magnetic relaxation characteristics of a single-molecule magnet, including the dependence of AC magnetic susceptibility on temperature and frequency. Magnetic relaxation can be described by the combination of thermally active Orbach and temperature-independent quantum tunneling processes. The application of a static magnetic field effectively suppressed the relaxation due to quantum tunneling.

Cooperation between single-molecule magnets and electrical conductivity holds promise for preparing high-density magnetic devices; however, there are only a few reports so far. Here we report a 4f-π-based molecular hybrid, k-(ET)5Dy(NCS)7(KCl)0.5 (1) (ET = bis(ethylenedithio)tetrathiafulvalene, NCS- = thiocyanate), which undergoes slow relaxation of the magnetization and electrical conductivity. Unlike common ET-based conductive salts, K+ ions were intercalated into ET layers and coordinated with ET radicals. We found that the ET charges were sensitive to temperature, resulting in rich conductive phases at 75-300 K. In particular, the upturn in conductivity with a clear hysteresis loop was explained by the formation of partially oxidized states with charges close to 0.5+, which accounts for a metallic state. From the results of electronic structure calculations, the hole concentration increased to 125 K, which is consistent with a partially oxidized state upon cooling. The weak antiferromagnetic interactions accompanied by a dual magnetic relaxation process below 4 K are closely associated with the weak 4f-π interactions.

Tethering metal complexes, like [Ru(bpy)2Cl2] (bpy = 2,2′-bipyridine), which are redox-active at low reduction potentials and have the ability to transfer electrons to another complex, to a [Ni(cyclen)]2+ electrocatalyst enhanced the reduction of CO2 to CO at low overpotentials. The [Ni(cyclen)]2+ electrocatalyst was modified by tethering redox-active metal complexes via 4-methylpyridyl linkers. The redox-active metal complexes were reduced after CO2 bound to the active site. In controlled potential electrolysis (CPE) experiments in 95 : 5 (v/v) CH3CN/H2O, [{([Ru]pic)4cyclen}NiCl]5+ ([Ru]+ = {Ru(bpy)2Cl}+; pic = 4-methylpyridyl) could be used to reduce CO2 into CO at a turnover frequency (TOF) of 708 s−1 with a faradaic efficiency (FE) of 80% at an onset potential of −1.60 V vs. NHE. At the same time, this electrocatalyst was active at an onset potential of −1.25 V vs. NHE, which is the reduction potential of one of the bpy ligands of the [Ru]+ moieties, with FE = 84% and TOF = 178 s−1. When the electrocatalysis was performed using [bn4cyclenNiCl]Cl (bn = benzyl) without tethered redox-active metal complexes, the TOF value was determined to be 8 s−1 with FE = 77% at an onset potential of −1.45 V vs. NHE. The results show that tethering redox-active metal complexes significantly improves the electrocatalytic activities by lowering the potential needed to reduce CO2.

Lanthanide (Ln) compounds are common research targets in the field of magnetism and optics. Their properties arise from the electron localized in the f-orbital. Moreover, the effect of the covalency between lanthanide and ligands on magnetism attracted significant attention. We provided insight into the Gd–Pt bond (of the heterometallic Ln-Pt complexes: {[Pt(PhSAc)4]Ln[(PhSAc)4Pt]} NEt4·2DMF (Ln = Y(0), La(1), Gd(2); PhSAc = thiobenzoate, NEt4 = tetraethylammonium)); single-crystal polarized X-ray absorption near edge structure (XANES) reveal the electronic states around metal ion, where spectra of Gd-LIII edges show the Gd–Pt direction has the highest covalency (less ionic) around Gd ion in 2. In addition, calculating natural bonding (NBO) analysis, natural population analysis (NPA), LOL, and atoms in molecules (AIM), ab initio calculations reveal the role of metallic and organic ligands in the electronic and magnetic properties of Ln complexes. The slow magnetization relaxation of the Gd complex, which has not been reported previously in the Pt–Gd–Pt system, was observed up to 45K, the highest temperature reported to date among isolated Gd-complexes.

Tethering metal complexes, like [Ru(bpy)

Porous coordination polymer (PCP) with 2,7-bis(4-pyridyl)-[1]benzothieno[3,2-b][1]benzothiophene (BTBT-4py) ligands was synthesized. The PCP provides both pores and infinite π-stacked columns via t...

