Reactions of Cadmium(II) Halides and Di-2-Pyridyl Ketone Oxime: One-Dimensional Coordination Polymers.

The coordination chemistry of 2-pyridyl ketoximes continues to attract the interest of many inorganic chemistry groups around the world for a variety of reasons. Cadmium(II) complexes of such ligands have provided models of solvent extraction of this toxic metal ion from aqueous environments using 2-pyridyl ketoxime extractants. Di-2-pyridyl ketone oxime (dpkoxH) is a unique member of this family of ligands because its substituent on the oxime carbon bears another potential donor site, i.e., a second 2-pyridyl group. The goal of this study was to investigate the reactions of cadmium(II) halides and dpkoxH in order to assess the structural role (if any) of the halogeno ligand and compare the products with their zinc(II) analogs. The synthetic studies provided access to complexes {[CdCl2(dpkoxH)∙2H2O]}n (1∙2H2O), {[CdBr2(dpkoxH)]}n (2) and {[CdI2(dpkoxH)]}n (3) in 50-60% yields. The structures of the complexes were determined by single-crystal X-ray crystallography. The compounds consist of structurally similar 1D zigzag chains, but only 2 and 3 are strictly isomorphous. Neighboring CdII atoms are alternately doubly bridged by halogeno and dpkoxH ligands, the latter adopting the η1:η1:η1:µ (or 2.0111 using Harris notation) coordination mode. A terminal halogeno group completes distorted octahedral coordination at each metal ion, and the coordination sphere of the CdII atoms is {CdII(η1 - X)(µ - X)2(Npyridyl)2(Noxime)} (X = Cl, Br, I). The trans-donor-atom pairs in 1∙2H2O are Clterminal/Noxime and two Clbridging/Npyridyl; on the contrary, these donor-atom pairs are Xterminal/Npyridyl, Xbridging/Noxime, and Xbridging/Npyridyl (X = Br, I). There are intrachain H-bonding interactions in the structures. The packing of the chains in 1∙2H2O is achieved via π-π stacking interactions, while the 3D architecture of the isomorphous 2 and 3 is built via C-H∙∙∙Cg (Cg is the centroid of one pyridyl ring) and π-π overlaps. The molecular structures of 1∙2H2O and 2 are different compared with their [ZnX2(dpkoxH)] (X = Cl, Br) analogs. The polymeric compounds were characterized by IR and Raman spectroscopies in the solid state, and the data were interpreted in terms of the known molecular structures. The solid-state structures of the complexes are not retained in DMSO, as proven via NMR (1H, 13C, and 113Cd NMR) spectroscopy and molar conductivity data. The complexes completely release the coordinated dpkoxH molecule, and the dominant species in solution seem to be [Cd(DMSO)6]2+ in the case of the chloro and bromo complexes and [CdI2(DMSO)4].

Forcing Twisted 1,7-Dibromoperylene Diimides to Flatten in the Solid State: What a Difference an Atom Makes.

Perylene diimides (PDI) are workhorses in the field of organic electronics, owing to their appealing n-semiconducting properties. Optimization of their performances is widely pursued by bay-atom substitution and diverse imide functionalization. Bulk solids and thin-films of these species crystallize in a variety of stacking configurations, depending on the geometry of the stable conformation of the polyaromatic core. We here demonstrate that 1,7-dibromo-substituted perylene diimides, PDI(H2 Br2 ), possessing a heavily twisted conformation in the gas phase, in solution and in the solids, can be easily flattened in the solid state into centrosymmetric molecules if the polyaromatic cores form π-π stabilized chains. This is achieved by using axial residues with low stereochemical hindrance, as guaranteed by a single CH2 /NH spacer directly linked to the imide function. Structural powder diffraction and DFT calculations on four newly designed species of the PDI(H2 Br2 ) class coherently show that, thanks to the flexibility of the N-X-Ar link (X=CH2 /NH), flat cores are indeed obtained by overcoming the interconversion barrier between twisted atropoisomers, of only 26.5 kJ mol-1 . This strategy may then be useful to induce "anomalously flat" polyaromatic cores of different kinds (substituted acenes/rylenes) in the solid state, towards suitable crystal packing and orbital interactions for improved electronic performances.

