Sergey V. Kolotilov

A new approach towards ferromagnetic conducting materials based on TTF-containing polynuclear complexes

Five complexes containing binuclear cation [Cu2(LH)2]2+ (LH2 = 1 : 2 Schiff base of 1,3-diaminobenzene and butanedione monoxime) were prepared and characterized. Metathesis of one perchlorate anion in [Cu2(LH)2(H2O)2](ClO4)2 (1) by anionic TTF-carboxylate (TTF–CO2−) leads to the complex [Cu2(LH)2(CH3OH)2](TTF–CO2)(ClO4)·H2O (2). Reactions of 1 with substituted pyridines bipy, dpe and TTF–CH = CH–py result in formation of the complexes {[Cu2(LH)2(bipy)](ClO4)2}n·2nH2O (3), [Cu2(LH)2(dpe)2](ClO4)2·2CH3OH (4) and [Cu2(LH)2(TTF–CH = CH–py)(H2O)](ClO4)2·1.5H2O (5), where bipy = 4,4′-bipyridine, dpe = trans-(4-pyridyl)-1,2-ethylene and TTF–CH = CH–py = 1-(2-tetrathiafulvalenyl)-2-(4-pyridyl)ethylene. Whereas complex 2 is built from discrete ionic particles (with rather long Cu–S contacts), compounds 1 and 3 contain 1D polymeric chains, in which structural units are bonded through Cu–O bonds or through bridging bipy molecule, respectively. Dinuclear complexes 4 and 5 are linked though π-stacking of dpe or TTF–CH = CH–py, respectively. All complexes are characterized by dominating ferromagnetic behavior with J values in the range from +9.92(8) cm−1 to +13.4(2) cm−1 for Hamiltonian H = –JS1S2. Magnetic properties of the compounds, containing stacks of aromatic molecules in crystal structures (4 and 5), correspond to ferromagnetic intradimer and antiferromagnetic intermolecular interactions (zJ′ = −0.158(3) and −0.290(2) cm−1, respectively). It was found that TTF–CH = CH–py ligand in [Cu2(LH)2(TTF–CH = CH–py)(H2O)]2+ could be electrochemically oxidized to cation-radical form in the solution.

Structural, magnetic and related attributes of some oximate-bridged tetranuclear nickel(ii) rhombs and a dinuclear congenerElectronic supplementary information (ESI) available: mass spectra, χT vs. T, response of magnetic properties, low-lying spin levels and UV-VIS data. See http://www.rsc.org/suppdata/dt/b3/b300539a/

New oximate-bridged tetranuclear nickel(II) complexes of compositions {Ni(Dien)}2(μ3-OH)2{Ni2(Moda)4}(ClO4)2·Solv (Solv = H2O, 1a; Solv = 2CH3NO2, 1b; Solv = 2H2O·2C4H8O2, 1c), {Ni(Sdien)}2(μ3-OH)2{Ni2(Moda)4}(ClO4)2·H2O (2), {Ni(Odien)}2(μ3-OH)2{Ni2(Moda)4}(ClO4)2·0.6H2O (3), {Ni(Dien)}2(μ3-OH)2{Ni2(Inaf)4}(ClO4)2·CH3NO2 (4) and {Ni(Odien)}2(μ3-OH)2{Ni2(Inaf)4}(ClO4)2·2NaClO4·2H2O (5) and the dinuclear complex (Ni{Odien})2(Moda)2(ClO4)2 (6) have been prepared (Dien = 1,5-diamino-3-azapentane, Odien = 1,5-diamino-3-oxapentane, Sdien = 1,5-diamino-3-thiapentane, ModaH = butane-2,3-dione monooxime, InafH = phenylglyoxaldoxime). X-ray examination revealed similar structures for 1a, 1b, 1c, 2 and 3, with a rhombic “chair” (out-of-phase “butterfly”) arrangement of the four nickel(II) atoms and two hydroxo-bridges. The complexes were examined by magnetochemistry, UV-VIS spectroscopy and voltammetry. 1–3 display antiferromagnetic coupling of the central with the terminal nickel(II) atoms and ferromagnetic spin alignment between the central nickel(II) atoms. In contrast, all the spin exchanges in 4 and 5 were found to be antiferromagnetic, as is the coupling in dinuclear 6.

