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Three new nickel phosphonate complexes {[Na2Ni8(L)6]·nSolv}m (L = SAA3− (1), BSAA3− (2), NAA3− (3); Solv = H2O, MeOH; m = ∞ (1, 2), 1 (3)) were synthesized. All three complexes possess a novel octanuclear {Ni8} phosphonate core, which consists of four dinuclear doubly oxygen-bridged units, further interconnected to each other by phosphonate oxygen bridges. The steric features of the ligands influence the aggregation degree. Molecules of 1 and 2 are interconnected by sodium cations into 2D layered and 1D chain extended structures, respectively, while the molecules of 3 with the bulkiest ligand are not bonded with each other. Magnetic properties of the obtained {Ni8} core unit were studied for complex 1 as a representative of this family of compounds and are reported in detail. Magnetic susceptibility at low temperature is indicative of a singlet ground state. The absence of saturation and the magnetization behavior points to zero-field splitting (ZFS). Simulation of the magnetization data revealed an easy-plane magnetic anisotropy with an axial ZFS parameter D = 7.4 cm−1. The magnetic properties of 1 were also studied by broken-symmetry DFT calculations (BS-DFT), which revealed the presence of ferromagnetic exchange interactions within the dinuclear units of the {Ni8} core with a dominant antiferromagnetic interaction between these dinuclear entities. These results are in good agreement with coupling constants derived from the experimental susceptibility and magnetization data.

Dysprosium(III) ions are promising candidates for the design of single-ion magnets (SIMs) as they show an intrinsic strong magnetic anisotropy. However, time-demanding multireference methods are usually necessary to reproduce low-lying magnetic states. In this work, we present an improved wave function-based semiempirical ligand-field (LF) theory approach to obtain magnetochemical properties of dysprosium(III)-based SIMs. We reduce the computational effort by replacing the central dysprosium(III) ion with either yttrium(III) or lutetium(III), which allows to obtain a closed-shell wave function from Hartree-Fock calculations. The wave function is subsequently used to determine a so-called diamagnetic-electrostatic pseudo-potential (DEPP) of the compound, which in turn can be applied to LF theory to obtain magnetochemical properties. The presented approach is tested against ab initio CASSCF/RASSI-SO reference calculations and shows accurate prediction of magnetic anisotropy axes and a significant accuracy improvement as compared to point charge-based LFT methods. In addition, we also introduce an improved electrostatic (IES) approach, which applies the obtained DEPPs to a known electrostatic method introduced by Chilton et al. (Nat. Commun. 2013, 4, 2551) to obtain the direction of the main anisotropy axis in dysprosium(III)-based SIMs. © 2018 Wiley Periodicals, Inc.

The synthesis of ethoxido-bridged dinuclear oxidovanadium(IV) complexes of the general formula (HNEt3)[(VOL1-3)2(μ-OEt)] (1-3) with the azo dyes 2-(2'-carboxy-5'-X-phenylazo)-4-methylphenol (H2L1, X = H; H2L2, X = NO2) and 2-(2'-carboxy-5'-Br-phenylazo)-2-naphthol (H2L3) as ligands is reported. The ligands differ in the substituents at the phenyl ring to probe their influence on the redox behavior, biological activity, and magnetochemistry of the complexes, for which the results are presented and discussed. All synthesized ligands and vanadium(IV) complexes have been characterized by various physicochemical techniques, namely, elemental analysis, electrospray ionization mass spectrometry, spectroscopic methods (UV/vis and IR), and cyclic voltammetry. X-ray crystallography of 1 and 3 revealed the presence of a twisted arrangement of the edged-shared bridging core unit. In agreement with the distorted nature of the twisted core, antiferromagnetic exchange interactions were observed between the vanadium(IV) centers of the dinuclear complexes with a superexchange mechanism operative. These results have been verified by DFT calculations. The complexes were also screened for their in vitro cytotoxicity against HeLa and HT-29 cancer cell lines. The results indicated that all the synthesized vanadium(IV) complexes (1-3) were cytotoxic in nature and were specific to a particular cell type. Complex 1 was found to be the most potent against HeLa cells (IC50 value 1.92 μM).

