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Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

Structures, Thermodynamic Relations, and Magnetism of Stable and Metastable Ni(NCS)2 Coordination Polymers Tristan Neumann,† Magdalena Ceglarska,‡ Luzia S. Germann,§ Michał Rams,‡ Robert E. Dinnebier,§ Stefan Suckert,† Inke Jess,† and Christian Naẗ her*,† †

Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Straße 2, 24118 Kiel, Germany Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30348 Kraków, Poland § Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany ‡

S Supporting Information *

ABSTRACT: Reaction of Ni(NCS)2 with 4-aminopyridine in different solvents leads to the formation of compounds with the compositions Ni(NCS)2(4-aminopyridine)4 (1), Ni(NCS)2(4aminopyridine) 2 (H 2 O) 2 (2), [Ni(NCS) 2 (4-aminopyridine)3(MeCN)]·MeCN (3), and [Ni(NCS)2(4-aminopyridine)2]n (5-LT). Compounds 1, 2, and 3 form discrete complexes, with octahedral metal coordination. In 5-LT the Ni cations are linked by single thiocyanate anions into chains, which are further connected into layers by half of the 4aminopyridine coligands. Upon heating, 1 transforms into an isomer of 5-LT with a 1D structure (5-HT), that on further heating forms a more condensed chain compound [Ni(NCS)2(4-aminopyridine)]n (6) that shows a very unusual chain topology. If 3 is heated, a further compound with the composition Ni(NCS)2(4-aminopyridine)3 (4) is formed, which presumably is a dimer and which on further heating transforms into 6 via 5-HT as intermediate. Further investigations reveal that 5-LT and 5-HT are related by enantiotropism, with 5-LT being the thermodynamic stable form at room-temperature. Magnetic and specific heat measurements reveal ferromagnetic exchange through thiocyanate bridges and magnetic ordering due to antiferromagnetic interchain interactions at 5.30(5) K and 8.2(2) K for 5-LT and 6, respectively. Consecutive metamagnetic transitions in the spin ladder compound 6 are due to dipolar interchain interactions. A convenient formula for susceptibility of the ferromagnetic Heisenberg chain of isotropic spins S = 1 is proposed, based on numerical DMRG calculations, and used to determine exchange constants.

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INTRODUCTION The synthesis of new coordination compounds and polymers is still a major topic in coordination chemistry, because of their diverse physical properties and the possibility for structure control.1−11 In most cases their synthesis is performed in solution leading to thermodynamically stable structures.12 In contrast, reports where metastable compounds were prepared are relatively rare and some selected examples are given in the reference list.11−27 This is a pity, because, metastable polymorphic modifications or isomers will have different structures and consequently different physical properties, which can be of importance in material development. For the synthesis of metastable coordination compounds, different methods can be applied. This includes, e.g., crystallization under kinetic control, which means that the reactants are mixed in solution and the product is immediately filtered off. If the product is completely dissolved, an antisolvent can be added, leading to fast precipitation under kinetic control. In some cases, also mechanochemical reactions can be used.28,29 Moreover, the solvents or part of the ligands can be thermally © XXXX American Chemical Society

removed, which leads to metastable compounds in several cases that are different from those obtained from solution under thermodynamic control. The latter approach is of extreme importance in our own work, which focuses on the synthesis of magnetic coordination polymers based on thio- and selenocyanates of 3d transition metal cations that are additionally coordinated by N-donor coligands that predominantly consist of pyridine derivatives.30,31 In most cases compounds with the general composition [M(NCS)2(coligand)2]n (M = Mn, Fe, Co, Ni) were obtained, in which the metal cations are linked by pairs of anionic ligands into chains, but we also found a few examples where the cations are linked by single and double thiocyanate anions into 2D networks.32−34 In most chain compounds the thiocyanate N and S atoms as well as the coligands are in the trans-position leading to linear chains, which might correspond to a very stable arrangement. In contrast, in [Ni(NCS)2(4-(boc-amino)pyridine)2]n (4-bocReceived: January 10, 2018

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DOI: 10.1021/acs.inorgchem.8b00092 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

Elemental analysis for C34H36N16Ni2S4 (914.4110 g/mol): calc. N 24.51, C 44.66, H 3.97, S 14.03. Exp.: N 24.32, C 44.43, H 3.968, S 13.89. Synthesis of [Ni(NCS)2(4-aminopyridine)2]n (5-HT). Single crystals suitable for single crystal X-ray diffraction were obtained from the reaction of Ni(NCS)2 (0.5 mmol, 87.5 mg) and 4aminopyridine (0.5 mmol, 47.1 mg) in 3.0 mL MeCN by annealing at 140 °C. A light green crystalline powder was obtained by the reaction of Ni(NCS)2 (0.5 mmol, 87.5 mg) with 4-aminopyridine (1.0 mmol, 94.1 mg) in 3.0 mL MeCN, which was stirred for 3d at 140 °C and immediately filtered off. Elemental analysis for C 12 H12 N6NiS 2 (363.0895 g/mol): calc. N 23.15, C 39.70, H 3.33, S 17.66. Exp.: N 22.92, C 39.55, H 3.15, S 17.61 Synthesis of [Ni(NCS)2(4-aminopyridine)2]n (5-LT). Single crystals suitable for single crystal X-ray diffraction were obtained from the reaction of Ni(NCS)2 (0.05 mmol, 8.8 mg) and 4aminopyridine (0.05 mmol, 4.7 mg) in 1.5 mL EtOH in a sealed test vessel, which was left to stand under air and ambient temperature, after a few days. A light blue crystalline powder was obtained from the reaction of Ni(NCS)2 (1.0 mmol, 174.9 mg) with 4-aminopyridine (1.0 mmol, 94.1 mg) in 4.0 mL EtOH after stirring the reactants for 1 day. Elemental analysis for C12H12N6NiS2 (363.0895 g/mol): calc. N 23.15, C 39.70, H 3.33, S 17.66. Exp.: N 22.81, C 39.37, H 3.21, S 17.58. Synthesis of [Ni(NCS)2(4-aminopyridine)]n (6). A lime green crystalline powder was obtained from the reaction of Ni(NCS)2 (1.0 mmol, 174.9 mg) with 4-aminopyridine (1.0 mmol, 94.1 mg) in 3 mL EtOH at a temperature of 140 °C within 3d. Elemental analysis for C7H6N4NiS2 (268.9734 g/mol): calc. N 20.83, C 31.26, H 2.25, S 23.84. Exp.: N 20.65, C 31.19, H 2.18, S 23.67. Elemental Analysis. CHNS analysis was performed using a “vario MICRO cube elemental analyzer”, fabricated by Elementar. Spectroscopy. All IR data were obtained using an ATI Mattson Genesis Series FTIR Spectrometer, control software: WINFIRST, from ATI Mattson. Differential Thermal Analysis and Thermogravimetry (DTATG). DTA-TG measurements were performed in a dynamic nitrogen atmosphere in Al2O3 crucibles using a STA PT 1000 thermobalance from Linseis. Different heating rates in the range of 1−8 K/min were used. The instrument was calibrated using standard reference materials. Differential Scanning Calorimetry (DSC). The DSC measurements were performed with a DSC 1 Star System with STARe Excellence Software from Mettler-Toledo AG. The instrument was calibrated using standard reference materials. Magnetic Measurements. Magnetic measurements were performed using a MPMS squid magnetometer from Quantum Design. Powders were pressed with some PTFE to immobilize sample grains. The diamagnetic contributions of sample holders and the core diamagnetism were subtracted, using measured and calculated values, respectively. Scanning Electron Microscopy (SEM). SEM images were measured in a secondary electron mode on a XL30 S-FEG instrument produced by FEI. Specific Heat Measurements. Specific heat was measured by the relaxation technique using a Quantum Design PPMS. Powders were pressed into pellets with no binder. ApiezonN grease was used to ensure thermal contact of the samples with the microcalorimeter. The heat capacity of the grease was measured before each run and subtracted from the measured data. Single-Crystal Structure Analyses. Data collections were performed with an imaging plate diffraction system (IPDS-2) from STOE & CIE using Mo Kα-radiation. Structure solution was performed with SHELXT36 and structure refinement was performed against F2 using SHELXL-2014.37 A numerical absorption correction was applied using programs X-RED and X-SHAPE of the program package X-Area.38−40 All non-hydrogen atoms were refined with anisotropic displacement parameters. All C−H hydrogen atoms were positioned with idealized geometry and were refined isotropic with Uiso(H) = −1.2 Ueq(C) using a riding model. The N−H and O−H H

