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Here we report magneto-chiral dichroism (MChD) detected through visible and near-infrared light absorption of a chiral dysprosium(III) coordination polymer. The two enantiomers of [DyIII(H6(py)2)(hfac)3]n[H6(py)2= 2,15-bis(4-pyridyl)ethynylcarbo[6]helicene; hfac–= 1,1,1,5,5,5-hexafluoroacetylacetonate], where the chirality is provided by a functionalized helicene ligand, were structurally, spectroscopically, and magnetically investigated. Magnetic measurements reveal a slow relaxation of the magnetization, with differences between enantiopure and racemic systems rationalized on the basis of theoretical calculations. When the enantiopure complexes are irradiated with unpolarized light in a magnetic field, they exhibit multiple MChD signals associated with the f–f electronic transitions of DyIII, thus providing the coexistence of MChD-active absorptions and single-molecule-magnet (SMM) behavior. These findings clearly show the potential that rationally designed chiral SMMs have in enabling the optical readout of magnetic memory through MChD.

Generating or even retaining slow magnetic relaxation in surface immobilized single-molecule magnets (SMMs) from promising molecular precursors remains a great challenge. Illustrative examples are organolanthanide compounds that show promising SMM properties in molecular systems, though surface immobilization generally diminishes their magnetic performance. Here, we show how tailored Lewis acidic Al(III) sites on a silica surface enable generation of a material with SMM characteristics via chemisorption of (Cpttt)2DyCl ((Cpttt)−= 1,2,4-tri(tert-butyl)-cyclopentadienide). Detailed studies of this system and its diamagnetic Y analogue indicate that the interaction of the metal chloride with surface Al sites results in a change of the coordination sphere around the metal center inducing for the dysprosium-containing material slow magnetic relaxation up to 51 K with hysteresis up to 8 K and an effective energy barrier (Ueff) of 449 cm–1, the highest reported thus far for a supported SMM.

Using an edaravone-based aryloxide ligand, we assemble four new mononuclear Dy(III) compounds, [Dy(L1)2(CH3OH)2]·Br (1); [Dy(L1)2(CH3OH)2]·Cl (2); [Dy(L1)2(CH3OH)(NO3)] (3); and [Dy(L2)3]·2CH3OH·H2O (4) (where L1 = methyl-substituted and L2 = p-tolyl-substituted ligands with NNO-tridentate coordination environments). As revealed by the magneto-structural and ab initio calculations, the complexes exhibited a slow relaxation of the magnetization at zero applied magnetic field where their magnetic properties were subtly tuned via chemical modifications on the dominant crystal field interaction. For the complexes with L1 analogue under eight-coordination, complexes 1and 2(D4dsymmetry) with noncoordinated halides showed better magnetic properties as compared to complex 3(C2vsymmetry) due to the presence of a strongly coordinated nitrate anion that leads to a change in the structural arrangement. However, complex 4(C4vsymmetry) with nine-coordination was found structurally unfavorable comparatively due to the coordination of an additional third ligand (L2) that leads to a higher coordination number as a result of the substituent change. Therefore, the presented compounds exhibit ligand substituent- as well as counterion-dependent magnetic property variations. A relatively higher effective energy barrier (Ueff) was obtained for the compounds having halide counter anions as compared with the neutral complexes. Moreover, the ab initio calculations revealed that the transition magnetic moment probabilities for these compounds present very small or even vanishing quantum tunneling of magnetization between the ground-state Kramers doublets and indicate that the slow relaxation might proceed through higher excited states. Finally, the described new compounds are expected to advance the aryloxide single-molecule magnets.

A series of homometallic dinuclear lanthanide complexes containing nonequivalent lanthanide metal centers [Ln2(LH2)(LH)(CH3OH)(N3)]·xMeOH·yH2O [1, Ln = DyIII, x= 0, y= 2; 2, Ln = TbIII, x= 1, y= 1] have been synthesized [LH4= 6-((bis(2-hydroxyethyl)amino)-N′-(2-hydroxybenzylidene)picolinohydrazide] and characterized. The dinuclear assembly contains two different types of nine-coordinated lanthanide centers, because the nonequivalent binding of the azide co-ligand as well as the varying coordination of the deprotonated Schiff base ligand. Detailed magnetic studies have been performed on the complexes 1and 2. Complex 1and its diluted analogue (15%) are zero-field SMMs with effective energy barriers (Ueff) of magnetization reversal equal to 59(3) K and 66(3) K and relaxation times of τ0= 10(4) × 10–6s and 10(4) × 10–8s, respectively. On the other hand, complex 2shows a field-induced SMM behavior. Combined ab initioand density functional theory calculations were performed to explain the experimental findings and to unravel the nature of the magnetic anisotropy, exchange-coupled spectra, and magnetic exchange interactions between the two lanthanide centers.

Synthesis of a bis-strapped porphyrin with a pyridyl residue on one side and a malonic acid on the other side gives after iron(II) insertion a six-coordinate complex in which both apical groups are the two axial ligands of the iron atom. Unexpectedly, this six-coordinate iron(II) complex proves to be high-spin, likely due to some stabilization of the axial metal−ligand antibonding orbitals.

Here we report the first experimental observation of magneto-chiral dichroism (MChD) detected through light absorption in an enantiopure lanthanide complex. The Pand Menantiomers of [YbIII((X)-L)(hfac)3] (X = P, M; L= 3-(2-pyridyl)-4-aza[6]-helicene; hfac= 1,1,1,5,5,5-hexafluoroacetylacetonate), where the chirality is held by the helicene-based ligand, were studied in the near-infrared spectral window. When irradiated with unpolarized light in a magnetic field, these chiral complexes exhibit a strong MChD signal (gMChDca. 0.12 T–1) associated with the 2F5/2← 2F7/2electronic transition of YbIII. The low temperature absorption and MChD spectra reveal a fine structure associated with crystal field splitting and vibronic coupling. The temperature dependence of the main dichroic signal detected up to 150 K allowed, for the first time, the disentanglement of the two main microscopic contributions to the dichroic signal predicted by the MChD theory. These findings pave the way toward probing MChD in chiral lanthanide-based single-molecule magnets.