Single-molecule magnets (SMMs) show superparamagnetic behaviour below blocking temperature at the molecular scale, so they exhibit large magnetic density compared to the conventional magnets. Combining SMMs and molecular conductors in one compound will bring about new physical phenomena, however, the synergetic effects between them still remain unexplored. Here we present a layered molecule-based compound, β′′-(BEDO-TTF)4 [Co(pdms)2]·3H2O (BO4), (BEDO-TTF (BO) and H2pdms are bis(ethylenedioxy)tetrathiafulvalene and 1,2-bis(methanesulfonamido)benzene, respectively), which was synthesized by using an electrochemical approach and studied by using crystal X-ray diffraction. This compound simultaneously exhibited metallic conductivity and SMM behaviour up to 11 K for the first time. The highest electrical conductivity was 400–650 S cm−1 at 6.5 K, which is the highest among those reported so far for conducting SMM materials. Furthermore, antiferromagnetic ordering occurred below 6.5 K, along with a decrease in conductivity, and the angle-independent negative magnetoresistance suggested an effective electron correlation between the conducting BO and Co(pdms)2 SMM layers (d–π interactions). The strong magnetic anisotropy and two-dimensional conducting plane play key roles in the low-temperature antiferromagnetic semiconducting state. BO4 is the first compound exhibiting antiferromagnetic ordering among SMMs mediated by π-electrons, demonstrating the synergetic effects between SMMs and molecular conductors., A metallic single-molecule magnet was synthesised demonstrating simultaneous metallic conduction and excellent SMM properties at the same temperature range for the first time, with potential applications in molecule-based quantum spintronics.

Single-molecule magnets exhibit magnetic bistabililties at the molecular level, making them promising for molecule-based spintronics due to high magnetic densities. The incorporation of SMM behavior and electrical conductivity in one compound is rare because these two physical properties often do not operate in the same temperature range, which further hinders their use in practical applications. Here we present an organic-inorganic molecular hybrid, β″-(BEDO-TTF)3[Co(pdms)2]·(MeCN)(H2O)2 (BO3) (BEDO-TTF = bis(ethylenedioxy)tetrathiafulvalene and H2pdms = 1,2-bis(methanesulfonamido)benzene), which manifests both metallic conduction (electrical conductivity up to 1000 S cm-1 at 12 K under 2.0 gigapascal pressure) and SMM behavior in the temperature range 12-26 K for the first time.

A binary system consisting of a ditopic planar pseudo-pincer ligand (qlca = quinoline-2-carbaldehyde (pyridine-2-carbonyl) hydrazone) coordinated to two metal centres affording [{Ru(bpy)2}(μ-qlca)NiCl2]Cl·4H2O·CH3OH (2) (bpy = 2,2'-bipyridine) is reported. The Ni2+ moiety acts as the electrocatalytic active site for CO2 reduction to CO. The turnover frequency (TOF) increased from 0.83 s-1 for [Ni(qlca)Cl2] (3) to 120 s-1 for 2, and the overpotential is 350 mV less than that for 3 due to the electronic influence of the {Ru(bpy)2}2+ moiety on the catalytic active site.

A heterometallic Tb-Pt complex, [Tb2 Pt3 (SAc)12 (H2 O)2 ] (SAc=thioacetate), was synthesized. Dual emission was modulated by the presence of a heterometallic Tb-Pt bonding environment. The heterometallic Tb-Pt bond lowers the symmetry of the Tb ion and enhanced the emission efficiency. In addition, the Tb-Pt complex shows field-induced multiple magnetic relaxation pathways. Furthermore, it served as an antenna for the observed dual emission. In other words, the heterometallic Tb-Pt bond has a significant effect on the luminescence and magnetic properties of the complex.

Three complexes, [Dy{5-(5-methylthiophen-2-yl)-2,2′-bipyridine}(hfac)3] (6), [Dy{5-(4-bromo-5-methylthiophen-2-yl)-2,2′-bipyridine}(hfac)3] (7) and [Dy{5-(4-ethynyl-5-methylthio-phen-2-yl)-2,2′-bipyridine}(hfac)3] (8) (hfac = hexafluoroacetylacetate), were synthesized to investigate the effects of substituents on the ligand far from the metal ion on the magnetic properties of the dysprosium ion. 7 crystallized in two polymorphs (P21/n for 7a and P21/a for 7b), whereas 6 and 8 crystallized in one polymorph (P21/n and P21/a, respectively). All of the complexes have columnar structures, and in 6 and 7a, there are π–π stacking interactions between neighboring aromatic rings in contrast to compounds 7b and 8, which do not show such interactions. Every complex underwent slow magnetic relaxation with a single relaxation time, except for complex 7a, for which there were two relaxation times. In order to clarify the role of distal substitution and crystal packing, the magnetic properties were studied in solution, ...