amino)pyridine = 4-(tert-butoxycarbonylamino)pyridine) the thiocyanate N atoms are trans, whereas the thiocyanate S and the 4-(boc-amino)pyridine N atoms are in the cis-position, leading to zigzag chains.18 It is noted that this compound contains channels, in which acetonitrile molecules are embedded, that can be removed in a topotactic reaction. For this compound a value for the intrachain interaction of J = 6.1 K for the solvate and of J = 3.9 K for the ansolvate were determined. In the course of our project we became interested in 4aminopyridine as coligand, in which the boc group is absent. With this ligand a discrete complex with the composition Ni(NCS)2(4-aminopyridine)4 as well as some solvates of this compound were already reported by Nassimbeni and Kilkenny.35 Interestingly, they also investigated the thermal properties of this complex by hot-stage microscopy and TGDSC measurements, from which they concluded that a 4aminopyridine deficient compound might exist, but surprisingly, no further investigations were performed. Therefore, we investigated this system in more detail. In the course of these investigations we obtained a compound with a novel Ni(NCS)2 2D network, which is thermodynamically stable at roomtemperature, but on thermal decomposition of Ni(NCS)2(4aminopyridine)4 two additional compounds were detected. This includes an isomeric Ni(NCS)2 chain compound with the same composition as that of the layered material, which becomes thermodynamically stable at higher temperatures, and a more 4-aminopyridine deficient compound that exhibits a condensed 1D network that, to the best of our knowledge, is without any precedence in the literature. Here we report on our investigations.

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EXPERIMENTAL SECTION

4-Aminopyridine was obtained from Acros. Ni(NCS)2 was obtained from the reaction of equimolar amounts of NiSO4·6H2O with Ba(NCS)2·3H2O in water. The white residue of BaSO4 was filtered off and the filtrate was concentrated until complete dryness. The purity was checked by X-ray powder diffraction (XRPD). The crystalline powders were synthesized by stirring the reactants in the respective solvents at room temperature. The residues were filtered off and washed with the used solvent and dried in air. The purity of all compounds was checked by XRPD. Synthesis of Ni(NCS)2(4-aminopyridine)4 (1). A crystalline pale violet powder was formed by the reaction of Ni(NCS)2 (0.5 mmol, 87.5 mg) with 4-Aminopyridine (2.0 mmol, 188.2 mg) in 3.0 mL ethanol after 1d. Elemental analysis for C22H24N10NiS2 (551.3216 g/ mol): calc. N 25.41, C 47.93, H 4.39, S 11.63. Exp.: N 25.22, C 47.77, H 4.30, S 11.49. Synthesis of Ni(NCS)2(4-aminopyridine)2(H2O)2 (2). Single crystals were obtained by reacting Ni(NCS)2 (1.0 mmol, 149.1 mg) and 4-aminopyridine (1.0 mmol, 94.1 mg) in 1.5 mL water. The precipitate was filtered off after 5 min and the filtrate was left to stand in a closed test tube for a few days. No pure crystalline powder was obtained. Synthesis of Ni(NCS)2(4-aminopyridine)3(MeCN)·MeCN (3). Single crystals suitable for single crystal X-ray diffraction were obtained from the reaction of Ni(NCS)2 (0.5 mmol, 87.5 mg) with 4aminopyridine (0.5 mmol, 47.1 mg) in 3.0 mL MeCN at 140 °C. A light blue crystalline powder was obtained by the reaction of Ni(NCS)2 (0.5 mmol, 87.5 mg) with 4-aminopyridine (1.5 mmol, 140.1 mg) in 4.0 mL MeCN after stirring for 1 day. Elemental analysis for C21H24N10NiS2 (539.3106 g/mol): calc. N 25.97, C 46.77, H 4.49, S 11.89. Exp.: N 25.5, C 46.12, H 4.302, S 12.12. Synthesis of Ni(NCS)2(4-aminopyridine)3 (4). This compound can only be obtained by thermal removal of MeCN from compound 3 and was only characterized by elemental analysis and IR spectroscopy. B


