Maria-Gabriela Alexandru

Self-assembly of [CuIITbIII]3+ and [W(CN)8]3− tectons: a case study of a mixture containing two complexes showing slow-relaxation of the magnetization

The reaction of [Cu(valen)] with Tb(NO(3))(3) and (Bu(3)NH)(3)[W(CN)(8)] affords two types of crystals: [{W(CN)(8)}Cu(valen)Tb(OH(2))(5)]·2H(2)O (1, a discrete trinuclear complex) and [{W(CN)(8)}Cu(valen)Tb(OH(2))(4)]·CH(3)CN·H(2)O (2, an infinite zig-zag chain), both compounds showing slow relaxation of the magnetization (H(2)valen is the Schiff base resulting from the reaction of o-vanillin with 1,2-ethanediamine).

Synthesis, Crystal Structures, and Magnetic Properties of Two Novel Cyanido-Bridged Heterotrimetallic {CuIIMnIICrIII} Complexes

The self-assembly process between the heteroleptic [CrIII(phen)(CN)4]- and [CrIII(ampy)(CN)4]- metalloligands and the heterobimetallic {CuII(valpn)MnII}2+ tecton afforded two heterotrimetallic complexes of formula [{CuII(valpn)MnII(μ-NC)2CrIII(phen)(CN)2}2{(μ-NC)CrIII(phen)(CN)3}2]·2CH3CN (1) and {[CuII(valpn)MnII(μ-NC)2CrIII(ampy)(CN)2]2·2CH3CN}n (2) [phen = 1,10-phenanthroline, ampy = 2-aminomethylpyridine, and H2valpn = 1,3-propanedyilbis(2-iminomethylene-6-methoxyphenol)]. The crystal structure of 1 consists of neutral CuII2MnII2CrIII4 octanuclear units, where two [Cr(phen)(CN)4]- anions act as bis-monodentate ligands through cyanide groups toward two manganese(II) ions from two [CuII(valpn)MnII]2+ units to form a [{Cu(valpn)Mn}2Cr2(CN)4]6+ square motif. Two [Cr(phen)(CN)4]- pendant anions in 1 are bound to the copper(II) ions with cis-trans geometry with respect to the bridging [Cr(phen)(CN)4]- anion. Compound 2 is a sheet-like coordination polymer, where chains constituted by {CrIII(ampy)(CN)4} spacers act as bis-monodentate ligands toward the manganese(II) ions belonging to the {CuII(valpn)MnII} nodes, which are interlinked by another {CrIII(ampy)(CN)4} unit that acts as a bridge between the copper(II) and manganese(II) ions of adjacent chains. Magnetic susceptibility measurements in the temperature range of 1.9-300 K were performed for 1 and 2. An overall antiferromagnetic behavior is observed for 1, the ground spin state being described by a spin triplet from the square motif plus two magnetically isolated spin triplets from the two peripheral chromium(III) ions. Ferrimagnetic chains with interacting spins 1/2 (resulting spin of the trimetallic {CuII(valpn)MnII(μ-NC)CrIII} fragment) and 3/2 (spin from the bis-monodentate [CrIII(ampy)(CN)4]- with weak interchain ferromagnetic interactions across the cyanide bridge between the chromium(III) and the copper(II) ion from adjacent chains [θ = +3.83(2) cm-1]) occur in 2, resulting into a ferromagnetic ordering below 3.5 K. The values of the magnetic coupling between the Cu(II) and Mn(II) ions through the double phenoxide bridge [J = -63.1(2) (1) and -62(3) cm-1 (2)] and those between the Cr(III) and the Mn(II) across the single cyanide bridge [J = -7.08(5) and -4.86(6) cm-1 (1) and -8.59(3) cm-1 (2)] agree with the values reported for these exchange pathways in other magnetostructural studies.

Synthesis, characterization and antitumor activity of Cu(II), Co(II), Zn(II) and Mn(II) complex compounds with aminothiazole acetate derivative

AbstractThis paper presents the synthesis of complex compounds of type [M(L1)2], where M(II)= Cu (1), Co (2), Zn (3), L1=2-aminothiazole-4-acetate and [Mn(L1)2(H2O)] (4) using ethyl 2-(2-aminothiazole-4-yl) acetate (L), and characterization by elemental analysis, magnetic susceptibilities, IR, 1H-NMR, UV-Vis spectroscopy and for [Mn(L1)2(H2O)] also by X-ray diffraction. In vitro cytotoxicity studies were performed on human cervix adenocarcinoma, HeLa cells. The antitumor selectivity was assessed using normal human peripheral blood mononuclear cells, PBMC as control.

{CoIIIMnIII}n corrugated chains based on heteroleptic cyanido metalloligands

The use of the cyanide-bearing complexes PPh4[CoIII(4,4′-dmbipy)(CN)4] and PPh4[CoII(dmphen)(CN)3] as metalloligands towards [Mn(salen)(H2O)]ClO4 affords one-dimensional coordination polymers with the formulas {[MnIII(salen)(μ-NC)2CoIII(4,4-dmbipy)(CN)2]·H2O}n (1) and {[MnIII(salen)(μ-NC)2CoIII(dmphen)(CN)2]}n (2) [PPh4+ = tetraphenylphosphonium cation, 4,4′-dmbipy = 4,4′-dimethyl-2,2′-bipyridine, dmphen = 2,9-dimethyl-1,10-phenanthroline and H2salen = N,N′-ethylenebis(salicylideneimine)]. Compounds 1 and 2 were structurally characterized. Their structures consist of neutral chains with regular alternating [Mn(salen)]+ and [CoIII(4,4′-dmbipy)(CN)4]− (1)/[CoIII(dmphen)(CN)4]− (2) moieties, the latter ones acting as bis-monodentate ligands towards the Mn(III) units through two of their four cyanide groups. During the synthesis, the cobalt(II) ion of the starting [CoII(dmphen)(CN)3]− metalloligand is oxidized to Co(III) and it takes an additional cyanide ligand to transform into {CoIII(dmphen)(CN)4} in 2. Magnetic studies have been carried out on 1 and 2 in the temperature range 1.9–300 K which yielded local negative zero-field splitting parameters of −3.26 (1) and −4.38 cm−1 (2). Frequency-dependent alternating current susceptibility signals under an external applied magnetic field (dc) were clearly observed for 1 and 2 indicating slow magnetic relaxation, that is, Single Ion Magnet (SIM) behaviour. The energy barriers (Ea) to reverse the magnetization direction under an applied dc magnetic field of 2000 Oe were 12.0(2) (1) and 9.4(3) cm−1 (2), whereas the values of the pre-exponential factor (τo) were 1.40(2) × 10−8 (1) and 2.5(2) × 10−8 s (2).

