Synthesis, structural characterization and magnetic properties of Mn(II) isothiocyanate complexes based on pyridine-N-oxide derivative co-ligands

Synthesis and crystal structure of poly[ethanol(μ-4-methyl-pyridine N-oxide)di-μ-thio-cyanato-cobalt(II)]

Reaction of 4-methyl-pyridine N-oxide and Co(NCS)2 in ethanol as solvent accidentally leads to the formation of single crystals of Co(NCS)2(4-methyl-pyridine N-oxide)(ethanol) or [Co(NCS)2(C6H7NO)(C2H6O)] n . The asymmetric unit of the title compound consists of one CoII cation, two crystallographically independent thio-cyanate anions, one 4-methyl-pyridine N-oxide coligand and one ethanol mol-ecule on general positions. The cobalt cations are sixfold coordinated by one terminal and two bridging thio-cyanate anions, two bridging 4-methyl-pyridine N-oxide coligands and one ethanol mol-ecule, with a slightly distorted octa-hedral geometry. The cobalt cations are linked by single μ-1,3(N,S)-bridging thio-cyanate anions into corrugated chains, that are further connected into layers by pairs of μ-1,1(O,O)-bridging 4-methyl-pyridine N-oxide coligands. The layers are parallel to the bc plane and are separated by the methyl groups of the 4-methyl-pyridine N-oxide coligands. Within the layers, intra-layer hydrogen bonding is observed.

Synthesis and crystal structure of diiso-thio-cyanato-tetra-kis-(4-methyl-pyridine N-oxide)cobalt(II) and diiso-thio-cyanato-tris-(4-methyl-pyridine N-oxide)cobalt(II) showing two different metal coordination polyhedra

The reaction of Co(NCS)2 with 4-methyl-pyridine N-oxide (C6H7NO) leads to the formation of two compounds, namely, tetra-kis-(4-methyl-pyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II), [Co(NCS)2(C6H7NO)4] (1), and tris-(4-methyl-pyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II), [Co(NCS)2(C6H7NO)3] (2). The asymmetric unit of 1 consists of one CoII cation located on a centre of inversion, as well as one thio-cyanate anion and two 4-methyl-pyridine N-oxide coligands in general positions. The CoII cations are octa-hedrally coordinated by two terminal N-bonding thio-cyanate anions in trans positions and four 4-methyl-pyridine N-oxide ligands. In the extended structure, these complexes are linked by C-H⋯O and C-H⋯S inter-actions. In compound 2, two crystallographically independent complexes are present, which occupy general positions. In each of these complexes, the CoII cations are coordinated in a trigonal-bipyramidal manner by two terminal N-bonding thio-cyanate anions in axial positions and by three 4-methyl-pyridine N-oxide ligands in equatorial positions. In the crystal, these complex mol-ecules are linked by C-H⋯S inter-actions. For compound 2, a nonmerohedral twin refinement was performed. Powder X-ray diffraction (PXRD) reveals that 2 was nearly obtained as a pure phase, which is not possible for compound 1. Differential thermoanalysis and thermogravimetry data (DTA-TG) show that compound 2 start to decompose at about 518 K.

Synthesis, crystal structure and properties of poly[(μ-2-methyl-pyridine N-oxide-κ2O:O)bis-(μ-thio-cyanato-κ2N:S)cobalt(II)]

The title compound, [Co(NCS)2(C6H7NO)]n or Co(NCS)2(2-methyl-pyridine N-oxide), was prepared by the reaction of Co(NCS)2 and 2-methyl-pyridine N-oxide in methanol. All crystals obtained by this procedure show reticular pseudo-merohedric twinning, but after recrystallization, one crystal was found that had a minor component with only a very few overlapping reflections. The asymmetric unit consists of one CoII cation, two thio-cyanate anions and one 2-methyl-pyridine N-oxide coligand in general positions. The CoII cations are octa-hedrally coordinated by two O-bonding 2-methyl-pyridine N-oxide ligands, as well as two S- and two N-bonding thio-cyanate anions, and are connected via μ-1,3(N,S)-bridging thio-cyanate anions into chains that are linked by μ-1,1(O,O) bridging coligands into layers. No pronounced directional inter-molecular inter-actions are observed between the layers. The 2-methyl-pyridine coligand is disordered over two orientations and was refined using a split model with restraints. Powder X-ray diffraction (PXRD) indicates that a pure sample was obtained and IR spectroscopy confirms that bridging thio-cyanate anions are present. Thermogravimetry and differential thermoanalysis (TG-DTA) shows one poorly resolved mass loss in the TG curve that is accompanied by an exothermic and an endothermic signal in the DTA curve, which indicate the decomposition of the 2-methyl-pyridine N-oxide coligands.

