Crystal structure and Hirshfeld surface analysis of 1,3-bis-{2,2-di-chloro-1-[(E)-phenyl-diazen-yl]ethen-yl}benzene

In the mol-ecule of the title compound, C22H14Cl4N4, the central benzene ring makes dihedral angles of 77.03 (9) and 81.42 (9)° with the two approximately planar 2,2-di-chloro-1-[(E)-phenyl-diazen-yl]vinyl groups. In the crystal, mol-ecules are linked by C-H⋯π, C-Cl⋯π, Cl⋯Cl and Cl⋯H inter-actions, forming a three-dimensional network. The Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H⋯H (30.4%), C⋯H/H⋯C (20.4%), Cl⋯H/H⋯Cl (19.4%), Cl⋯Cl (7.8%) and Cl⋯C/C⋯Cl (7.3%) inter-actions.

Crystal structure and Hirshfeld surface analysis of dimethyl 5-[2-(2,4,6-trioxo-1,3-diazinan-5-yl-idene)hydrazin-1-yl]benzene-1,3-di-carboxyl-ate 0.224-hydrate

In the crystal, the whole mol-ecule of the title compound, C14H12N4O7·0.224H2O, is nearly planar with a maximum deviation from the least-squares plane of 0.352 (1) Å. The mol-ecular conformation is stabilized by an intra-molecular N-H⋯O hydrogen bond, generating an S(6) ring motif. In the crystal, mol-ecules are linked by centrosymmetric pairs of N-H⋯O hydrogen bonds, forming ribbons along the c-axis direction. These ribbons connected by van der Waals contacts, forming sheets parallel to the ac plane. There are also inter-molecular van der Waals contacts and and C-H⋯π inter-actions between the sheets. A Hirshfeld surface analysis indicates that the most prevalent inter-actions are O⋯H/H⋯O (41.2%), H⋯H (19.2%), C⋯H/H⋯C (12.2%) and C⋯O/ O⋯C (8.4%).

Stabilization of an elusive tautomer by metal coordination

The solid-state isolation of the different tautomers of a chemical compound can be a challenging problem. In many cases, tautomers with an energy very close to the most stable one cannot be isolated (elusive tautomers). In this article, with reference to the 4-methyl-7-(pyrazin-2-yl)-2H-[1,2,4]triazolo[3,2-c][1,2,4]triazole ligand, for which the elusive 3H-tautomer has an energy only 1.4 kcal mol-1 greater than the most stable 2H form, we show that metal complexation is a successful and reliable way for stabilizing the elusive tautomer. We have prepared two complexes of the neutral ligand with CuBr2 and ZnBr2, namely, aquabromidobis[4-methyl-7-(pyrazin-2-yl)-3H-[1,2,4]triazolo[3,2-c][1,2,4]triazole]copper(II) bromide trihydrate, [CuBr(C8H7N7)2(H2O)]Br·3H2O, and dibromido[4-methyl-7-(pyrazin-2-yl)-2H-[1,2,4]triazolo[3,2-c][1,2,4]triazole][4-methyl-7-(pyrazin-2-yl)-3H-[1,2,4]triazolo[3,2-c][1,2,4]triazole]zinc(II) monohydrate, [ZnBr2(C8H7N7)2]·H2O. The X-ray analysis shows that, in both cases, the elusive 3H-tautomer is present. The results of the crystallographic analysis of the two complexes reflect the different coordination preferences of CuII and ZnII. The copper(II) complex is homotautomeric as it only contains the elusive 3H-tautomer of the ligand. The complex can be described as octahedral with tetragonal distortion. Two 3H-triazolotriazole ligands are bis-chelated in the equatorial plane, while a water molecule and a bromide ion in elongated axial positions complete the coordination environment. The zinc(II) complex, on the other hand, is heterotautomeric and contains two bromide ions and two monodentate ligand molecules, one in the 2H-tautomeric form and the other in the 3H-tautomeric form, both coordinated to the metal in tetrahedral geometry. The observation of mixed-tautomer complexes is unprecedented for neutral ligands. The analysis of the X-ray molecular structures of the two complexes allows the deduction of possible rules for a rational design of mixed-tautomer complexes.