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Inorganic Chemistry

formed (Figure S2 in the ESI).35 The asymmetric CN stretching vibration is observed at 2094 cm−1 with IR spectroscopy measurements, which is in agreement with the presence of terminal N-bonded anionic ligands (Figure S3). For 5-LT the CN stretch is found at 2104 cm−1, indicating that μ1,3-bridging anionic ligands are present (Figure S4 in the ESI). From acetonitrile as solvent, a further compound with the composition Ni(NCS)2(4-aminopyridine)3(MeCN)2 (MeCN = acetonitrile) (3) was obtained, for which the CN-stretch is observed at 2091 cm−1, indicating that a discrete complex with terminal anionic ligands has been obtained (Figure S5). For 3 and 5-LT single crystals were obtained and characterized by SC-XRD, which show that 3 consists of discrete complexes and that 5-LT forms a novel layered coordination network (see below). Within these investigations a few crystals of a further compound with the composition of Ni(NCS) 2 (4aminopyridine)2(H2O)2 (2) consisting of discrete complexes were obtained, but no pure samples could be prepared. The formation of the 2D network is somehow surprising because as mentioned above, in most cases, compounds with linear M(NCS)2 double chains (M = Mn, Fe, Co, or Ni) were obtained. A different phase might be available by thermal decomposition of precursors with terminal N-bonded thiocyanate anions as previously shown by us.47 Therefore, compound 1 was investigated by thermoanalysis. In this context also compound 3 is of interest, because one can assume that a compound with the composition Ni(NCS)2(4aminopyridine)3 might be prepared, if the MeCN molecules can be removed separately. Measurements of 1 using simultaneous differential thermoanalysis and thermogravimetry (DTA-TG) with a heating rate of 8 °C/min show two mass steps until 400 °C, which are each accompanied by endothermic events in the DTA curves (Figure S6). The experimental mass loss in both steps of 33.1% and 32.5% is in reasonable agreement with the removal of each of the two 4-aminopyridine ligands. To investigate the intermediate obtained in the first TG step, XRPD measurements were performed, which proves that a new crystalline phase with the composition [Ni(NCS)2(4-aminopyridine)2]n (5-HT) has formed, that is different from 5-LT (Figure S7). The CN stretching vibrations occur at 2094 and 2129 cm−1, which indicates that μ-1,3-bridging anionic ligands are present (Figure S8). Moreover, from the DTA and DTG curve it is obvious that the second TG step might consist of two successive reactions that are not completely resolved. Therefore, temperature dependent XRPD measurements were performed, which clearly show that a further crystalline phase (6) has formed before decomposition occurs (Figure S9). To obtain large amounts of this new crystalline phase, heating rate dependent measurements were performed, leading to a much better resolved TGcurve. The one with a heating rate of 1 °C/min shows three separate TG steps (Figure 1). The XRPD pattern of the intermediate formed in the second TG step is different from that of 5-HT but corresponds to that of 6, already detected in the temperature dependent XRPD measurements (Figure S9 and Figure S10). In the IR spectra the CN-stretch is observed at 2105 and 2139 cm−1, which proves that μ-1,3-bridging anionic ligands are present (Figure S11). DTA-TG measurements on the acetonitrile solvate 3 showed three mass steps, of which the first one is in reasonable agreement with that calculated for the removal of two molecules of acetonitrile, whereas the second and third steps

atoms were located in difference map, their bond lengths were set to ideal values and finally they were refined isotropic with Uiso(H) = −1.5 Ueq(N, O) using a riding model. The crystal of 2 is racemically twinned and therefore, a twin refinement was performed leading to an BASF parameter of 0.44(2). This compound shows pseudosymmetry and this might be the reason why the absolute structure cannot be determined. If the structure is refined neglecting the twinning, significant poorer reliability factors were obtained (R1 = 3.13%), which support the correctness of the space group. Selected crystal data and details on the structure refinements can be found in Table S1. CCDC-1815975 (2), CCDC-1815976 (3), CCDC- 1815977 (5LT), CCDC-1815979 (5-HT), CCDC-1815978 (6) and contain the supplementary crystallographic data for this paper. These data can be obtained free charge from the Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif. X-ray Powder Diffraction (XRPD). The temperature dependent XRPD measurements of 1 were performed with an PANalytical X’Pert Pro MPD Reflection Powder Diffraction System with CuKα radiation (λ= 154.0598 pm) equipped with an Anton Paar HTK 1200 N high temperature chamber and with a PIXcel semiconductor detector from PANalytical. Phase analysis and measurements for indexing were performed on a Stoe Transmission Powder Diffraction System (STADI P) with CuKα1 radiation that was equipped with a linear position-sensitive MYTHEN 1K detector (Dectris Ltd.) and a Johann-type Ge(111) monochromator from STOE & CIE. Measurements for ab initio crystal structure solution and Rietveld refinement were performed at room temperature on another Stoe Stadi P machine (Mo Kα1, λ = 0.7093 Å, equipped with a Johann Ge(111) monochromator) using a Mythen Dectris 1K detector (Dectris Ltd.). All samples were gently ground, filled into ϕ 0.5 mm glass capillaries for ambient measurements and in quartz capillaries for high temperature measurements (Hilgenberg). The capillaries were spun during the experiments for better particle statistics. The XRPD pattern for ab initio structure solution of 6 was collected in the range of 2−60° 2θ within 40 h. All Pawley41 and Rietveld42 refinements were performed using TOPAS V5.43 Indexing of 6 was carried out by an iterative use of singular value decomposition leading to a triclinic space group with the lattice parameters reported in Table S2.44 The peak profile was determined by a Pawley refinement41 using the fundamental parameter approach as implemented in TOPAS.45 The background was modeled using Chebychev polynomials of 10th order. The crystal structure of [Ni(NCS)2(4-aminopyridine)]n 6 was determined by applying the global optimization method of simulated annealing (SA).44 The two thiocyanate anions and the 4-aminopyridine ligand were described using rigid bodies in z-matrix notation with optimized bond lengths and angles, taken from related single crystal structure data. The position of the two nickel atoms and all ligands were gradually fixed during the simulated annealing process, once the coordination geometry was reasonable. The background, peak profile, all lattice parameters, rotations and translations of the rigid body as well as fractional coordinates of Ni were subsequently refined without any constraints during the final Rietveld refinement.42 Light preferred orientation, originating from the needle habitus of the crystallites, was successfully modeled by a spherical harmonics correction function of fourth order (Figure S1).46

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RESULTS AND DISCUSSION Synthetic Investigations and Thermoanalytical Measurements. Reaction of Ni(NCS)2 with 4-aminopyridine in different ratios in water, methanol, or ethanol leads to the formation of two crystalline phases, for which an elemental analysis indicates a composition of Ni(NCS)2(4-aminopyridine)4 (1) and [Ni(NCS)2(4-aminopyridine)2]n (5-LT). Comparison of the experimental X-ray powder pattern of 1 with that calculated for the discrete complex bis(thiocyanato)tetrakis(4-aminomethylpyridine) nickel(II) reported by Nassimbeni and Kilkenny proves that this crystalline phase has C


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Inorganic Chemistry

Investigations on the Thermodynamic Relation between Both Isomers. The synthetic investigations presented above indicate that 5-HT might be thermodynamically stable at higher temperatures. To investigate the stability of the isomers in more detail, a suspension of both isomers was stirred in acetonitrile at room-temperature and the residue formed was investigated as a function of time by XRPD (Figure S23). This shows that within 2 days all reflections of 5-HT disappeared, and thus, the layered isomer 5-LT represents the thermodynamic stable form at room-temperature, where 5-HT is metastable. Similar experiments at different temperatures revealed that 5-LT is also the more stable form at elevated temperatures up to about 112 °C and that 5-HT becomes more stable above 135 °C (Figure S24). This clearly shows that 5-LT is the low- and 5-HT the high-temperature phase, which is also in agreement with the densities of both forms, because the density of 5-LT is larger than that of 5-HT (Table S1). To prove if the LT form can be transformed into the HT form, measurements using differential scanning calorimetry (DSC) were performed (Figure 2). 5-HT decomposes at 302 °C upon