Confirming the Molecular Basis of the Solvent Extraction of Cadmium(II) Using 2-Pyridyl Oximes through a Synthetic Inorganic Chemistry Approach and a Proposal for More Efficient Extractants.

The present work describes the reactions of CdI2 with 2-pyridyl aldoxime (2paoH), 3-pyridyl aldoxime (3paoH), 4-pyridyl aldoxime (4paoH), 2-6-diacetylpyridine dioxime (dapdoH2) and 2,6-pyridyl diamidoxime (LH4). The primary goal was to contribute to understanding the molecular basis of the very good liquid extraction ability of 2-pyridyl ketoximes with long aliphatic chains towards toxic Cd(II) and the inability of their 4-pyridyl isomers for this extraction. Our systematic investigation provided access to coordination complexes [CdI2(2paoH)2] (1), {[CdI2(3paoH)2]}n (2), {[CdI2(4paoH)2]}n (3) and [CdI2(dapdoH2)] (4). The reaction of CdI2 and LH4 in EtOH resulted in a Cd(II)-involving reaction of the bis(amidoxime) and isolation of [CdI2(L'H2)] (5), where L'H2 is the new ligand 2,6-bis(ethoxy)pyridine diimine. A mechanism of this transformation has been proposed. The structures of 1, 2, 3, 4·2EtOH and 5 were determined by single-crystal X-ray crystallography. The complexes have been characterized by FT-IR and FT-Raman spectra in the solid state and the data are discussed in terms of structural features. The stability of the complexes in DMSO was investigated by 1H NMR spectroscopy. Our studies confirm that the excellent extraction ability of 2-pyridyl ketoximes is due to the chelating nature of the extractants leading to thermodynamically stable Cd(II) complexes. The monodentate coordination of 4-pyridyl ketoximes (as confirmed in our model complexes with 4paoH and 3paoH) seems to be responsible for their poor performance as extractants.

Indium(III) in the "Periodic Table" of Di(2-pyridyl) Ketone: An Unprecedented Transformation of the Ligand and Solid-State 115In NMR Spectroscopy as a Valuable Structural Tool.

Reactions of di(2-pyridyl) ketone, (py)2CO, with indium(III) halides in CH3NO2 have been studied, and a new transformation of the ligand has been revealed. In the presence of InIII, the C═O bond of (py)2CO is subjected to nucleophilic attack by the carbanion -:CH2NO2, yielding the dinuclear complexes [In2X4{(py)2C(CH2NO2)(O)}2] (X = Cl, 1; X = Br, 2; X = I, 3) in moderate to good yields. The alkoxo oxygens of the two η1:η2:η1-(py)2C(CH2NO2)(O)- ligands doubly bridge the InIII centers and create a {In2(µ2-OR)2}4+ core. Two pyridyl nitrogens of different organic ligands and two terminal halogeno ions complete a distorted-octahedral stereochemistry around each In(III) ion. After maximum excitation at 360 or 380 nm, the solid chloro complex 1 emits blue light at 420 and 440 nm at room temperature, the emission being attributed to charge transfer within the coordinated organic ligand. Solid-state 115In NMR spectra, in combination with DFT calculations, of 1-3 have been studied in detail at both 9.4 and 14.1 T magnetic fields. The nuclear quadrupolar and chemical shift parameters provide valuable findings concerning the electric field gradients and magnetic shielding at the nuclei of indium, respectively. The experimentally derived CQ values are 40 ± 3 MHz for 1, 46 ± 5 MHz for 2, and 50 ± 10 and 64 ± 7 MHz for the two crystallographically independent InIII sites for 3, while the δiso values fall in the range 130 ± 30 to -290 ± 60 ppm. The calculated CQ and asymmetry parameter (ηQ) values are fully consistent with the experimental values for 1 and 2 and are in fairly good agreement for 3. The results have been analyzed and discussed in terms of the known (1, 3) and proposed (2) structural features of the complexes, demonstrating that 115In NMR is an effective solid-state technique for the study of indium(III) complexes.

Dinuclear Lanthanide(III) Complexes from the Use of Methyl 2-Pyridyl Ketoxime: Synthetic, Structural, and Physical Studies.