The first three–dimensional (3D) conductive single-ion magnet (SIM), (TTF)2[Co(pdms)2] (TTF = tetrathiafulvalene and H2pdms = 1,2-bis(methanesulfonamido)benzene), was electrochemically synthesized and investigated structurally, physically and theoretically. The quite close oxidation potential between neutral TTF and the coordination precursor, (HNEt3)2[M(pdms)2] (M = Co, Zn) causes multiple charge transfers (CTs) between SIM donor [M(pdms)2]n– and the TTF●+ acceptor as well as an intra-donor CT from the pdms ligand to Co ion upon electrocrystallization. Usually TTF works as a donor, whereas in our system, TTF works as both a donor and an accepter due to the close oxidation potentials. Furthermore, the [M(pdms)2]n– donor and TTF●+ acceptor are not segregated but strongly interact with each other, contrary to reported layered donor-acceptor electrical conductors. The strong intermolecular and intramolecular interactions, combined with the CT, cause relatively high electrical conductivity to very low temperature. Furthermore, SIM behaviour with slow magnetic relaxation and opening of hysteresis loops were observed. (TTF)2[Co(pdms)2] (2-Co) is an excellent building block for preparing new conductive SIM.

A series of two-dimensional (2D)-layered coordination polymers (CPs) based on the heterosubstituted anilate ligand ClCNAn2- derived from 3-chloro-6-cyano-2,5-dihydroxybenzoquinone and DyIII are reported. By changes in the synthetic methods (layering technique, solvothermal or conventional one-pot reactions) and conditions (solvent, concentration, etc.), different types of 2D extended networks could be prepared and structurally characterized. Compounds 1 and 1', two polymorphs with the formula [Dy2(ClCNAn)3(DMSO)6]n·(H2O)x [x = 7 (1), 0 (1')], were prepared by a conventional one-pot reaction and recrystallized at different concentrations. Compound 2, formulated as [Dy2(ClCNAn)3(DMF)6]n, was prepared by a layering technique, while compound 3, formulated as {(Me2NH2)2[Dy2(ClCNAn)4(H2O)2]·(DMF)2·(H2O)5}n, was obtained by a solvothermal method. Compounds 1 and 2 are neutral 2D CPs of the ClCNAn2- ligand and DyIII ions, while 3 presents 2D anionic layers of [Dy2(ClCNAn)4(H2O)2]2- alternating with cationic layers of Me2NH2+ ions. These compounds show very diverse networks, with compound 1 forming 2D (8,3) and (4,3) topology with eight- and four-membered rings with square cavities, 1' and 2, respectively, a 2D (6,3) topology with six-membered rings (a rectangular cavity for 1' and a regular hexagonal cavity for 2), and 3 a 2D (4,4) topology with distorted square cavities. In this respect, 1 and 1' represent the first examples of polymorphism in the family of anilate-based CPs. Thermal analysis measurements (differential scanning calorimetry and thermogravimetry) show an exothermic polymorphic transformation from the kinetically stable 1' phase to the thermodynamically stable phase 1. The magnetic behavior of 1-3 very likely indicates depopulation of the mJ levels, while the presence of weak antiferromagnetic coupling between the DyIII centers mediated by the anilate bridge cannot be excluded.

The first three-dimensional (3D) conductive single-ion magnet (SIM), (TTF)2 [Co(pdms)2 ] (TTF=tetrathiafulvalene and H2 pdms=1,2-bis(methanesulfonamido)benzene), was electrochemically synthesised and investigated structurally, physically, and theoretically. The similar oxidation potentials of neutral TTF and the molecular precursor [HNEt3 ]2 [M(pdms)2 ] (M=Co, Zn) allow for multiple charge transfers (CTs) between the SIM donor [M(pdms)2 ]n- and the TTF.+ acceptor, as well as an intradonor CT from the pdms ligand to Co ion upon electrocrystallisation. Usually TTF functions as a donor, whereas in our system TTF is both a donor and an accepter because of the similar oxidation potentials. Furthermore, the [M(pdms)2 ]n- donor and TTF.+ acceptor are not segregated but strongly interact with each other, contrary to reported layered donor-acceptor electrical conductors. The strong intermolecular and intramolecular interactions, combined with CT, allow for relatively high electrical conductivity even down to very low temperatures. Furthermore, SIM behaviour with slow magnetic relaxation and opening of hysteresis loops was observed. (TTF)2 [Co(pdms)2 ] (2-Co) is an excellent building block for preparing new conductive SIMs.