Figure 1. Heating rate dependent TG and DTG curves for 1.

correspond to the stepwise removal of the 4-aminopyridine ligands (Figure S12). The XRPD pattern of the compound obtained in the first TG step shows that a new phase (4) of very poor crystallinity has formed that is different from all other compounds (Figure S13). Elemental analysis indicates a composition of Ni(NCS)2(4-aminopyridine)3 (4) in agreement with the results of the TG measurements (see Experimental Section). It is noted that in some cases the residue obtained after MeCN removal is amorphous. Therefore, it can be assumed that the solvent removal leads to pure amorphous or semicrystalline samples that can recrystallize on further heating, which might explain the low crystallinity of 4. Measurements using differential scanning calorimetry show an exothermic event for some samples after MeCN removal that might correspond to the recrystallization of 4 (Figure S13). Indexing of the powder pattern failed and all attempts to crystallize this compound were unsuccessful, and thus, its structure remains unknown. However, based on simple structural considerations, this compound should consist of dimers, in which each Ni cation is coordinated by one terminal and two bridging thiocyanate anions, as well as three 4-aminopyridine ligands. This is supported by IR measurements of 4, where the CN stretching vibration is observed at 2085 and 2125 cm−1, indicating that terminal and bridging anionic ligands are present (Figure S15). All attempts to obtain single crystals of 5-HT and 6 at roomtemperature failed, but under solvothermal conditions crystals of 5-HT were obtained and characterized by single crystal X-ray diffraction, which proves that a new chain isomer has formed (see below). Additional synthetic investigations reveal that crystalline powders obtained at elevated temperatures using Ni(NCS)2 and 4-aminopyridine in ratio 1:2 only show reflections of 5-HT and that in the reaction of Ni(NCS)2 and 4-aminopyridine in ratio 1:1, obviously 6 is obtained as a pure phase (Figure S16 and S17). For 6, no single crystals were obtained, and therefore, its crystal structure was solved from XRPD data (Figure S18 and Table S2), which revealed that 6 forms an unusual 1D structure that to the best of our knowledge has never been observed before (see below). Based on the structural results, XRPD patterns were calculated and compared with the experimental pattern, which proves that 3, 5-LT, 5-HT, and 6 were obtained as pure phases (Figures S19−S22).

Figure 2. DSC curves for 5-HT and 5-LT at 4 °C/min.

heating, without any sign of a previous transformation. In contrast, for 5-LT an endothermic signal occurs at 256 °C, before decomposition is observed at 298 °C. The heat of transition ΔHtrs of about 7.3 kJ/mol is in the range expected for such transitions. To prove the reversibility of this event, a further sample was heated until 266 °C, cooled down, and heated again, which shows that in the second heating cycle this signal is absent (Figure S25). If the residue formed at 256 °C is investigated by XRPD, it is proven that 5-LT has been transformed into 5-HT (Figure S26). According to the heat of transition rule, the endothermic nature of this transition proves that both forms are related by enantiotropism, with a thermodynamic transition temperature somewhere between 112 and 135 °C, as determined by the solvent mediated conversion experiments (see above).48 A semiempirical energy temperature diagram can be found in Figure S27.49 The reason why in the DSC measurement the transition temperature is shifted to much higher values can be traced back to the kinetics of such reactions. We also tried to suppress this transition by fast heating to prove if also the 2D structure (5LT) transforms into 6, but even at a heating rate of 100 °C/ min the transition remains present (Figure S28). Finally, it is noted that on further heating an endothermic signal is observed, followed by an exothermic transition. If the residue formed at the peak of the endothermic signal is investigated by XRPD a mixture of 5-HT and 6 is obtained, whereas the D


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Inorganic Chemistry exothermic events lead to the formation of sulfides, which indicates that even 6 might be metastable (Figure S29). Crystal Structures. Compounds 2 and 3 crystallize in the monoclinic space group P21 with all atoms in general positions (Figure S30 and S32 and Table S1). In compound 2 the metal cations are octahedrally coordinated by two terminal N-bonded thiocyanate anions, two water molecules, and two 4-aminopyridine coligands, all of them in trans-position (Figure 3: top).

Figure 4. Crystal structure of 5-HT with view of a single chain. An Ortep plot of 5-HT can be found in Figure S34.

alternates with all ligands in trans position for one cation (Ni2), and the thiocyanate N atoms in trans and the thiocyanate S atoms as well as the 4-aminopyridine N atoms in cis position for the second (Ni1; Figure 4). However, the Ni cations are linked by pairs of anionic ligands into chains, which because of the different coordination are not linear but zigzag like (Figure 4). This means that two neighbored Ni(NCS)2Ni units are coplanar, whereas the following two units are rotated by 81° relative to the former plane. According to a search in the CCDC database this chain geometry was never observed before. It is noted that in [Ni(NCS)2(4-(boc-amino)pyridine)2]n, reported recently, each of the Ni cations shows only a cis-cis-trans coordination, and thus, these chains are different.18 The Ni−N distances are a bit longer for the Ni cation with an all-trans coordination, whereas the Ni−N as well as the Ni−S distances of both cations are comparable (Table S7). The Ni···Ni intrachain distance is 5.6106(2) Å. The low-temperature form of [Ni(NCS)2(4-aminopyridine)2]n (5-LT) crystallizes in the triclinic space group P-1, with two crystallographically independent Ni cations that are located on centers of inversion (Figure S35 and Table S1). Even this compound shows a very unusual Ni coordination that alternates. One of the two Ni cations (Ni1) shows the usual octahedral coordination with the two thiocyanate N and S atoms as well as the two pyridine N atoms in trans-position, whereas the second Ni cation (Ni2) is coordinated by two thiocyanate N atoms and four amino N atoms of the coligands (Figure 5: top and Figure S35). The Ni−N distances to the amino groups are significantly shorter than those to the pyridine N atoms, whereas the Ni−Npyridine and Ni−S bond lengths are comparable for both cations (Table S8). Only the two thiocyanate anions that coordinate with the S atoms to the metal centers act as bridging ligand, whereas the other two anionic ligands are only terminally N-bonded (Figure 5: top). The Ni cations are linked via single μ-1,3-bridging thiocyanate anions into chains that are further linked via some of the 4-aminopyridine ligands into layers with a network topology never observed before. In this context it is mentioned that a Ni compound with Ni thiocyanate single chains was already reported by Palion-Gazda et al., but the Ni coordination was different and the chains were not linked into a 2D network.50 However, only two of the four 4-aminopyridine ligands that coordinate to Ni2 act as bridging ligands, whereas the other two are only terminal bonded via the pyridine N atom (Figure S22). The network is additionally stabilized and linked into a 3D network by a number of N−H···S and C−H···S

Figure 3. Crystal structure of 2 (top) and 3 (bottom) with view of the Ni coordination. Ortep plots of both compounds can be found in Figures S30 and S31. Solvate molecules are not shown for clarity.