The first use of methyl 2-pyridyl ketoxime (mepaoH) in homometallic lanthanide(III) [Ln(III)] chemistry is described. The 1:2 reactions of Ln(NO3)3·nH2O (Ln = Nd, Eu, Gd, Tb, Dy; n = 5, 6) and mepaoH in MeCN have provided access to complexes [Ln2(O2CMe)4(NO3)2(mepaoH)2] (Ln = Nd, 1; Ln = Eu, 2; Ln = Gd, 3; Ln = Tb, 4; Ln = Dy, 5); the acetato ligands derive from the LnIII-mediated hydrolysis of MeCN. The 1:1 and 1:2 reactions between Dy(O2CMe)3·4H2O and mepaoH in MeOH/MeCN led to the all-acetato complex [Dy2(O2CMe)6(mepaoH)2] (6). Treatment of 6 with one equivalent of HNO3 gave 5. The structures of 1, 5, and 6 were solved by single-crystal X-ray crystallography. Elemental analyses and IR spectroscopy provide strong evidence that 2-4 display similar structural characteristics with 1 and 5. The structures of 1-5 consist of dinuclear molecules in which the two LnIII centers are bridged by two bidentate bridging (η1:η1:µ2) and two chelating-bridging (η1:η2:µ2) acetate groups. The LnIII atoms are each chelated by a N,N'-bidentate mepaoH ligand and a near-symmetrical bidentate nitrato group. The molecular structure of 6 is similar to that of 5, the main difference being the presence of two chelating acetato groups in the former instead of the two chelating nitrato groups in the latter. The geometry of the 9-coordinate LnIII centers in 1, 5 and 6 can be best described as a muffin-type (MFF-9). The 3D lattices of the isomorphous 1 and 5 are built through H-bonding, π⋯π stacking and C-H⋯π interactions, while the 3D architecture of 6 is stabilized by H bonds. The IR spectra of the complexes are discussed in terms of the coordination modes of the organic and inorganic ligands involved. The Eu(III) complex 2 displays a red, metal-ion centered emission in the solid state; the TbIII atom in solid 4 emits light in the same region with the ligand. Magnetic susceptibility studies in the 2.0-300 K range reveal weak antiferromagnetic intramolecular GdIII…GdIII exchange interactions in 3; the J value is -0.09(1) cm-1 based on the spin Hamiltonian H = -J(SGd1·SGd2).

The First Use of a ReX5 Synthon to Modulate FeIII Spin Crossover via Supramolecular Halogen⋠⋠⋠Halogen Interactions.

We have added the {ReIV X5 }- (X=Br, Cl) synthon to a pocket-based ligand to provide supramolecular design using halogen⋅⋅⋅halogen interactions within an FeIII system that has the potential to undergo spin crossover (SCO). By removing the solvent from the crystal lattice, we "switch on" halogen⋅⋅⋅halogen interactions between neighboring molecules, providing a supramolecular cooperative pathway for SCO. Furthermore, changes to the halogen-based interaction allow us to modify the temperature and nature of the SCO event.

A potent, selective, and orally bioavailable inhibitor of the protein-tyrosine phosphatase PTP1B improves insulin and leptin signaling in animal models.

The protein-tyrosine phosphatase PTP1B is a negative regulator of insulin and leptin signaling and a highly validated therapeutic target for diabetes and obesity. Conventional approaches to drug development have produced potent and specific PTP1B inhibitors, but these inhibitors lack oral bioavailability, which limits their potential for drug development. Here, we report that DPM-1001, an analog of the specific PTP1B inhibitor trodusquemine (MSI-1436), is a potent, specific, and orally bioavailable inhibitor of PTP1B. DPM-1001 also chelates copper, which enhanced its potency as a PTP1B inhibitor. DPM-1001 displayed anti-diabetic properties that were associated with enhanced signaling through insulin and leptin receptors in animal models of diet-induced obesity. Therefore, DPM-1001 represents a proof of concept for a new approach to therapeutic intervention in diabetes and obesity. Although the PTPs have been considered undruggable, the findings of this study suggest that allosteric PTP inhibitors may help reinvigorate drug development efforts that focus on this important family of signal-transducing enzymes.

Multifunctionality in Two Families of Dinuclear Lanthanide(III) Complexes with a Tridentate Schiff-Base Ligand.