Oxido- and Dioxido-Vanadium(V) Complexes Supported on Carbon Materials: Reusable Catalysts for the Oxidation of Cyclohexane

Oxidovanadium(V) and dioxidovanadium(V) compounds, [VO(OEt)L] (1) and [Et3NH][VO2L] (2), were synthesized using an aroylhydrazone Schiff base (5-bromo-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H2L). They were characterized by elemental analysis, Fourier-transform infrared spectroscopy (FT-IR), (1H and 51V) nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS) and single crystal X-ray diffraction analyses. Both complexes were immobilized on functionalized carbon nanotubes and activated carbon. The catalytic performances of 1 and 2, homogenous and anchored on the supports, were evaluated for the first time towards the MW-assisted peroxidative oxidation (with tert-butylhydroperoxide, TBHP) of cyclohexane under heterogeneous conditions. The immobilization of 1 and 2 on functionalized carbon materials improved the efficiency of catalytic oxidation and allowed the catalyst recyclability with a well-preserved catalytic activity.

Crystal structure and Hirshfeld surface analysis of 4,5-di-bromo-2-(4-meth-oxy-phen-yl)-2,3,4,4a,5,6,7,7a-octa-hydro-1H-4,6-ep-oxy-1H-cyclo-penta-[c]pyridin-1-one

The mol-ecule of the title compound, C15H15Br2NO3, comprises a fused tricyclic system consisting of two five-membered rings (cyclo-pentane and tetra-hydro-furan) and one six-membered ring (tetra-hydro-pyridinone). Both five-membered rings of the tricyclic system have envelope conformations, and the conformation of the six-membered cycle is inter-mediate between chair and half-chair. In the crystal, the mol-ecules are linked by C-H⋯O hydrogen bonds and C-H⋯π, C-Br⋯π and C⋯O inter-actions into double layers. The layers are connected into a three-dimensional network by van der Waals inter-actions.

(3aS,4R,5R,6S,7aR)-4,5-Di-bromo-2-[4-(tri-fluoro-meth-yl)phen-yl]-2,3,3a,4,5,6,7,7a-octa-hydro-3a,6-ep-oxy-1H-isoindol-1-one: crystal structure and Hirshfeld surface analysis

The asymmetric unit of the title compound, C15H12Br2F3NO2, consists of two crystallographically independent mol-ecules. In both mol-ecules, the pyrrolidine and tetra-hydro-furan rings adopt an envelope conformation. In the crystal, mol-ecule pairs generate centrosymmetric rings with R 2 2(8) motifs linked by C-H⋯O hydrogen bonds. These pairs of mol-ecules form a tetra-meric supra-molecular motif, leading to mol-ecular layers parallel to the (100) plane by C-H⋯π and C-Br⋯π inter-actions. Inter-layer van der Waals and inter-halogen inter-actions stabilize mol-ecular packing. The F atoms of the CF3 groups of both mol-ecules are disordered over two sets of sites with refined site occupancies of 0.60 (3)/0.40 (3) and 0.640 (15)/0.360 (15). The most important contributions to the surface contacts of both mol-ecules are from H⋯H (23.8 and 22.4%), Br⋯H/H⋯Br (18.3 and 12.3%), O⋯H/H⋯O (14.3 and 9.7%) and F⋯H/H⋯F (10.4 and 19.1%) inter-actions, as concluded from a Hirshfeld surface analysis.

Syntheses, crystal structures of two Fe(III) Schiff base complexes with chelating o-vanillin aroylhydrazone and exploration of their bio-relevant activities