In Compound 3 the cations are octahedral coordinated by two N-bonded thiocyanate anions in cis-position, three 4-aminopyridine, and one MeCN ligand (Figure 3). Bond lengths and angles are comparable and in agreement with values reported in the literature (Table S3 and S5). In 2, the discrete complexes are linked by intermolecular O− H···O and O−H···N hydrogen bonding into layers, that are parallel to the b-c-plane (Figure S31). The amino H atoms are additionally linked to the thiocyanate S atoms via N−H···S hydrogen bonding, forming a three-dimensional network. In 3Ni the complexes are linked into chains along the a-axis, via pairs of intermolecular N−H···S hydrogen bonds between the two amino H atoms of one complex and the two thiocyanate S atoms of a neighbored complex (Figure S33). These chains are connected by N−H···N hydrogen bonding into layers parallel to (010), that are further linked into a three-dimensional network via N−H···S hydrogen bonding. By this arrangement channels are formed along the b-axis, in which the acetonitrile solvate molecules are embedded (Figure S33). The high-temperature form of [(Ni(NCS)2(4-aminopyridine)2]n (5-HT) crystallizes in the monoclinic space group C2/c, with two crystallographically independent Ni cations, of which one is located on the 2-fold rotation axis, whereas the second occupies a center of inversion (Figure S34 and Table S1). The Ni cations are octahedrally coordinated by two thiocyanate N and two S atoms as well as two 4-aminopyridine N atoms, within slightly distorted octahedra (Figure 4 and Table S7). In contrast to most other compounds with the same ratio between Ni(NCS)2 and the pyridine derivative, the Ni coordination E


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Inorganic Chemistry

Figure 6. Crystal structure of 6 with view of a part of a single chain.

polymers. In this context it is noted that at least two magnetic exchange pathways exist, with one via the S atoms and one along the NCS chains, which is indicative for a spin ladder. The coordination geometry is not discussed in detail as this structure was solved and refined using XRPD data using geometrical restraints. Magnetic Investigations. The temperature dependence of magnetic susceptibility measured at 1 kOe for compounds 5HT, 5-LT, and 6 is shown in Figure 7. In all three cases the

Figure 5. Crystal structure of 5-LT with view along the crystallographic a-axis and N−H···S hydrogen bonding shown as dashed lines. Please note that in the top of this figure two of the terminal coordinated coligands are omitted to show that the thiocyanate chains are linked into layers by any second 4-aminopyridine ligand. An Ortep plot of 5-LT can be found in Figure S35.

hydrogen bonds between the amino H atoms and the thiocyanate S atoms (Figure 5: bottom, Figure S36 and Table S9). There is also one N−H···S hydrogen bond to the thiocyanato anion that is only terminally N-bonded to the Ni cation, and this might be one of the reason why the value for the CN-stretching vibration is shifted to a value expected for μ1,3-briding thiocyanate anions. The most 4-aminopyridine deficient compound [Ni(NCS)2(4-aminopyridine)]n (6) crystallizes in the triclinic space group P-1, with two crystallographically independent Ni cations in general positions. The asymmetric unit consists, besides of the two Ni cations, of four symmetry independent thiocyanates and two 4-aminopyridine coligands. Each Ni cation is coordinated by two trans-coordinating N atoms and three S atoms of five thiocyanate anions as well as one N atom of the 4aminopyridine ligand (Figure 6). The symmetry independent nickel cations are connected over two S-ends of two thiocyanates, creating a rhombus, which is further linked by pairs of anionic ligands into linear chains, in which the two trans-S and two-trans N atoms are involved and which corresponds to the usual chain geometry observed in most other such compounds (Figure 6). Adjacent nickel distances are Ni(1)−Ni(2) 3.904 Å (rhombus) and 5.575 Å (linear chains). To the best of our knowledge, this chain geometry was never observed before in paramagnetic thiocyanate coordination

Figure 7. Magnetic susceptibility χ for 5-HT, 5-LT, and 6, measured at 1 kOe, presented as temperature dependence of the χT product. Solid lines were fitted using the model of the Heisenberg chain of spins S = 1 (see text).

room temperature value of the χT product corresponds to S = 1 spin of NiII with the g value 2.17−2.2. Decreasing the temperature makes χT higher, which points to dominant ferromagnetic exchange interactions in all three cases. The NiII ion in a crystal may have a significant zero-field splitting (zfs); however, its influence on magnetic properties usually manifests itself only below 20 K.51 For 5-HT the coordination chain comprises two different Ni sites that have different local anisotropy but are alternatively linked by (NCS)2 bridges of identical geometry. Similarly in the structure of 5-LT, two different Ni sites are linked by identical NCS bridges. For analysis of the magnetic behavior at higher temperature, it is possible to neglect different zero-field splitting of all Ni sites and treat Ni spins as isotropic. Therefore, we use the Heisenberg chain Hamiltonian with isotropic spins F


Article

Inorganic Chemistry Ĥ = −J ∑ Si⃗ Si⃗ + 1 + gμB H⃗ ∑ Si⃗ i

i

that includes exchange interaction J along respective (NCS)m bridges and the Zeeman term. In this analysis all interchain interactions are also omitted. To calculate the susceptibility for such a Hamiltonian, we applied density matrix renormalization group and quantum Monte Carlo methods, as presented in ref 18, where also zero-field splitting was included. Within the present work, to facilitate the usage of such numerically computed curves for experimental data analysis, we approximated the χT(T) curve (see Figure S37) as a function of J and g parameters using Padé approximant with an additional exponent c. χT =

NAμB2 kB

x = J /T ,

⎛ a + a x + a x 2 ⎞c 0 1 2 ⎟ g ⎜ 2 3 ⎝ 1 + b1x + b2x + b3x ⎠ 2

c = −0.81086,

a0 = 1.65273, a1 = 2.05175,

a 2 = 2.84018,

b1 = 2.88478, b2 = 4.65762, b3 = 4.30349

Figure 8. Top: zero-field cooled (circles) and field cooled (lines) susceptibility χ measured for 5-HT, 5-LT, and 6. Bottom: Temperature dependence of specific heat, C, shown as C/T.

