Franz A. Mautner

Synthesis, Structural Characterisation, and Monte Carlo Simulation of the Magnetic Properties of the 3D-Stacked Honeycomb Csn[{Mn(N3)3}n] and the Irregular Double Chain [{N(C2H5)4}n][{Mn2(N3)5(H2O)}n]

Two new polymeric manganese-azido systems with formula Cs(n)-[[Mn(N3)3]n] (1) and [[N(C2H5)4]n][[Mn2-(N3)5(H2O)]n] (2) were synthesised and structurally characterised. Compound 1 crystallises in the P2(1)/n group and consists of a three-dimensional system with end-to-end and end-on azido bridges with the caesium atoms in the holes of the net. Magnetically, compound 1 is a rare case of a three-dimensional network with alternate ferro-antiferromagnetic interactions. Compound 2 crystallises in the P1 group and consists of double chains of manganese atoms bridged by end-on and, the exceptional, (mu-1,1,1)-azido bridges. Magnetically, compound 2 shows net ferromagnetic behaviour. Exact fit of the magnetic data was performed for the two compounds by means of Monte Carlo simulations based on the Metropolis algorithm on sets of 10 x 10 x 10 (1) and 1 x 1 x 320 (2) S = 5/2 classical spin centres.

Three new dinuclear copper(II) complexes with [Cu(μ1,3-N3)2Cu]2+ and [Cu(μ1,1-N3)2Cu]2+ asymmetrical cores: syntheses, structures and magnetic behaviour

Three new dinuclear copper(II) complexes, derived from end-to-end and end-on azido bridging ligands and triamine derivatives, have been synthesized and their crystal structures have been determined by X-ray diffraction methods. These are the dinuclear end-to-end compounds, [Cu2(μ1,3-N3)2(Et3dien)2](ClO4)2 (1) and [Cu2(μ1,3-N3)2(Medpt)2](ClO4)2 (2), and the dinuclear end-on compound [Cu2(μ1,1-N3)2(Medien)2](ClO4)2 (3) (Et3dien is triethyldiethylenetriamine, Medpt is methyldipropylenetriamine and Medien is methyldiethylenetriamine). The [Cu(μ-N3)2Cu]2+ cores are asymmetrical in all 3 compounds. Variable temperature magnetic susceptibility data were collected and fitted to the appropriate equation derived from the Hamiltonian H = −JS1S2. 1 shows unusual ferromagnetic interactions with J = 9 cm−1 through the end-to-end azido bridges while 2 shows an antiferromagnetic interaction through the end-to-end azido bridges with the highest reported absolute magnitude of J = −105 cm−1. The magnetic data of 1 and 2 have been correlated with the Addison parameter, τ, and mainly with the Cu–N3–Cu torsion angle, Δ. 3 shows an unusual antiferromagnetic interaction with J = −16.8 cm−1 through the end-on azido bridges.

An unusual 3D-topology and dominant ferromagnetic couplings in two Cu(II)–azide coordination polymers

The coordination polymers [(Cu(N(3))(2))(2)Cu(N(3))(2)(methylpyrazine)(2)](n) 1 and [Cu(4-bromopyridine)(N(3))(2)](n) 2, were prepared from NaN(3), Cu(NO(3))(2).3H(2)O and nitrogen-containing heterocycles. 1 contains a three- and four-connected 3D (4.10(2))(2)(4(2).10(4))-dmd-net based on tetrahedral and trigonal planar nodes, whereas 2 is a sheet-structure formed by a uninodal three-connected 8(2).4 2D-net with additional BrBr (mean 3.903(2) A) and BrN(azide) (3.035(5) A) contacts. Both compounds contain end-on-type azide bridges, and 2 has in addition one end-to-end bridge as well. The corresponding magnetic interactions are J(1,2) = +14.9(6) cm(-1) for the end-on azido interactions in 1 with an additional -1.7 cm(-1) coupling through the pyrazine, and J(1) = 36(6) cm(-1) for the end-on azido interactions and J(2) = 2.5(1) cm(-1) for the orthogonal end-to-end azido interactions found in 2.