An unprecedented combination of isotopic enrichment and magnetic dilution approaches for a prolate ytterbium(III)-based complex was performed. It results in the appearance of the first observations of a nuclear spin effect on both quantum tunneling of magnetization and slow magnetic relaxation for an ytterbium complex under a zero applied field.

We report persistent chiral organic mono- and diradical cations based on bicarbazole molecular design with an unprecedented stability dependence on the type of chirality, namely, axial versus helical. An unusual chemical stability was observed for sterically unprotected axial bicarbazole radical in comparison with monocarbazole and helical bicarbazole ones. Such results were experimentally and theoretically investigated, revealing an inversion in energy of the singly occupied molecular orbital (SOMO) and the highest (doubly) occupied molecular orbital (HOMO) in both axial and helical bicarbazole monoradicals along with a subtle difference of electronic coupling between the two carbazole units, which is modulated by their relative dihedral angle and related to the type of chirality. Such findings allowed us to explore in depth the SOMO–HOMO inversion (SHI) in chiral radical molecular systems and provide new insights regarding its impact on the stability of organic radicals. Finally, these specific electronic properties allowed us to prepare a persistent, intrinsically chiral, diradical which notably displayed near-infrared electronic circular dichroism responses up to 1100 nm and almost degenerate singlet–triplet ground states with weak antiferromagnetic interactions evaluated by magnetometry experiments.

A series of four isomorphous, 1:2 (complex/L) rare cocrystals of coordination compounds of Ln(III) ions as [Ln(L)(NO3)3(H2O)]2[L]2(Ln(III) = Gd (1), Tb (2), Dy (3), and Ho (4)), were synthesized with N,N-diisobutylisonicotinamide (L) using a metal-to-ligand ratio of 1:1. All compounds are dimeric in nature with two cocrystallized Lmolecules centro-symmetrically interspersed between two dimeric units with H-bonded bridges between them to form interesting, self-assembled H-bonded tapes along the c-axis. Detailed Shape analysis and Hirshfeld analysis are done to demonstrate geometry around the metal centers and various noncovalent interactions present in the systems, respectively. Magnetic studies show that compound 3is a field-induced single-molecule magnet (SMM) for which the magnetization relaxes through a combination of Orbach (Δ = 51 K and τ0= 3.1 × 10–7s) and Raman mechanisms. Solid-state luminescence studies reveal that compounds 1, 2, and 3are photoluminescent in the visible range, while 4exhibits luminescence in the NIR region. Compound 3shows cold white-light emission with Commission Internationale de l’Eclairage (CIE) coordinates (0.31, 0.30) and correlated color temperature (CCT) value of 6942 K.

Four hexanuclear circular helicates, {[Dy6L6(DMF)12]·6CF3SO3·12DMF}2(1Dy), {[Gd6L6(DMF)12]·6CF3SO3·12DMF}2(1Gd), [Dy6L6(DMF)10(H2O)2]·6ClO4·4H2O·10DMF (2Dy), and [Gd6L6(DMF)12]·6ClO4·2H2O·10DMF (2Gd), where DMF = N,N-dimethylformamide, were synthesized by employing a glutaratedihydrazide-bridged bis(3-methoxysalicylaldehyde) ligand (H2L) and characterized structurally and magnetically. Direct-current magnetic susceptibility studies indicated predominant weak antiferromagnetic exchange interactions among gadolinium analogues, which were quantified using the PHIsoftware, giving J= −0.003 cm–1with g= 2.00 for 1Gdand J= −0.001 cm–1with g= 2.02 for 2Gd. Alternating-current magnetic susceptibility measurements indicated that complexes 1Dyand 2Dyshow slow relaxation of magnetization behavior, further supported by theoretical calculations that also highlighted the toroidal arrangement of the magnetic moments.

Four new dinuclear complexes, [Co(μ-L)(μ-CCl3COO)Y(NO3)2]·2CHCl3·CH3CN·2H2O (1), [Co(μ-L)(μ-CH3COO)Y(NO3)2]·CH3CN (2), [Co(μ-L)(μ-PhCOO)Y(NO3)2]·3CH3CN·2H2O (3), and [Co(μ-L)(μ-tBuCOO)Y(NO3)2]·CHCl3·2H2O (4), having a CoIIYIIIcore, have been synthesized by employing a ferrocene based compartmental ligand which was synthesized by the reaction of diacetyl ferrocene with hydrazine hydrate followed by a condensation reaction with o-vanillin. A general synthetic protocol was employed to synthesize complexes 1–4, where the metallic core was kept the same with changing the bridging carboxylate groups. In all the complexes, the main structural motif is kept similar by only slightly varying the substitution on the bridging acetate groups. This variation has resulted in a small but subtle influence on the magnetic relaxation of all these four compounds. Ab initioCASSCF/NEVPT2 calculations were carried out to assess the effect of the different substitutions of the bridging ligands on the magnetic anisotropy parameters and on orbital arrangements. Ab initiocalculations yield a very large positive Dvalue, which is consistent with the geometry around the CoIIion and easy plane anisotropy (gxx, gyy> gzz), with the order of the calculated Din the range of 72.4 to 91.7 cm–1being estimated in this set of complexes. To ascertain the sign of zero-field splitting in these complexes, EPR spectra were recorded, which support the sign of Dvalues estimated from ab initiocalculations.

Complete and restricted active space self-consistent field (CAS-/RAS-SCF) wave function methods are applied for the calculation of circular dichroism (CD) and circularly polarized luminescence (CPL) of a series of molecules comprising four organic ketones, the chiral cobalt(III) complex [Co(en)3]3+, and the europium(III) complex [Eu(DPA)3]3–. The ab initio results are in good agreement with the experimental data and previous results obtained with Kohn–Sham density functional theory in the case of the spin-allowed transitions. CD and CPL properties are calculated ab initio for the spin-forbidden transitions of both a transition metal and a lanthanide complex.

