Linear polarization analysis of hard x-rays is employed to probe electronic anisotropies in metal-containing complexes with very high selectivity. We use the pronounced linear dichroism of nuclear resonant x-ray scattering to determine electric field gradients in an iron(II) containing compound as they evolve during a temperature-dependent high-spin/low-spin phase transition. This method constitutes a novel approach to analyze changes in the electronic structure of metal-containing molecules as function of external parameters or stimuli. The polarization selectivity of the technique allows us to monitor defect concentrations of electronic valence states across phase transitions. This opens new avenues to trace electronic changes and their precursors that are connected to structural and electronic dynamics in the class of metal compounds ranging from simple molecular solids to biological molecules.

Single-molecule toroics host closed magnetic vortices carrying toroidal moments τ, whose electric-dipole symmetry enables magnetoelectric spin control. Yet opposite toroidal chiralities are degenerate in conventional magnetic fields, making direct detection of τ challenging. Current approaches probe toroidal dynamics only indirectly through weak residual magnetism, while finite-temperature toroidal polarisation and realistic preparation/readout conditions remain unestablished. Here we show that the Fe10Dy10 molecule hosts a 62-billion-dimensional low-energy manifold pervaded by toroidal character, rendered tractable by an ab initio-informed transfer-matrix framework that reproduces experimental data. The model reveals a large toroidal response robust to thermal fluctuations, quantified by a finite-temperature toroidal susceptibility ξ. We then propose a preparation-and-readout protocol in which a train of temporally asymmetric near-infrared pulses accumulates toroidal polarisation, converted through magnetoelectric response into a measurable electric-field-induced magnetic signal. These results establish Fe10Dy10 as a molecular system where τ can be prepared, accumulated and read out under realistic conditions.

The asymmetric Schiff base prepared in situ from ethylenediamine and pyridine-2-carboxaldehyde reacts with Fe(ClO4)3·6H2O to form the Fe(II) complex [FeL2](ClO4)2 with L = N,N-diethyl-N′-(pyridin-2-yl)methylene)ethane-1,2-diamine, where the Fe(III) starting material has been unexpectedly reduced to Fe(II). This complex was characterized by elemental analysis, infrared spectra, single crystal and powder X-ray diffraction measurements, variable temperature DC magnetic measurement and room temperature Mössbauer spectroscopy. The asymmetric ligand L coordinates in a tridentate fashion through its pyridyl, azomethine and amino nitrogen atoms, generating a distorted octahedral geometry around the central metal ion. Variable temperature magnetic studies and a Mössbauer measurement show that the iron is locked in the low spin Fe(II) states.

Halogen bonding is increasingly recognized as a further elaboration of supramolecular effects between coordination moieties. Here, we report two isostructural trigonal prismatic Er6 coordination clusters for which one has no halogen on the ligand (E)-N '-(2-hydroxy-3-ethoxybenzylidene)pyrazine-2-carbohydrazide (H2oepch) (1), whereas the other has a bromine on the o-vanillin component (E)-N '-(5-bromo-2-hydroxy-3-methoxybenzylidene)pyrazine-2-carbohydrazide (H2opch-Br) (2). This allows us to gauge the effect of the supramolecular interactions on network formation via halogen bonding. Furthermore, the topological analysis on the network in (2) reveals a completely novel and unexpectedly 7-connected uninodal network that has to conform with the symmetry imposed by the tetragonal space group P421 c. In addition, in-depth theoretical calculations were performed to investigate the strength of the halogen bonding interactions and reveal cooperative effects unprecedented for inorganic coordination clusters.

Asymmetrical condensation of ethylenediamine with 5-bromo-2-hydroxybenzaldehyde yielded a Schiff base, (E)-2-(((2-aminoethyl)imino)methyl)-4-bromophenol (5-Brsaen), and the reaction with Fe(NO3)39H2O generated the complex [Fe(5-Brsaen)2]NO3CH3OH (1). The complex was characterised by single crystal XRD measurements, elemental analysis, FT-IR spectra, DC magnetic susceptibility measurements and variable temperature M & ouml;ssbauer spectroscopy. The single crystal XRD studies of 1 at 293 K and 173 K reveal that the Fe-N and Fe-O bond lengths are intermediate between what would be expected for HS and LS Fe(iii). The hydrogen bonds result in a 2D supramolecular structure. DC magnetic measurements between 300 and 2 K reveal that the compound does not reach a pure HS state even at RT. Furthermore, the proportion of HS to LS decreases as the temperature decreases and reaches a LS state at 2 K. Variable temperature M & ouml;ssbauer spectra are in line with this conclusion.