Synthesis, crystal structure and thermal behavior of tetra-kis-(3-cyano-pyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II), which shows strong pseudo-symmetry

The title compound, [Co(SCN)2(C6H4N2O)4], was prepared by the reaction of cobalt(II)thio-cyanate with 3-cyano-pyridine N-oxide in ethanol. In the crystal, the cobalt(II) cations are octa-hedrally coordinated by two terminal N-bonded thio-cyanate anions and four O-bonded 3-cyano-pyridine N-oxide coligands, forming discrete complexes that are located on centers of inversion, hence forming trans-CoN2O4 octa-hedra. The structure refinement was performed in the monoclinic space group P21/n, for which a potential lattice translation and new symmetry elements with a fit of 100% is suggested. The structure can easily be refined in the space group I2/m, where the complexes have 2/m symmetry. However, nearly all of the reflections that violate the centering are observed with significant intensity and the refinement in P21/n leads to significantly lower R(F) values (0.027 versus 0.033). Moreover, in I2/m much larger components of the anisotropic displacement parameters are observed and therefore, the crystal structure is presented in the primitive unit cell. IR investigations confirm that the anionic ligands are only terminally bonded and that the cyano group is not involved in the metal coordination. PXRD investigations show that a pure crystalline phase has been obtained and measurements using simultaneously thermogravimetry and differential thermoanalysis reveal that the compound decomposes in an exothermic reaction upon heating, without the formation of a coligand-deficient inter-mediate phase.

Synthesis, crystal structure and properties of catena-poly[[[bis-(3-methyl-pyridine-κN)nickel(II)]-di-μ-1,3-thio-cyanato] aceto-nitrile monosolvate]

In the crystal structure of the title compound, {[Ni(NCS)2(C6H7N)2]·CH3CN} n , the NiII cation is octa-hedrally coordinated by two N-bonding and two S-bonding thio-cyanate anions, as well as two 3-methyl-pyridine coligands, with the thio-cyanate S atoms and the 3-methyl-pyridine N atoms in cis-positions. The metal cations are linked by pairs of thio-cyanate anions into chains that, because of the cis-cis-trans coordination, are corrugated. These chains are arranged in such a way that channels are formed in which disordered aceto-nitrile solvate mol-ecules are located. This overall structural motif is very similar to that observed in Ni(NCS)2[4-(boc-amino)-pyridine]2·CH3CN reported in the literature. At room temperature, the title compound loses its solvent mol-ecules within a few hours, leading to a crystalline phase that is structurally related to that of the pristine material. If the ansolvate is stored in an aceto-nitrile atmosphere, the solvate is formed again. Single-crystal X-ray analysis at room-temperature proves that the crystals decompose immediately, presumably because of the loss of solvent mol-ecules, and from the reciprocal space plots it is obvious that this reaction, in contrast to that in Ni(NCS)2[4-(boc-amino)-pyridine]2·CH3CN, does not proceed via a topotactic reaction.

Exploring the structure-property schemes in anion-π systems of d-block metalates

Anion-π based compounds, materials, and processes have gained significant interest due to the diversity of their aesthetic non-covalent synthons, and thanks to their significance in biological systems, catalytic processes, anion binding and sensing, or the supramolecular organization of hierarchical architectures. While systems based on typical inorganic anions or organic residues have been widely reviewed in recent years, those involving anionic d metal comlexes as the main components have been treated with a rather secondary interest. However, actively exploring the new systems of the latter type we have recognized systematic advances in the field. As a result, in the current review we describe the landscape that has recently emerged. Focusing on the established groups of π-acidic species, i.e. polycarbonitirles, polyazines, polyazine N-oxides, diimide derivatives, fluoroarenes, and nitroarenes, we explore and discuss anion-π crystal engineering together with the structure-property schemes important from the standpoint of charge transfer (CT) and electron transfer (ET), magnetism, luminescence, reactivity and catalysis, and the construction of core-shell crystalline composites.

Structure, DFT Calculations, and Magnetic Characterization of Coordination Polymers of Bridged Dicyanamido-Metal(II) Complexes

Three coordination polymers of metal(II)-dicyanamido (dca) complexes with 4-methoxypyridine-N-oxide (4-MOP-NO); namely, catena-[Co(µ1,5-dca)2(4-MOP-NO)2] (1), catena-[Mn(µ1,5-dca)2(4-MOP-NO)2] (2), catena-[Cd(µ1,5-dca)2(4-MOP-NO)2] (3), and the mononuclear [Cu(κ1dca)2(4-MOP-NO)2] (4), were synthesized in this research. The complexes were analyzed by single crystal X-ray diffraction as well as spectroscopic methods (UV/vis, IR). The polymeric 1-D chains in complexes 1–3 were achieved by the doubly µ1,5-bridging dca ligands and the O-donor atoms of two axial 4-MOP-NO molecules in trans configuration around the distorted M(II) octahedral. On the other hand, the two “trans-axial” pyridine-N-oxide molecules in complexes 2 and 3 display opposite orientation (s-trans). The DFT (density functional theory) computational studies on the complexes 1–3 were consistent with the experimentally observed crystal structures. Compounds 1 and 2 display weak antiferromagnetic coupling between metal ions (J = −10.8 for 1 and −0.35 for 2).

A functional nitroxide ligand builds up two 2p–3d complexes with different spin ground states and a 2p–3d–4f chain of rings

Three new 2p–3d and 2p–3d–4f complexes derived from a functional nitroxide radical with different spin ground states and spin topologies have been synthesized.