The tailoring of the coordination chemistry around f-element centers is a crucial step for the development of compounds with slow magnetic relaxation, including single-molecule magnets (SMMs), which have great potential in molecular spintronics and for future quantum computing devices. Lanthanide ions are particularly interesting because the predominant electrostatic model of their bonding allows rationalizing their coordination symmetry. However, to the best of our knowledge, the redox properties of the lanthanides are not taken into account for the design of SMMs, and therefore all SMMs reported to date contain lanthanide ions in their trivalent oxidation state. In this Article, divalent lanthanide compounds presenting field-induced slow magnetic relaxation are reported. The rational design and synthesis of two TmIIcomplexes with the 18-crown-6 ligand are presented along with their emission and EPR properties, which help to probe the desired nature of the ground state, that is, maximizing the anisotropy. The observed magnetic properties demonstrate their slow magnetic relaxation behavior in a moderate external magnetic field.

The design of a coordination complex that involves a ligand combining both a tetrathiafulvalene core and a helicene fragment was achieved thanks to the reaction between the new 2-{1-[2-methyl[6]helicene]-4,5-[4,5-bis(propylthio)tetrathiafulvalenyl]-1H-benzimidazol-2-yl}pyridine ligand (L) and the Dy(hfac)3·2H2O metalloprecursor. Magnetic investigations showed field-induced single-molecule-magnet (SMM) behavior under an applied magnetic field of 1000 Oe for [Dy(hfac)3(L)]·0.5CH2Cl2, while experimentally oriented single-crystal magnetic measurements allowed for determination of the magnetic anisotropy orientation. The magnetic behavior was rationalized through ab initio CASSCF/SI-SO calculations. This redox-active chiral-field-induced SMM paves the way for the design of switchable-multiproperty SMMs.

The rational design of molecular chains made of 4f ions and substituted 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical is presented. The reaction of Ln(hfac)3·2H2O (hfac–= hexafluoroacetylacetonate) and the 4-cyano-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO-CN) radical affords air- and moisture-stable isostructural molecular chains of the formula [Ln(hfac)3TEMPO-CN]nfor Ln = GdIIIand TbIII, whereas zero-dimensional complexes of the formula [Dy(hfac)3(TEMPO-CN)2][Dy(hfac)3(H2O)2]2are obtained for Ln = DyIII. To the best of our knowledge, the Gd derivative, Gd-TEMPO-CN, shows one of the strongest antiferromagnetic (AF) couplings for Gd–radical pairs ever reported with JGd–rad/kB= −21.18 K, 14.72 cm–1(H= −JSradSGdspin Hamiltonian convention). The TbIIIderivative, Tb-TEMPO-CN, also shows strong Tb–radical AF coupling, which has been rationalized using the ab initio CASSCF approach (JTb–rad= −23.02 K, −16.7 cm–1) and confirmed by luminescence measurements. Tb-TEMPO-CNshows remarkable properties for a Tb–radical-based single-molecule magnet (Ueff= 69.3 ± 1 K; τ0= 1.3 × 10–7s) and two different relaxation processes triggered by interchain magnetic coupling.

The study of mononuclear lanthanide-based systems, where the observed single-molecule magnets (SMMs) properties originate from the local description of the magnetic properties of the lanthanide ion, has been widely investigated through the literature. The case of polynuclear SMMs becomes more challenging both experimentally and theoretically due to the complexity of such architectures involving interactions between the magnetic centers. Many efforts have been focused on the understanding of the nature of these interactions and their effects on the SMM properties. In this work, a series of three structurally related tetranuclear dysprosium(III) SMMs, namely, [Dy4(L)4(OH)2(DMF)4(NO3)2]·2(DMF)·(H2O) (1), [Dy4(L)4(OH)2(DMF)2(tfaa)2]·2(CH3CN) (2), and [Dy4(L)4(OH)2(DMF)2(acac)2]·2(DMF) (3) (H2L = 2-(2-hydroxy-3-methoxybenzylideneamino)phenol, Htfaa = trifluoroacetylactone, Hacac = acetylacetonate), has been synthesized and investigated. By a fine-tuning of the ligands on the changeable coordination sites in these Dy(III)4SMMs, the intramolecular magnetic interactions can be modified, switching from antiferromagnetic (for 1and 2) to ferromagnetic (for 3). Ab initiocalculations support these statements. In addition, the formation of 1has been analyzed by ESI-MS analysis of the reaction mixture, indicating rather quick and high-yield formation of the [Dy4] framework in solution. The combination of experimental work and ab initiocalculations offers further insight into the relationship between structures and magnetic properties and sheds light on how to tune magnetic interactions in future polynuclear dysprosium complexes.

Three mononuclear DyIIIcomplexes with the same auxiliary ligand Lz (2,4-diamino-6-pyridyl-1,3,5-triazine), [Dy(TTA)3Lz] (1Dy) (TTA = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionate), [Dy(acac)3Lz]·CH3OH·0.5H2O (2Dy) (acac = acetylacetonate), and [Dy(MQ)2Lz2]Br·CH3OH (3Dy) (HMQ = 2-methyl-8-quinolinol), have been synthesized through alteration of the ligands containing O donors. In all three complexes, the DyIIIions are eight-coordinate and submitted to pseudo-D4dsymmetry in the first coordination sphere. It is noteworthy that the TTA ligands in 1Dyare easily substituted by other bidentate capping ligands with O donors, leading to distinct magnetic properties, which were studied experimentally and via ab initiocalculations. All three complexes were found to exhibit single-molecule magnet behavior with Ueffof 22 cm–1(1Dy), 112 cm–1(2Dy), and 56 cm–1(3Dy) under zero applied dc field. Complex 1Dydemonstrates inferior SIM properties compared with 2Dyand 3Dy, which can be attributed to the strong electron-withdrawing effects of TTA ligands, as confirmed by theoretical calculations. However, butterfly-shaped magnetic hysteresis in 1Dyand 3Dywas observed at 1.9 K, while not in 2Dy.

