Two new transition metal thiocyanate coordination polymers with the composition [Co(NCS)(4-vinylpyridine)] (1) and [Co(NCS)(4-benzoylpyridine)] (2) were synthesized and their crystal structures were determined. In both compounds the Co cations are octahedrally coordinated by two trans-coordinating 4-vinyl- or 4-benzoylpyridine co-ligands and four μ-1,3-bridging thiocyanato anions and linked into chains by the anionic ligands. While in 1 the N and the S atoms of the thiocyanate anions are also in trans-configuration, in 2 they are in cis-configuration. A detailed magnetic study showed that the intra-chain ferromagnetic coupling is slightly stronger for 2 than for 1, and that the chains in both compounds are weekly antiferromagnetically coupled. Both compounds show a long range magnetic ordering transition at T = 3.9 K for 1 and T = 3.7 K for 2, which is confirmed by specific heat measurements. They also show a metamagnetic transition at a critical field of 450 Oe (1) and 350 Oe (2), respectively. Below T1 and 2 exhibit magnetic relaxations resembling relaxations of single chains. The exchange constants obtained from magnetic and specific heat data are in good accordance with those obtained from constrained DFT calculations carried out on isolated model systems. The ab initio calculations allowed us to find the principal directions of anisotropy.

NiMnGe is investigated by meam of X-ray diffraction, neutron diffraction, and magnetometric methods. The orthorhombic distorsion of hexagonal lattice is observed below 470 K. The compound NiMnGe is antiferromagnetic with a NBel temperature T N = 346 K.The jump observed a t temperature Tt = 186 K on the temperature dependence of magnetic susceptibility points a t the change of a magnetic structure. From the analysis of the neutron diffraction patterns .the following models of spiral magnetic structure are obtained: a t T < Tt the spiral axis is in the bc-plane. The angle between the spiral axis and the b-axis is 45", magnetic moment a t 80 K is 2 . 7 5~~; at T, < T < T N the spiral axis is along the a-axis. !The magnetic moment a t 295 K is 2 . 2 ,~~.

Reaction of cobalt thiocyanate with 4-acetylpyridine leads to the formation of [Co(NCS)2(4-acetylpyridine)2]n (3/I). In its crystal structure the Co cations are connected by pairs of μ-1,3-bridging thiocyanato ligands into dimers that are further connected into layers by single anionic ligands. DTA-TG measurements of Co(NCS)2(4-acetyl-pyridine)4 (1) led to the formation of 3/I. In contrast, when the hydrate Co(NCS)2(4-acetyl-pyridine)2(H2O)2 (2) is decomposed, a mixture of 3/I and a thermodynamically metastable form 3/II is obtained. Further investigations reveal that thermal annealing of 2 leads to the formation of 3/II, that contains only traces of the stable form 3/I. DSC and temperature dependent X-ray powder diffraction (XRPD) measurements prove that 3/II transforms into 3/I on heating. The crystal structure of 3/II was determined ab initio from XRPD data. In its crystal structure the Co cations are linked by pairs of bridging thiocyanato anions into a 1D coordination polymer, and thus, 3/II is an isomer of 3/I. Magnetic measurements disclose that the stable form 3/I only shows paramagnetism without any magnetic anomaly down to 2 K. In contrast, the metastable form 3/II shows ferromagnetic behavior. The phase transition into ordered state at Tc = 3.8 K was confirmed by specific heat measurements. Alternating current susceptibility measurements show frequency dependent maxima in χ' and χ″, which is indicative for a slow relaxation of the magnetization.