Such formula provides predictable behavior in low and high limits of T/J and introduces additional relative error below 0.05% (see Figure S38). It is valid for a quantum, isotropic S = 1 spin chain with ferromagnetic Heisenberg exchange (J > 0), in the limit of small applied fields. The critical exponent of susceptibility at the T = 0 limit, χT ∼ T−γ, in this approximation is γ = 0.811. This value differs slightly from classical spin chain behavior, γ = 1, but is identical to the value γ = 0.811 estimated by extrapolation of results obtained by exact diagonalization for rings of up to 10 spins S = 1.52 Fitting the parameters g and J in the above formula (and also including a small diamagnetic correction) to the χT data above 10 K leads to values J = 3.0(1) K, g = 2.18(3) for 5-HT. A similar procedure applied to 5-LT data above 40 K leads to values J = 9.5(3) K, g = 2.23(3). At lower temperature experimental points deviate from calculated curves, which is the effect of anisotropy and interchain interactions. It is noted that the J value for 5-HT is similar to that for the ansolvate of [Ni(NCS)2(4-(boc-amino)pyridine)2]n (J = 3.9 K). Even if this compound exhibits a slightly different Ni coordination, it also consists of zigzag chains.18 In contrast, for 5-LT a significant higher J value is obtained, indicating that Ni(II) compounds with linear NCS chains will lead to an increase in the magnetic exchange. In the structure of 6 the exchange interactions between NiII spins create a spin ladder, with two different Ni sites and different exchange paths via Ni1-(NCS)2-Ni2, Ni1-(NCS)2Ni1, Ni2-(NCS)2-Ni2, and Ni1-S2-Ni2 bridges. Even though it is possible to calculate susceptibility for such an isotropic system for given exchange values, e.g. using the quantum Monte Carlo method like in ref 32, it is not possible in the case of 6 to unambiguously determine all these values using a limited range of high temperature susceptibility data. For sure, the exchange through NCS and also the exchange through S2 have to be ferromagnetic to ensure a monotonous increase of χT(T), faster than for 5-LT and 5-HT. The ferromagnetic exchange Ni1-S2-Ni2 is in accord with reported ferromagnetic exchange in, e.g., S = 1 Ni chains built up of Ni2S2 dimers.53 Magnetic ordering is detected by low-field susceptibility and specific heat (C) temperature dependences (Figure 8). The

peak of C/T(T) is observed at temperatures 1.06(3) K, 5.30(5) K, and 8.2(2) K for 5-HT, 5-LT, and 6, respectively. The χ(T) also shows a peak at 5.35(5) K and 8.5(1) K for 5-LT and 6, respectively, while for 5-HT the χ(T) curve increases at least down to 1.8 K. The C(T) peak in the case of 5-HT suggests that this compound orders magnetically around 1 K. The presented data allow us to conclude that compounds 5-LT and 6 order in an antiferromagnetic structure. An interchain interaction is essential to induce the observed magnetic ordering, as strictly one-dimensional systems of spins cannot order. The ordering of 5-LT is antiferromagnetic. This, together with ferromagnetic intrachain interaction, points to antiferromagnetic interaction between the chains. One probable exchange path is through the coordination bonds of the bridging 4-aminopyridine ligands in-between the chains, but also an influence of dipolar interaction cannot be excluded. The magnetization curve measured at 1.8 K (Figure 9) supports such a scenario, as a metamagnetic transition starts around Hsf

Figure 9. Magnetization of 5-HT and 5-LT measured at 1.8 K, with decreasing field. Inset: zoomed low-field region. G


Article

Inorganic Chemistry

the synthesis of metastable phases. On further heating, the 1D compound loses half of the 4-aminopyridine ligands and transforms into a novel chain compound, whose structure was solved ab initio from XRPD data. This compound shows an unusual coordination topology that to the best of our knowledge was never observed before in thiocyanate chemistry. The magnetic properties of 5 and 6 are governed by ferromagnetic exchange interaction along the Ni(NCS) chains. A convenient formula for the susceptibility of the ferromagnetic Heisenberg chain of isotropic spins S = 1 is proposed, based on numerical DMRG calculations, and used to determine the exchange constants. This leads to different J values for the zigzag chain in 5-HT and the linear chain in 5-LT, indicating that the magnetic exchange depends strongly on the geometry of the chains. Much weaker AF interactions between chains produce an antiferromagnetic ground state, observed for 5-LT and 6. Consecutive metamagnetic transitions in 6 are explained, as a result of ordering induced by dipolar interchain interactions. Finally, it is noted that for all three compounds AC magnetic measurements were performed, which as expected show that the AC susceptibility follows the dc low-field susceptibility, with no out of phase component (Figure S40).

= 300 Oe. Based on this value, the estimated interchain interaction is zJ′ ≈ − 0.022 K, which is indeed much smaller than J. The magnetic structure of 6 is more complicated. All Ni spins within a single coordination chain are ferromagnetically coupled. The anisotropy of Ni1 and Ni2 decides which are the easy axes. As Ni1 and Ni2 may have different orientations, the magnetic moments inside the single chain may be slightly canted. The magnetization at 50 kOe reaches 1.8 μB and is still not saturated, which is related to overcoming of the local NiII ion anisotropy by an external field. The ground state is AF, due to interchain interactions, but the M(H) curve reveals two metamagnetic transitions, presented in Figure 10. The first

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.8b00092. Crystal data and refinement results; SEM image; IR spectra; DTA-TG and DSC curves; XRPD pattern (PDF)

Figure 10. Magnetization hysteresis loops measured for 6 at different temperatures, revealing two metamagnetic transitions.

(MT1) is centered around 750 Oe, and is accompanied by a pronounced hysteresis loop, which is wider the lower the temperature. Following this transition, the magnetization reaches a plateau, around 0.35 μB per Ni ion at 2 kOe. To estimate the fraction of spins that undergo this MT1 transition, we compare this value with the M(H) curve extrapolated linearly to zero field from the data in the range 10−40 kOe, i.e. with the value 1.05 μB. This agrees exactly if only one per six spins flips during MT1. Several possible magnetic structures can accommodate such metamagnetic transition, and one possible scenario is shown in Figure S39. The second metamagnetic transition (MT2), centered around 3 kOe, displays much narrower hysteresis and is caused by flipping of the remaining fraction of spins. Such consecutive metamagnetic transitions are possible if long-range magnetic interactions, i.e. the dipolar interactions, are responsible for the AF ordering.54

Accession Codes

CCDC 1815975−1815979 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Fax: +49-431-8801520. ORCID

Christian Näther: 0000-0001-8741-6508 Notes

■

The authors declare no competing financial interest.