The employment of N-(2-carboxyphenyl)salicylideneimine in 4f metal chemistry has led to two families of dinuclear complexes depending on the lanthanide(III) used. Representative members exhibit interesting magnetic, optical, and catalytic properties.

Connectivity and Topology Invariance in Self-Assembled and Halogen-Bonded Anionic (6,3)-Networks.

We report here that the halogen bond driven self-assembly of 1,3,5-trifluorotriiodobenzene with tetraethylammonium and -phosphonium bromides affords 1:1 co-crystals, wherein the mutual induced fit of the triiodobenzene derivative and the bromide anions (halogen bond donor and acceptors, respectively) elicits the potential of these two tectons to function as tritopic modules (6,3). Supramolecular anionic networks are present in the two co-crystals wherein the donor and the acceptor alternate at the vertexes of the hexagonal frames and cations are accommodated in the potential empty space encircled by the frames. The change of one component in a self-assembled multi-component co-crystal often results in a change in its supramolecular connectivity and topology. Our systems have the same supramolecular features of corresponding iodide analogues as the metric aspects seem to prevail over other aspects in controlling the self-assembly process.

Polyfluorinated Naphthalene-bis-hydrazimide for Solution-Grown n-Type Semiconducting Films.

Naphthalene tetracarboxylic diimides (NDIs), possessing low-lying and tunable LUMO levels, are of wide interest for their aptitude to provide cost-effective, flexible, and environmentally stable n-type organic semiconductors through simple solution processing. NDI-based aromatic hydrazidimides are herein studied in relation to their chemical and environmental stability and as spin-coated stable thin films. In the case of the pentafluorinated residue, these were found to be crystalline, highly oriented, and molecularly flat (roughness = 0.3 nm), based on optical and atomic force microscopy, X-ray diffraction in specular and grazing incidence geometry, and X-ray reflectivity measurements. A new polymorph, previously undetected during the isolation of bulk powders or in their controlled thermal treatments, is found in the thin film and was metrically and structurally characterized from 2D GIWAXS patterns (monoclinic, P2/c, a = 17.50; b = 4.56; c = 14.24 Å; ß = 84.8°). This new thin-film phase, TF-F5, is formed no matter whether silicon, glass, or polymethylmethacrylate substrates are used, thus opening the way to the preparation of solution-grown flexible semiconducting films. The TF-F5 films exhibit a systematic and rigorous molecular alignment with both orientation and packing favorable to electron mobility (µ = 0.02 cm2 V-1 s-1). Structural and morphological differences are deemed responsible for the absence of measurable conductivity in thin films of polyfluorinated analogues bearing -CF3 residues on the hydrazidimide aromatic rings.

Use of the 2-Pyridinealdoxime/N,N'-Donor Ligand Combination in Cobalt(III) Chemistry: Synthesis and Characterization of Two Cationic Mononuclear Cobalt(III) Complexes.

The use of 2-pyridinealdoxime (paoH)/N,N'-donor ligand (L-L) "blend" in cobalt chemistry has afforded two cationic mononuclear cobalt(III) complexes of the general type [Co(pao)(2)(L-L)](+), where L-L = 1,10-phenanthroline (phen) and 2,2'-bipyridine (bpy). The CoCl(2)/paoH/L-L (1 : 2 : 1) reaction system in MeOH gives complexes [Co(III)(pao)(2)(phen)]Cl.2H(2)O (1.2H(2)O) and [Co(III)(pao)(2)(bpy)]Cl.1.5MeOH (2.1.5MeOH). The structures of the complexes were determined by single-crystal X-ray crystallography. The Co(III) ions are six-coordinate, surrounded by three bidentate chelating ligands, that is, two pao(-) and one phen or bpy. The deprotonated oxygen atom of the pao(-) ligand remains uncoordinated and participates in hydrogen bonding with the solvate molecules. IR data of the complexes are discussed in terms of the nature of bonding and the known structures.

Synthesis, Crystal Structures, and DNA Binding Properties of Zinc(II) Complexes with 3-Pyridine Aldoxime.