The DyIII quintuple-decker complex DyCdCdDy and hetero quadruple-decker complex DyCdY were synthesized, and their magnetic properties were compared with those of the quadruple-decker complex DyCdDy. Single-crystal X-ray analysis revealed that the coordination geometries around the DyIII ions of DyCdCdDy, DyCdY, and DyCdDy were similar. dc (direct current) magnetic measurements indicated that DyCdCdDy had very weak ferromagnetic DyIII–DyIII interactions but DyCdY did not. From a comparison of the magnetic relaxation times (τ) of the three complexes, the τ values of DyCdCdDy and DyCdDy, which have weak DyIII–DyIII interactions, are longer than that of DyCdY. In other words, weak DyIII–DyIII interactions effectively suppress magnetic relaxation.

Two new coordination assemblies were prepared by combining the open and close forms of 1,2-bis(5-carboxyl-2-methyl-3-thienyl)perfluorocyclopentene (H2dae) with [Mn2(saltmen)2(H2O)2](PF6)2, where H2saltmen = 2,2′-((1E,1′E)-((2,3-dimethylbutane-2,3-diyl)bis(azaneylylidene)) bis(methaneylylidene))diphenol. From X-ray diffraction analyses, the complexes had the following formula: [Mn2(saltmen)2(dae-open)] (1open) and [Mn(saltmen)(dae-close)]·H2O·Et3N (1close). Both complexes crystallized in the C2/c monoclinic space group. In 1open, dae-o2– behaves as a bidentate ligand attached to the outer Mn-saltmen monomer via the oxygen atom of carboxylato groups, whereas in 1close, the dae-c2– ligand behaves as a monodentate ligand attached to the external Mn-saltmen dimer by only one carboxylato group of the photochromic ligand. The complexes showed reversible photochromic responses to UV/vis light and showed single-molecule magnet-like behavior. The relaxation times and energy barriers of the metal complexes are clear...

The work in this present investigation reports the syntheses, crystal structures and magnetic properties of five dinuclear lanthanide complexes having compositions [Tb2(HL)4(NO3)6] (1), [Tb2(HL)4Cl6]·2EtOH (2), [Yb2(HL)4(NO3)6] (3), [Yb2(HL)4Cl6]·2EtOH (4) and [Y2(HL)4(NO3)6] (5) with HL = 8-hydroxyquinaldine. It is evident from the crystal structures that the coordination number of trivalent lanthanide ions in compounds 1, 3 and 5 is nine, whereas that for compounds 2 and 4 is six. A dynamic magnetic study shows that both compounds 1 and 3 exhibit single-molecule-magnet (SMM) behavior while compounds 2 and 4 do not have any SMM property.

Heterometallic Ln-Pt complexes, with the formula [Ln2Pt3(H2O)2(SAc)12] (Ln = Ho(1), Er(2); SAc = thioacetate), were synthesized. From natural bond orbital (NBO) and local orbital locator (LOL) analyses and X-ray absorption fine structure (XAFS) measurements, it was clear that the Ln-Pt interactions or electron polarization occurred. Butterfly-type hysteresis was observed for both 1 and 2. 1 and 2 underwent field-induced slow magnetic relaxation up to 4 K. These magnetic properties were induced by Ln-Pt electron polarization.

Incorporating palladium in the first coordination sphere of acetato-bridged lanthanoid complexes, [Pd2 Ln2 (H2 O)2 (AcO)10 ]⋅2 AcOH (Ln=Gd (1), Y (2), Gd0.4 Y1.6 (3), Eu (4)), led to significant bonding interactions between the palladium and the lanthanoid ions, which were demonstrated by experimental and theoretical methods. We found that electron density was donated from the d8 Pd2+ ion to Gd3+ ion in 1 and 3, leading to the observed slow magnetic relaxation by using local orbital locator (LOL) and X-ray absorption near-edge structure (XANES) analysis. Field-induced dual slow magnetic relaxation was observed for 1 up to 20 K. Complex 3 and frozen aqueous and acetonitrile solutions of 1 showed only one relaxation peak, which confirms the role of intermolecular dipolar interactions in slowing the magnetic relaxation of 1. The slow magnetic relaxation occurred through a combination of Orbach and Direct processes with the highest pre-exponential factor (τo =0.06 s) reported so far for a gadolinium complex exhibiting slow magnetic relaxation. The results revealed that transition metal-lanthanoid (TM-Ln) axial interactions indeed could lead to new physical properties by affecting both the electronic and magnetic states of the compounds.

