Vassilis Tangoulis

Di-2-pyridyl Ketone/Benzoate/Azide Combination as a Source of Copper(II) Clusters and Coordination Polymers: Dependence of the Product Identity on the Solvent

The reactions of di-2-pyridyl ketone with Cu(O2CPh)2 in the presence of NaN3 and LiOH have led to an antiferromagnetically coupled (S = 0) Cu(II)6 cluster with a novel core and to (Cu(II)8)n and (Cu(II)2)n coordination polymers (the former 1D and the latter 2D) with interesting structures. The cluster or polymer formation depends on the reaction solvent.

Self‐Assembly of High‐Nuclearity Copper Cages: Tricorne Cu21 and Saddlelike Cyclic Cu16

Reaction of cupric salts with H(2)Rppz (R = H, Me; H(2)ppz = 3-(2-hydroxyphenyl)pyrazole; H(2)Meppz = 3-(2-hydroxy-5-methylphenyl)pyrazole) in the presence of sodium azide and triethylamine as bases gave two high-nuclearity copper cage compounds [HNEt(3)](2)[Cu(21)(CH(3)CN)(2)(H(2)O)(mu(2)-N(3))(6)(mu(3)-N(3))(2)(ppz)(18)](H(2)O)(3)(EtOH)(2) (1) and [Cu(16)(EtOH)(2)(H(2)O)(2)(Meppz)(16)]9.5 H(2)O (2), respectively. X-ray crystallographic studies revealed that molecular skeletons of 1 and 2 are unique tricorne Cu(21) and saddlelike cyclic Cu(16) aggregates, respectively. The magnetic properties studies showed overall antiferromagnetic interactions in 1 and 2. Quantum Monte Carlo simulations by using a 3-J model for 1 and a 2-J model for 2 were performed, which indicated that the magnetic couplings within the triangular copper units in 1 are ferromagnetic and those between other copper ions are antiferromagnetic, whereas in 2 all magnetic couplings between adjacent copper ions are exclusively antiferromagnetic.

Heptanuclearity in nickel(II) chemistry: preparation, characterization, crystal structure and magnetic properties of [Ni7(OH)2(acac)8(btaO)4(H2O)2] (btaO−=the 1-hydroxybenzotriazolate ion)

Abstract The use of the substituted benzotriazole ligand btaOH (1-hydroxybenzotriazole) in nickel(II) chemistry has yielded a structurally and magnetically interesting polynuclear complex. The [Ni(acac)2(H2O)2]–btaOH·H2O (4:1, 3:1, 7:4) reaction system in refluxing MeCN gives light green–blue [Ni7(OH)2(acac)8(btaO)4(H2O)2] (4) in good yield (∼75%). The structure of 4·MeCN·0.9H2O was determined by single-crystal X-ray crystallography. The heptanuclear assembly is held together by two μ3 hydroxo ligands, two terminal H2O molecules, four chelating acac− groups, two μ2 acac− groups, two μ3 acac− groups, two μ4 btaO− ligands and two μ2 btaO− ligands. The Ni(II) atoms have distorted octahedral geometries. The IR and UV–Vis data of 4 are discussed in terms of the nature of bonding and the known structure. Variable-temperature magnetic susceptibility data (3–300 K), fitted with a 3-J model, show ferromagnetic and antiferromagnetic interactions. Magnetization data at 4 K are in line with an S=1 ground state for 4. The versatility of the 1-hydroxybenzotriazolate ligand is also discussed.

The [Cu2(O2CMe)4(btd)2] complex as a bridging unit: preparation, characterisation, X-ray structure and magnetism of the 2D coordination polymer {[Cu6(O2CMe)8(OMe)4(btd)2]}n (btd=2,1,3-benzothiadiazole)