Five new lanthanide(III) sandwich and half-sandwich complexes with bulky cyclooctatetraenyl ligands have been prepared and fully characterized, including single-crystal X-ray structure determination. Treatment of anhydrous lanthanide(III) chlorides, LnCl3 (Ln = Pr, Tb, Yb), with 2 equiv. of Li2COT'' (COT'' = 1,4-bis(trimethylsilyl)-cyclooctatetraene dianion) followed by crystallization in the presence of coordinating solvent afforded the anionic sandwich complexes [Li(THF)4][Pr(COT″)2] (1), [Li(DME)3][Tb(COT″)2] (2), and [Li(TMEDA)2][Yb(COT″)2] (3). Attempted oxidation of 2 with silver iodide did not afford the neutral terbium(IV) sandwich complex Tb(COT″)2. Instead, the tri(µ-iodido)-bridged dinuclear half-sandwich complex Li(DME)2Tb2(µ-I)3(COT'')2 was isolated in 72% yield. In this complex, a Li(DME)2 fragment is attached to one of the µ-iodido ligands. A closely related binuclear lutetium complex, [Li(DME)3][Lu2(µ-Cl)3(COTbig)2]∙DME (5), was obtained using the "superbulky" COTbig ligand (COTbig = 1,4-bis(triphenylsilyl)cyclooctatetraenyl dianion). In addition to the spectroscopic and structural characterization, the magnetic properties of the paramagnetic terbium(III) derivative 2 have been investigated and further complemented by ab initio computational methods. These results are used to discuss the structural requirement for potential terbium(III) single-ion magnets.

Two novel dioxidomolybdenum(VI) complexes [MoO2L′1] (1) and [MoO2L′2] (2) containing the MoO22+ motif with unexpected coordination motifs due to ligand rearrangement through Mo-mediated interligand C–C bond formation are reported. The ligands (H2L′1–2) are tetradentate C–C-coupled O2N2-donor systems formed in situ during synthesis of the complexes by reaction of [MoVIO2(acac)2] with Schiff base ligands of 2-aminophenol with 2-pyridinecarbaldehyde (HL1) and 2-quinolinecarbaldehyde (HL2). To confirm that the ligand rearrangement is assisted by molybdenum, the corresponding vanadium complexes [VO2L1] (3) and [VO2L2] (4) containing original Schiff base ligand (HL1,2) are also reported here. All complexes 1–4 are characterized by several physicochemical techniques and the structural features of 1 and 2 have been solved by X-ray crystallography. The proposed mechanism of molybdenum-mediated interligand C–C bond formation is supported by DFT calculations including the comparisons with the synthesized vanadium analogues. The catalytic potentials of 1–4 for the epoxidation of styrene and cyclohexene have also been explored.

The new tritopic triaminoguanidine-based ligand 1,2,3-tris[(pyridine-2-ylmethylidene)amino]guanidine (H2pytag) was synthesized. The reaction of a mixture of cobalt(II) chloride and cobalt(II) perchlorate with the ligand H2pytag in pyridine solution leads to the formation of the trinuclear cobalt(II) complex [Co3(pytag)(py)6Cl3]ClO4. Three octahedrally coordinated high-spin cobalt(II) ions are linked through the bridging triaminoguanidine backbone of the ligand leading to an almost equilateral triangular arrangement. The magnetic properties of the complex were investigated by magnetic measurements, variable-temperature, variable-field magnetic circular dichroism (MCD) spectroscopy, and density functional theory as well as ab initio calculations. A rather strong antiferromagnetic exchange interaction between the cobalt(II) centers of ca. −12 cm–1 is determined together with a strong local anisotropy. The single-ion anisotropy of all three cobalt(II) centers is found to be easy-plane, which coincides with th...