A series of mononuclear DyIIIcomplexes with the general formula [DyLz2(salicylaldehyde)2]·X·solvent (Lz = 6-pyridin-2-yl[1,3,5]triazine-2,4-diamine; X = OH–(1·OH), Cl–(2·Cl), Br–(3·Br)) have been synthesized using mixed salicylaldehyde/pyridinyl-triazine ligands and discriminative counteranions. The DyIIIion in these three complexes resides in a similar D4dcoordination geometry with counteranions perturbing the coordination environment and bond lengths and angles in the lattice. Magnetostructural studies reveal that the asymmetric distribution of salicylaldehyde/pyridinyl-triazine ligands and the presence of discriminative counteranions result in the coexistence of large anisotropy and quantum tunneling of magnetization. The magnetic anisotropy is dominated by the axial ligand field with short Dy–Osalidistances and large ∠Osali–Dy–Osaliangles, while the quantum tunneling relaxation is probably dictated by the π–π stacking of the Lz ligands, which induces an axial constriction of the coordinating plane. Ab initio calculations substantiate the diversity of the magnetic behaviors in these complexes and highlight the importance of axial ligand field with short Dy–Osalidistances, large ∠Osali–Dy–Osaliangles and less ligand stacking in these pseudo-D4d-symmetrical single-molecule magnets.

We report a combined theoretical and experimental investigation of the exchange interactions governing the magnetic behavior of a series of nitronyl nitroxide (NIT)-based Y(III) complexes, i.e., Y(hfac)3(NIT-R)2with R = PhOPh (1), PhOEt (2), and PhOMe (3a, 3b). Even though some of these complexes or their Dy(III) parents were previously described in the literature [Zhao et al. Transition Met. Chem.2006, 31, 593; Bernot et al. J. Am. Chem. Soc.2009, 131, 5573], their synthesis procedure as well as their structural and magnetic properties were completely reconsidered. Depending on the nature of R and the crystallization conditions, Y(hfac)3(NIT-R)2units can be organized as supramolecular dimers or linear or orthogonal chains. Such structural diversity within the series induces extremely different magnetic behaviors. The observed behaviors are rationalized by state-of-the-art wave function-based quantum-chemical approaches (CASSCF/DDCI) that demonstrate the existence of not only effective intramolecular interactions between the NIT-R radical ligands of an isolated Y(hfac)3(NIT-R)2molecule but also intermolecular interactions between NIT-R moieties belonging to different Y(hfac)3(NIT-R)2units. These results are supported by the use of spin Hamiltonian models going beyond the basic Bleaney–Bowers formalism to properly fit the experimental magnetic data. Finally, the microscopic mechanisms behind the evidenced intramolecular exchange interactions are elucidated through the inspection of the calculated wave functions. In particular, whereas the role of Y orbitals was already proposed, we herein demonstrate the contribution of the hfac–ancillary ligands in mediating the magnetic interactions between the NIT radicals.

Achieving magnetic remanence at single isolated metal sites dispersed at the surface of a solid matrix has been envisioned as a key step toward information storage and processing in the smallest unit of matter. Here, we show that isolated Dy(III) sites distributed at the surface of silica nanoparticles, prepared with a simple and scalable two-step process, show magnetic remanence and display a hysteresis loop open at liquid 4He temperature, in contrast to the molecular precursor which does not display any magnetic memory. This singular behavior is achieved through the controlled grafting of a tailored Dy(III) siloxide complex on partially dehydroxylated silica nanoparticles followed by thermal annealing. This approach allows control of the density and the structure of isolated, “bare” Dy(III) sites bound to the silica surface. During the process, all organic fragments are removed, leaving the surface as the sole ligand, promoting magnetic remanence.

The article reports the synthesis and structural characterization of a series of Ln(C9H9)3complexes with the cyclononatetraenyl (Cnt, C9H9) ligand (Ln = Y, Gd, Tb, Dy, Ho, Er, Tm). The Yb and Sm complexes were not obtained, and the reaction of the potassium salt of the Cnt ligand with trivalent halide salts of the corresponding metals led to the known bis-Cnt sandwich compounds Ln(C9H9)2. The X-ray diffraction studies on the trivalent complexes show that the Cnt ligand is significantly bent in order to accommodate the large size of the ligand while it maintains its aromaticity. When the size of the lanthanide ion decreases, the ligand does not switch away but swings over the metal ion in order to maximize the electrostatic interactions. 1H NMR and UV–visible spectra, as well as the solid-state magnetism, were recorded. UV–visible spectroscopy highlights a remarkable charge-transfer band in the Tm complex, while ligand-based transitions are principally observed with all other metal ions. The magnetic behavior of the series agrees with trivalent lanthanide ions, and the computations at the CASSCF level confirm the trivalent electronic structure.

The reaction of bulky trimethylsilylanilide (N-TMSA) ligand with various lanthanide salts led us to isolate unusual and unique four-coordinate monomeric Ln(III) complexes which are challenging to isolate and not surprisingly rare in the literature. The single crystal X-ray diffraction unveils that all the complexes are monomeric and isostructural with the general molecular formula of [Ln(N-TMSA)3(THF)] where Ln = Dy (1) or Yb (2). Both complexes are found to possess distorted tetrahedral geometry. For all the complexes, detailed dc and ac susceptibility measurements were performed and both 1and 2show frequency-dependent out-of-phase susceptibility signals only in the presence of an optimum external magnetic field. The experimental observations are well supported by theoretical calculations and developed magneto-structural correlation using the various model complexes.

We report a new molecular design to afford persistent chiral organic open-shell systems with configurational stability and an inversion in energy of the singly occupied molecular orbital (SOMO) and the highest doubly occupied molecular orbital (HOMO) for both mono- and diradical states. The unpaired electron delocalization within the designed extended helical π-conjugated systems is a crucial factor to reach chemical stabilities, which is not obtained using the classical steric protection approach. The unique features of the obtained helical monoradicals allow an exploration of the chiral intramolecular electron transfer (IET) process in solvents of different polarity by means of optical and chiroptical spectroscopies, resulting in an unprecedented electronic circular dichroism (ECD) sign inversion for the radical transitions. We also characterized the corresponding helical diradicals, which show near-infrared electronic circular dichroism at wavelengths up to 1100 nm and an antiferromagnetic coupling between the spins, with an estimated singlet–triplet gap (ΔEST) of about −1.2 kcal mol–1. The study also revealed an intriguing double SOMO–HOMO inversion (SHI) electronic configuration for these diradicals, providing new insight regarding the peculiar energetic ordering of radical orbitals and the impact on the corresponding (chiral) optoelectronic properties.

