Exploring the Spatial Arrangement of Simple 18-Membered Hexaazatetraamine Macrocyclic Ligands in Their Metal Complexes.

Hexaazamacrocyclic Schiff bases have been extensively combined with lanthanoid (Ln) ions to obtain complexes with a highly axial geometry. However, the use of flexible hexaazatetraamine macrocycles containing two pyridines and acyclic spacers is rather uncommon. Accordingly, we obtained [DyL(OAc)]OAc·7HO·EtOH and [DyL(Cl)]Cl·2HO, where L and L are the 18-membered macrocycles 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane and 3,10-dimethyl-3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane, respectively, which contain ethylene and methylethylene spacers between their moieties.

Dy, Dy, and Ho Complexes of an Aminophenol Donor: A Dy-µ-Peroxide Single Molecule Magnet.

The reactivity of the new flexible potentially pentadentate aminophenol ligand HL (2,2'-((pyridine-2,6-diylbis(methylene))bis(azanediyl))diphenol) towards different dysprosium salts and holmium(III) nitrate was investigated. Accordingly, this reactivity seems to greatly depend on the metal ion and salt employed. In this way, the reaction of HL with dysprosium(III) chloride in air leads to the oxo-bridged tetranuclear complex [Dy(HL)(Cl)(μ-O)(EtOH)(HO)]·2EtOH·HO (·2EtOH·HO), while the same reaction just changing the chloride salt by the nitrate one renders the peroxo-bridged pentanuclear compound [Dy(HL)(HL)(NO)(µ-O)]·2HO (·2HO), where both peroxo ligands seem to come from the fixation and reduction of atmospheric oxygen.

Experimental and Computational Studies on the Interaction of a Dansyl-Based Fluorescent Schiff Base Ligand with Cu Ions and CuO NPs.

We studied the interaction of Cu ions and CuO nanoparticles with the fluorescent Schiff base ligand HL, which derives from the condensation of 4-formyl-3-hydroxybenzoic acid with -(2-aminobenzyl)-5-(dimethylamino)naphthalene-1-sulfonamide (DsA). A detailed assignment of the most significant bands of the electronic and infrared spectra of HL and DsA was performed using DFT methods, based on both crystal structures. The affinity of HL to react with Cu ions in solution (K = 9.

Luminescence thermometry in a Dy single molecule magnet.

The tetranuclear linear complex [Dy(1,1,4-HL)(OAc)]·CHOH (1·CHOH) was satisfactorily prepared and characterized. Its X-ray structure shows that it contains two types of octacoordinated Dy ions, with distorted triangular dodecahedral and square antiprism geometries. This complex is an SMM, with multiple relaxation pathways, and with an anisotropic energy barrier of 39.

Semiconductor Quantum Dots as Target Analytes: Properties, Surface Chemistry and Detection.

Since the discovery of Quantum Dots (QDs) by Alexey I. Ekimov in 1981, the interest of researchers in that particular type of nanomaterials (NMs) with unique optical and electrical properties has been increasing year by year. Thus, since 2009, the number of scientific articles published on this topic has not been less than a thousand a year.

Dinuclear Fluoride Single-Bridged Lanthanoid Complexes as Molecule Magnets: Unprecedented Coupling Constant in a Fluoride-Bridged Gadolinium Compound.

A new synthetic method allows isolating fluoride-bridged complexes BuN{[M(3NO,5Br-HL)](μ-F)} (M = Dy, ; M = Ho, ; M = Gd, ) and BuN{[Dy(3Br,5Cl-HL)](μ-F)}·2HO, ·2HO. The crystal structures of ·5CHCH,··2HO·0.75THF, , and ·2HO·2THF show that all of them are dinuclear compounds with linear single fluoride bridges and octacoordinated metal centers.

Eight coordinated mononuclear dysprosium complexes of heptadentate aminophenol ligands: the influence of the phenol substituents and the ancillary donors on the magnetic relaxation.

The mononuclear complexes [Dy(3Br,5Cl-HL)(D)]·solvate (D = HO, solvate = 0.25MeOH, 1W·0.25MeOH; D = Py without solvate, 1Py), and [Dy(3NO,5Br-HL)(HO)] (2W) were isolated.

