Selective Generation of Aldimine and Ketimine Tautomers of the Schiff Base Condensates of Amino Acids with Imidazole Aldehydes or of Imidazole Methanamines with Pyruvates-Isomeric Control with 2- vs. 4-Substituted Imidazoles.

The Schiff base condensation of 5-methyl-4-imidazole carboxaldehyde, 5Me4ImCHO, and the anion of an amino acid, HN-CH(R)CO (R = -CH, -CH(CH) and -CHCH(CH)), gives the aldimine tautomer, Im-CH=N-CH(R)CO, while that of 5-methylimidazole-4-methanamine, 5MeIm-4-CHNH, with a 2-oxocarboxylate anion, R-C(O)-CO, gives the isomeric ketimine tautomer, Im-CH-N=C(R)CO. All are isolated as the neutral nickel(II) complexes, NiL, and are characterized by single crystal structure determination, IR, and positive ion ESI MS. In the cases of the 4 substituted imidazoles, either 5MeIm-4-CHO or 5MeIm-4-CHNH, both the aldimine and ketimine complexes are isolated cleanly with no evidence of an equilibrium between the two tautomers under the experimental conditions.

Structural Diversity of Lanthanide 3-Nitrotrispyrazolylborates: Tunable Nuclearity and Intra-Ligand Charge Transfer Sensitization of Visible and NIR Ln Emission.

Reported are the syntheses, crystal structures, and photophysical properties of 28, novel lanthanide compounds across five structural types, [Ln(3-NOTp)(NO)] (-Ln, Ln = La-Tm, except Pm), [BuN][Ln(3-NOTp)(NO)] (-Ln, Ln = Yb, Lu), [Eu(3-NOTp)Cl(HO)]·2PrOH (-Eu), [{Ln(3-NOTp)}(μ-CO)]·MeOH (-Ln, Ln = La-Gd, except Pm), and [{Ln(3-NOTp)}(μ-OMe)(μ-O)] (-Ln, Ln = Pr-Tb, except Pm) with the 3-nitrotrispyrazolylborate (3-NOTp) ligand. The reaction of methanol or isopropanol solutions of LnX (X = Cl, NO) with the tetrabutyl ammonium salt of the flexidentate 3-NOTp ([BuN][3-NOTp]) yields Ln(3-NOTp) complexes of various nuclearities as either monomers (-Ln, -Ln, -Eu), dimers (-Ln), or tetramers (-Ln) owing to the efficient conversion of atmospheric CO to CO (dimers) or ligand controlled solvolysis of lanthanide ions (tetramers). 3-NOTp is an efficient sensitizer for both the visible and near-IR (NIR) emissions of most of the lanthanide series, except thulium.

Combination of single-molecule magnet behaviour and luminescence properties in a new series of lanthanide complexes with tris(pyrazolyl)borate and oligo(β-diketonate) ligands.

A series of tris(pyrazolyl)borate mono-, di- and trinuclear complexes, [TpLn]X (Ln = Eu, Tb, Gd, Dy, X = various mono-, bis- and tris(β-diketonates) has been prepared. The Tb and Dy complexes are luminescent single molecular magnets (SMM) and exhibit luminescence quantum efficiencies up to 73% for the Tb and 4.4% for the Dy compounds.

Use of Pyrazole Hydrogen Bonding in Tripodal Complexes to Form Self Assembled Homochiral Dimers.

The 3:1 condensation of 5-methyl-1H-pyrazole-3-carboxaldehyde (MepyrzH) with tris(2-aminoethyl)amine (tren) gives the tripodal ligand tren(MePyrzH). Aerial oxidation of a solution of cobalt(II) with this ligand in the presence of base results in the isolation of the insoluble Co(tren)(MePyrz) This complex reacts with acids, HCl/NaClO, NHClO, NHBF, and NHI to give the crystalline compounds Co(tren)(MePyrzH)(ClO), {[Co(tren)(MePyrzH)](ClO)} {[Co(tren)(MePyrzH)](BF)} and [Co(tren)(MePyrzH)][Co(tren)(MePyrzH)]I The latter three complexes are dimeric, held together by three N -HN hydrogen bonds. The structures and symmetries of these homochiral dimers or pseudodimers are discussed in terms of their space group.

Potassium chlorido-tris-(hypersil-oxy)aluminate dimer.

The tris-(tri-methyl-silylsiloxide) ligand, also known as hypersiloxide, is an extremely bulky group. In an attempt to make the monomeric Al(OSi(SiMe)), AlCl was combined with 3 equiv. of potassium hypersiloxide.

Crystal structure and thermal properties of bis-[μ-2-(meth-oxy-carbonyl-hydrazinyl-idene)acetato-κ ,:]bis-[di-aqua-(thio-cyanato-κ)manganese(II)] tetra-hydrate.