Trinuclear building block {Fe2NiO(Piv)6} (Piv=pivalate), which possessed pseudo‐D3hsymmetry, was linked by two ligands, pseudo‐D3hligand tris‐(4‐pyridyl)pyridine (L1) and C2vligand 4‐(N,N‐dimethylamino)phenyl‐2,6‐bis(4‐pyridyl)pyridine (L2) into two products with different topologies: 2D coordination polymer [Fe2NiO(Piv)6(L1)]n(1), and discrete molecule [{Fe2NiO(Piv)6}8{L2}12], which had a nanocube structure (2). In compound 1, trinuclear {Fe2NiO(Piv)6} blocks were linked through ligand L1 into layers with honeycomb topology. In compound 2, eight trinuclear blocks were located in the vertices of the nanocube, with each L2 ligand linked to two {Fe2NiO(Piv)6} units. In the crystal structure, these nanocubes formed infinite catenated chains. Analysis of possible structures that could be assembled from these building blocks showed that compounds 1and 2corresponded to their respective predicted topologies. Compound [1⋅solvent] possessed a porous structure, in which the voids were filled by solvent molecules (DMF or DMSO). This structure was retained following desolvation, and compound 1absorbed significant quantities of N2and H2at 78 K (SBET=730 m2g−1, H2sorption capacity: 0.9 % by weight at 865 Torr). Desolvation of [2⋅solvent] led to disorder of its crystal structure, and compound 2only adsorbed negligible quantities of N2but adsorbed 0.27 % H2(by weight) at 855 Torr and 78 K. The magnetic properties of these complexes (temperature dependence of molar magnetic susceptibility) were governed by the magnetic properties of the trinuclear “building block”.

The temperature dependence of crystal structure parameters of isostructural coordination polymers Fe2MO(Piv)6(bipy)1.5·2DMF [1·2DMF and 2·2DMF, where M = NiIIor CoII, respectively, Piv = (CH3)3CCO2–, bipy = 4,4‐bipyridine and DMF is N,N‐dimethylformamide] was studied at five temperatures in the range from 120 to 296 K. The X‐ray structure of the N,N‐diethylformamide (DEF) solvate of the same coordination polymer 1, Fe2NiO(Piv)6(bipy)1.5·2DEF (1·2DEF), was studied at 173 and 260 K. Both the DMF and DEF solvates possess similar crystal structures, consisting of a series of parallel 2D polymeric layers with honeycomb voids. These series of parallel layers intersect, leading to their interpenetration and formation of zig‐zag channels. It was found that the change of temperature and/or solvent molecule in the pores causes significant structural rearrangement associated with a change of the separation between parallel layers and the angle between intersecting layers. These structural changes lead to a variation of the calculated solvent‐accessible volume from 0.21 cm3g–1(120 K, 2·2DMF) to 0.30 cm3g–1(260 K, 1·2DEF) for a probe molecule with r= 1.4 Å. These changes can model structural transformations which can occur at desolvation and adsorption of guests. Adsorption of n‐hexane, n‐octane, methanol and ethanol by Fe2MO(Piv)6(bipy)1.5was studied. The sorption isotherms of alkanes were typical for microporous sorbents and in this case the behaviour of the coordination polymers resembled that which is typical for sorbents with a rigid structure. In a contrast, alcohol sorption capacity continuously grew at increasing pressure which may be caused by structural transformations, similar to temperature‐induced structural transformations. Among the studied sorbates, sorption capacity grew in order methanol < ethanol < n‐hexane < n‐octane which may be caused by the hydrophobic nature of the channels (due to the presence of tert‐butyl groups).

(TTF‐salphen)M compounds (TTF‐salphen2−=4,5‐bis(propylthio)tetrathiafulvalene‐N,N′‐phenylenebis(salicylideneimine) dianion; M=CuIIand NiII) have been treated with Ln(hfac)3⋅2 H2O precursors (hfac−=1,1,1,5,5,5‐hexafluoroacetylacetonate anion; Ln=GdIII, TbIII, and DyIII) 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‐salphen2−ligand coordinated to the 3d metal ions in the inert tetradentate N2O2site. The Ln(hfac)3fragment is coordinated to the (TTF‐salphen)M one through the two phenolate bridges. Even if the complexes are similar in both CuIIand NiIIfamilies, the crystal packing is different. In the first case, dimers of TTF‐salphen2−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 CuIIand GdIIIin 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 CuIIand TbIIIions, whereas unusual antiferromagnetic interactions have been identified between CuIIand DyIIIions.

The reactions between the [Ln(tta)3]⋅2 H2O precursors (tta−=2‐thenoyltrifluoroacetonate anion) and the tetrathiafulvalene‐3‐pyridine‐N‐oxide ligands (L1) lead to dinuclear complexes of formula [{Ln(tta)3(L1)}2]⋅xCH2Cl2(x=0.5 for Ln=DyIII(1) and x=0 for Ln=GdIII(2)). The crystal structure reveals that two {Ln(tta)3} moieties are bridged by two donors through the nitroxide groups. The DyIIIcentre adopts a distorted square antiprismatic oxygenated polyhedron structure. The antiferromagnetic nature of the exchange interaction between the two DyIIIions has been determined by two methods: 1) an empirical method using the [Dy(hfac)3(L2)2] mononuclear complex as a model (3) (hfac−=1,1,1,5,5,5‐hexafluoroacetylacetonate anion, L2=tetrathiafulvaleneamido‐2‐pyridine‐N‐oxide ligand), and 2) assuming an Ising model for the DyIIIion giving an exchange energy of −2.30 cm−1, g=19.2 in the temperature range of 2–10 K. The antiferromagnetic interactions have been confirmed by a quantitative determination of Jfor the isotropic GdIIIderivative (J=−0.031 cm−1, g=2.003). Compound 1displays a slow magnetisation relaxation without applied external magnetic fields. Alternating current susceptibility shows a thermally activated behaviour with pre‐exponential factors of 5.48(4)×10−7s and an energy barrier of 87(1) K. The application of an external field of 1.6 kOe compensates the antiferromagnetic interactions and opens a new quantum tunnelling path.

