Synthesis, crystal structure and Hirshfeld surface analysis of bis-{2-[(pyridin-2-yl)amino]-pyridinium} tetra-cyano-nickelate(II)

In the title mol-ecular salt, (C10H10N3)2[Ni(CN)4], the dihedral angle between the pyridine rings in the cation is 1.92 (13)° and the complete anion is generated by a crystallographic centre of symmetry. An intra-molecular N-H⋯N hydrogen bond occurs in the cation, which closes an S(6) ring. In the crystal, the components are linked by N-H⋯N and weak C-H⋯N hydrogen bonds, which generate chains propagating in the [101] direction. Weak aromatic π-π stacking inter-actions are also observed. A Hirshfeld surface analysis and two-dimensional fingerprint plots indicate that the most important contact types in the crystal packing are N⋯H/H⋯N, C⋯H/H⋯C and H⋯H with contributions of 37.2, 28.3 and 21.9%, respectively.

Octacyanidometallates for multifunctional molecule-based materials

Octacyanidometallates have been successfully employed in the design of heterometallic coordination systems offering a spectacular range of desired physical properties with great potential for technological applications. The [M(CN)8]n- ions comprise a series of complexes of heavy transition metals in high oxidation states, including NbIV, MoIV/V, WIV/V, and ReV. Since the discovery of the pioneering bimetallic {MnII4[MIV(CN)8]2} and {MnII9[MV(CN)8]6} (M = Mo, W) molecules in 2000, octacyanidometallates were fruitfully explored as precursors for the construction of diverse d-d or d-f coordination clusters and frameworks which could be obtained in the crystalline form under mild synthetic conditions. The primary interest in [M(CN)8]n--based networks was focused on their application as molecule-based magnets exhibiting long-range magnetic ordering resulting from the efficient intermetallic exchange coupling mediated by cyanido bridges. However, in the last few years, octacyanidometallate-based materials proved to offer varied and remarkable functionalities, becoming efficient building blocks for the construction of molecular nanomagnets, magnetic coolers, spin transition materials, photomagnets, solvato-magnetic materials, including molecular magnetic sponges, luminescent magnets, chiral magnets and photomagnets, SHG-active magnetic materials, pyro- and ferroelectrics, ionic conductors as well as electrochemical containers. Some of these materials can be processed into the nanoscale opening the route towards the development of magnetic, optical and electronic devices. In this review, we summarise all important achievements in the field of octacyanidometallate-based functional materials, with the particular attention to the most recent advances, and present a thorough discussion on non-trivial structural and electronic features of [M(CN)8]n- ions, which are purposefully explored to introduce desired physical properties and their combinations towards advanced multifunctional materials.

Heterometallic 3d-4d coordination polymers assembled from trans-[RuIII(L)(CN)2]- tectons and 3d cations

Five new cyanido-bridged heterometallic coordination polymers have been obtained by reacting PPh4[RuIII(salpn)(CN)2]·H2O (1) and AsPh4[RuIII(valen)(CN)2]·8.5H2O (2) (H2salpn and H2valen being Schiff-base proligands resulting from the condensation reaction of salicylaldehyde with 1,3-propanediamine and, respectively, o-vanillin with 1,2-ethanediamine) with divalent transition metal perchlorate salts: ∞1[{RuIII(salpn)(CN)2}3{MII(DMF)3}2](ClO4)·4DMF (MII = Mn, 3; Co, 4) and ∞2[{RuIII(valen)(CN)2}4{MII(DMF)3}2{MII(DMF)4}](ClO4)2·4DMF (MII = Mn, 5; Co, 6; Ni, 7), respectively. The dicyanido species, trans-[Ru(salpn)(CN)2]- and trans-[Ru(valen)(CN)2]-, act as metalloligands with the 3d metal ions. Compounds 3 and 4 are isostructural one-dimensional (1D) coordination polymers with a ladder topology. Each MII ion is hexacoordinated by three cyanido groups arising from three {Ru(salpn)(CN)2} units and by the oxygen atoms from three DMF molecules, which are coordinated at meridional positions. Compounds 5-7 are also isostructural, their structures consisting of 2D networks with a herringbone topology. The magnetic susceptibility measurements of these 1D and 2D systems reveal the presence of dominating RuIII-MII antiferromagnetic (AF) interactions in compounds 3, 4, 5 and 6, while ferromagnetic RuIII-NiII interactions are observed in 7. All these compounds stay in their paramagnetic state down to 1.8 K except compound 4 which possesses a 3D ordered AF ground state.