Multifunctional molecular materials exhibiting electrical conductivity and single-molecule magnet (SMM) behaviour are particularly attractive for electronic devices and related applications owing to the interaction between electronic conduction and magnetization of unimolecular units. The preparation of such materials remains a challenge that has been pursued by a bi-component approach of combination of SMM cationic (or anionic) units with conducting networks made of partially oxidized (or reduced) donor (or acceptor) molecules. The present status of the research concerning the preparation of molecular materials exhibiting SMM behaviour and electrical conductivity is reviewed, describing the few molecular compounds where both SMM properties and electrical conductivity have been observed. The evolution of this research field through the years is discussed. The first reported compounds are semiconductors in spite being able to present relatively high electrical conductivity, and the SMM behaviour is observed at low temperatures where the electrical conductivity of the materials is similar to that of an insulator. During the recent years, a breakthrough has been achieved with the coexistence of high electrical conductivity and SMM behaviour in a molecular compound at the same temperature range, but so far without evidence of a synergy between these properties. The combination of high electrical conductivity with SMM behaviour requires not only SMM units but also the regular and as far as possible uniform packing of partially oxidized molecules, which are able to provide a conducting network.

The synthesis, structures, and magnetic properties of two heterometallic Cu(II)-Dy(III) clusters are reported. The first structural motif displays a pentanuclear Cu(II)4Dy(III) core, while the second one reveals a nonanuclear Cu(II)6Dy(III)3 core. We employed o-vanillin-based Schiff base ligands combining o-vanillin with 3-amino-1-propanol, H2vap, (2-[(3-hydroxy-propylimino)-methyl]-6-methoxy-phenol), and 2-aminoethanol, H2vae, (2-[(3-hydroxy-ethylimino)-methyl]-6-methoxy-phenol). The differing nuclearities of the two clusters stem from the choice of imino alcohol arm in the Schiff bases, H2vap and H2vae. This work is aimed at broadening the diversity of Cu(II)-Dy(III) clusters and to perceive the consequence of changing the length of the alcohol arm on the nuclearity of the cluster, providing valuable insight into promising future synthetic directions. The underlying topological entity of the pentanuclear Cu4Dy cluster is reported for the first time. The investigation of magnetic behaviors of 1 and 2 below 2 K reveals slow magnetic relaxation with a significant influence coming from the variation of the alcohol arm affecting the nature of magnetic interactions.

A photo-switchable single molecule-magnet (SMM) with two Dy ions bridged by a bis-bipyridine-dithienylethene ligand was synthesised. Isomerisation effects on the magnetic properties were investigated. Particular attention was paid to the slow relaxation of the magnetisation in order to determine precisely the role played by the ligand. Photo-isomerization of the ligand induced a geometric rearrangement of the complex and an electronic reconfiguration. The changes were studied by solid and solution state magnetic measurements.

Practical implementation of highly coherent molecular spin qubits for challenging technological applications, such as quantum information processing or quantum sensing, requires precise organization of electronic qubit molecular components into extended frameworks. Realization of spatial control over qubit-qubit distances can be achieved by coordination chemistry approaches through an appropriate choice of the molecular building blocks. However, translating single qubit molecular building units into extended arrays does not guarantee a priori retention of long quantum coherence and spin-lattice relaxation times due to the introduced modifications over qubit-qubit reciprocal distances and molecular crystal lattice phonon structure. In this work, we report the preparation of a three-dimensional (3D) metal-organic framework (MOF) based on vanadyl qubits, [VO(TCPP-Zn2-bpy)] (TCPP = tetracarboxylphenylporphyrinate; bpy = 4,4?-bipyridyl) (1), and the investigation of how such structural modifications influence qubits' performances. This has been done through a multitechnique approach where the structure and properties of a representative molecular building block of formula [VO(TPP)] (TPP = tetraphenylporphyrinate) (2) have been compared with those of the 3D MOF 1. Pulsed electron paramagnetic resonance measurements on magnetically diluted samples in titanyl isostructural analogues revealed that coherence times are retained almost unchanged for 1 with respect to 2 up to room temperature, while the temperature dependence of the spin-lattice relaxation time revealed insights into the role of low-energy vibrations, detected through terahertz spectroscopy, on the spin dynamics.

Two double-decker complexes with annulene ligands functionalized with indolenine groups were synthesized and characterized. The position of the proton acting as a counterion on one of the four indolenine nitrogen atoms was determined by using DFT calculations. Deprotonation and protonation of the complex induced by adding a base and an acid, respectively, were monitored by using NMR spectroscopy. Moreover, a correlation among the degree of protonation of the complex, the opening of the hysteresis, and the slow relaxation time is discussed.