A Tetrameric Nickel(II) “Chair” with both Antiferromagnetic Internal Coupling and Ferromagnetic Spin Alignment

Interest in polynuclear complexes of the 3d metals has been stimulated by the search for new magnetic materials[1, 2] and by demonstration of the occurrence of oligonuclear metal centers in proteins such as urease.[3] Of the relatively small number of reported tetranuclear complexes of S 1 nickel( ) of known structure, the majority have a hemicubaneor TMbutterfly-∫ rather than a squarelike core.[4] Of these molecules, just one is entirely antiferromagnetic,[5] while the remainder entail purely ferromagnetic interactions amongst the nickel( ) ions.[6±10] Oximes have shown promise as bridging ligands for the preparation of polynuclear complexes.[11, 12] The reaction of 1,4,7-triazaheptane (diethylenetriamine, Dien) with the monooxime of 2,3-butanedione (ModaH) in the presence of NiII ions, instead of yielding the anticipated Schiff base derivative, gave the tetranuclear NiII compound 1 (dark brown crystals; C4H8O2 1,4-dioxane), containing uncondensed but coordinated ketone and amine groups. Figure 1a shows the structure of the the cation of 1, while Figure 1b highlights its NiII core.

Heterometallic Coordination Polymers Assembled from Trigonal Trinuclear Fe2Ni-Pivalate Blocks and Polypyridine Spacers: Topological Diversity, Sorption, and Catalytic Properties.

Linkage of the trigonal complex [Fe2NiO(Piv)6] (where Piv(-) = pivalate) by a series of polypyridine ligands, namely, tris(4-pyridyl)triazine (L(2)), 2,6-bis(3-pyridyl)-4-(4-pyridyl)pyridine (L(3)), N-(bis-2,2-(4-pyridyloxymethyl)-3-(4-pyridyloxy)propyl))pyridone-4 (L(4)), and 4-(N,N-diethylamino)phenyl-bis-2,6-(4-pyridyl)pyridine (L(5)) resulted in the formation of novel coordination polymers [Fe2NiO(Piv)6(L(2))]n (2), [Fe2NiO(Piv)6(L(3))]n (3), [Fe2NiO(Piv)6(L(4))]n·nHPiv (4), and [{Fe2NiO(Piv)6}4{L(5)}6]n·3nDEF (5, where DEF is N,N-diethylformamide), which were crystallographically characterized. The topological analysis of 3, 4, and 5 disclosed the 3,3,4,4-connected 2D (3, 4) or 3,4,4-connected 1D (5) underlying networks which, upon further simplification, gave rise to the uninodal 3-connected nets with the respective fes (3, 4) or SP 1-periodic net (4,4)(0,2) (5) topologies, driven by the cluster [Fe2Ni(μ3-O)(μ-Piv)6] nodes and the polypyridine μ3-L(3,4) or μ2-L(5) blocks. The obtained topologies were compared with those identified in other closely related derivatives [Fe2NiO(Piv)6(L(1))]n (1) and {Fe2NiO(Piv)6}8{L(6)}12 (6), where L(1) and L(6) are tris(4-pyridyl)pyridine and 4-(N,N-dimethylamino)phenyl-bis-2,6-(4-pyridyl)pyridine, respectively. It was shown that a key structure-driven role in defining the dimensionality and topology of the resulting coordination network is played by the type of polypyridine spacer. Compounds 2 and 3 possess a porous structure, as confirmed by the N2 and H2 sorption data at 78 K. Methanol and ethanol sorption by 2 was also studied indicating that the pores filled by these substrates did not induce any structural rearrangement of this sorbent. Additionally, porous coordination polymer 2 was also applied as a heterogeneous catalyst for the condensation of salicylaldehyde or 9-anthracenecarbaldehyde with malononitrile. The best activity of 2 was observed in the case of salicylaldehyde substrate, resulting in up to 88% conversion into 2-imino-2H-chromen-3-carbonitrile.

Synthesis, structure and magnetic properties of Nd3+ and Pr3+ 2D polymers with tetrafluoro-p-phthalate