The design and development of suitable biomimetic catalytic systems capable of mimicking the functional properties of enzymes continues to be a challenge for bioinorganic chemists. In this study, we report on the synthesis, X-ray structures, and physicochemical characterization of the novel isostructural [Fe III Co ] complex as the catalytically active species in diester hydrolysis reactions. Kinetic studies on the hydrolysis of the model substrate bis(2,4-dinitrophenyl)phosphate by 1 and 2 show Michaelis-Menten behavior, with 2 being 35% more active than 1. In combination with k H /k D isotope effects, the kinetic studies suggest a mechanism in which a terminal M III -bound hydroxide is the hydrolysis-initiating nucleophilic catalyst. In addition, the complexes show maximum catalytic activity in DNA hydrolysis near physiological pH. The modest reactivity difference between 1 and 2 is consistent with the slightly increased nucleophilic character of the Ga

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Three new coordination compounds with the composition Co(NCS)2(4-(3-phenylpropyl)pyridine)4 (1), Co(NCS)2(4-(3-phenylpropyl)pyridine)4(H2O)2 (2) and [Co(NCS)2(4-(3-phenylpropyl)pyridine)2]n (3) were prepared and investigated. The crystal structures of compounds 1 and 2 consist of discrete complexes, in which the Co(II) cations are coordinated by only terminal N-bonded thiocyanato anions. In the crystal structure 3 of the Co(II) cations are linked into chains by pairs of μ-1,3-bridging thiocyanato anions. DTA-TG measurements on compound 1 show decomposition without the formation of 3 as an intermediate. In contrast, on heating compound 2 two water molecules are removed in the first step leading to the formation of compound 3 in the second step. Magnetic measurements on reveal ferromagnetic interactions between Co(II) ions along chains with J = 29.5(1) K, and also ferromagnetic interactions between chains with zJ' = 0.38(1) K. The ferromagnetic transition is observed at 3.3 K, which is confirmed by specific heat measurements. The temperature dependent ac susceptibility shows slow relaxations above and below 3.3 K. The results for this quasi-one dimensional Ising ferromagnet, having also some features of a cluster spin-glass, are compared with those of related compounds.

The reaction of Co(NCS)2 with 4-(4-chlorobenzyl)pyridine (ClBP) leads to the formation of Co(NCS)2(4-(4-chlorobenzyl)pyridine)4 () and [Co(NCS)2(4-(4-chlorobenzyl)pyridine)2]n (). In the crystal structure of the Co(ii) cations are octahedrally coordinated by two terminal bonded thiocyanato anions and four ClBP ligands, whereas in the Co(ii) cations are linked into chains by pairs of μ-1,3-bridging thiocyanato anions. Magnetic measurements of show an antiferromagnetic phase transition with TN = 3.9 K. A metamagnetic transition is observed at the critical magnetic field of 260 Oe. Magnetic relaxations in the zero field are consistent with single chain magnetic behavior. These results are compared with those obtained for similar compounds reported recently.

Reaction of Co(NCS)2 with 4-ethylpyridine leads to the formation of three new compounds of composition Co(NCS)2(4-ethylpyridine)4 (1), [(Co(NCS)2]2(4-ethylpyridine)6 (2), and [Co(NCS)2(4-ethylpyridine)2]n (3). In all compounds the coordination of the Co(II) ions is distorted octahedral. 1 consists of discrete monomeric complexes and in 2 two Co(II) cations are linked by pairs of μ-1,3-bridging thiocyanato ligands into dimers. In the crystal structure of 3 the Co(II) cations are connected into chains by the same bridge as in 2. Magnetic studies show that 1 and 2 are paramagnets down to a temperature of 2 K, while compound 3, which is the main object of this study, is an antiferromagnet with the Néel temperature T(N) = 3.4 K. Its magnetic structure is built from ferromagnetic chains, which are weakly antiferromagnetically coupled. With increasing magnetic field a metamagnetic transition starts at ~175 Oe, as observed for a polycrystalline sample. Magnetic relaxations, which were observed in the antiferromagnetic state, are retained at the metamagnetic transition. With decreasing field 3 remains in a state, in which except of the faster magnetic relaxation process in single chains also a slower process coexists resulting in the appearance of a magnetic hysteresis loop.