The employment of 3-pyridine aldoxime, (3-py)CHNOH, in Zn(II) chemistry has afforded two novel compounds: [Zn(acac)(2){(3-py)CHNOH}]·H(2)O (1·H(2)O) [where acac(-) is the pentane-2,4-dionato(-1) ion] and [Zn(2)(O(2)CMe)(4){(3-py)CHNOH}(2)] (2). Complex 1·H(2)O crystallizes in the monoclinic space group P2(1)/n. The Zn(II) ion is five-coordinated, surrounded by four oxygen atoms of two acac(-) moieties and by the pyridyl nitrogen atom of the (3-py)CHNOH ligand. Molecules of 1 interact with the water lattice molecules forming a 2D hydrogen-bonding network. Complex 2 crystallizes in the triclinic P-1 space group and displays a dinuclear paddle-wheel structure. Each Zn(II) exhibits a perfect square pyramidal geometry, with four carboxylate oxygen atoms at the basal plane and the pyridyl nitrogen of one monodentate (3-py)CHNOH ligand at the apex. DNA mobility shift assays were performed for the determination of the in vitro effect of both complexes on the integrity and the electrophoretic mobility of pDNA.

Synthesis, X-Ray Structure, and Characterization of Catena-bis(benzoate)bis{N,N-bis(2-hydroxyethyl)glycinate}cadmium(II).

The reaction of N, N-bis(2-hydroxyethyl)glycine (bicine; bicH(3)) with Cd(O(2)CPh)(2) · 2H(2)O in MeOH yielded the polymeric compound [Cd(2)(O(2)CPh)(2)(bicH(2))(2)](n)(1). The complex crystallizes in the tetragonal space group P4(1)2(1)2. The lattice constants are a = b = 12.737(5) and c = 18.288(7) Å. The compound contains chains of repeating {Cd(2)(O(2)CPh)(2)(bicH(2))(2)} units. One Cd(II) atom is coordinated by two carboxylate oxygen, four hydroxyl oxygen, and two nitrogen atoms from two symmetry-related 2.21111 (Harris notation) bicH(2) (-) ligands. The other Cd(II) atom is coordinated by six carboxylate oxygen atoms, four from two bicH(2) (-) ligands and two from the monodentate benzoate groups. Each bicinate(-1) ligand chelates the 8-coordinate, square antiprismatic Cd(II) atom through one carboxylate oxygen, the nitrogen, and both hydroxyl oxygen atoms and bridges the second, six-coordinate trigonal prismatic Cd(II) center through its carboxylate oxygen atoms. Compound 1 is the first structurally characterized cadmium(II) complex containing any anionic form of bicine as ligand. IR data of 1 are discussed in terms of the coordination modes of the ligands and the known structure.

Tetranuclear oxido-bridged thorium(iv) clusters obtained using tridentate Schiff bases.

Thorium(iv) complexes are currently attracting intense attention from inorganic chemists due to the development of liquid-fluoride thorium reactors and the fact that thorium(iv) is often used as a model system for the study of the more radioactive Np(iv) and Pu(iv). Schiff-base complexes of tetravalent actinides are useful for the development of new separation strategies in nuclear fuel processing and nuclear waste management. Thorium(iv)-Schiff base complexes find applications in the colorimetric detection of this toxic metal ion and the construction of fluorescent on/off sensors for Th(iv) exploiting the ligand-based light emission of its complexes. Clusters of Th(iv) with hydroxide, oxide or peroxide bridges are also relevant to the environmental and geological chemistry of this metal ion. The reactions between Th(NO3)4·5H2O and N-salicylidene-o-aminophenol (LH2) and N-salicylidene-o-amino-4-methylphenol (L'H2) in MeCN have provided access to complexes [Th4O(NO3)2(LH)2(L)5] (1) and [Th4O(NO3)2(L'H)2(L')5] (2) in moderate yields. The structures of 1·4MeCN and 2·2.4 MeCN have been determined by single-crystal X-ray crystallography. The complexes have similar molecular structures possessing the {Th4(µ4-O)(µ-OR')8} core that contains the extremely rare {Th4(µ4-O)} unit. The four ThIV atoms are arranged at the vertexes of a distorted tetrahedron with a central µ4-O2- ion bonded to each metal ion. The H atom of one of the acidic -OH groups of each 3.21 LH- or L'H- ligand is located on the imine nitrogen atom, thus blocking its coordination. The ThIV centres are also held together by one 3.221 L2- or (L')2- group and four 2.211 L2- or (L')2- ligands. The metal ions adopt three different coordination numbers (8, 9, and 10) with a total of four coordination geometries (triangular dodecahedral, muffin, biaugmented trigonal prismatic, and sphenocorona). A variety of H-bonding interactions create 1D chains and 2D layers in the crystal structures of 1·4 MeCN and 2·2.4 MeCN, respectively. The structures of the complexes are compared with those of the uranyl complexes with the same or similar ligands. Solid-state and IR data are discussed in terms of the coordination mode of the organic ligands and the nitrato groups. 1H NMR data suggest that solid-state structures are not retained in DMSO. The solid complexes emit green light at room temperature upon excitation at 400 nm, the emission being ligand-centered.