We synthesized heterometallic Gd-Pt complexes ([Gd2Pt3(H2O)2(SAc)12] (1) (SAc = thioacetate), [Y1.4Gd0.6Pt3(H2O)2(SAc)12] (3), [La2Pt3(H2O)2(SAc)12] (4) and [Gd2Pt3(H2O)6(SAc)12]·7(H2O) (5). Crystal structure and DFT calculation indicated a Gd***Pt heretometallic bond. Single-crystal ESR spectra determined the direction of magnetic anisotropy as direction of the Gd***Pt bond. In other word, Gd***Pt bond lead the direction of magnetic anisotropy. The hetero metallic Gd-Pt bond lower the symmetry of the Gd ion, splitting the Kramers doublet in a dc field. Thus, we observed clear field induced slow magnetic relaxation of 3 up to 36 K. We determined the relaxation process to be a direct process.

Heterometallic Gd-Pt complexes ([Gd

The Dy

A major roadblock to fully realizing molecular electronic devices is the ability to control the properties of each molecule in the device. Herein we report the control of the magnetic properties of single-molecule magnets (SMMs), which can be used in memory devices, by using a photo-isomerizable diarthylenthene ligand. Photo-isomerization of the diarylethene ligand bridging two manganese salen complexes with visible light caused a significant change in the SMM behavior due to opening of the six-membered ring of diarylethene ligand, accompanied by reorganization of the entire molecule. The ring-opening activated the frequency-dependent magnetization of the complex. Our results are a major step towards the realization of molecular memory devices composed of SMMs because the SMM behaviour can be turned on and off simply by irradiating the molecule.

International audience; (TTF-salphen)M compounds (TTF-salphen(2-)=4,5-bis(propylthio)tetrathiafulvalene-N,N'-phenylenebis(salicylideneimine) dianion; M=Cu(II) and Ni(II)) have been treated with Ln(hfac)(3)*2H(2)O precursors (hfac(-)=1,1,1,5,5,5-hexafluoroacetylacetonate anion; Ln=Gd(III), Tb(III), and Dy(III)) to elaborate unprecedented 3d/4f TTF-based heterobimetallic complexes of formula [(TTF-salphen)MLn(hfac)(3)]. All the structures of these compounds have been resolved by X-ray diffraction on single crystals. The structures of these complexes are formed by a TTF-salphen(2-) ligand coordinated to the 3d metal ions in the inert tetradentate N(2)O(2) site. The Ln(hfac)(3) fragment is coordinated to the (TTF-salphen)M one through the two phenolate bridges. Even if the complexes are similar in both Cu(II) and Ni(II) families, the crystal packing is different. In the first case, dimers of TTF-salphen(2-) donors constitute the organic network. In the other case, a reminiscent organic network is observed with S***S contacts. The photophysical properties of [(TTF-salphen)CuDy(hfac)(3)] (3) in chloroform solution highlight the redshift of the TTF→salphen charge transfer (400 cm(-1)) relative to the analogue excitations in (TTF-salphen)Cu, which attest to the stability of these structures in solution. Static magnetic measurements have allowed us to quantify the ferromagnetic interactions (J=+1.29 cm(-1)) between Cu(II) and Gd(III) in the [(TTF-salphen)CuGd(hfac)(3)] complex. Finally, an empirical method that consists of the comparisons of the magnetic properties of [(TTF-salphen)CuTb(hfac)(3)] with [(TTF-salphen)NiTb(hfac)(3)] and [(TTF-salphen)CuDy(hfac)(3)] with [(TTF-salphen)NiDy(hfac)(3)] has established that ferromagnetic interactions take place between Cu(II) and Tb(III) ions, whereas unusual antiferromagnetic interactions have been identified between Cu(II) and Dy(III) ions.

Two-dimensional Dy(III) and Ho(III) homometal coordination polymers containing the photochromic ligand 1,2-bis(5-carboxyl-2-methyl-3-thienyl)perfluorocyclopentene (DTE) with the general formula [Ln2(DTE)3(bipyridine)2(H2O)2]n (Ln = Dy and Ho) were obtained, and the magnetic properties of their open (Dy-o and Ho-o) and closed forms (Dy-c and Ho-c) were investigated. The Dy complexes exhibited slow magnetic relaxation without an external dc field. The magnetic properties of the Dy complexes were irreversibly affected by the conformation of the ligand.

Chemists and physicists are continuously working to understand the mechanisms controlling molecular magnetism, especially single-molecule magnetism, to improve the magnetic properties, such as the blocking temperature. With the current research focused on preparing molecular devices, methods to control the components of the devices are necessary. Extensive research has shown that stimuli, such as light, electric current, etc., can be used to change the properties of the molecules making up the devices. Bis(carboxylato)dithienylethene (DTE) derivatives can be photo-isomerized between open and closed forms, i.e., unconjugated and π-conjugated forms, and because of the carboxylate groups, it can be used to link 3d and/or 4f metal ions. Herein the use of DTE ligands to remotely control the magnetic properties of single-molecule magnets is discussed.