A Combined Experimental and Theoretical Investigation on the Role of Halide Ligands on the Catecholase-like Activity of Mononuclear Nickel(II) Complexes with a Phenol-Based Tridentate Ligand

Three new mononuclear nickel(II) complexes, namely, [NiL(1)(H2O)3]I2·H2O (1), [NiL(1)(H2O)3]Br2·H2O (2), and [NiL(1)(H2O)3]Cl2·2H2O (3) [HL(1) = 2-[(2-piperazin-1-ylethylimino)methyl]phenol], have been synthesized and structurally characterized. Structural characterization reveals that they possess similar structure: [NiL(1)(H2O)3](2+) complex cations, two halide counteranions, and lattice water molecules. One of the nitrogen atoms of the piperazine moiety is protonated to provide electrical neutrality to the system, a consequence observed in earlier studies (Inorg. Chem. 2010, 49, 3121; Polyhedron 2013, 52, 669). Catecholase-like activity has been investigated in methanol by a UV-vis spectrophotometric study using 3,5-di-tert-butylcatechol (3,5-DTBC) as the model substrate. Complexes 1 and 2 are highly active, but surprisingly 3 is totally inactive. The coordination chemistries of 1 and 2 remain unchanged in solution, whereas 3 behaves as a 1:1 electrolyte, as is evident from the conductivity study. Because of coordination of the chloride ligand to the metal in solution, it is proposed that 3,5-DTBC is not able to effectively approach an electrically neutral metal, and consequently complex 3 in solution does not show catecholase-like activity. Density functional theory (DFT) calculations corroborate well with the experimental observations and thus, in turn, support the proposed hypothesis of inactivity of 3. The cyclic voltametric study as well as DFT calculations suggests the possibility of a ligand-centered reduction at -1.1 V vs Ag/AgCl electrode. An electron paramagnetic resonance (EPR) experiment unambiguously hints at the generation of a radical from EPR-inactive 1 and 2 in the presence of 3,5-DTBC. Generation of H2O2 during catalysis has also been confirmed. DFT calculations support the ligand-centered radical generation, and thus a radical mechanism has been proposed for the catecholase-like activity exhibited by 1 and 2. Upon heating, 2 and 3 lose water molecules in two steps (first lattice waters, followed by coordinating water molecules), whereas 3 loses four water molecules in a single step, as revealed from thermogravimetric analysis. The totally dehydrated species are red, in all cases having square-planar geometry, and have amorphous nature, as is evident from a variable-temperature powder X-ray diffraction study.

Trinuclear, Tetranuclear, and Polymeric CuII Complexes from the First Use of 2-Pyridylcyanoxime in Transition Metal Chemistry: Synthetic, Structural, and Magnetic Studies

The first use of 2-pyridylcyanoxime, (py)C(CN)NOH, in transition metal chemistry is described. Depending on the nature of the metal starting material and the reaction conditions employed, the Cu(II)/(py)C(CN)NOH system has provided access to complexes [Cu(3)O{(py)C(CN)NO}(3)(NO(3))(H(2)O)(2)(MeOH)] (1), [Cu(4)O{(py)C(CN)NO}(4)(O(2)CMe)(2)] (2), [Cu(4)(OH)(2){(py)C(CN)NO}(2)(O(2)CPh)(4)](2n)·n[Cu(4)(OH)(2){(py)C(CN)NO}(2)(O(2)CPh)(4)] (3), and [Cu{(py)C(CN)NO}(2)](n) (4). The molecule of 1 consists of three Cu(II) atoms in a strictly equilateral arrangement bridged by a central μ(3)-oxide group. The molecule of 2 consists of a tetrahedron of Cu(II) atoms held together by a central μ(4)-oxide ion, four η(1):η(1):η(1):μ-(py)C(CN)NO(-) ligands and two η(1):η(1):μ-MeCO(2)(-) groups. The crystal structure of 3 consists of [Cu(4)(OH)(2){(py)C(CN)NO}(2)(O(2)CPh)(4)](2n) double chains and discrete cluster [Cu(4)(OH)(2){(py)C(CN)NO}(2)(O(2)CPh)(4)] molecules. The crystal structure of 4 consists of neutral polymeric chains based on centrosymmetric mononuclear [Cu{(py)C(CN)NO}(2)] units. The Cu(II) atoms are doubly bridged by the oximate groups of two η(1):η(1):η(1):μ-(py)C(CN)NO(-) ligands. Variable-temperature, solid-state direct current (dc) magnetic susceptibility studies were carried out for 1-4. The data indicate very strong antiferromagnetic exchange interactions for 1-3. The obtained J values are discussed in depth on the basis of the structural parameters of the complexes, literature reports, and existing magnetostructural correlations.