Composition dependence of magnetic relaxation for CoIIxNiII1−x chain-based compounds with mixed double azide–tetrazolate bridges

A series of isomorphous random bimetallic compounds based on CoIIxNiII1−x (0 ≤ x ≤ 1) chains with simultaneous azide–tetrazolate bridges exhibit composition-dependent magnetic relaxation were investigated.

Distortion Pathways of Transition Metal Coordination Polyhedra Induced by Chelating Topology

A continuous shape measures analysis of the coordination polyhedra of a host of transition metal complexes with bi- and multidentate ligands discloses the distortion pathway associated with each particular topology of the chelate rings formed. The basic parameter that controls the degree of distortion is the metal-donor atom bond distance that induces nonideal bond angles due to the rigidity of the ligands. Thus, the degree of distortion within each family of complexes depends on the atomic size, on which the high- or low-spin state has a large effect. Special attention is therefore paid to several spin-crossover systems and to the enhanced distortions that go along with the transition from low- to high-spin state affected by temperature, light, or pressure. Several families of complexes show deviations from the expected distortion pathways in the high-spin state that can be associated to the onset of intermolecular interactions such as secondary coordination of counterions or solvent molecules. Also, significant displacement of counterions in an extended solid may result from the changes in metal-ligand bond distances when ligands are involved in intermolecular hydrogen bonding.

Towards a better understanding of honeycomb alternating magnetic networks

The honeycomb mixed-ligand complex {[Co₂(bpm)(ox)₂]_n·5nH₂O} was prepared and magneto-structurally characterized. The values of the antiferromagnetic interactions through bpm (J_bpm= −5.0 cm⁻¹) and ox (J_ox= −11.1 cm⁻¹) ligands obtained by fit were suported by DFT type calculations.

A Co(II) thiocyanato coordination polymer with 4-(3-phenylpropyl)pyridine: the influence of the co-ligand on the magnetic properties

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.

Design of one-dimensional coordination networks from a macrocyclic {3d-4f} single-molecule magnet precursor linked by [W(CN)8]3- anions

The outcome of 1:1 reactions of the tetranuclear 3d-4f Single Molecule Magnet (SMM) [Cu3Tb(L(Pr))(NO3)2(H2O)]NO3 (1) with (TBA)3[W(CN)8] (TBA = tri-n-butyl ammonium cation, [(n-Bu)3N-H](+)) in dimethylformamide (DMF) is dependent on the crystallization method employed: liquid-liquid diffusion of the reagents together gives {[Cu3Tb(L(Pr))W(CN)8(DMF)4]·(DMF)}n (2) whereas diethyl ether vapor diffusion into the reaction solution gives {[Cu3Tb(L(Pr))W(CN)8(DMF)3(H2O)3]·(DMF)1.5·(H2O)0.5}n (3). Both compounds are obtained as black single crystals and feature one-dimensional (1D) coordination networks (chains) of [1](3+) macrocycles linked by [W(CN)8](3-) anions. The two assemblies differ from a structural point of view. Complex 2 has a stepped arrangement with the linkers bound to the opposite faces of the macrocycle, whereas 3 has a square-wave arrangement due to the linkers binding to the same face of the macrocycle. Both compounds display an antiferromagnetic ground state below 3.5 and 2.4 K with a metamagnetic and antiferromagnetic (T, H) phase diagram for 2 and 3, respectively. Remarkably the slow dynamics of the magnetization of the [1](3+) macrocycle units is preserved in 3 while this property is quenched in 2 because of stronger intra- and interchain magnetic interactions inducing a higher critical temperature.