13689-92-4Relevant academic research and scientific papers
Thiocyanato Coordination Polymers with Isomeric Coordination Networks - Synthesis, Structures, and Magnetic Properties
Werner, Julia,Run?evski, Tom?e,Dinnebier, Robert,Ebbinghaus, Stefan G.,Suckert, Stefan,N?ther, Christian
, p. 3236 - 3245 (2015)
The reactions of M(NCS)2 (M = Mn, Fe, and Ni) with 4-acetylpyridine (4-Acpy) in water lead to the formation of discrete complexes of composition M(NCS)2(4-Acpy)2(H2O)2, in which the metal cations are coordinated only N-terminally to the thiocyanato anions. When heated, these precursors dehydrate, and some of them transform into compounds of composition [M(NCS)2(4-Acpy)2]n, in which the metal cations are linked by pairs of μ-1,3-bridging anionic ligands into chains (1D isomer). In contrast, the thermal decomposition of Ni(NCS)2(4-Acpy)4 or crystallization from solution leads to the formation of an isomeric 2D network of the same composition, which is thermodynamically more stable than the 1D isomer. Temperature-dependent magnetic measurements of the 1D isomer [Fe(NCS)2(4-Acpy)2]n at 200 Oe reveal antiferromagnetic ordering at TN = 4.5 K. Field-dependent measurements show a metamagnetic transition into a saturated paramagnetic phase at a critical field of ca. 700 Oe. In contrast, magnetic measurements of the 2D isomer [Ni(NCS)2(4-Acpy)2]n at 1000 Oe show a ferromagnetic transition at TC = 8.6 K, whereas only paramagnetic behavior is observed for the Ni 1D isomer.
Transition metal complexes with pyrazole based ligands, part 15. Cobalt(iii)-, nickel(ii)- and copper(ii)-complexes with 3,5-dimethyl-1-thiocarboxamidepyrazole
Meszaros Szecsenyi,Leovac,Ja?imovi?,Pokol
, p. 943 - 952 (2003)
The complex formation of cobalt(II)-, nickel(II) and copper(II) sulphate hydrates with 3,5-dimethyl-1-thiocarboxamidepyrazole (HL) was studied. The influence of the anions on the course of the reaction was also examined, using nickel(II) salts with various anions. Beside the NiSO4.7H 2O the reaction has been carried out with Ni(OAc)2, Ni(CF3COO)2 and Ni(SCN)2, Compounds with the following composition were obtained: Co(L)3, Ni(L)2 and [Cu(SCN)L]2. The structure of the ligand and the Co(L)3 complex was determined by single crystal X-ray analysis, while that of the Ni(L)2 was solved by analysis of powder diffraction X-ray data, The most probable structure of the copper(II) complex is proposed on the basis of the elemental analyses data, FT-IR spectrometry and magnetic measurement. The thermal decomposition of the complexes was investigated by thermogravimetry, DSC and coupled TG-MS measurements. In the case of the nickel(II) compound, a relatively stable intermediate was detected in the 550-650 K temperature range. The composition of the intermediate, Ni(SCN)(NCS), was determined by FT-IR-spectrometry.
A very low-temperature calorimeter with a (3He + 4He) dilution refrigerator. The heat capacity of trans-bis(ethylenediamine)-bis(isothiocyanato)nickel(II)
Murakawa, Shigemi,Wakamatsu, Tomio,Nakano, Motohiro,Soral, Michio,Suga, Hiroshi
, p. 1275 - 1292 (1987)
A calorimeter with a (3He + 4He) dilution refrigerator capable of measuring heat capacity between 20 mK and 25 K has been constructed.The calorimeter works under three operational modes in accordance with the temperature region suitable for heat-capacity measurements: the isoperibol low-temperature mode covers the range below 200 mK, the adiabatic high-temperature mode is used in the range from 0.2 to 25 K, and the isoperibol third mode is adopted when the thermal relaxation time of a sample is long.The accuracy of the calorimeter has been determined indirectly by comparing heat capacities of a common sample with those measured by a 3He calorimeter whose accuracy has been established on the basis of the 1965 Calorimetry Conference Copper Standard.The heat capacity of a paramagnetic nickel complex (en = H2NCH2CH2NH2) has been measured between 0.3 and 20 K.A Schottky anomaly centred around 3.3 K was detected.This anomaly was well accounted for in terms of the zero-field splitting of a single nickel ion arising from the crystalline-field anisotropy.The best fit between theory and experiment was obtained for D/k = 8.98 K and /E//k = 1.62 K (or /E//D = 0.18) where D and E are the uni- and bi-axial crystalline-field anisotropy parameters, respectively, and k is the Boltzmann constant.The heat-capacity anomaly can likewise be accounted for in terms of different set of the parameters (D/k = -6.92 K and /E//k = 3.67 K or /E//D = 0.53) because both the sets bring about identical splitting with respect to the spin energy-level.