We report the synthesis of two new biquinoxen-σH-adducts (3,3′-diisopropoxy-4,4′-dimethyl-3,3′,4,4′-tetrahydro-2,2′-biquinoxaline (Mbqn-(OiPr)2) (1) and 3,3′-bis(isopropylthio)-4,4′-dimethyl-3,3′,4,4′-tetrahydro-2,2′-biquinoxaline (Mbqn-(SiPr)2) (2)) with the same molecular structure other than the exchange of two oxygen atoms with sulphur atoms. This enables us to directly compare the optical properties and stability of the compounds as a result of this substitution. For freshly prepared solutions of 1, a fluorescence quantum yield of 97% is observed, whereas for 2, the value is much lower at 7%. We furthermore note a decrease in quantum yields for solutions investigated after certain storage times, indicating a reactive channel. We note that this decomposition is much faster for solutions of 2 compared with compound 1. For 1, the decomposition likely proceeds to the biquinoxen dipseudobase via an equilibrium, whereas for 2 the decomposition product remains unidentified. The decomposition of 1 in particular was followed using ultrafast transient absorption spectroscopy, investigating the dynamics of the biquinoxen system after photoexcitation. Given the redox activity of biquinoxens, additionally the oxidation of the compounds was investigated using (spectro)electrochemistry.

Lanthanide-based single-molecule magnets are attractive candidates for applications in quantum information processing or data storage. The low symmetry ligand field environment often encountered in these complexes, combined with a sparsity of information in the common magnetic susceptibility and magnetization data recorded on powder samples, leads to massive overparametrization. This limits the application of ligand field models, such as the point charge or angular overlap models, for describing the data. In this work, the radical approach is taken to consider these models as black boxes, whereby they suspend their chemical or physical significance. Instead, the transferability of parameters across a series of structurally related compounds is enforced to achieve a reduced parametrization. This methodology is applied to four members of the isostructural series of [M2IIILn2III(μ3-OH)2(pmide)2(p-Me-PhCO2)6]·2MeCN (pmideH2 = N-(2-pyridylmethyl)-iminodiethanol) butterfly complexes, with M = Al, Fe, and Ln = Er, Dy. It is shown that the powder magnetic susceptibility and magnetization data can be described simultaneously with remarkable accuracy using only two parameters for characterizing the lanthanide ligand fields in all four compounds. Interestingly, the resulting parametrization and its values lie within the range of chemical intuition despite the black box procedure used to obtain them. Implications of this approach are discussed.

We present three air-stable radical-containing compounds [MIII2(phsq)4(NO3)2(MeOH)2]∙2MeOH (M = Dy (1), Y (2), Gd (3); Hphsq = 9,10-phenanthrenesemiquinone) in which strong intramolecular inter-radical interactions force two lan-thanide ions into close proximity and isolate them from the lattice. Magnetic measurements on (1) showed it to be an SMM with maxima in the ac susceptibility up to 18 K (1000 Hz). Modeling the magnetic data using three different analytical approaches reveals the absence of zero-field quantum tunneling of magnetization (ZFQTM) as a relaxation pathway. This is a result of significant internal magnetic fields identified by ab initio calculations that appear to quench the ZFQTM. This can be verified from the measurements performed on a Y-doped sample (1a) in which one of the DyIII ions is largely replaced by diamagnetic YIII and switches ZFQTM back on.

The spin frustration and other magnetic properties of the "cartwheel" heptanuclear cluster [FeIII 7O3(O2C t Bu)9(Me-dea)3(H2O)3] (Me-deaH2 = N-methyldiethanolamine) have been previously investigated; we present here a Mossbauer spectroscopic study and sub-Kelvin magnetization and ac susceptibility measurements which enable a complete magnetic picture of this frustrated cluster. 57Fe Mossbauer spectra above 150 K showed three doublets in a 1:3:3 ratio, which could be assigned by their respective quadrupole splittings to the central Fe(1) and the peripheral Fe(2) and Fe(3). The field dependence of the corresponding magnetic sextets at 3 K showed that the spins on the central Fe(1) and the three peripheral Fe(2) sites with O5N coordination are oriented mutually coparallel, while these are antiparallel to the spins on the peripheral Fe(3) sites with O6 coordination, resulting in an overall S = 5/2 ground state. This provides experimental confirmation of the previously proposed spin ground state structure. Upon cooling to sub-Kelvin temperatures, a crossover to spin blocking with T B approximate to 0.21 K could be observed. This single-molecule magnet behavior had been expected but had not been observable with a conventional SQUID. The anisotropy barrier, of 3-fold symmetry, can be described in terms of the parameter D/k B = -0.47 K and a fourth-order perturbation; the latter enables thermally activated quantum tunneling through the excited sublevel m z = +/- 3/2, with an activation barrier of U/k B = 1.9 K.