A systematic investigation of the [Cu2(O2CMe)4(H2O)2]/btd reaction system is described, where btd = 2,1,3-benzothiadiazole. Reaction of [Cu2(O2CMe)4(H2O)2] with 5–8 equiv. of btd in both MeCN and MeOH yields [Cu2(O2CMe)4(btd)2 ]( 1) in 40–50% yields. Treatment of [Cu2(O2CMe)4(H2O)2] with 1.4 or 0.7 equiv. of btd in MeOH leads to the precipitation of the polymeric compound {[Cu6(O2CMe)8(OMe)4(btd)2]} (2) in 82% yield. Reaction of 1 with two equivalents of [Cu2(O2CMe)4(H2O)2] in MeOH under reflux provides an additional route to 2. The structure of 1 consists of centrosymmetric dinuclear [Cu2(O2CMe)4(btd)2] molecules of the paddle-wheel cage type. The two Cu II ions are bridged by four 1 : 1 :2 acetates, while a monodentate btd is at the apex of the square pyramid of each metal centre. The 2D structure of 2 consists of chains of tetranuclear, planar Cu4(OMe)4(O2CMe)4 repeating units running along the a axis, which are connected along the cell body diagonal via Cu2(O2CMe)4(btd)2 paddle-wheel dinuclear units. The btd molecules behave as bidentate bridging ligands. Within the tetranuclear units, each Cu II ion is connected via two acetate bridges with one neighbouring Cu II ion and via two methoxo bridges with the other neighbouring Cu II ion; intertetranuclear linking is provided by two monoatomic acetate bridges. The results of solid state magnetic susceptibility studies are described for complex 2 in the temperature range 3–300 K. The results reveal antiferromagnetic exchange interactions between the Cu II ions. The complicated structure of 2 does not permit an exact treatment for the determination of the various exchange interactions. However, an approximate 3-J magnetic model was constructed, resulting in an excellent fit. An orbital interpretation of the J-trend derived is also attempted.

Tris(N,N′-dimethylurea)bis(nitrato-O,O′)manganese(II), the first example of a seven-coordinate manganese(II) complex with a monodentate organic ligand

Employing a variety of solvents and molar ratios, the reactions of Mn(NO3)2P6H2O with N,N9-dimethylurea (DMU) afforded the adduct [Mn(NO3)2(DMU)3 ]( 1). X-ray analysis shows that the high-spin complex has a pentagonal bipyramidal geometry with two DMU oxygen atoms in axial positions and with two types of monodentate O-bonding for the DMU molecules, one of them being very unusual. The spectroscopic properties of the prepared complex are also discussed. q 1999 Elsevier Science S.A. All rights reserved.

Solvent-Dependent Access to Two Different Ni4II Core Topologies from the First Use of Pyridine-2,6-dimethanol in Nickel(II) Cluster Chemistry

The use of pyridine-2,6-dimethanol, pdmH2, in reactions with nickel(ii) acetate has led to two Ni4 clusters, depending on the solvent. [Ni4(O2CMe)4(pdmH)4]·MeCN (1·MeCN) can be obtained from MeCN and [Ni4(O2CMe)6(pdmH)2(EtOH)2]·1.2EtOH (2·1.2EtOH) from EtOH. Each cluster can be converted into the other in the appropriate solvent. The tetranuclear cluster molecule 1 possesses a distorted cubane {Ni4(μ3-OR)4}4+ core (RO– = pdmH–) with the NiII atoms and the alkoxide-type oxygen atoms from the η3 : η1 : μ3 pdmH– ligands occupying alternate vertices of the cube; four η1 : η1 : μ MeCO2– groups cap four faces of the cube. The four NiII atoms in molecule 2 are located at four vertices of a defective dicubane and are bridged by six oxygen atoms, two μ3 from the η3 : η1 : η1 : μ3 pdmH– ligands and four from four monoatomically bridging MeCO2– groups; peripheral ligation is provided by two η1 : η1 : μ MeCO2– groups and two terminal EtOH ligands. IR data are discussed in terms of the coordination modes of the ligands. Variable-temperature direct-current magnetic susceptibility data of 1 and 2 were modelled with two and three J values respectively, indicating diamagnetic ground states (S = 0). The sign and the magnitude of the J values are discussed in terms of structural features of the complexes.