Dinuclear lanthanide(III)/zinc(II) complexes with methyl 2-pyridyl ketone oxime.

The first use of methyl 2-pyridyl ketone oxime (mpkoH) in zinc(II)/lanthanide(III) chemistry leads to the [ZnLn(mpko)3(mpkoH)3](ClO4)2 and [ZnLn(NO3)2(mpko)3(mpkoH)] families of dinuclear Zn(II)Ln(III) complexes displaying blue-green, ligand-based photoluminescence; the Zn(II)Dy(III) compound shows field-induced relaxation of magnetization.

Zn(II)/pyridyloxime complexes as potential reactivators of OP-inhibited acetylcholinesterase: in vitro and docking simulation studies.

In order to investigate the ability of metal complexes to act as reactivators of organophosphorus compounds (OP)-inhibited acetylcholinesterase (AChE), we have synthesized and crystallographically characterized three novel mononuclear Zn(II) complexes formulated as [ZnCl2{(4-py)CHNOH}2] (1), [ZnBr2{(4-py)CHNOH}2] (2) and [Zn(O2CMe)2{(4-py)CHNOH}2]∙2MeCN (3∙2MeCN), where (4-py)CHNOH is 4-pyridinealdoxime. Their reactivation potency was tested in vitro with a slight modification of the Ellman's method using Electric eel acetylcholinesterase and the insecticide paraoxon (diethyl 4-nitrophenyl phosphate) as inhibitor. The activity of the already reported complex [Zn2(O2CPh)2{(4-py)CHNOH}2]·2MeCN (4·2MeCN) and of the clinically used drug obidoxime 1,1'-[oxybis(methylene)]bis{4-[(E)- (hydroxyimino)methyl]pyridinium} was also examined. The results of the in vitro experiments demonstrate moderate reactivation of the metal complexes compared to the drug obidoxime. On the other hand, it is clearly shown that the metal complex is the responsible molecular entity for the observed activity, as the reactivation efficacy of the organic ligand (4-pyridinealdoxime) is found to be inconsequential. Docking simulation studies were performed in the light of predicted complex-enzyme interactions using the paraoxon-inhibited enzyme along with the four Zn(II) complexes and obidoxime as a reference reactivator. The results showed that the three mononuclear metal complexes possess the required characteristics to be accommodated into the active site of AChE, while the entrance of the dinuclear Zn(II) compound is unsuccessful. An interesting outcome of docking simulations is the fact that the mononuclear compounds accommodate into the active site of AChE in a similar mode as obidoxime.

Investigation of the zinc(II)-benzoate-2-pyridinealdoxime reaction system.

The employment of pyridine-2-carbaldehyde oxime (paoH) in zinc(II) benzoate chemistry, in the absence or presence of azide ions, is described. The syntheses, crystal structures and spectroscopic characterization are reported for the complexes [Zn(O(2)CPh)(2)(paoH)(2)] (1), [Zn(12)(OH)(4)(O(2)CPh)(16)(pao)(4)] (2) and [Zn(4)(OH)(2)(pao)(4)(N(3))(2)] (3). The Zn(II) centre in octahedral 1 is coordinated by two monodentate PhCO(2)(-) groups and two N,N'-chelating paoH ligands. The metallic skeleton of 2 describes a tetrahedron encapsulated in a distorted cube. The {Zn(12)(µ-OH)(4)(µ(3)-ΟR)(4)}(16+) core of the cluster can be conveniently described as consisting of a central {Zn(4)(µ(3)-ΟR)(4)}(4+) cubane subunit (RO(-) = pao(-)) linked to four {Zn(2)(µ-OH)}(3+) subunits via the OH(-) group of each of the latter, which becomes µ(3). The molecule of 3 has an inverse 12-metallacrown-4 topology. Two triply bridging hydroxido groups are accommodated into the metallacrown ring. Each pao(-) ligand adopts the η(1) : η(1) : η(1) : µ coordination mode, chelating one Zn(II) atom and bridging a Zn(II)(2) pair. Complexes 1 and 2 display photoluminescence with maxima at ∼355 nm and ∼375 nm, upon maximum excitation at 314 nm; the origin of the photoluminescence is discussed.