Two lanthanide tetrafluoro-p-phthalate (L(2-)) complexes, Ln(L)(1.5)·DMF·H(2)O (Ln = Pr(3+) (1), Nd(3+) (2)), were synthesized using pyridine as a base. The compounds were found to be isostructural, and the structure of 1 has been determined by single crystal X-ray diffraction (monoclinic, space group C2, a = 22.194(2) Å, b = 11.4347(12) Å, c = 11.7160(12) Å, β = 94.703(2)°, V = 2963.3(5) Å(3), Z = 4). The crystal structure of 1 consists of dinuclear Pr(3+) units, which are connected by tetrafluoro-p-phthalate, forming separate 2D polymeric layers. The Ln(3+) ions in the dinuclear Ln(2) units are linked by two μ-O atoms and by two bridging O-C-O groups. The structure is porous with DMF and water molecules located between layers. Non-coordinated DMF molecules occupy about 27% of the unit cell volume. A systematic analysis of reported structures of Ln(III) polymers with p-phthalate and its derivatives shows that the ca. known 60 structures can be divided into six possible structural types depending on the presence of certain structural motifs. The magnetic properties of compounds 1 and 2 were studied. The dependence of χ(M)T on T (where χ(M) is magnetic susceptibility per dinuclear lanthanide unit) for 1 and 2 was simulated using two different models, based on: (i) the Hamiltonian Ĥ = ΔĴ(z)(2)+ μ(B)g(J)HĴ, which utilises an axial splitting parameter Δ and temperature-independent paramagnetism (tip) and (ii) crystal field splitting. It was found that both models gave satisfactory fits, indicating that the Ln-Ln exchange interactions are small and the symmetry of the coordination environment is the main factor influencing the magnetic properties of these compounds.

Structural trends in a series of isostructural lanthanide–copper metallacrown sulfates (LnIII = Pr, Nd, Sm, Eu, Gd, Dy and Ho): hexaaquapentakis[μ3‐glycinehydroxamato(2−)]sulfatopentacopper(II)lanthanide(III) heptaaquapentakis[μ3‐glycinehydroxamato(2−)]sulfatopentacopper(II)lanthanide(III) sulfate hexahydrate

The seven isostructural complexes, [Cu(5)Ln(C(2)H(4)N(2)O(2))(5)(SO(4))(H(2)O)(6.5)](2)(SO(4))·6H(2)O, where Ln(III) = Pr, Nd, Sm, Eu, Gd, Dy and Ho, are representatives of the 15-metallacrown-5 family. Each dianion of glycinehydroxamic acid (GlyHA) links two Cu(II) cations forming a cyclic [CuGlyHA](5) frame. The Ln(III) cations are located at the centre of the [CuGlyHA](5) rings and are bound by the five hydroxamate O atoms in the equatorial plane. Five water molecules are coordinated to Cu(II) cations, and one further water molecule, located close to an inversion centre between two adjacent [Cu(5)Ln(GlyHA)(5)](2+) cations, is disordered around this inversion centre and coordinated to a Cu(II) cation of either the first or second metallacrown ether. Another water molecule and one of the two crystallographically independent sulfate anions are coordinated, the latter in a bidentate fashion, to the Ln(III) cation in the axial positions. The second sulfate anion is not coordinated to the cation, but is located in an interstitial position on a crystallographic inversion centre, thus leading to disorder of the O atoms around the centre of inversion. The Ln-O bond distances follow the trend of the lanthanide contraction. The apical Ln-O bond distances are very close to the sums of the ionic radii. However, the Ln-O distances within the metallacrown units are slightly compressed and the Ln(III) cations protrude significantly from the plane of the otherwise flat metallacrown ligand, thus indicating that the cavity is somewhat too small to accommodate the Ln(III) ions comfortably. This effect decreases with the size of the lanthanide cation from complex (I) (Ln(III) = Pr; 0.459) to complex (VII) (Ln(III) = Ho; 0.422), which indicates that the smaller lanthanide cations fit the cavity of the pentacopper metallacrown ring better than the larger ones. The diminished contraction of Ln-O distances within the metallacrown planes leads to an aniostropic contraction of the unit-cell parameters, with a, c and V following the trend of the lanthanide contraction. The b axes, which are mostly aligned with the rigid planes of the metallacrown units, show only a little variation between the seven compounds.

Redox-Active Porous Coordination Polymers Prepared by Trinuclear Heterometallic Pivalate Linking with the Redox-Active Nickel(II) Complex: Synthesis, Structure, Magnetic and Redox Properties, and Electrocatalytic Activity in Organic Compound Dehalogenation in Heterogeneous Medium