Lanthanide-based extended coordination frameworks showing photocontrolled single-molecule magnet (SMM) behavior were prepared by combining highly anisotropic Dy(III) and Ho(III) ions with the carboxylato-functionalized photochromic molecule 1,2-bis(5-carboxyl-2-methyl-3-thienyl)perfluorocyclopentene (H2 dae), which acts as a bridging ligand. As a result, two new compounds of the general formula [{Ln(III) 2 (dae)3 (DMSO)3 (MeOH)}⋅10 MeOH]n (M=Dy for 1 a and Ho for 2) and two additional pseudo-polymorphs [{Dy(III) 2 (dae)3 (DMSO)3 (H2 O)}⋅x MeOH]n (1 b) and [{Dy(III) 2 (dae)3 (DMSO)3 (DMSO)}⋅x MeOH]n (1 c) were obtained. All four compounds have 2D coordination-layer topologies, in which carboxylate-bridged Ln2 units are linked together by dae(2-) anions into grid-like frameworks. All four compounds exhibited a strong reversible photochromic response to UV/Vis light. Moreover, both 1 a and 2 show field-induced SMM behavior. The slow magnetic relaxation of 1 a is influenced by the photoisomerization reaction leading to the observation of the cross-effect: photocontrolled SMM behavior.

Mononuclear complexes with the formula [Ln(hfac)3(L1)] and [Ln(hfac)3(L2)] with hfac– = 1,1,1,5,5,5-hexafluoroacetylacetonate, L1 = 2-{4,5-[4,5-bis(propylthio)tetrathiafulvalenyl]-1H-benzimidazol-2-yl}pyridine and L2 = 2-{1-methylpyridyl-4,5-[4,5-bis(propylthio)tetrathiafulvalenyl]-1H-benzimidazol-2-yl}pyridine are reported for Ln = YIII, ErIII and YbIII. The X-ray structures reveal that the Ln(hfac)3 moieties are coordinated to the bidentate 1-(2-pyridylmethyl)benzimidazole acceptor. The coordination polyhedron is described as a more or less distorted triangular dodecahedron prism (D2d symmetry), depending on the degree of alkylation of the ligand. The influence of this distortion on the magnetic and photophysical properties is determined by the fit of the static magnetic measurements and luminescence spectra. Irradiation of the lowest-energy intraligand charge transfer (ILCTs) bands (21740 cm–1) induces the metal-centred 4I13/2 4I15/2 and 2F5/2 2F7/2 luminescence for the ErIII and YbIII complexes, respectively. The alkylation enhances both the intensity and lifetime of the YbIII luminescence. The ErIII luminescence can be sensitised by the antenna effect, whereas the YbIII luminescence could involve a photoinduced electron transfer (PET). Finally, the evolution of the YbIII luminescence spectra shape due to the alkylation is directly correlated to the energy splitting of the MJ states that stem from the 2F7/2 multiplet ground state. Ab initio calculations give evidence of the nature of the MJ ground state as well as the orientation of the associated magnetic anisotropy axis (i.e., the one that lies along the less electronegative direction). The key role of the imidazole proton of L2 is highlighted. The calculated energy splitting of the 2F5/2 multiplet state perfectly matches the emission lines.

International audience; Reaction of the ligands 4,5-bis(propylthio)tetrathiafulvalene-2-(2-pyridyl)benzimidazole (L(1)) and 4,5-bis(propylthio)tetrathiafulvalene-2-(2-pyridyl)-3-(2-pyridinylmethyl)benzimidazole (L(2)) with Dy(hfac)3⋅2 H2O (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate) gave mononuclear complexes [Dy(hfac)3(L(1))] (1) and [Dy(hfac)3(L(2))] (2). In both compounds the Dy(III) ion is surrounded by six oxygen and two nitrogen atoms. Complex 1 displays single-ion magnet (SIM) behaviour only in solution (Δ=12(1) K and τ0 =1.9(4)×10(-6) s), while complex 2 is a SIM in both solution (Δ=15(2) K and τ0 =1.5(3)×10(-6) s) and solid state (Δ=17(2) K and τ0 =9.5(2)×10(-6) s). The SIM behaviour is obtained if the hydrogen bond is broken by dissolution (1 in solution) or by alkylation (2). Multiple relaxation processes were identified for 2 with two competing processes: a fast one in zero field and a slow one for fields higher than 500 Oe. The two processes coexist for intermediate applied magnetic field. Magnetic-dilution and frozen-solution measurements led to the conclusion that the origin of these multiple relaxation processes is not due to the property of a single molecule.