Synthesis, crystal structure and magnetic properties of a cyanide-bridged heterometallic {CoIIMnIII} chain

The assembly reaction between the low-spin [CoII(dmphen)(CN)3]- metalloligand and the [MnIII(salen)(H2O)]+ complex cation yielded the one-dimensional compound {[MnIII(salen)(μ-NC)2CoII(dmphen)(CN)]·2H2O}n (1), which behaves as a ferrimagnetic chain, the intrachain magnetic coupling being J = -1.71(1) cm-1.

Cyanido-Bridged {LnIIIWV} Heterobinuclear Complexes: Synthesis and Magneto-Structural Study

A new series of cyanido-bridged {LnIIIWV} heterobinuclear complexes of formula [LnIII(pyim)2(i-PrOH)(H2O)2(μ-CN)WV(CN)7]·2H2O [Ln = Gd (1), Tb (2), Dy (3), Ho (4), and Er (5); pyim = 2-(1H-imidazol-2-yl)-pyridine) and i-PrOH = isopropyl alcohol] were synthesized by one-pot reaction between (NH3Bu)3[W(CN)8] and [Ln(pyim)2]2+ complexes (generated in situ by mixing the corresponding LnIII ions and the pyim ligand). Compounds 1-5 are isomorphous and crystallize in the monoclinic system P21/n space group. Their crystal structure consists of binuclear units in which the octacyanotungstate(V) anion coordinates to the corresponding LnIII ion through a single cyanide ligand. The tungsten(V) and lanthanide(III) ions are eight-coordinated, in distorted square antiprism (WV) and distorted trigonal dodecahedron (LnIII) geometries, respectively. The direct-current (dc) magnetic properties for 1-5 reveal the occurrence of weak antiferromagnetic interactions between WV and LnIII cation, with 8S7/2, 7F6, 6H15/2, 5I8, and 4I15/2 as ground terms for GdIII, TbIII, DyIII HoIII, and ErIII, respectively [JWLn = -1.19(1) (1), -1.02(2) (2), -1.10(2) (3), -1.30(2) (4), and -1.50(3) cm-1 (5), the spin Hamiltonian being defined as H = -JWLn SW·SLn]. The fit of the χMT data of 2-4 points out a positive value for the energy gap between the ML components (Δ). This feature is corroborated by their Q-band electron paramagnetic resonance spectra at low temperature, which clearly show MJ = 0 (2 and 4) and ±1/2 (3 and 5). Incipient frequency-dependent alternating-current magnetic susceptibility signals are observed for 3 and 5 under applied dc fields supporting the presence of slow magnetic relaxation behavior, the blocking temperatures being below 2.0 K. This new series of {LnIIIWV} heterobinuclear compounds provides more insights into the exchange magnetic interaction between 5d and 4f centers via the cyanide-bridge, for which scarce information is available to date.

Crystal structure of tris­(μ-bis­{4-[(pyridin-2-yl­methyl­idene)amino]­phen­yl}methane-κ4N,N′:N′′,N′′′)dizinc tetra­kis­(tetra­fluorido­borate) aceto­nitrile tris­olvate

The asymmetric unit of the title compound, [Zn2(C25H20N4)3](BF4)4·3CH3CN, consists of one dinuclear ZnII complex cation with a triple-helical [Zn2 L 3]4+ motif (L is bis{4-[(pyridin-2-ylmethylidene)amino]phenyl}methane), four BF4 − anions and three CH3CN solvent molecules. The Zn⋯Zn separation is 11.3893 (14) Å and the ligands wrap around the two ZnII atoms, forming a triple helix as defined by the Zn—N—N—Zn torsion angles of 104.05 (18), 99.06 (19) and 101.40 (19)°. The Zn—N(pyridyl) distances in the octahedral ZnN6 coordination sphere are in the range 2.128 (5)–2.190 (5) Å and the Zn—N(imine) distances are in the range 2.157 (5)–2.277 (5) Å.

Aggregation of two different coordination polymers by reacting zinc nitrate and cadmium chloride with N,N′-ethylenebisacetamide

Two different coordination polymers are obtained from d10 metal ions [Zn(II) and Cd(II)] and N,N′-ethylenebisacetamide (EBA). {[Zn(EBA)1.5(NO3)] · (NO3)} n (1) is a 1-D coordination polymer assembled from zinc ions and EBA molecules acting as a bridging ligand. Cd(H2O)2Cl2(EBA) (2) is constructed from 1-D inorganic polymeric chains {Cd(OH2)2Cl2} n and uncoordinated N,N′-ethylenebisacetamide molecules. These chains are interconnected through hydrogen bonds resulting in a 3-D supramolecular network. The luminescent properties of the organic molecule EBA, as well as of the coordination polymers 1, and 2 have been investigated.