Linking of the trinuclear pivalate fragment Fe2CoO(Piv)6 by the redox-active bridge Ni(L)2 (compound 1; LH is Schiff base from hydrazide of 4-pyridinecarboxylic acid and 2-pyridinecarbaldehyde, Piv(-) = pivalate) led to formation of a new porous coordination polymer (PCP) {Fe2CoO(Piv)6}{Ni(L)2}1.5 (2). X-ray structures of 1 and 2 were determined. A crystal lattice of compound 2 is built from stacked 2D layers; the Ni(L)2 units can be considered as bridges, which bind two Fe2CoO(Piv)6 units. In desolvated form, 2 possesses a porous crystal lattice (SBET = 50 m(2) g(-1), VDR = 0.017 cm(3) g(-1) estimated from N2 sorption at 78 K). At 298 K, 2 absorbed a significant quantity of methanol (up to 0.3 cm(3) g(-1)) and chloroform. Temperature dependence of molar magnetic susceptibility of 2 could be fitted as superposition of χMT of Fe2CoO(Piv)6 and Ni(L)2 units, possible interactions between them were taken into account using molecular field model. In turn, magnetic properties of the Fe2CoO(Piv)6 unit were fitted using two models, one of which directly took into account a spin-orbit coupling of Co(II), and in the second model the spin-orbit coupling of Co(II) was approximated as zero-field splitting. Electrochemical and electrocatalytic properties of 2 were studied by cyclic voltammetry in suspension and compared with electrochemical and electrocatalytic properties of a soluble analogue 1. A catalytic effect was determined by analysis of the catalytic current dependency on concentrations of the substrate. Compound 1 possessed electrocatalytic activity in organic halide dehalogenation, and such activity was preserved for the Ni(L)2 units, incorporated into the framework of 2. In addition, a new property occurred in the case of 2: the catalytic activity of PCP depended on its sorption capacity with respect to the substrate. In contrast to homogeneous catalysts, usage of solid PCPs may allow selectivity due to porous structure and simplify separation of product.

The 1,8-bis(2′-pyridyl)-3,6-dithiaoctane Complex of Nickel(II): X-ray Crystal Structure and Borohydride Adduct Formation

The quadridentate dipyridyl-dithioether ligand 1, 8-bis(2′-pyridyl)-3, 6-dithiaoctane (Pdto) forms a pseudooctahedral complex with nickel(II). Blue [Ni(Pdto)(OH 2 ) 2 ](ClO 4 ) 2 crystallizes in the space group P /2 1 c , with a = 11.677(5), b = 13.255(2), c = 15.804(4)A, β = 107.45(3)° and Z = 4. The ligand is folded about the Ni(II) ion so that the water ligands are cis within an O 2 S 2 plane and the pyridines mutually trans . Reduction by sodium amalgam yields a nickel(I) complex with an axial EPR spectrum, whereas borohydride reduction is very slow. Indeed, the pink adduct [Ni(Pdto)(BH 4 )] + has substantial stability in solution.

The Influence of Diamagnetic Substrates Absorption on Magnetic Properties of Porous Coordination Polymers

Reported cases of the influence of guest molecules absorption/desorption on magnetic properties of porous co- ordination polymers (PCP) of transition metals are reviewed. Interaction of PCPs with guest molecules can modify mag- netic susceptibility in wide temperature range, as well as can lead to change of the magnetic ordering or spin-crossover temperature and other magnetic characteristics. The reasons of such influence can be divided into several groups - guest molecule coordination to metal ion or decoordination; formation or cleavage of bonds in the group, which transmits ex- change interactions between metal ions; or change of bond lengths or angles in coordination polymer because of crystal lattice adaptation to the guest molecule.

Antiferromagnetic ordering in cobalt(II) and nickel(II) 1D coordination polymers with the dithioamide of 1,3-benzenedicarboxylic acid

A series of 1D coordination polymers [Co(m-dtab)Cl2]n (1), [Co(m-dtab)Br2]n (2) and [Ni(m-dtab)2(Br)2]n (3), where m-dtab = the dithioamide of 1,3-benzenedicarboxylic acid, were prepared. The structures of all complexes were determined by X-ray diffraction. Magnetic properties of the compounds were characterized by molecular susceptibility vs. T dependence in the temperature range from 2 to 300 K. All compounds possess antiferromagnetic exchange interactions, and antiferromagnetic ordering was found in [Co(m-dtab)Br2]n and [Ni(m-dtab)2Br2]n at TN = 2.9 K and 2.6 K, respectively. DFT calculations showed that exchange interactions in [Co(m-dtab)(Hal)2]n could be transferred through two pathways: m-dtab between metal ions or interchain π–π stacking of aromatic rings, so the systems are not 1D from the viewpoint of magnetochemistry. The results of DFT calculations are consistent with the existence of magnetic ordering.