Two new polymeric cadmium(II) complexes containing end-to-end bridging azido or thiocyanato ligands with different topologies

Abstract Two new polymeric cadmium(II) complexes; [Cd(3,5-DMP)2(N3)2] (1) and [Cd(4-Brpy)2(NCS)2] (2), where 3,5-DMP=3,5-dimethylpyridine and 4-Brpy=4-bromopyridine, have been synthesized and characterized. IR spectral data suggest end-to-end bridging azido and thiocyanato ligands. X-ray crystal structure determination has shown the 1-D complex 1 to contain each cadmium octahedrally coordinated by two double μ(1,3)-bridging azides and the other two sites are occupied by two pyridine ligands in a cis-arrangement. The CdCd distances in the Cd2(N3)2 eight membered rings are 5.142(2) and 5.152(2) A, the azide ligands are almost symmetrical and linear [NN distances: 1.167(5)–1.182(5) A; ∠NNN=176.7(4)° and 177.6(4)°]. In complex 2 each octahedrally cadmium atom is coordinated by two trans pyridine ligands and two trans nitrogen or sulfur atoms from four μ(N,S) bridging thiocyanato groups. The other end atoms of these four thiocyanato ligands bind four different cadmium atoms giving a 2-D layer structure.

Synthesis and crystal structure of three new 2D polymeric cadmium(II) complexes of some pyridine derivatives with different cadmium(II)–azide topologies

Three new polymeric complexes [Cd(2-Acpy)(N3)2]n1, [Cd(4-Acpy)2(N3)2]n2 and [Cd3(4-Brpy)4(N3)6]n3 (2-Acpy = 2-acetylpyridine, 4-Acpy = 4-acetylpyridine, and 4-Brpy = 4-bromopyridine) have been synthesized and characterized by single crystal X-ray diffraction. The coordination environment of the cadmium atom in all the complexes is distorted octahedral with two-dimensional polynuclear layers. The cadmium atoms are linked by both μ-1,1 and μ-1,3 in 1, by only μ-1,3 in 2 and by μ-1,1 and μ-1,1,3 azide bridges in 3 giving different cadmium(II)–azide topologies.

Synthesis, spectral and structural characterization of a monomeric chloro complex of Zinc(II) with picolinic acid, [Zn(C5H4NCO2H)(C5H4NCO2)Cl]

Abstract The title compound of zinc(II) and picolinic acid was synthesized and characterized by X-ray crystallographic and spectroscopic methods. In the structure of [Zn(C5H4NCO2H)(C5H4NCO2)Cl], each zinc atom is coordinated by two nitrogen atoms at ZnN distances of 2.040(8) A and two oxygen atoms, O(1), at ZnO bond lengths of 2.152(5) A, belonging to two picolinate ligands. Coordination number five of the zinc atom is completed by a ZnCl bond [2.221 (3) A]. The O(2)⋯O(2) separation between non-coordinated picolinate oxygen atoms of adjacent polyhedra is 2.41 (1) A. The IR and Raman spectral results confirm the existence of neutral picolinic acid as well as the picolinate anion.

Assembly of [MnII2MnIII2]S= 9 Clusters via Azido Bridges: a New Single-Chain Magnet

In the present work, we report a new manganese single-chain magnet built from tetranuclear Mn(II)(2)Mn(III)(2) mixed-valence units linked by end-on azido and oximato bridges. All of the intra- and intercluster interactions involve end-on azido bridges, resulting in one ferromagnetic chain of ferromagnetic clusters with local ground state S = 9.

Synthesis and characterization of binuclear and polymeric five-coordinate copper(II) complexes derived from 3,3′,3″-triaminotripropylamine (trpn): Crystal structure of [Cu(trpn)(N3)]ClO4 (I) and [Cu2(trpn)(tren)(NO2)(H2O)](ClO4)3 (II)

Abstract The synthesis and characterization of five-coordinate copper(II) complexes derived from 3,3′,3″-triaminotripropylamine (trpn) are described. The X-ray diffraction studies have established the structures [Cu(trpn)(N3)]ClO4 (I) and [Cu2(trpn)(tren)(NO2)(H2O)](ClO4)3 (II). Compound (I) consists of a polymeric cation chain and ClO4− counter ions. The coordination geometry of the Cu(II) centers may be described as distorted square pyramidal (SP) with the azido group at the apical site and three nitrogen donors of the trpn molecule occupy the basal sites. The CuN5 chromophore is completed by a bridging aminopropyl group of neighboring trpn ligand. Compound (II) is a dinuclear complex cation with two different cation geometries in the unit cell. The geometry of the Cu(II) binding tren ligand is close to trigonal bipyramidal (TBP), with the basal and apical sites are occupied by the four nitrogen atoms of the tren ligand. The fifth coordination site is bridged to one of the aminopropyl arms of the trpn ligand. The geometry of the second Cu(II) center may be described as close to distorted SP, where the trpn ligand is binding the Cu(II) ion via the two primary aminopropyl groups and the tertiary nitrogen. The remaining two sites are occupied by oxygen atoms of a water molecule and nitrite ion. The intramolecular Cu…Cu distance in I and II ranges from 7.55 A to 7.94 A. The visible spectra of the complexes in DMSO are consistent with the X-ray results found for I and II and show a greater tendency toward SP geometry.