Dysprosium-based complexes with a flat pentadentate donor: a magnetic and ab initio study.

The reactivity of the well-known pentadentate N3O2 Schiff base H2L (2,6-bis(2-hydroxyphenyliminomethyl)pyridine) towards a lanthanoid metal, in this case DyIII, has been investigated for the first time. This reactivity markedly depends on the pH of the medium and, accordingly, two different complexes, [Dy(HL)(NO3)2]·H2O (1·H2O) and [Dy(L)(NO3)(EtOH)(H2O)]·2H2O (2·2H2O), could be isolated from dysprosium(iii) nitrate and H2L. In addition, reaction of H2L with dysprosium(iii) chloride in methanol yields [Dy(HL')2][Dy(L)(Cl2)] (3), where H2L' ((6-(2-hydroxyphenyliminomethyl)-2-methoxyhydroxymethyl)pyridine) is an N2O2 hemiacetal donor derived from the partial hydrolysis of the H2L ligand, and subsequent addition of the methanol solvent to the carbonyl group.

Field-Induced Single Molecule Magnets of Phosphine- and Arsine-Oxides.

The coordination chemistry of dysprosium and terbium toward phosphine and arsine oxides was further explored. Thus, the new nitrate [M(NO)(PhPO)] ( = Tb, ; Dy, ), [Dy(NO)(EtOH)(PhXO)] ( = P, ; As, ), chloride [DyCl(PhAsO)]Cl (), triflate [Dy(OTf)(MePhPO)]OTf (; OTf = triflate) and hexafluoroacetylacetonate [M(hfa)(PhPO)] (hfa = hexafluoroacetylacetonate; = Tb, ; Dy, ) complexes were isolated and fully characterized. The crystal structures of ·CHCN, ·CHCN, , ·2.

Tb, Dy, and ZnDy Complexes Showing the Unusual Versatility of a Hydrazone Ligand toward Lanthanoid Ions: a Structural and Magnetic Study.

Three dinuclear complexes, [Tb(Hdaps)(CHOH)(HO)](Cl) (TbCl), [Dy(Hdaps)(Cl)(CHOH)(HO)]Cl (DyCl), and [Dy(Hdaps)(HO)](CFSO) (DyCFSO), as well as the heterohexanuclear compound [ZnDy(daps)(Hdaps)(Cl)(OH)(CHOH)(HO)] (ZnDy) (Hdaps: 2,6-bis(1-salicyloylhydrazonoethyl)pyridine), which crystallize with different lattice molecules, show their hexa- or heptadentate hydrazone ligands acting with hitherto unknown μ-κ:κ, μ-κ:κ:κ, μ-κ:κ:κ:κ, or μ-κ:κ:κ:κ bridging modes. The single X-ray crystal structures of the dinuclear complexes show nine-coordinated N O environments for lanthanoid atoms in TbCl and DyCFSO, with distorted geometries, between spherical capped square antiprism and muffin-like, while the dysprosium atoms in DyCl are eight-coordinated, with distorted triangular dodecahedron geometries. In the case of ZnDy, both eight-coordinated, O and O Cl, as well as nine-coordinated N O environments coexist in the crystal structure, with biaugmented trigonal prism, triangular dodecahedron, and muffin-like pseudogeometries.

Improving the SMM and luminescence properties of lanthanide complexes with LnO cores in the presence of Zn: an emissive ZnDy single ion magnet.

Mononuclear complexes of stoichiometry [Ln(HL)(HO)(NO)](NO) (Ln = Tb, 1; Dy, 2, Er, 3), which crystallise with different solvates, and the heterotrinuclear compound [ZnDy(L)(NO)(OH)] (4) can be obtained with the same HL compartmental ligand. The single X-ray crystal structure of the mononuclear complexes shows a LnO core with a muffin-like disposition while the geometry of the DyO core in 4 seems to be closer to spherical capped square antiprism. The analysis of the magnetic properties of all the complexes demonstrates that the mononuclear lanthanide compounds do not show slow relaxation of the magnetization, even when the samples are diluted with a diamagnetic matrix and subjected to a dc applied field of 1000 Oe.

Exploration of an easily synthesized fluorescent probe for detecting copper in aqueous samples.