Two novel Fe(III) complexes, Fe(HL¹)₂Cl·1.25H₂O (1) and Fe(HL²)₂·Et₃NH·H₂O (2) (H₂L¹ = o-vanillin benzoylhydrazone, H₃L² = o-vanillin salicylhydrazone) are prepared. X-ray single crystal diffraction confirms that the hydrazone ligands can be chelated to iron centre resulting in a six-coordinate octahedral configuration. Both complexes show major intercalation effect to the herring sperm deoxyribonucleic acid (HS-DNA) with high binding constants of 2.01 × 10⁴ M^-1 and 2.24 × 10⁴ M^-1, respectively. Molecular docking studies reveal both complexes can intercalate at the gap of DC5-DG2 and DG6-DC1 base pairs of DNA hexamer (1Z3F). The interaction of the complex 1 with plasmid pBR322 DNA induces distinguishable alterations of the DNA morphology. Further, the structure of plasmid pBR322 DNA treated with complex 1 in the presence of ascorbic acid has been damaged probably due to the reactive oxygen species (ROS) generation. What's more, both complexes show high affinity with bovine serum albumin (BSA), the binding constants measured by fluorescence techniques are 5.75 × 10⁶ M^-1 and 4.39 × 10⁷ M^-1, respectively. Molecular docking demonstrates that the complexes prefer the binding pocket of site III (subdomain IIB) of BSA (PDB ID: 4F5S). Similarly, dynamic light scattering (DLS) reveals that the complexes not only bind to BSA but also induce bigger size aggregates as the concentration increases.

Effective methods for the synthesis of hydrazones, quinazolines, and Schiff bases: reaction monitoring using a chemometric approach

Synthesis of hydrazones (1a-4a and 1b-4b), quinazolines (3c·MeOH and 3d·MeOH), and hydrazone-Schiff bases (4c and 4d) is achieved by combining suitable aldehydes (2,3- or 2,4-dihydroxybenzaldehyde) with four hydrazides (isonicotinic, nicotinic, and 2- or 4-aminobenzoic acid hydrazide). A suite of approaches for their preparation is described: solution-based synthesis, mechanosynthesis, and solid-state melt reactions. The mechanochemical approach is generally a better choice for the quinazolines, while the solid-state melt reaction is more efficient for derivatives of (iso)nicotinic based hydrazones. Crystalline amine-functionalised hydrazones 4a and 4b undergo post-synthetic modifications in reactions with 3- or 4-pyridinecarbaldehyde vapours to form hydrazone-Schiff bases 4a-3py, 4b-3py, 4a-4py, and 4b-4py. Mechanochemical and vapour-mediated reactions are followed by ex situ powder X-ray diffraction and IR-ATR methods, respectively. The chemometric analysis of these data using principal component analysis provided an insight into the reaction profiles and reaction times. Azines (5a and 5b), achieved from aldehydes and hydrazine, reversibly change colour in response to temperature changes. The structures of all products are ascertained by a combined use of spectroscopic and X-ray diffraction methods. The cytotoxic and antimicrobial activities of all compounds against selected human cancer cell lines and bacterial strains are evaluated.

Fe(III) Complexes in Cyclohexane Oxidation: Comparison of Catalytic Activities under Different Energy Stimuli

In this study, the mononuclear Fe(III) complex [Fe(HL)(NO3)(H2O)2]NO3 (1) derived from Nʹ-acetylpyrazine-2-carbohydrazide (H2L) was synthesized and characterized by several physicochemical methods, e.g., elemental analysis, infrared (IR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and single crystal X-ray diffraction analysis. The catalytic performances of 1 and the previously reported complexes [Fe(HL)Cl2] (2) and [Fe(HL)Cl(μ-OMe)]2 (3) towards the peroxidative oxidation of cyclohexane under three different energy stimuli (microwave irradiation, ultrasound, and conventional heating) were compared. 1-3 displayed homogeneous catalytic activity, leading to the formation of cyclohexanol and cyclohexanone as final products, with a high selectivity for the alcohol (up to 95%). Complex 1 exhibited the highest catalytic activity, with a total product yield of 38% (cyclohexanol + cyclohexanone) under optimized microwave-assisted conditions.