Toward Multifunctional Materials Incorporating Stepladder Manganese(III) Inverse-[9-MC-3]-Metallacrowns and Anti-Inflammatory Drugs

The interaction of Mn(ClO4)2·6H2O with salicylaldoxime (H2sao) in the presence of nonsteroidal anti-inflammatory drug (NSAID) sodium diclofenac (Nadicl) or indomethacin (Hindo) leads to the formation of the hexanuclear Mn(III) clusters [Mn6(O)2(dicl)2(sao)6(CH3OH)6] (1) and [Mn6(O)2(indo)2(sao)6(H2O)4] (2) both characterized as stepladder inverse-9-metallacrown-3 accommodating dicl- or indo- ligands, respectively. When the interaction of MnCl2·4H2O with Nadicl or Hindo is in the absence of H2sao, the mononuclear Mn(II) complexes [Mn(dicl)2(CH3OH)4] (3) and [Mn(indo)2(CH3OH)4] (4) were isolated. The complexes were characterized by physicochemical and spectroscopic techniques, and the structure of complexes 1 and 2 was characterized by X-ray crystallography. Magnetic measurements (dc and ac) were carried out in order to investigate the nature of magnetic interactions between the magnetic ions and the overall magnetic behavior of the complexes.

A step-ladder manganese(III) metallacrown hosting mefenamic acid and a manganese(II)–mefanamato complex: synthesis, characterization and cytotoxic activity

The interaction of Mn(II) with the non-steroidal anti-inflammatory drug mefenamic acid (Hmef) in the presence or absence of salicylaldoxime (H2sao) leads to the formation of the hexanuclear Mn(III) cluster [Mn6(O)2(mef)2(sao)6(CH3OH)4] 1, characterized as stepladder inverse-9-metallacrown-3 accommodating mefenamato ligands, or the mononuclear Mn(II) complex [Mn(mef)2(CH3OH)4], 2, respectively. Both complexes were characterized by physicochemical and spectroscopic techniques and the structure of complex 1 was characterized by X-ray crystallography. The overall magnetic behavior of compound 1 is antiferromagnetic with a high-spin well-isolated ground state S = 4. The in vitro cytotoxic effects of the complexes were evaluated against three cancer cell lines (HeLa, MCF-7 and A549 cells) as well as their combinatory activity with the well-known chemotherapeutic drugs cisplatin and 5-fluorouracil. Furthermore, in silico predictive tools have been employed to study the properties and acute rat toxicity and cell line cytotoxicity of the most active complex.

Guest induced hysteretic tristability in 3D pillared Hofmann-type microporous metal–organic frameworks

Herein we report the synthesis, isolation and structural characterization of hybrid microporous Hofmann-like spin crossover polymers with the molecular formula {Fe(C4H4N2)[M(CN)4]}·(C4H4N2)·1.2H2O where M = Pt(II) (1), Pd(II) (2). Magnetic susceptibility studies showed well-resolved hysteretic three-step for 1 and two-step for 2 thermally induced spin transitions.

Noncovalent Grafting of a DyIII2 Single-Molecule Magnet onto Chemically Modified Multiwalled Carbon Nanotubes

While synthetic methods for the grafting of nanoparticles or photoactive molecules onto carbon nanotubes (CNTs) have been developed in the last years, a very limited number of reports have appeared on the grafting of single-molecule magnets (SMMs) onto CNTs. There are many potential causes, mainly focused on the fact that the attachment of molecules on surfaces remains not trivial and their magnetic properties are significantly affected upon attachment. Nevertheless, implementation of this particular type of hybrid material in demanding fields such as spintronic devices makes of utmost importance the investigation of new synthetic protocols for effective grafting. In this paper, we demonstrate a new experimental protocol for the noncovalent grafting of DyIII2 SMM, [Dy2(NO3)2(saph)2(DMF)4], where H2saph = N-salicylidene- o-aminophenol and DMF = N, N-dimethylformamide, onto the surface of functionalized multiwalled CNTs (MWCNTs). We present a simple wet chemical method, followed by an extensive washing protocol, where the cross-referencing of data from high-resolution transmission electron microscopy combined with electron energy loss spectroscopy, conventional magnetic measurements (direct and alternating current), X-ray photoelectron spectroscopy, and Raman spectroscopy was used to investigate the physical properties, chemical nature, and overall magnetic behavior of the resulting hybrids. A key point to the whole synthesis involves the functionalization of MWCNTs with carboxylic groups, which proved to be a powerful strategy for enhancing the ability to process MWCNTs and facilitating the preparation of hybrid composites. While in the majority of analogous hybrid materials the raw carbon material (multiwalled or single-walled nanotubes) is heavily treated to minimize the contribution of contaminant traces of magnetic nanoparticles with important effects on their electronic properties, this method can lead easily to elimination of the largest part of the impurities and provide an effective way to investigate/discriminate the magnetic contribution of the SMM molecules.