Large-ring chain and sheet polymeric metal complexes of extended-reach siloxypyridine ligands of type O[iPr2SiO(CH2)npy]2
Goodgame, David M.L.,Lickiss, Paul D.,Rooke, Stephanie J.,White, Andrew J.P.,Williams, David J.
, p. 61 - 73 (2003)
The preparations are reported of a range of metal complexes of Mn(II), Co(II), Ni(II) and Zn(II) with the 'extended reach' ligands O[iPr2SiO(CH2)npy]2 (n=0, 1 or 3, I-III) and with Cu(II), Cd(II) and Ag(I) for II; six of them have been shown by X-ray studies to have polymeric structures. The compounds M[O(iPr2SiOpy)2]2Cl2 (M=Co, Cu) form chains of 24-membered macrocycles, as does Co[O(iPr2SiOCH2py)2] 2I2(H2O)2. A similar structure is formed by Mn[O(iPr2SiOCH2py)2] 2Cl2 but in this case the rings are 28-membered. The complex Cu[O(iPr2SiOpy)2]Cl2 forms sheets of 52-membered macrocycles with chloride bridged Cu2Cl4 units at the node points. The structure of Cu2[O(iPr2SiOpy)2]4Cl 3 comprises sheets of 48-membered rings which are linked into pairs of sheets by linear, but weak, Cu-Cl-Cu bridges. X- and Q-band EPR spectra of the manganese compounds are also reported, as are relevant spectroscopic results for the other complexes.
Tuning of the Critical Temperature in Magnetic 2D Coordination Polymers by Mixed Crystal Formation
Wellm, Carsten,Rams, Micha?,Neumann, Tristan,Ceglarska, Magdalena,N?ther, Christian
, p. 3117 - 3123 (2018)
Reaction of Co(NCS)2 and Ni(NCS)2 with 4-acetylpyridine under different conditions leads to the formation of mixed crystals of the layered compound with the composition [CoxNi1-x(NCS)2(4-acetylpyridine)2]n (x = 0.15 0.3, 0.5, and 0.7). Mixed crystal formation was investigated by a combination of X-ray powder diffraction (XRPD), atomic absorption spectroscopy (AAS), simultaneous scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), differential scanning calorimetry (DSC), and magnetic and heat capacity measurements. Dependent on the synthetic method, homo- or heterogeneous mixed crystals were obtained as already indicated by XRPD, where significant differences to the pattern of physical mixtures of the homometallic counterparts [M(NCS)2(4-acetylpyridine)2]n with M = Co or Ni) with the same Co/Ni ratio are observed. Mixed crystals can also be obtained from physical mixtures under thermodynamic control, indicating that they are more stable than the homometallic compounds. This is further supported by AAS, which indicates that the solubility of the mixed crystals is lower than that of the homometallic compounds. Magnetic and heat capacity measurements show a linear increase of the critical temperature of magnetic ordering with increasing Ni content and also confirm that homogeneous samples were obtained.
A thermochemical investigation of guest-host interactions in labile Werner clathrates of the [Ni(4-EtPy)4(NCS)2]·G type (G = methyl derivatives of benzene)
Jona,Simon,Jorik,Koman
, p. 219 - 225 (1997)
The stoichiometry of thermal decomposition has been studied for (I): [Ni(4-EtPy)4(NCS)2] as a host complex as well as for its clathrates [Ni(4-EtPy)4(NCS)2]·G where guest molecule G - toluene, (II): T, (III): o-xylene (o-X) and (IV): p-xylene (p-X). The loss of volatile components proceeds in three steps (-2L, -1L, -1L) for I and in four steps (-G, -2L, -1L, -1L) for II, III and IV. DSC and X-ray powder measurements indicated a phase transition in all compounds under study. However, this process is overlapped by the escape of G in II and III. The differences in enthalpy changes are associated with different guest-host interactions in the particular clathrates.
Field effects to slow magnetic relaxation in a mononuclear Ni(II) complex
Lomjansky,Moncol,Rajnák,Titi?,Bo?a
, p. 6930 - 6932 (2017)
A mononuclear Ni(ii) complex [Ni(NCS)2(nqu)2(H2O)2]·2nqu (nqu-5-nitroquinoline) shows a field induced slow magnetic relaxation with three relaxation domains. The relaxation time for the low-frequency mode is as slow as τ = 0.3 s at T = 1.9 K and BDC = 0.4 T.