Metal ion-assisted transformations of 2-pyridinealdoxime and hexafluorophosphate.

Metal-ion mediated reactions of 2-pyridinealdoxime and hexafluorophosphate lead to Zn(II) complexes containing picolinic acid, picolinamide and monofluorophosphate (-2) as ligands.

A tetrahedron in a cube: a dodecanuclear Zn(II) benzoate cluster from the use of 2-pyridinealdoxime.

The reactions of 2-pyridinealdoxime with Zn(O(2)CPh)(2)·2H(2)O have led to a mononuclear complex and a dodecanuclear cluster; the Zn(12) compound, whose metallic skeleton describes a tetrahedron encapsulated in a distorted cube, is the biggest Zn(II) oxime cluster discovered to date and displays photoluminescence with a maximum at 354 nm upon maximum excitation at 314 nm.

Wheel-like Mn(II)6 and Ni(II)6 complexes from the use of 2-pyridinealdoxime and carboxylates.

The employment of 2-pyridinealdoxime, (py)C(H)NOH, in nickel(II) and manganese(II) carboxylate chemistry under solvothermal conditions is reported. The syntheses, crystal structures and magnetochemical characterization (for two representative compounds) are described for [Ni(6)(O(2)CMe)(6){(py)C(H)NO}(6)].H(2)O (1.H(2)O), [Ni(6)(O(2)CPh)(6){(py)C(H)NO}(6)].2EtOH (2.2EtOH), [Ni(6){(4-Cl)O(2)CPh}(6){(py)C(H)NO}(6)].2EtOH (3.2EtOH) and [Mn(6)(O(2)CMe)(6){(py)C(H)NO}(6)].H(2)O (4.H(2)O), where (4-Cl)PhCO(2)(-) is 4-chlorobenzoate. The reactions of M(O(2)CMe)(2).4H(2)O (M = Ni, Mn) with one equivalent of (py)C(H)NOH in EtOH at 120 degrees C under autogenous pressure give isostructural 1.H(2)O and 4.H(2)O. Complexes 2.2EtOH and 3.2EtOH were obtained from the 1 : 1 : 1 Ni(O(2)CMe)(2).4H(2)O/{(py)C(H)NOH/(X)PhCO(2)H reaction mixtures in EtOH under solvothermal conditions (X = H, 4-Cl). The structurally similar clusters 1-4 have a wheel-like topology with the six metal ions in a chair conformation. Each metal site is bound to four oxygen and two nitrogen atoms; the donor atoms come from two carboxylate oxygens, two oximate oxygens, one pyridyl nitrogen and one oximate nitrogen atom. The carboxylate ligands show the syn, syn eta(1):eta(1):mu mode, while the (py)C(H)NO(-) ions behave as eta(1):eta(1):eta(2):mu(3) ligands. Each metal...metal vector is bridged by one carboxylate group, one mu-O derived from a (py)C(H)NO(-) ligand and by one diatomic oximate-NO- group from an adjacent (py)C(H)NO(-) group. The IR spectra of the complexes are discussed in terms of the coordination modes of the ligands. Variable-temperature, solid-state dc magnetic susceptibility studies were carried out on polycrystalline samples of 1 and 4. The data in the 2.0-300 K range have been fit to a model with one J value revealing moderate (1) or weak (2) antiferromagnetic M(II)...M(II) exchange interactions. This work demonstrates the synthetic potential of combining (py)C(H)NOH with carboxylate ligands and the usefulness of solvothermal techniques in 3d-metal cluster chemistry.