The synthesis, structure, and magnetic properties of two mononuclear cobalt(ii) complexes [Co(LSal,2-Ph)2] (1) and [Co(LNph,2-Ph)2] (2) are reported. The utilized sterically demanding Schiff-base ligands HLSal,2-Ph (2-(([1,1'-biphenyl]-2-ylimino)methyl)phenol) and HLNph,2-Ph (1-(([1,1'-biphenyl]-2-ylimino)methyl)naphthalen-2-ol) lead to a strong distortion of the [N2O2] coordination environment in the complexes 1 and 2, which can be primarily attributed to the variation in the dihedral angle between the planes of the two chelate ligands. Magnetic susceptibility and FD-FT THz-EPR measurements as well as ab initio calculations reveal that both complexes exhibit an easy-axis type of anisotropy. For both compounds frequency-dependent ac susceptibility measurements show an out-of-phase susceptibility under applied static fields of 400 and 1000 Oe. A detailed analysis of the underlying relaxation process is given, revealing significant differences in the contributions of Orbach, Raman, and direct processes within the observed temperature range. Fitting of the magnetic data leads to a spin-reversal barrier of 49 cm-1 for 1 at an applied field of 1000 Oe. For 2 the barrier is not well defined by the analysis of the relaxation times and is, therefore, approximated by the experimental barrier derived from FD-FT THz-EPR measurements (62.8 cm-1). The results from ab initio calculations and FD-FT THz-EPR measurements show that the distortion of the coordination sphere in complexes 1 and 2 from the pseudotetrahedral towards a square-planar coordination geometry leads to an increase in both the axial (D) and the rhombic zero-field splitting (E).

Reaction of cobalt(II) and nickel(II) thiocyanate with ethylisonicotinate leads to the formation of [M(NCS)2(ethylisonicotinate)2]n with M = Co (2-Co) and M = Ni (2-Ni), which can also be obtained by thermal decomposition of M(NCS)2(ethylisonicotinate)4 (M = Co (1-Co), Ni (1-Ni)). The crystal structure of 2-Ni was determined by single crystal X-ray diffraction. The Ni(II) cations are octahedrally coordinated by two N and two S bonding thiocyanate anions and two ethylisonicotinate ligands and are linked by pairs of anionic ligands into dimers, that are connected into layers by single thiocyanate bridges. The crystal structure of 2-Co was refined by Rietveld analysis and is isostructural to 2-Ni. For both compounds ferromagnetic ordering is observed at 8.7 K (2-Ni) and at 1.72 K (2-Co), which was also confirmed by specific heat measurements. Similar measurements on [Co(NCS)2(4-acetylpyridine)2]n that exhibits the same layer topology also prove magnetic ordering at 1.33 K. Constrained DFT calculations (CDFT) support the ferromagnetic interactions within the layers. The calculated exchange constants in 2-Ni were used to simulate the susceptibility by quantum Monte Carlo method. The single-ion magnetic anisotropy of the metal ions has been investigated by CASSCF/CASPT2 calculations indicating significant differences between 2-Ni and 2-Co.

Four new triphenylamine ligands with different substituents in the para position and their corresponding copper(II) complexes are reported. This study includes their structural, spectroscopic, magnetic, and electrochemical properties. The complexes possess a dinuclear copper(II) paddle‐wheel core, a building unit that is also common in metal‐organic frameworks. Electrochemical measurements demonstrate that the triphenylamine ligands and the corresponding complexes are susceptible to oxidation, resulting in the formation of stable radical cations. The square‐wave voltammograms observed for the complexes are similar to those of the ligands, except for a slight shift in potential. Square‐wave voltammetry data show that, in the complexes, these oxidations can be described as individual one‐electron processes centered on the coordinated ligands. Spectroelectrochemistry reveals that, during the oxidation of the complexes, no difference can be detected for the spectra of successively oxidized species. For the absorption bands of the oxidized species of the ligands and complexes, only a slight shift is observed. ESR spectra for the chemically oxidized complexes indicate ligand‐centered radicals. The copper ions of the paddle‐wheel core are strongly antiferromagnetic coupled. DFT calculations for the fully oxidized complexes indicate a very weak ferromagnetic coupling between the copper ions and the ligand radicals, whereas a very weak antiferromagnetic coupling is found among the ligand radicals.

The Front Cover shows a scene illustrating the need to investigate the properties of building blocks for complex systems to enable the basic design of new functional materials. It shows a model of the investigated paddle‐wheel complexes with copper‐bonded triphenylamines. Both paddle‐wheel units and triarylamine linkers are basic constituents found in several frameworks such as the networks shown in the image. More information can be found in the Full Paper by O. Akintola et al. on page 266 in Issue 3, 2019 (DOI: 10.1002/open.201800243).