The tetrathiafulvalene‐amido‐2‐pyridine‐N‐oxide (L) ligand has been employed to coordinate 4f elements. The architecture of the complexes mainly depends on the ionic radii of the lanthanides. Thus, the reaction of Lin the same experimental protocol leads to three different molecular structure series. Binuclear [Ln2(hfac)5(O2CPhCl)(L)3]⋅2 H2O (hfac−=1,1,1,5,5,5‐hexafluoroacetylacetonate anion, O2CPhCl−=3‐chlorobenzoate anion) and mononuclear [Ln(hfac)3(L)2] complexes were obtained by using rare‐earth ions with either large (LnIII=Pr, Gd) or small (LnIII=Y, Yb) ionic radius, respectively, whereas the use of TbIIIthat possesses an intermediate ionic radius led to the formation of a binuclear complex of formula [Tb2(hfac)4(O2CPhCl)2(L)2]. Antiferromagnetic interactions have been observed in the three dinuclear compounds by using an extended empirical method. Photophysical properties of the coordination complexes have been studied by solid‐state absorption spectroscopy, whereas time‐dependent density functional theory (TD‐DFT) calculations have been carried out on the diamagnetic YIIIderivative to build a molecular orbital diagram and to reproduce the absorption spectrum. For the [Yb(hfac)3(L)2] complex, the excitation at 19 600 cm−1of the HOMO→LUMO+1/LUMO+2 charge‐transfer transition induces both line‐shape emissions in the near‐IR spectral range assigned to the 2F5/2→2F7/2(9860 cm−1) ytterbium‐centered transition and a residual charge‐transfer emission around 13 150 cm−1. An efficient antenna effect that proceeds through energy transfer from the singlet excited state of the tetrathiafulvalene‐amido‐2‐pyridine‐N‐oxide chromophore is evidence of the YbIIIsensitization.

Reaction of a dinuclear cationic copperII complex of 4,4′[23hydroxyiminobutylimino]biphenyl [CuII2LH2]2+with N3–resulted in the formation of a dinuclear azido [CuII2LH2N32H2O2] complex or a 2D coordination polymer [CuII2LH2N32]n. Reaction of the dinuclear complex with [CrIIINCS6]3–or [CrIIINCS4NH32]–produced a 2D polymer [CuII2LH2CH3CN2]3[CrIIINCS6]2nor a 1D chain, constructed from tetranuclear units [CuII2LH2][CrIIINCS4NH32]2n. Structures of the compounds were determined by Xray crystallography and complexes were characterised by the temperature dependency of the magnetic susceptibility and by ESR spectroscopy. Magnetic properties of homometallic compounds were fit with the model of a dimer with the Hamiltonian = –J1·2. For heterometallic complexes χMTcurves were fit as the superposition of magnetism resulting from both [CuII2LH2]2+and the adjacent CrIIIcontaining anion. Jvalues for the complexes lie in the range from –12.744 to –17.778 cm–1. It was shown that the 4,4′biphenyl bridge efficiently mediates exchange interactions.

The oxidation of 2,3,6,7tetrakis2cyanoethylthiotetrathiafulvalene TCETTF with hexafluoroacetylacetonate hfac salts of paramagnetic CoII, MnII and diamagnetic ZnII, CdII ions in the presence of tetrahedral anions BF4–and ClO4– resulted in the isolation of four isostructural salts. The structure of these salts revealed an infinite twodimensional network due to the coordination of the nitrilo arms of TCETTF to the metal. Short interplanar S···S interactions between two planes involving TCETTF give a third dimension to this polymer. TTF ligands are fully oxidized, and hence these materials show semiconducting behaviour. Spectroscopic and magnetic studies of the paramagnetictransitionmetalcontaining polymers are also presented.© WileyVCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009

3pPyridyl1,5diphenylverdazyl pPyV and its binuclear copperII complex [Cu2OCOCH34pPyV2] have been synthesized and structurally characterized. The magnetic behavior of a single crystal of pPyV and [Cu2OCOCH34pPyV2] have been studied by magnetic susceptibility measurements in the temperature range 2–300 K and by ESR spectroscopy. Data fitting for pPyV using the singlettriplet equilibrium model revealed the existence of antiferromagnetic interactions in the radical crystal lattice. The exchange interactions between the copperII ion and pPyV in Cu2OCOCH34pPyV2were found to be negligibly small compared to the strong intramolecular copper–copper antiferromagnetic interaction. Intermolecular antiferromagnetic coupling between pPyV molecules was detected in the crystal lattice of complex.© WileyVCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009