Reversible and Topotactic Solvent Removal in a Magnetic Ni(NCS)2 Coordination Polymer
Suckert, Stefan,Rams, Micha?,Rams, Marek M.,N?ther, Christian
, p. 8007 - 8017 (2017)
Reaction of Ni(NCS)2 with 4-(Boc-amino)pyridine in acetonitrile leads to the formation of a new coordination polymer with the composition Ni(NCS)2(4-(Boc-amino)pyridine)2·MeCN (1-MeCN). In the crystal structure the Ni(II) cations are linked by the anionic ligands into chains that are further connected into layers by intermolecular N-H···O hydrogen bonding. These layers are stacked and channels are formed, in which acetonitrile molecules are located. Solvent removal leads to the ansolvate 1, which shows microporosity as proven by sorption measurements. Single crystal X-ray investigations reveal that the solvent removal leads to a change in symmetry from primitive to C-centered, which is reversible and which proceeds via a topotactic reaction leaving the network intact. The magnetic properties of 1-MeCN and 1 are governed by the ferromagnetic exchange between spins of Ni(II) forming chains. The susceptibility and specific heat for such a quantum Heisenberg chain of S = 1 spins with zero-field splitting are calculated using the DMRG method and compared with the experimental results.
Isoquinoline-based Werner clathrates with xylene isomers: Aromatic interactions vs. molecular flexibility
Wicht, Merrill M.,Báthori, Nikoletta B.,Nassimbeni, Luigi R.
, p. 6863 - 6870 (2015)
The crystal structures of the Werner clathrates Ni(NCS)2(isoquinoline)4 (H) with para-xylene (px), meta-xylene (mx) and ortho-xylene (ox) have been elucidated. The kinetics of thermal decomposition of the three inclusion compounds were performed using the isothermal technique of Flynn and Wall. Selectivity of H for the xylene isomers was determined for both the liquid and vapour phase binary mixtures of the xylenes. The chosen ligand has a larger aromatic system to improve the possible π interactions between H and the selected guests. The planarity of the isoquinoline ligand causes H rigidity and its selectivity was compared to a related Werner complex containing the more flexible 4-phenylpyridine. This journal is
New isomeric Ni(NCS)2 coordination compounds: Crystal structures, magnetic properties as well as: Ex situ and in situ investigations on their synthesis and transition behaviour
Ceglarska, Magdalena,Dinnebier, Robert E.,Gallo, Gianpiero,N?ther, Christian,Neumann, Tristan,Rams, Micha?,Wellm, Carsten
, p. 2350 - 2360 (2020)
The reaction of Ni(NCS)2 with 3-ethylpyridine in water leads to the formation of two known modifications of Ni(NCS)2(3-ethylpyridine)4 (1-I and 1-II) as well as of Ni(NCS)2(3-ethylpyridine)2(H2O)2 (2) that consist of discrete complexes. If the synthesis is performed in ethyl acetate, the new compound [Ni(NCS)2(3-ethylpyridine)2]n (3-lc) formed that comprises linear and corrugated Ni(NCS)2 chains in one crystal. By changing the solvent to dichloromethane, a solvate of compound 3 is obtained that consists exclusively of corrugated chains (3c-CH2Cl2). 3c-CH2Cl2 is unstable and transforms immediately into 3-lc. Upon heating the precursor complexes 1-I, 1-II and 2, the 3-ethylpyridine ligands are removed in two steps leading to a mixture of 3-lc and an additional isomer of 3 (3-l) in the first step that decomposes upon further heating into a compound with the composition [Ni(NCS)2(3-ethylpyridine)]n (4). Ex and in situ XRPD measurements reveal that a mixture of two modifications (4-I and 4-II) is always formed, preventing their structure determination by XRPD. Time dependent investigations in solution prove that 3-l is formed under kinetic control and transforms into 3-lc within several hours that is thermodynamically stable at roomerature. Structure analysis of 3-l shows that in contrast to 3-lc and 3c-CH2Cl2 this isomer consists exclusively of linear Ni(NCS)2 chains. Magnetic measurements of the new chain compounds 3-l and 3-lc shows χT values that are typical for Ni(ii) cations with S = 1. For 3-l the exchange constant was determined by fitting of the magnetic data leading to a value that is similar to that of [Ni(NSC)2(2,2′-bipyridine)2]n.