The title compound, [Mn(CHNO)(NCS)(HO)]·4HO (I), exists as a centrosymmetric dimer. Each dimeric unit consists of tridentate (,,)-chelating Schiff bases with symmetry-maintained μ--bridged carboxyl-ate anions, terminally bound thio-cyanate anions, and ligated and solvated water mol-ecules. The complex exhibits a distorted octa-hedron geometry and the centrosymmetric μ--bridged carboxyl-ate anions connect the two manganese atoms to form an O ring.

Design of two series of 1:1 cocrystals involving 4-amino-5-chloro-2,6-dimethylpyrimidine and carboxylic acids.

Two series of a total of ten cocrystals involving 4-amino-5-chloro-2,6-dimethylpyrimidine with various carboxylic acids have been prepared and characterized by single-crystal X-ray diffraction. The pyrimidine unit used for the cocrystals offers two ring N atoms (positions N1 and N3) as proton-accepting sites. Depending upon the site of protonation, two types of cations are possible [Rajam et al.

Potent Anticancer Activity with High Selectivity of a Chiral Palladium N-Heterocyclic Carbene Complex.

Five enantiomeric pairs of palladium complexes of 1,2,4-triazole-derived chiral N-heterocyclic carbene ligands were investigated to probe the influence of chirality on the compound's anticancer activity. Although no chirality-related influence was observed for any of the enantiomeric pair, strong anticancer activity was seen for a particular pair, (1,2)- and (1,2,5)-, which was significantly more active than the benchmark drug cisplatin for human breast cancer cells, MCF-7 (ca. 24-27-fold), and human cervical cancer cells, HeLa (ca.

Synthesis and Structure of SnCl(CHSiMe): Toward Nanoclusters of 4-Coordinate α-Sn.

Orange crystals of a Sn cluster have been isolated in up to 22% yield from a reaction between MeSiCHSnCl, SnCl, and LiAlH. The structure determined by single crystal X-ray diffraction shows three unique Sn atoms in a 6:6:2 ratio, with all Sn atoms 4-coordinate, similar to the tetrahedral bonding in elemental gray Sn. The solid state Sn MAS NMR spectrum shows the three types of distinct Sn atoms in the expected 3:3:1 intensity ratio with respective chemical shifts of 87.

Unprecedented tetranuclear complexes with "weighing balance shaped" topology: single crystal structures, unusual EPR spectra, magnetic properties and antioxidant activity.

Using the 2-hydroxy-N'-[(E)-phenyl(pyridin-2-yl)methylidene]benzohydrazide ligand and dicarboxylate anions (succinate and malonate), two new copper(ii) complexes of formula [Cu(μ-L)(μ-CH(COO))(HO)](NO)·4HO (1) and [Cu(μ-L)(μ-CH-CH(COO))(HO)](NO)] (2) have been synthesized and characterized by single crystal X-ray diffraction. Complexes 1 and 2 contain a dicarboxylate bridged tetranuclear Cu(ii) cationic unit with "weighing balance shaped" topology. These compounds have also been studied by variable temperature magnetic susceptibility measurements, X-band EPR spectroscopy and electrochemistry.

Synthesis and magnetochemistry of heterometallic triangular FeLn (Ln = La, Gd, Tb, Dy, and Ho) and FeY complexes.

A series of FeLn (Ln = La, Gd, Tb, Dy and Ho) and FeY complexes have been synthesized via metal substitution and characterized by single crystal X-ray diffraction. All the molecules are isostructural and have a FeLnO triangular core with the oxygen atom existing as an μ-oxo anion. DC and AC magnetic susceptibility studies were performed on all the molecules.

Responsive nature of 1,2,4,5-tetrakis(2-pyridylthiomethyl)benzene toward group 12 metal nitrates: activity of coordinated nitrate in metal complexes.

This study provides a detailed analysis on the responsive behavior of 1,2,4,5-tetrakis(2-pyridylthiomethyl)benzene (L) toward group 12 metal nitrates in both aqueous and nonaqueous media. The ligand L proved to be an environmentally responsive species, and structural investigations of its complexes with respective M(NO3)2 (M = Zn, Cd, and Hg) allowed one to remark on the inherent activity of the nitrate ion, resulting in a distinctively higher coordination number and dimensionality to the metal cations.

Di-aqua-bis-(nicotinamide-κN (1))bis-(thio-cyanato-κN)nickel(II).