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Extended investigations of the reaction sequence [Cp′2Nb(Te2)H]/CH3Li/[Co2(CO)8] (Cp′ = tBuC5H4) led to the identification of Lin[3] {3= [Co9Te6(CO)8]; n= 1, 2} salts through their transformation with [PPN]Cl into [PPN]n[3] (PPN = Ph3PNPPh3). These compounds form in the solid state columnar ([PPN][3]) or undulated 2D ([PPN]2[3]) supramolecular networks. Electrochemical studies of [Cp*2Nb(CO)2][3] (Cp* = C5Me5) or [Na(THF)6][3] revealed the presence of the redox couples [3]–/[3]2–/[3]3–/[3]4–/[3]5–regardless of the nature of the cation, whereas in the anodic part oxidative degradation of the cluster takes place. This behavior is in agreement with the observation that [3]–containing salts form with PPh3AuCl or dppe decomposition products like [(PPh3)2Au][CoCl3PPh3] or [Co(CO)2dppe]2(μ-Te). A neutral cluster comprising the Co@Co8(μ4-Te)6core formed in the reaction of [Cp*2Nb(CO)2][Co11Te7(CO)10] with PPh3AuCl, which gave [Co9Te6(CO)4(PPh3)4] (4) after oxidative cluster degradation and CO substitution. 4was characterized by X-ray crystallography. DFT calculations carried out on all members of the [3]n(n= +1 to –5) family and on related species indicate that there is no significant Jahn–Teller distortion (and therefore no connectivity change) for any of the considered electron counts. Magnetic investigations on [PPN][3] show that the ground state of [3]–is a spin triplet with spins interacting antiferromagnetically in a 1D space.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Homo‐ and heterometallic 1D coordination polymers of transition metals (CoII, MnII, ZnII) have been synthesized by an in‐situ ligand generation route. Carboxylato‐based complexes [Co(PhCOO)2]n(1 a, 1 b), [Co(p‐MePhCOO)2]n(2), [ZnMn(PhCOO)4]n(3), and [CoZn(PhCOO)4]n(4) (PhCOOH=benzoic acid, p‐MePhCOOH=p‐methylbenzoic acid) have been characterized by chemical analysis, single‐crystal X‐ray diffraction, and magnetization measurements. The new complexes 2and 3crystallize in orthorhombic space groups Pnaband Pcabrespectively. Their crystal structures consist of zigzag chains, with alternating MIIcenters in octahedral and tetrahedral positions, which are similar to those of 1 aand 1 b. Compound 4crystallizes in monoclinic space group P21/cand comprises zigzag chains of MIIions in a tetrahedral coordination environment. Magnetic investigations reveal the existence of antiferromagnetic interactions between magnetic centers in the heterometallic complexes 3and 4, while ferromagnetic interactions operate in homometallic compounds (1 a, 1 b, and 2). Compound 1 borders ferromagnetically at TC=3.7 K whereas 1 adoes not show any magnetic ordering down to 330 mK and displays typical single‐chain magnet (SCM) behavior with slowing down of magnetization relaxation below 0.6 K. Single‐crystal measurements reveal that the system is easily magnetized in the chain direction for 1 awhereas the chain direction coincides with the hard magnetic axis in 1 b. Despite important similarities, small differences in the molecular and crystal structures of these two compounds lead to this dramatic change in properties.

The synthesis of the new ligand, BEDT-TTF-bipy [4,5-ethylenedithio-4′,5′-(4′-methyl-2,2′-dipyrid-4-ylethylenedithio)tetrathiafulvalene] is reported. The first FeII coordination complex, namely [Fe(NCS)2(BEDT-TTF-bipy)2]·CHCl3, with this redox-active ligand is obtained. Magnetic measurements and Mössbauer spectroscopy revealed the coexistence of high-spin and low-spin FeII species with a ratio of 40:60 in this compound. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The preparation, crystal structures, extended Hückel theory band structure, and density functional theory (DFT) calculations and conducting and magnetic properties of seven new charge-transfer salts, formulated as (D)2[MIII(isoq)2(NCS)4], where D = DIET (diiodo(ethylenedithio)tetrathiafulvalene), DIETS (diiodo(ethylenedithio)diselenadithiafulvalene), M = Cr, Ga, and isoq = isoquinoline, are reported. For each donor two different phases called a and b were obtained. Crystal data for (DIET)2[Cr(isoq)2(NCS)4] (1) are as follows: phase a, triclinic P&onemacr;, a = 9.8645(6) Å, b = 10.3255(8) Å, c = 13.7712(8) Å, α = 87.905(5)°, β = 75.981(5)°, γ = 80.712(2)° phase b, triclinic P&onemacr;, a = 10.6760(5) Å, b = 11.3000(6) Å, c = 11.3930(9) Å, α = 101.256(2)°, β = 96.755(2)°, γ = 97.342(5)°. All compounds exhibit semiconductive behavior with room-temperature resistivity ranging from 2 × 103 to 5 × 104 Ω cm. Donors in the mixed-valence-state form dimers. They are connected to anions through very short I···S contacts (S2···I2 = 3.248(2) Å for 1a). The magnetic measurements and spin density DFT calculations revealed that iodine atoms are good structural agents but are poor magnetic mediators to promote superexchange interactions between the donors and the inorganic anions. Our analyses reveal also that in these charge-transfer salts the magnetic interactions between spin carriers are mainly ensured by short intermolecular S···S contacts.

Synthesis, crystal structures, electrochemical and physical properties of the new ligand, EDO-EDT-TTF-py L1 4,5-ethylenedioxy-4′,5′-4-pyridylethylenedithiotetrathiafulvalene, and the paramagnetic transition metal coordination complexes, Mhfac2EDO-EDT-TTF-py2; M Cuii2, Mnii3, and Cuiihfac2EDO-EDT-TTF-py 4 are reported where hfac hexafluoroacetylacetonato. Crystal data: L1 triclinic system, space group P1, a 8.40603, b 10.50933, c 11.53185 , α 64.7582, β 86.9232, γ 72.4442°, V 875.226 3, Z 2, 2and 3are isostructural data for 3are given in brackets, triclinic system, space group P1, a 7.10854 7.10139, b 11.12107 11.1112, c 16.362811 16.3463 , α 91.6822 91.6626, β 91.0143 91.0367, γ 93.5473° 93.6516°, V 1290.31 31286.33 3, Z 1, 4 triclinic system, space group P1, a 9.29371, b 15.18972, c 24.31746 , α 92.4611, β 93.0481, γ 105.4911°, V 3297.61 3, Z 4.CCDC reference numbers 275856–275859. See http://dx.doi.org/10.1039/b507163afor crystallographic data in CIF or other electronic format.In the compounds 2, 3and 4, the ligand L1is coordinated to the transition metals through the nitrogen atom of the pyridine group. In the crystal, the organic and inorganic layers are segregated. The arrangement of the organic layers is similar to the well known βphase in BEDT-TTF bisethylenedithiotetrathiafulvalene charge transfer complexes, showing that the crystal packing is mainly governed by π–π stacking of the organic molecules. L1is a TTF derivative and shows the electron donating ability with oxidation potential E1½ 0.52 V versusSCE in benzonitrile. The same oxidation potentials were observed for complexes 2and 3, indicating the negligible interactions between the ligands and the metals in solution.