Novel asymmetrical Fe(iii) Schiff base coordination complexes, with the N4O2 coordination environment, exhibiting abrupt spin crossover (SCO) behaviour with a wide hysteresis loop of 27 K, have been synthesised from an ethylenediamine based asymmetrical Schiff base ligand viz. N-(2-aminoethyl)salicylaldimine (saen) and characterised via single crystal XRD measurements, variable temperature magnetic studies and M & ouml;ssbauer measurements. The single crystal XRD measurements prove that the compound is a mixture of two fractions, one with methanol and the other without methanol, viz, [Fe(saen)(2)]NO3CH3OH at 299 K (1-299) and at 173 K (1-173) and [Fe(saen)(2)]NO3 at 173 K (2-173), confirming that the Fe(iii) centre has a distorted octahedral coordination geometry having two deprotonated asymmetrical tridentate saen ligands, counterbalanced by a nitrate anion and methanol solvent molecule in 1 while 2 has a non-solvate form. An extended hydrogen bonding network between the amino hydrogen atoms of the saen ligand, nitrate counteranion, and methanol solvate molecule is observed in fraction 1, while an extended zig-zag hydrogen bonding between the nitrate anion and amino hydrogens of saen is observed in fraction 2. Furthermore, the complex has been characterised by variable temperature magnetic susceptibility measurements and( 57)Fe Mossbauer spectroscopy, confirming the SCO nature.

Four new Ni16 molecular wheels with the general formula [L4Ni16(RCOO)16(H2O)x(MeOH)12-x] (where H4L=1,4-bis((E)-((2'-hydroxybenzyl)imino)methyl)-2,3-naphthalenediol, and R=H or Me) have been isolated and structurally characterised. Complexes C1-C3 (R=Me) were formed using nickel (II) acetate and presented as polymorphs with the same formulation of charged components. The same wheel-like architecture was observed in C4 (R=H), which was prepared using nickel (II) formate, demonstrating the potential for further versatility of the system. In contrast to similar four-fold symmetric Ni(II) wheel clusters, measurements of the static magnetic properties of C1 indicated the presence of dominant antiferromagnetic interactions and an S=0 ground state.

A new iron(III) complex (Et3NH)2[Fe(L)2](ClO4)·MeOH (1) where H2L = 2-{(E)-[2-hydroxyphenyl)imino]methyl}phenol has been synthesised and characterised by single crystal XRD, elemental analysis and DC magnetic susceptibility measurements. The dianionic ligands L2− coordinate in a tridentate fashion with the Fe(III) through their deprotonated phenolic oxygens and azomethine nitrogen atoms, resulting in a trans-FeO4N2 chromophore. Variable-temperature magnetic measurements were performed between 300 and 5 K under an applied field of 0.1 T and show that 1 is in the high spin state (S = 5/2) over the whole measured temperature range. This is confirmed by Mössbauer spectroscopy at 77 and 300 K.

We report the synthesis, structures and magnetic behaviour of two isostructural dinuclear Dy3+ complexes where the metal ions of a previously reported monomeric building block are connected by a peroxide (O2 2-) or a pair of fluoride (2×F-) bridges. The nature of the bridge determines the distance between the metal ion dipoles leading to a dipolar coupling in the peroxido bridged compound of only ca. 70 % of that in the bis-fluorido bridged dimer. The sign of the overall coupling between the metals is antiferromagnetic for the peroxido bridged compound and ferromagnetic for the bis-fluorido bridged complex. This in turn influences the magnetisation dynamics. We compare the relaxation characteristics of the dimers with those of the previously reported monomeric building block. The relaxation dynamics for the bis-fluorido system are very fast. On the other hand, comparing the properties of the monomer, the peroxido bridged sample and the corresponding Y-doped sample show that the relaxation properties via a Raman process have very similar parameters. We show that a second dysprosium is important for either tuning or detuning the Single Molecule Magnet (SMM) properties of a system.

The 20-nuclearity compound [Fe8Dy12(tea)8(teaH)12(NO3)12]·8MeCN (where teaH3 = triethanolamine) was synthesised and characterised through single crystal X-ray diffraction and magnetic measurements. The shape of the magnetic hysteresis in the microSQUID measurements was rationalised using the MAGELLAN program.