Beside damages of infrastructure in industrial regions, extreme floods can cause contamination with particle-bound pollutants, e.g., due to erosion of soils and sediments. In order to predict contamination with inorganic pollutants, the transport and fate of arsenic, lead, and mercury during a fictive flood event of River Vereinigte Mulde in the region of Bitterfeld (Germany) with 200 years recurrence time was modeled. The finite element model system Telemac2D, which is subdivided into a hydrodynamic (Telemac-2D), a transport (Subief-2D), and a water quality module (wq2subief) was applied. The transport and water quality model models were calibrated using results of sediment trap exposures in the floodplain of River Vereinigte Mulde. Model results exhibited that the spatial patterns of particle-associated arsenic and lead concentrations significantly changed. Extended, mostly agriculturally used areas showed arsenic and lead concentrations between 150 and 200 mg kg -1 and 250 and 300 mg kg -1 , respectively, while urban areas were to a great extent spared from high contamination with arsenic and lead. Concentrations of particle-associated mercury showed a pattern distinct from those of arsenic and lead. Outside of small patches with concentrations up to 63 mg kg -1 , concentrations of particle-associated mercury remained close to zero. Differences in the spatial patterns of the three pollutants regarded mainly arise from significantly different initial and boundary conditions. Sensitivity analyses of initial and boundary conditions revealed a high sensitivity of particle-bound pollutant concentrations, whereas the sensitivities of concentrations of suspended sediments and soluble pollutants were mediocre to negligible.

Applying the two-dimensional model system Telemac2D, the transport of arsenic and oil during extreme flood events was modeled for the region Bitterfeld (Germany). Telemac2D includes sub-routines that describe hydrodynamics, transport and first-order partitioning of soluble and particle-bound pollutants. Oil spills were numerically treated as particulate pollutants with zero settling velocity. Simulations of the inundation of a small region after a dam-break revealed distinct small-scale contamination patterns and partly exhibited severe contamination. Comparison with measurements from the Mulde flood in August 2002 gives reasonable agreement. The model will be calibrated and validated by several measurements with sediment traps during flood events.

The sugar-modified Schiff-base ligands derived from benzyl 2-deoxy-2-salicylideneamino-α-D-glucopyranoside (H2L(5-Br) and H2L(3-OMe)) were used to prepare the chiral oxidovanadium(V) complexes [VO(L(5-Br))(OMe)] (1) and [VO(L(3-OMe))(OMe)] (2) which can be isolated from a methanol solution as the six-coordinate complexes with an additional methanol ligand [VO(L(5-Br))(OMe)(MeOH)] (1-MeOH) and [VO(L(3-OMe))(OMe) (MeOH)] (2-MeOH). Both complexes crystallize in the orthorhombic space group P2(1)2(1)2(1) together with two solvent molecules of methanol as 1-MeOH·2MeOH and 1-MeOH·2MeOH. In both crystal structures, only diastereomers with A configuration at the chiral vanadium centre (OC-6-24-A) are observed which corresponds to an cis configuration of the oxido group at the vanadium centre and the benzyl group at the anomeric carbon of the sugar backbone. Upon recrystallization of 2-MeOH from chloroform, the five-coordinate complex 2 was obtained which crystallizes in the monoclinic space group P2(1) with one co-crystallized chloroform molecule (2·CHCl3). For the chiral vanadium centre in 2·CHCl3, a C configuration (SPY-5-43-C) is observed which corresponds to an trans structure as far as the orientations of the oxido and benzyl groups are concerned. (1)H and (51)V NMR spectra of 1 and 2 indicate the presence of two diastereomers in solution. Their absolute configurations can be assigned based on the magnetic anisotropy effect of the oxidovanadium group. This effect leads to significant differences for the (1)H NMR chemical shifts of the H-2 (1.1 ppm) and H-3 protons (0.3 ppm) of the glucose backbone of the two diastereomers, with the downfield shift observed for the H-2 proton of the C-configured and the H-3 proton of the A-configured diastereomer at the vanadium centre. For 1 and 2 the difference between the (51)V NMR chemical shifts of the two diastereomers is 30 and 28 ppm, respectively. Also in the (13)C NMR significant chemical shift differences between the two diastereomers are observed for the carbon atoms C2 (2 ppm) and C3 (4 ppm). DFT calculations of the NMR chemical shift parameters have been performed which are in good agreement with the experimental data. Moreover, the isomerization mechanism between the diastereomers is analysed on the basis of DFT calculations which indicate the required presence of methanol molecules as protic donors.