An easily synthesized fluorescent probe for detecting copper in aqueous samples, with a short response time and at neutral pH, has been investigated. Through the chelation of Cu ions or by binding to CuO nanoparticles, the fluorescence emission of the 2-(aminomethyl)aniline derivative HL is quenched by over 50%. Spectroscopic determination of the association constants of HL with some metal ions showed that the ligand has a higher affinity toward Cu than toward other d-block metal ions.

Designing Ligands to Isolate ZnLn and ZnLn Complexes: Field-Induced Single-Ion Magnet Behavior of the ZnDy, ZnDy, and ZnEr Analogues.

A new HL Schiff base ligand with three defined compartments, namely, two internal NNO and one external O, was designed to allocate metal ions of different size. This ligand allows isolating heterodinuclear [ZnLn(HL)(NO)(OAc)(D)](NO) (Ln = Tb, D = HO, ZnTb; Ln = Dy, D = CHOH, ZnDy; and Ln = Er, D = CHOH, ZnEr) complexes, where one of the NNO pockets allocates a zinc(II) ion, while the other one is empty, or heterotrinuclear [ZnLn(L)(NO)(OAc)(HO)] (Ln = Dy, ZnDy and Ln = Er, ZnEr) compounds, where each NNO compartment accommodates Zn. All these compounds crystallize with different solvates, and their structures were unequivocally determined by single-crystal X-ray diffraction studies.

Predetermined Ferromagnetic Coupling via Strict Control of M-O-M Angles.

An imidazolidine-phenolate ligand HL yields quadruple-bridged (μ-NCN)(μ-O) ferromagnetic dinuclear nickel and cobalt complexes. Both kinds of bridges contribute to the ferromagnetic coupling, but the ferromagnetism of these samples is mainly ascribed to the double μ-O links, on the basis of density functional theory calculations. These studies demonstrate not only that the short M-O-M angles of the MO cores favors the parallel alignment of the electrons but also that these angles are the optimal ones for maximizing the ferromagnetic contribution in these complexes.

Dual role of 2-tosylaminomethylaniline as a ligand and a nucleophile in the copper-mediated oxidation of methanol.

Some reactivity in the oxidation of methanol to formaldehyde has been spectroscopically detected on the methanolic mother liquors of a copper(ii) complex of a Schiff base ligand derived from the condensation of 8-hydroxyquinoline-2-carboxaldehyde and 2-tosylaminomethylaniline. An investigation has shown that 2-tosylaminomethylaniline (HA(TS)) plays a dual role in the oxidative process acting as a N-donor ligand and reacting in situ with formaldehyde, which leads to 3-tosyl-1,2,3,4-tetrahydroquinazoline (1). This was characterized by using both spectroscopic and X-ray diffraction techniques.

Encapsulation of atmospheric CO2 by a self-assembled decanuclear cadmium complex via unfamiliar perchlorato and carbonato bridges.

A decanuclear Cd complex has been found as a carbonate-containing capsule. The structure strongly resembles a ten-blade waterwheel with a central carbonate ligand surrounded by two superimposed Cd(5)O(5) crowns with a pentagonal antiprism-like disposition. The capsule is doubly capped by two pentadentate perchlorate anions.

Structural variety of zinc and copper complexes based on a 2,3-disubstituted 1,2,3,4-tetrahydroquinazoline ligand.

The ring-chain tautomerism of 2-(3-tosyl-1,2,3,4-tetrahydroquinazolin-2-yl)quinolin-8-ol (H(2)L(ring)) has been exploited to produce mononuclear complexes or, alternatively, dinuclear complexes, as desired, by varying the stoichiometry of the ligand. Cu(2+) and Zn(2+) stabilise the ring tautomeric form of the ligand in their mononuclear complexes M(HL(ring))(2). The structural characterisation of Zn(HL(ring))(2)·2MeOH·0.

Metal-assisted ring-closing/opening process of a chiral tetrahydroquinazoline.

The ring-chain tautomerism of a 2-aryl-1,2,3,4-tetrahydroquinazoline has been exploited to induce reversible changes in the aminal-imine equilibrium, as desired, by coordination of a suitable metal ion. This process was studied by NMR and UV-vis spectroscopies, X-ray crystallography, and molecular modeling approach. The results obtained show that the imine H(2)L(i) undergoes a selective ring-closing reaction upon complexation with Ni(2+).