Dysprosium(III)-containing single-molecule magnets (SMMs) show blocking of the molecular magnetization and hysteresis effects in one molecule. They belong to the class of the best performing SMMs at present. Here, we present first results of 161 Dy-Nuclear Resonance Vibrational Spectroscopy (NRVS) experiments on the dysprosium(III) complex [Dy(H 2 dapp)(NO 3 ) 2 ](NO 3 ) with H 2 dapp being 2,6-bis((E)-1-(2-(pyridine-2-yl)-hydrazineylidene)ethyl)pyridine. For the 161 Dy-NRVS experiments a compact novel He flow cryostat was used at the Advanced Photon Source, Argonne National Laboratories, which enables low temperature NRVS experiments in helium vapour circumventing the often-observed difference between sensor read and “real” sample temperature in mostly used LHe and/or closed cycle cryostats with the NRVS sample being in vacuum. To explore the vibrational modes of the molecule simulations based on first density functional theory (DFT) calculations are presented.

A one-pot reaction of 2-pyridincarboxyaldehyde, 2-amino-1,3-propandiol, FeCl3 and NaN3 in MeOH leading to an in-situ oxazolidine ligand formation enabled the preparation of a new dimeric complex [Fe2(pdom)2(N3)4 (1), where (pdom)- is (2-(pyridin-2-yl)-4,5-dihydrooxazol-4-yl)methanol (pdomH) ligand. Complex 1 was characterised by infrared spectroscopy, elemental analysis and single crystal X-ray diffraction. The structural analysis indicates that 1 is a centrosymmetic molecule where two Fe (III) are bridged by two (pdom)- ligands. The theoretical study of 1 was carried out to assess the structural properties of the complex where the non-covalent interactions and the data indicate good agreement between the theoretical and experimental results. From the density functional theory (DFT) calculations, it was determined that complex 1 adopts the triplet state. In order to get an insight into the possible biological activity of the complex, molecular docking of complex 1 was per -formed with the DNA topoisomerase I (TOP1), and various conformations of 1 bound with TOP1 were analysed in terms of energy, hydrogen-bonding and hydrophobic interaction. NCI analysis has been investigated to shows its bonding nature. The docking study reveals that complex 1 binds proficiently with TOP1 along the major groove of the DNA with a free energy of 11.72 kcal mol-1, and hydrogen bonds, as calculated by Hirshfeld analysis, are responsible for promoting binding with DNA.

[(2-{[6-(1,3-Benzo-thia-zol-2-yl)pyridin-2-yl]carbonyl-aza-nid-yl}phen-yl)sulf-anido]nickel(II), [Ni(C19H11N3OS2)], crystallizes in the centrosymmetric monoclinic space group P21/n with one mol-ecule in the asymmetric unit. The expected ligand, a bis-Schiff base derived from pyridine-2,6-dicarbaldehyde and 2-amino-thio-phenol, had modified in situ in a both unexpected and unsymmetrical fashion. One arm had cyclized to form a benzo[d]thia-zol-2-yl functionality, while the imine linkage of the second arm had oxidized to an amide group. The geometry about the central NiII atom is distorted square-planar N3S. The mol-ecules form supra-molecular face-to-face dimers via rather strong π-π stacking inter-actions, with these dimers then linked into chains via pairwise C-H⋯O inter-actions.

Three one-dimensional Ln(III) (Ln = Dy, Dy/Y, andGd) complexes based on the hydrazone Schiff-base ligand were reported,in which the Dy-III analogue exhibits a field-induced SMMwith U (eff) = 43 K originated from the single-ionproperties of Dy-III, which is proved by the Y-III diluted analogue. And the Gd-III analogue exhibits a remarkablemagnetic thermal effect with a maximum -& UDelta;S (m) value of 21.32 J kg(-1) K-1 at 3 K and 7 T. Three isostructural one-dimensional lanthanide complexeswith formulaeof [Dy(H2L)(H2O)(2)]& BULL;Cl & BULL;6H(2)O (1), [Dy0.067Y0.933(H2L)(H2O)(2)]& BULL;Cl & BULL;6H(2)O (1 & PRIME;,) and [Gd(H2L)(H2O)(2)]& BULL;Cl & BULL;6H(2)O (2), whereH(2)L(2-) is the dianion of the bis-hydrazone(N & PRIME;,N"'E,N & PRIME;,N"'E)-N & PRIME;,N"'-(pyridine-2,6-diylbis(methanylylidene))bis(2-hydroxybenzohydrazide),were synthesized and structurally characterized. Single-molecule magnet(SMM) behavior was observed for the Dy-III compound underan applied dc field, which is rarely seen for a nine-coordinate Dy-III compound with a hula-hoop coordination geometry. The SMMbehavior is ascribed to the single-ion properties of Dy-III, which is proved by comparison of the ac magnetic susceptibilitiesof 1 and the Y/Dy diluted complex 1 & PRIME;. Magnetic studies indicate that the Gd-III analogue showsa magnetocaloric effect with a maximum entropy change -& UDelta;S (m) of 21.32 J kg(-1) K-1 at & UDelta;H = 7 T and 3 K.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.