Syntheses, crystal structures and magnetic properties of complexes based on [Ni(L-L)3]2+ complex cations with dimethylderivatives of 2, 2'-bipyridine and TCNQ

From the aqueous-methanolic systems Ni(NO3)2 – LiTCNQ – 5, 5'-dmbpy and Ni(NO3)2 – LiTCNQ – 4, 4'-dmbpy three novel complexes [Ni(5, 5'-dmbpy)3](TCNQ)2 (1), [Ni(4, 4'-dmbpy)3](TCNQ)2 (2) and [Ni(4, 4'-dmbpy)3]2(TCNQ-TCNQ)(TCNQ)2·0.60H2O (3), were isolated in single crystal form. The new compounds were identified using chemical analyses and IR spectroscopy. Single crystal studies of all samples corroborated their compositions and have shown that their ionic structures contain the complex cations [Ni(5, 5'-dmbpy)]2+ (1) or [Ni(4, 4'-dmbpy)]2+ (2 and 3). The anionic parts of the respective crystal structures 1–3 are formed by TCNQ·- anion-radicals and in 3 also by a s-dimerized dianion (TCNQ-TCNQ)2- with a C-C distance of 1.663(5) Å. The supramolecular structures are governed by weak hydrogen bonding interactions. The variable-temperature (2–300 K) magnetic studies of 1 and 3 confirmed the presence of magnetically active Ni(II) atoms with S = 1 and TCNQ·- anion-radicals with S = 1/2 while the (TCNQ-TCNQ)2- dianion is magnetically silent. The magnetic behavior was described by a complex magnetic model assuming strong antiferromagnetic interactions between some TCNQ·- anion-radicals

Hilbert Space Structures on the Solution Space of Klein-Gordon Type Evolution Equations

We use the theory of pseudo-Hermitian operators to address the problem of the construction and classification of positive-definite invariant inner-products on the space of solutions of a Klein-Gordon type evolution equation. This involves dealing with the peculiarities of formulating a unitary quantum dynamics in a Hilbert space with a time-dependent inner product. We apply our general results to obtain possible Hilbert space structures on the solution space of the equation of motion for a classical simple harmonic oscillator, a free Klein-Gordon equation, and the Wheeler-DeWitt equation for the FRW-massive-real-scalar-field models.Comment: 29 pages, slightly revised version, accepted for publication in Class. Quantum Gra

New members of MOF-76 family containing Ho(III) and Tm(III) ions: Characterization, stability and gas adsorption properties

International audienc

Frustrated zig-zag spin chains formed by hydrogen bonds in [Cu(H₂O)(OH)(tmen)]₂[Pd(CN)₄]·2H₂O

The magnetic properties of the novel dimeric compound [Cu(H₂O)(OH)(tmen)]₂[Pd(CN)₄]·2H₂O (tmen=N,N,N',N'-tetramethylethylenediamine) with modulated crystal structure were studied in the temperature range from 95 mK to 300 K. Magnetic measurements revealed a presence of weak antiferromagnetic exchange coupling in the compound. The temperature dependence of specific heat is characterized by the presence of a Schottky-like maximum at 0.47 K and a λ-anomaly at 0.28 K, indicating the formation of long-range order in the system. The comparison of the experimental data with theoretical predictions revealed the presence of antiferromagnetic intradimer exchange coupling J/k_{B}= -1.2 K and interdimer coupling of a similar strength mediated via hydrogen bonds between dimeric units forming a frustrated magnetic zig-zag chain structure

Ag(I) and Zn(II) isonicotinate complexes: Design, characterization, antimicrobial effect and CT–DNA binding studies

<div><p></p><p>Trinuclear Ag(I) (<b>1</b>) and dinuclear and mononuclear Zn(II) isonicotinate (<b>2</b> and <b>3</b>) complexes were prepared and characterized by X–ray crystallography, elemental analysis, IR spectroscopy and thermal analysis. Single crystal analysis of the Ag(I) complex reveals two different monodentate carboxylate coordination modes, protonated and deprotonated, respectively. IR spectra showed correlations between isonicotinate coordination modes and <i>Δ</i>(<i>ν</i>_as–<i>ν</i>_s)_IR values. In addition, the hydrogen bonds significantly influence a position of carboxylate absorption bands. Moreover, IC₅₀ and MIC data for bacteria, yeasts and filamentous fungi were determined and the binding of Ag(I) and Zn(II) complexes to calf thymus DNA was investigated using electronic absorption, fluorescence and CD measurements. Biological tests showed that the Ag(I) complex is more active than commercially used Ag(I) sulfadiazine against <i>E. Coli</i>. The fluorescence spectral results indicate that the complexes can bind to DNA through an intercalative mode. The Stern–Volmer quenching constants for investigated complexes obtained from the linear quenching plot are in the range of 1.67 × 10⁴ to 3.42 × 10⁴ M^–1.</p></div

Five complexes containing N,N-bis(2- hydroxyethyl)-ethylenediamine with tetracyanidopalladate(II): synthesis, crystal structures, thermal, magnetic, and catalytic properties

Five cyanide complexes, [Ni(N-bishydeten)Pd(CN)4] (1), [Cu(N-bishydeten)Pd(μ-CN)2(CN)2]n (2), [Cu(N-bishydeten)2][Pd(CN)4] (3), [Zn(N-bishydeten)Pd(CN)4] (4), and [Cd(N-bishydeten)2][Pd (CN)4] (5) (N-bishydeten = N,N-bis(2-hydroxyethyl)-ethylenediamine), have been synthesized and characterized using various techniques. Different structures were formed when the M: L ratio was varied in copper complexes. The single-crystal X-ray diffraction analysis reveals that 2, a 1-D cyanide-bridged complex with 2,2-CT-type zigzag chain, was obtained by using 1 : 1M: L ratio whereas 3 was formed as a complex salt in a molar ratio of 1 : 2. The thermal stabilities determined from DTGmax values of the first decomposition stages change in the order 1 > 5 > 4 > 3 > 2. Although an EPR signal was not observed for 1, the g parameters obtained from the EPR spectra of 2 and 3 indicate that CuII ions are located in tetragonally distorted octahedral sites (D4h), and the ground state of the unpaired electron is dx2 y2 (2B1g). The magnetic behavior indicates a very small antiferromagnetic interaction below 10K for 1–3. In 3, there is a temperature-independent paramagnetism (α) due to the orbital moments of the d electrons. 1–3 were tested as catalysts in Suzuki and Heck coupling reactions.TUBİTAK, Grant TBAG-104T205) Gaziosmanpaşa University Research Foundation (Grant 2010/110