Ferromagnetic heterotrinuclear Cu-Ni complexes of a compartmental chiral Schiff base.

Nickel(II) and copper(II) acetate react with the trinucleating compartmental Schiff base H(4)L (H(4)L = 6,6'-(E)-3,3'-(ethane-1,2-diyl)bis(1-(2-((E)-3-bromo-5-chloro-2-hydroxybenzylideneamino)ethyl)imidazolidine-3,2-diyl)bis(2-bromo-4-chlorophenol)) to produce the heterotrinuclear complexes [Ni(2)CuL(OAc)(2)]·0.25H(2)O·2.5MeOH (1·0.

One pot-synthesis of chiral Ni6 clusters involving Ni3 subunits: a combined structural, magnetic and DFT study.

Ni(6) clusters of the general formula [{Ni(3)L(n)(OAc)(OH)}(2)(X)(OAc)(H(2)O)(2)] (n = 1, 2; X = Cl(-) or N(3)(-), (L(n))(3-) = hexadentate tritopic ligands) can be isolated by spontaneous self-assembly, from mixtures of Ni(OAc)(2), H(3)L(n), NMe(4)OH·5H(2)O and NaX in adequate molar ratios. Thus, four new hexanuclear complexes [{Ni(3)L(1)(OAc)(OH)}(2)Cl(OAc)(H(2)O)(2)]·7.5H(2)O (1·7.

Discovering the complex chemistry of a simple Ni(II)/H(3)L system: magnetostructural characterization and DFT calculations of Di- and polynuclear nickel(II) compounds.

The simple nickel(II) acetate/H(3)L system (H(3)L = 2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) presents an unusually complicated reactivity scheme, which strongly depends on the Ni(OAc)(2)/H(3)L molar ratio and on the pH of the medium. Thus, in addition to the formerly reported compounds [Ni(2)L(OAc)(H(2)O)(2)][Ni(2)L(OAc)(H(2)O)(HOAc)].3.

Zn(3), Ni(3), and Cu(3) complexes of a novel tricompartmental acyclic ligand.

A new tricompartmental acyclic ligand (H(4)L) was prepared and fully characterized. It reacts with zinc, nickel, and copper(II) acetate to yield [Zn(3)L(OAc)(2)].H(2)O (1.

Complexes of 2-acetyl-gamma-butyrolactone and 2-furancarbaldehyde thiosemicarbazones: antibacterial and antifungal activity.

Cobalt, nickel, copper and zinc coordination compounds of two thiosemicarbazones with general composition ML(2) (L: monodeprotonated ligand corresponding to 2-acetyl-gamma-butyrolactone thiosemicarbazone, HL(1), and 2-furancarbaldehyde thiosemicarbazone, HL(2)) and also complexes with general composition MCl(2)(HL(2)) were synthesized (except [NiCl(2)(HL(2))] and [Co(L(2))(2)]). The interaction of CuCl(2) with HL(2) gave [CuCl(HL(2))], a copper(I) complex. The ligands and metal complexes were characterized by IR, (1)H and (13)C NMR spectroscopy, and magnetic susceptibility measurements.

Asymmetric self-assembly with atmospheric CO2 fixation of a pentanuclear carbonate NiI) complex based on dissimilar building blocks.

Formation in basic solution of an asymmetric pentanuclear carbonate Ni(II) complex with a compartmental ligand involves atmospheric CO(2) uptake, either by reaction of two slightly different dinuclear precursors that yield its di- and trinuclear "building blocks", or directly, by spontaneous self-organization of metal and ligand starting reactants.

Complexes of 2-thiophenecarbonyl and isonicotinoyl hydrazones of 3-(N-methyl)isatin. A study of their antimicrobial activity.

Cobalt(II), nickel(II), copper(II) and zinc(II) complexes of 2-thiophenecarbonyl and isonicotinoyl hydrazones of 3-(N-methyl)isatin (HL(1) and HL(2), respectively) were synthesized and characterized, being the crystal structures of HL(1), HL(2) and [Ni(L(1))(2)].2CHCl(3) elucidated by X-ray diffraction techniques. The in vitro antimicrobial activity of all these compounds was tested against several bacteria and fungi.