In the title complex, [Ni(NCS)2(C6H6N2O)2(H2O)2], the Ni(II) ion is located on an inversion center and is coordinated in a distorted octa-hedral environment by two N atoms from two nicotinamide ligands and two water mol-ecules in the equatorial plane, and two N atoms from two thio-cyanate anions in the axial positions, all acting as monodentate ligands. In the crystal, weak N-H⋯S hydrogen bonds between the amino groups and the thio-cyanate anions form an R 4 (2)(8) motif. The complex mol-ecules are linked by O-H⋯O, O-H⋯S, and N-H⋯S hydrogen bonds into a three-dimensional supra-molecular structure.

A hexaicosametallic copper(II) phosphonate.

Structure and characterization of [Cu26{2,3,5,6-(Me)4C6H-CH2-PO3}18(μ2-OH)4(μ3-OH)6(μ4-Cl)6(μ-OH2)2(OH2)2(MeCN)4]·6MeCN·15H2O (1) is reported. Complex 1 is the largest discrete molecular homometallic transition metal phosphonate assembly. Remarkably, this gigantic molecular phosphonate has been prepared at room temperature using a normal solution synthetic method.

Enaminones 11. An examination of some ethyl ester enaminone derivatives as anticonvulsant agents.

In this paper, we investigated the previously synthesized anticonvulsant enaminone ethyl ester analogs using the computational gaussian 03 programs. The significant chemical features of the enaminone compounds that lead to positive anticonvulsant activity were identified. From our analyses, we believe that the neutrality of the phenyl ring may be important for binding in the hydrophobic pocket of the active site and that the binding of the phenyl substituent is the main reason why some analogs are active and others are inactive.

Light uncages a copper complex to induce nonapoptotic cell death.

Cu3G is a Cu(II) complex of a photoactive tetradentate ligand that is cleaved upon UV irradiation to release Cu. Here we show that the cytotoxicity of Cu3G increases in response to brief UV stimulation to result in extensive cytoplasmic vacuolization that is indicative of nonapoptotic cell death.

Carbonate-templated self-assembly of an alkylthiolate-bridged cadmium macrocycle.

In the presence of Cd(ClO4)2 and a base, a new mixed N,S-donor alkylthiolate ligand supported both carbonate formation from atmospheric CO2 and the self-assembly of a novel bicapped puckered (CdS)6 molecular wheel. The remarkable stability of the complex was demonstrated by slow intermolecular ligand exchange on the (2)J(HH) and J((111/113)Cd(1)H) time scales at elevated temperature. Both CO2 and the base were required to convert amorphous "CdLClO4" precipitated in the absence of air to the carbonate complex.

Tandem chain extension-Mannich reaction: an approach to β-proline derivatives.

A zinc carbenoid-initiated chain extension reaction provides access to an organometallic intermediate, which can be used to capture activated imines. Deprotection of the nitrogen and reduction provides access to racemic derivatives of β-proline. The relative stereochemistry of the β-proline can be controlled through use of different activating groups on the imine nitrogen.

Synthesis and conformation of fluorinated β-peptidic compounds.

Experimental and theoretical data indicate that, for α-fluoroamides, the F-C-C(O)-N(H) moiety adopts an antiperiplanar conformation. In addition, a gauche conformation is favoured between the vicinal C-F and C-N(CO) bonds in N-β-fluoroethylamides. This study details the synthesis of a series of fluorinated β-peptides (1-8) designed to use these stereoelectronic effects to control the conformation of β-peptide bonds.

Enaminones 12. An explanation of anticonvulsant activity and toxicity per Linus Pauling's clathrate hypothesis.

The x-ray crystal structure of 3-((5-methylisoxazol-3-yl)amino)-5-methylcyclohex-2-enone (12b) and 3-((5-methylisoxazolyl-3-yl)amino)-5,5-dimethylcyclohex-2-enone (12c) were determined and correlated to their anticonvulsant activity in mice and rats. A hypothesis for the toxicity of the analogs are advanced. In addition, a series of 5-methyl-N-(3-oxocyclohex-1-enyl)-isoxazole-3-carboxamides were synthesized and evaluated for anticonvulsant activity.

Bis[methyl 3-(propyl-amino)-but-2-eno-ato]zinc.

The title compound, [Zn(C(8)H(14)NO(2))(2)], represents a zinc complex with the Zn(2+) cation coordinated by two O and two N atoms in a distorted tetrahedral geometry.

Hydrogen-bonding 2D metal-organic solids as highly robust and efficient heterogeneous green catalysts for Biginelli reaction.

Two new Zn(II) and Cd(II) MOFs have been synthesized. These MOFs have been applied as heterogeneous catalysts for the green synthesis of a variety of dihydropyrimidinone derivatives through the Biginelli reaction and the desired products were obtained in high yields with short reaction time under mild solvent- free conditions. Moreover, the MOF catalysts may be readily recovered after the reaction and reused for many cycles.