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CONCLUSION In the present contribution new thiocyanate coordination polymers were synthesized and structurally characterized including two isomers with a novel 1D structure and a 2D network. Detailed investigations using solvent mediated conversion experiments and thermoanalytical measurements prove that the 2D compound (5-LT) is thermodynamically stable at lower temperatures up to 112 °C and that the 1D isomer (5-HT) becomes thermodynamically stable above 135 °C. On heating, an endothermic transition of 5-LT into 5-HT is observed, which proves that both forms are related by enantiotropism with the chain compound as the HT phase. Interestingly, the HT form was detected in the thermal decomposition reaction of a simple discrete precursor complex, which emphasizes the power of such solid state reactions for

ACKNOWLEDGMENTS This project was supported by the Deutsche Forschungsgemeinschaft (Project No. Na 720/6-1) and the State of Schleswig-Holstein and by National Science Centre, Poland (Project no. 2017/25/B/ST3/00856). We thank Prof. Dr. Wolfgang Bensch for access to his experimental facilities.

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REFERENCES

(1) Craig, G. A.; Murrie, M. 3d single-ion magnets. Chem. Soc. Rev. 2015, 44, 2135−2147. (2) Bar, A. K.; Pichon, C.; Sutter, J.-P. Magnetic anisotropy in two- to eight-coordinated transition−metal complexes: Recent developments in molecular magnetism. Coord. Chem. Rev. 2016, 308 (Part 2), 346− 380.

H


Article

Inorganic Chemistry (3) Silva, P.; Vilela, S. M. F.; Tome, J. P. C.; Almeida Paz, F. A. Multifunctional metal-organic frameworks: from academia to industrial applications. Chem. Soc. Rev. 2015, 44, 6774−6803. (4) Caneschi, A.; Gatteschi, D.; Totti, F. Molecular magnets and surfaces: A promising marriage. A DFT insight. Coord. Chem. Rev. 2015, 289−290, 357−378. (5) Dhers, S.; Feltham, H. L. C.; Brooker, S. A toolbox of building blocks, linkers and crystallisation methods used to generate singlechain magnets. Coord. Chem. Rev. 2015, 296, 24−44. (6) Coulon, C.; Pianet, V.; Urdampilleta, M.; Clérac, R. In Molecular Nanomagnets and Related Phenomena; Gao, S., Ed.; Springer: Berlin Heidelberg, 2015; Chapter 154, Vol. 164, pp 143−184. (7) Maspoch, D.; Ruiz-Molina, D.; Veciana, J. Old materials with new tricks: multifunctional open-framework materials. Chem. Soc. Rev. 2007, 36, 770−818. (8) Escuer, A.; Esteban, J.; Perlepes, S. P.; Stamatatos, T. C. The bridging azido ligand as a central “player” in high-nuclearity 3d-metal cluster chemistry. Coord. Chem. Rev. 2014, 275, 87−129. (9) Kitagawa, S.; Matsuda, R. Chemistry of coordination space of porous coordination polymers. Coord. Chem. Rev. 2007, 251, 2490− 2509. (10) Robin, A. Y.; Fromm, K. M. Coordination polymer networks with O- and N-donors: What they are, why and how they are made. Coord. Chem. Rev. 2006, 250, 2127−2157. (11) Moulton, B.; Zaworotko, M. J. From Molecules to Crystal Engineering: Supramolecular Isomerism and Polymorphism in Network Solids. Chem. Rev. 2001, 101, 1629−1658. (12) Ohtsu, H.; Kawano, M. Kinetic assembly of coordination networks. Chem. Commun. 2017, 53, 8818−8829. (13) Näther, C.; Bhosekar, G.; Jeß, I. Preparation of Stable and Metastable Coordination Compounds: Insight into the Structural, Thermodynamic, and Kinetic Aspects of the Formation of Coordination Polymers. Inorg. Chem. 2007, 46, 8079−8087. (14) Werner, J.; Rams, M.; Tomkowicz, Z.; Runčevski, T.; Dinnebier, R. E.; Suckert, S.; Näther, C. Thermodynamically Metastable Thiocyanato Coordination Polymer that shows Slow Relaxations of the Magnetization. Inorg. Chem. 2015, 54, 2893−2901. (15) Wöhlert, S.; Runčevski, T.; Dinnebier, R. E.; Ebbinghaus, S. G.; Näther, C. Synthesis, Structures, Polymorphism, and Magnetic Properties of Transition Metal Thiocyanato Coordination Compounds. Cryst. Growth Des. 2014, 14, 1902−1913. (16) Wöhlert, S.; Boeckmann, J.; Jess, I.; Näther, C. Synthesis of New Stable and Metastable Thiocyanato Coordination Polymers by Thermal Decomposition and by Solution Reactions. CrystEngComm 2012, 14, 5412−5420. (17) Wöhlert, S.; Jess, I.; Englert, U.; Näther, C. Synthesis and crystal structures of Zn(II) and Co(II) coordination compounds with ortho substituted pyridine ligands: Two structure types and polymorphism in the region of their coexistence. CrystEngComm 2013, 15, 5326− 5336. (18) Suckert, S.; Rams, M.; Rams, M. M.; Näther, C. Reversible and topotactic solvent removal in a magnetic Ni(NCS)2 coordination polymer. Inorg. Chem. 2017, 56, 8007−8017. (19) Butterhof, C.; Barwinkel, K.; Senker, J.; Breu, J. Polymorphism in co-crystals: a metastable form of the ionic co-crystal 2 HBz•1 NaBz crystallised by flash evaporation. CrystEngComm 2012, 14, 6744−6749. (20) Clérac, R.; Miyasaka, H.; Yamashita, M.; Coulon, C. Evidence for Single-Chain Magnet Behavior in a MnIII−NiII Chain Designed with High Spin Magnetic Units: A Route to High Temperature Metastable Magnets. J. Am. Chem. Soc. 2002, 124, 12837−12844. (21) Braga, D.; Grepioni, F. Organometallic polymorphism and phase transitions. Chem. Soc. Rev. 2000, 29, 229−238. (22) Kalf, I.; Mathieu, P.; Englert, U. From crystal to crystal: a new polymorph of (4-carboxylatopyridine)silver(i) by topotactic dehydration of its monohydrate. New J. Chem. 2010, 34, 2491−2495. (23) Werner, J.; Runčevski, T.; Dinnebier, R.; Ebbinghaus, S. G.; Suckert, S.; Näther, C. Thiocyanato Coordination Polymers with Isomeric Coordination Networks − Synthesis, Structures, and Magnetic Properties. Eur. J. Inorg. Chem. 2015, 2015, 3236−3245.