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This paper concerns the chemistry and the physic of two compounds with a fully interlocked structure. The general formula is [Etrad2M2{Cu(opba)}3]·S, with M=Mg2+, Ni2+, where Etrad stands for an organic radical cation, opba stands for ortho-phenylenebis(oxamato) and S for solvent molecules (DMSO and/or H2O). The structure consists of two interpenetrating graphite-like networks with edge sharing hexagons. The magnetic properties have been investigated in detail. The Mg2+ derivative behaves as a paramagnet with weak ferromagnetic interactions between Cu2+ and Etrad+ ions whereas the Ni2+ derivative is a molecule-based magnet below Tc=28 K. The magnetization changes its sign below Tc at the so-called compensation temperature Tcomp under a small external field. For a higher field the magnetic poles may reverse two times at temperatures which depend on the measurement process (warming or cooling mode) and/or field history. A double thermal hysteresis is observed in a constant field in cycling the temperature between 35 and 2 K. Furthermore, the strength of the cooling magnetic field is strongly memorized because the magnetic poles orientation at any field or any temperature is directly related to the field history of the sample. We show that these original results can be understood on the basis of the combination of the molecular field theory and the magnetic anisotropy.

The fine‐tuning of the critical temperatureand the coercivity of compounds with two interpenetrating quasi‐perpendicular honeycomblike networks (see diagram) are presented. Molecule‐based magnets of formula [(Etrad)2M2{Cu(opba)}3]⋅S and mixed compounds of formula [Etrad2Mn2−2xCo2xCu3] were synthesized and their magnetic properties were investigated.

This paper is devoted to a thorough study of the magnetic properties, both in the dc and ac modes, of two-dimensional ferrimagnetic materials. The general formula of the compounds, abbreviated as A2M2Cu3 , is A2M2 [Cu(opba)]3 nsolv where A+ stands for a counter cation (radical cation, alkali-metal or tetraalkylammonium), opba is ortho-phenylenebis(oxamato), MII is MnII or CoII , and solv is a solvent molecule (Me2SO or H2O). The dc magnetic susceptibility data for all compounds down to ca. 50 K are characteristic of two-dimensional ferrimagnets. In the A2Mn2Cu3 series, three classes of compounds have been distinguished. Class I has a unique representative, A2Mn2Cu3 , where A+ is the radical cation 2-(1-methylpyridinium-4-yl)-4,4,5,5-tetramethylimadozolin-1-oxyl-3-oxide, the structure of which has already been solved. This compound is a magnet with Tc=22.5 K. Class II corresponds to compounds with large cations (tetraethyl- and n-tetrabutylammonium). They also behave as magnets with Tc around 15 K. Class III corresponds to compounds with small cations (alkali-metal ions and tetramethylammonium). They behave as metamagnets with a long-range antiferromagnetic ordering in zero field around 15 K, and a field-induced ferromagnetic state. The critical fields are of the order of 0.15 kOe. All the A2Co2Cu3 compounds are magnets with Tc around 30 K. Furthermore, the cobalt derivatives show a very strong coercivity, with coercive fields of several kOe at 5 K. They also display a pronounced magnetic after-effect in the ordered phase. In the course of this work several peculiar features have been observed. In particular, the A2Mn2Cu3 compounds have been found to present weak but significant negative out-of-phase ac magnetic signals at temperatures just above Tc . All the observed phenomena are discussed and, in particular, a mechanism for the long-range ordering in these two-dimensional compounds has been proposed.

AbstractThe goal of this paper is to emphasize the multidisciplinary character of molecular magnetism as a whole, and of our own activity in this field. For that, we have briefly described some of our results concerning the theoretical simulation of thermodynamical properties of molecular magnetic materials, the study of spin density maps, and the synergy between optical (or photophysical) and magnetic properties. We have also reported on two new chain compounds exhibiting dominant ferromagnetic interactions, one involving transition metal ions, the other one involving organic radicals.

Single-molecule magnets (SMMs) hold promise for unmatched information storage density as well as for applications in quantum computing and spintronics. To date, the most successful SMMs have been organometallic lanthanide complexes. However, their surface immobilization, one of the requirements for device fabrication and commercial application, remains challenging due to the sensitivity of the magnetic properties to small changes in the electronic structure of the parent SMM. Thus, finding controlled approaches to SMM surface deposition is a timely challenge. In this contribution we apply the concept of isolobality to identify siloxides present at the surface of partially dehydroxylated silica as a suitable replacement for archetypal ligand architectures in organometallic SMMs. We demonstrate theoretically and experimentally that isolated siloxide anchoring sites not only enable successful immobilization but also lead to a 2 orders of magnitude increase in magnetization relaxation times.

The coordination polymers [Fe2MO(piv)6(bipy)1.5]n[M = NiII, compound 1, and M = CoII, compound 2; piv = (CH3)3CCO2–and bipy = 4,4′‐bipyridine] were prepared by linking trinuclear heterometallic pivalates, possessing D3hsymmetry, by linear molecules of bipy. The complexes are isostructural and are built from 2D doubly interpenetrated “honeycomb” layers. The structure of the starting polynuclear building blocks is retained, which opens the way for the creation of materials with predetermined properties. Zigzag channels in the crystal structures of the compounds can adsorb N2and H2. Unusual N2adsorption/desorption hysteresis was observed. Magnetic properties of the polymers are governed by exchange interactions in trinuclear blocks. The χMTvs. Tcurve for 2was fitted by taking into account the zero‐field splitting of the CoIIion by using software specially developed for this purpose.

The replacing of CH2Cl2solvent molecules with their deuterated analogues in a Co complex undergoing valence-tautomeric interconversion drastically modifies its magnetic properties giving rise to a thermal hysteresis.

The replacing of CH₂Cl₂ solvent molecules with their deuterated analogues in a Co complex undergoing valence-tautomeric interconversion drastically modifies its magnetic properties giving rise to a thermal hysteresis.