Electrochemical oxidation of a solution containing KDy(hfac)4 (hfac, hexafluoroacetyacetone) and Bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) afforded a hybrid material formulated as [β′-(BEDT-TTF)2Dy(CF3COO)4∙MeCN]n. The complex crystallizes in the triclinic space group P 1 ¯ . The before mentioned complex has a chain structure containing 4f ions bridged by mono-anion CF3COO− ligand, and acts as single-molecule magnet (SMM) at low temperature. The conducting layer was composed of partially oxidized BEDT-TTF molecules in β′ type arrangement. The presence of radical cation and its charge ordering was assigned on the basis of optical spectra. Electrical resistivity measurements revealed semiconducting behaviour (conductivity at room temperature of 1.1 × 10−3 S·cm−1, activation energy of 158.5 meV) at ambient pressure.

Three isostructural 1D lanthanoid complexes with the general formula {[Ln2(DTE)(H-DTE)(MeOH)2]·2H2O}n (Ln = Tb, Dy, and Yb; DTE = 1,2-bis(5-carboxyl-2-methyl-3-thienyl) perfluorocyclopentene) were synthesized. In the 1D chain structure of each complex, lanthanide ions are seven coordinate with a capped trigonal prism geometry. The 1,2-bis(5-carboxyl-2-methyl-3-thienyl) perfluorocyclopentene (DTE) ligand adopts a parallel configuration in these complexes, which results in the loss of the photo-isomerization ability of the ligand. From magnetic measurements, each complex undergoes slow relaxation of the magnetization via multiple processes in a dc field.

International audience; Six new 3d4f heterobimetallic dinuclear complexes, [(L(1))MLn(hfac)(3)] [M = Cu(II), Ni(II); Ln = Y(III), Er(III), Yb(III); L(1) = 4,5-bis(propylthio)tetrathiafulvalene-N,N'-phenylenebis(salicylideneimine) and hfac(-) = 1,1,1,5,5,5-hexafluoroacetylacetonate], and one tetranuclear complex, [(L(2))Cu(OH)Er(hfac)(3)](2) (where L(2) = 4,5-bis(propylthio)tetrathiafulvalene-N,N'-phenyleneaminosalicylideneimine), have been synthesized. All of the X-ray structures of the coordination complexes have been resolved from single-crystal diffraction. A quantitative magnetic approach has allowed one to determine the Cu-Ln ferromagnetic interaction for Gd(III) (1.29 cm(-1)) and Tb(III) (0.40 cm(-1)) and the antiferromagnetic interaction for Dy(III) (-0.46 cm(-1)) and Yb(III) (-2.25 cm(-1)), while in the case of Er(III), the magnetic interactions are negligible. The UV-visible absorption properties have been studied in a chloroform solution and rationalized by DFT and TD-DFT calculations. Upon oxidation, intramolecular SOMO → LUMO (20,800 cm(-1)) and SOMO-n → SOMO (11,350 cm(-1)) charge transfers appear, while the HOMO → LUMO charge transfers (20,750 cm(-1)) disappear. The reversibility of the oxidation has been confirmed by electrochemistry and absorption properties upon the addition of a reducing agent. Irradiation at the HOMO → LUMO charge-transfer energy of the dinuclear complex [(L(1))NiY(hfac)(3)] induces a ligand-centered fluorescence at 14,450 cm(-1).

The tetrathiafulvalene based 2-immino-pyrazine derivative (TTF-CHN-2-pyz) (1) was synthesized and characterized. Its radical cation salt (1˙+PF6−) was prepared as single crystals by electrocrystallisation. 1˙+PF6− crystallizes in the triclinic P space group. Four 1 : 2 bis(hexafluoroacetylacetonate)M(II) complexes coordinated with 1 were prepared (M = Mn for 2, M = Co for 3, M = Cu for 4 and M = Zn for 5). Complex 2 crystallizes in the monoclinic C2/c space group, complexes 4 and 5 crystallize in the triclinic space group P. Two pyrazine N atoms from two different donors are coordinated in cis configuration for 2 and trans configuration for 4 and 5 to the metallic ion of M(hfac)2 (hfac−=hexafluoroacetylacetonate anion). The manganese atom adopts a pseudo-compressed octahedral geometry while the copper and the zinc ions adopt axially elongated octahedral geometries. Both crystal packing structures and electrochemical properties are appropriate for their potential use as starting molecular bricks for conducting and magnetic materials.