(24) Forster, P. M.; Burbank, A. R.; Livage, C.; Ferey, G.; Cheetham, A. K. The role of temperature in the synthesis of hybrid inorganicorganic materials: the example of cobalt succinates. Chem. Commun. 2004, 0, 368−369. (25) Ghosh, S. K.; Kaneko, W.; Kiriya, D.; Ohba, M.; Kitagawa, S. A Bistable Porous Coordination Polymer with a Bond-Switching Mechanism Showing Reversible Structural and Functional Transformations. Angew. Chem. 2008, 120, 8975−8979. (26) Kawano, M.; Haneda, T.; Hashizume, D.; Izumi, F.; Fujita, M. A Selective Instant Synthesis of a Coordination Network and Its Ab Initio Powder Structure Determination. Angew. Chem., Int. Ed. 2008, 47, 1269−1271. (27) Batten, S. R.; Neville, S. M.; Turner, D. R. Coordination Polymers: Design, Analysis and Application; The Royal Society of Chemistry: Cambridge, 2009; p P001−P424. (28) Braga, D.; Curzi, M.; Grepioni, F.; Polito, M. Mechanochemical and solution reactions between AgCH3COO and [H2NC6H10NH2] yield three isomers of the coordination network {Ag[H2NC6H10NH2]+}. Chem. Commun. 2005, 2915−2917. (29) James, S. L.; Adams, C. J.; Bolm, C.; Braga, D.; Collier, P.; Friscic, T.; Grepioni, F.; Harris, K. D. M.; Hyett, G.; Jones, W.; Krebs, A.; Mack, J.; Maini, L.; Orpen, A. G.; Parkin, I. P.; Shearouse, W. C.; Steed, J. W.; Waddell, D. C. Mechanochemistry: opportunities for new and cleaner synthesis. Chem. Soc. Rev. 2012, 41, 413−447. (30) Rams, M.; Böhme, M.; Kataev, V.; Krupskaya, Y.; Büchner, B.; Plass, W.; Neumann, T.; Tomkowicz, Z.; Näther, C. Static and dynamic magnetic properties of the ferromagnetic coordination polymer [Co(NCS)2(py)2]n. Phys. Chem. Chem. Phys. 2017, 19, 24534−24544. (31) Rams, M.; Tomkowicz, Z.; Böhme, M.; Plass, W.; Suckert, S.; Werner, J.; Jess, I.; Näther, C. Influence of the Metal Coordination and the Co-ligand on the Relaxation Properties of 1D Co(NCS) 2 Coordination Polymers. Phys. Chem. Chem. Phys. 2017, 19, 3232− 3243. (32) Suckert, S.; Rams, M.; Böhme, M.; Germann, L. S.; Dinnebier, R. E.; Plass, W.; Werner, J.; Näther, C. Synthesis, structures, magnetic and theoretical investigations of Co and Ni coordination polymers with layered thiocyanate networks. Dalton Trans. 2016, 45, 18190− 18201. (33) Werner, J.; Tomkowicz, Z.; Reinert, T.; Näther, C. Synthesis, Structure, and Properties of Coordination Polymers with Layered Transition-Metal Thiocyanato Networks. Eur. J. Inorg. Chem. 2015, 2015, 3066−3075. (34) Suckert, S.; Rams, M.; Germann, L.; Cegiełka, D. M.; Dinnebier, R. E.; Näther, C. Thermal transformation of a 0D thiocyanate precursor into a ferromagnetic 3D coordination network via a layered intermediate. Cryst. Growth Des. 2017, 17, 3997−4005. (35) Nassimbeni, L. R.; Kilkenny, M. L. Tetrakis(4-aminopyridine)diisothiocyanatonickel(II) and its clathrates with EtOH, Me2CO and DMSO: structures, thermal stabilities and guest exchange †. Dalton Trans. 2001, 0, 1172−1175. (36) Sheldrick, G. M. SHELXT - Integrated space-group and crystalstructure determination. Acta Crystallogr., Sect. A: Found. Adv. 2015, A71, 3−8. (37) Sheldrick, G. M. Crystal structure refinement with SHELXL. Acta Crystallogr., Sect. C: Struct. Chem. 2015, C71, 3−8. (38) X-Red, Version 1.11, Program for Data Reduction and Absorption Correction; STOE & CIE GmbH: Darmstadt (Germany), 1998. (39) X-Shape, Version 1.03, Program for the Crystal Optimization for Numerical Absorption Correction; STOE & CIE GmbH: Darmstadt (Germany), 1998. (40) X-Area, Version 1.44, Program Package for Single Crystal Measurements, STOE & CIE GmbH: Darmstadt (Germany), 2008. (41) Pawley, G. S. Unit-cell refinement from powder diffraction scans. J. Appl. Crystallogr. 1981, 14, 357−361. (42) Rietveld, H. A profile refinement method for nuclear and magnetic structures. J. Appl. Crystallogr. 1969, 2, 65−71. (43) Bruker, A. X. S. TOPAS, 5.0; 2014. I


Article

Inorganic Chemistry (44) Coelho, A. Whole-profile structure solution from powder diffraction data using simulated annealing. J. Appl. Crystallogr. 2000, 33, 899−908. (45) Cheary, R. W.; Coelho, A.; Cline, J. P. Fundametal Parameters Line Profile Fitting in Laboratory Diffractometers. J. Res. Natl. Inst. Stand. Technol. 2004, 109, 1−25. (46) Jarvinen, M. Application of symmetrized harmonics expansion to correction of the preferred orientation effect. J. Appl. Crystallogr. 1993, 26, 525−531. (47) Näther, C.; Wöhlert, S.; Boeckmann, J.; Wriedt, M.; Jeß, I. A Rational Route to Coordination Polymers with Condensed Networks and Cooperative Magnetic Properties. Z. Anorg. Allg. Chem. 2013, 639, 2696−2714. (48) Burger, A.; Ramberger, R. On the Polymorphism of Pharmaceutical and Other Molecular Crystals I. Microchim. Acta 1979, 72, 259−271. (49) Hilfiker, R. Polymorphism: in the Pharmaceutical Industry; WileyVCH Verlag GmbH & Co. KGaA: Weinheim, 2006. (50) Palion-Gazda, J.; Machura, B.; Lloret, F.; Julve, M. Ferromagnetic Coupling Through the End-to-End Thiocyanate Bridge in Cobalt(II) and Nickel(II) Chains. Cryst. Growth Des. 2015, 15, 2380−2388. (51) Kahn, O. Molecular Magnetism; VCH: 1993. (52) Souletie, J.; Rabu, P.; Drillon, M. In Magnetism: Molecules to Materials V; Miller, J. S., Drillon, M., Eds.; Wiley: Weinheim, 2005; Chapter 10, p 366. (53) Miyake, T.; Ishida, T.; Hashizume, D.; Iwasaki, F.; Nogami, T. Ferromagnetic S = 1 chain formed by a square Ni2S2 motif in Ni(qt)2 (qt = quinoline-8-thiolate). Magnetic properties of related compounds. Polyhedron 2001, 20, 1551−1555. (54) Panissod, P.; Drillon, M. In Magnetism: Molecules to Materials IV; Miller, J. S., Drillon, M., Eds.; Wiley: 2003; pp 233−270.

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