Iron Complexes of an Antiproliferative Aroyl Hydrazone: Characterization of Three Protonation States by Electron Paramagnetic Resonance Methods

Tridentate aroyl hydrazones are effective metal chelators in biological settings, and their activity has been investigated extensively for medicinal applications in metal overload, cancer, and neurodegenerative diseases. The aroyl hydrazone motif is found in the recently reported prochelator (AH1-S)2, which has shown antiproliferative proapoptotic activity in mammalian cancer cell lines. Intracellular reduction of this disulfide prochelator leads to the formation of mercaptobenzaldehyde benzoylhydrazone chelator AH1 and to iron sequestration, which in turn impacts cell growth. Herein, we investigate the iron coordination chemistry of AH1 to determine the structural and spectroscopic properties of the iron complexes in the solid state and in solution. A neutral iron(III) complex of 2:1 ligand-to-metal stoichiometry was isolated and characterized fully to reveal two different binding modes for the tridentate AH1 ligand. Specifically, one ligand binds in the monoanionic keto form, whereas the other ligand coordinates as a dianionic enolate. Continuous-wave electron paramagnetic resonance experiments in frozen solutions indicated that this neutral complex is one of three low-spin iron(III) complexes observed depending on the pH of the solution. Electron spin echo envelope modulation (ESEEM) experiments allowed assignment of the three species to different protonation states of the coordinated ligands. Our ESEEM analysis provides a method to distinguish the coordination of aroyl hydrazones in the keto and enolate forms, which influences both the ligand field and overall charge of the complex. As such, this type of analysis could provide valuable information in a variety of studies of iron complexes of aroyl hydrazones, ranging from the investigation of spin-crossover behavior to tracking of their distribution in biological samples.

Aroylhydrazone Schiff Base Derived Cu(II) and V(V) Complexes: Efficient Catalysts towards Neat Microwave-Assisted Oxidation of Alcohols

A new hexa-nuclear Cu(II) complex [Cu3(μ2-1κNO2,2κNO2-L)(μ-Cl)2(Cl)(MeOH)(DMF)2]2 (1), where H4L = N'1,N'2-bis(2-hydroxybenzylidene)oxalohydrazide, was synthesized and fully characterized by IR spectroscopy, ESI-MS, elemental analysis, and single crystal X-ray diffraction. Complex 1 and the dinuclear oxidovanadium(V) one [{VO(OEt)(EtOH)}2(1κNO2,2κNO2-L)]·2H2O (2) were used as catalyst precursors for the neat oxidation of primary (cinnamyl alcohol) and secondary (1-phenyl ethanol, benzhydrol) benzyl alcohols and of the secondary aliphatic alcohol cyclohexanol, under microwave irradiation using tert-butyl hydroperoxide (TBHP) as oxidant. Oxidations proceed via radical mechanisms. The copper(II) compound 1 exhibited higher catalytic activity than the vanadium(V) complex 2 for all the tested alcohol substrates. The highest conversion was found for 1-phenylethanol, yielding 95.3% of acetophenone in the presence of 1 and in solvent and promoter-free conditions. This new Cu(II) complex was found to exhibit higher activity under milder reaction conditions than the reported aroylhydrazone Cu(II) analogues.

1D Copper(II)-Aroylhydrazone Coordination Polymers: Magnetic Properties and Microwave Assisted Oxidation of a Secondary Alcohol

The 1D Cu(II) coordination polymers [Cu₃(L¹)(NO₃)₄(H₂O)₂]_n (1) and [Cu₂(H₂L²)(NO₃)(H₂O)₂]_n(NO₃)_n (2) have been synthesized using the aroylhyrazone Schiff bases N'¹,N'²-bis(pyridin-2-ylmethylene)oxalohydrazide (H₂L¹) and N'¹,N'³-bis(2-hydroxybenzylidene)malonohydrazide (H₄L²), respectively. They have been characterized by elemental analysis, infrared (IR) spectroscopy, UV-Vis spectroscopy, electrospray ionization mass spectrometry (ESI-MS), single crystal X-ray diffraction and variable temperature magnetic susceptibility measurements (for 2). The ligand (L¹)²⁻ coordinates in the iminol form in 1, whereas the amide coordination is observed for (H₂L²)²⁻ in 2. Either the ligand bridge or the nitrate bridge in 2 mediates weak antiferromagnetic coupling. The catalytic performance of 1 and 2 has been investigated toward the solvent-free microwave-assisted oxidation of a secondary alcohol (1-phenylethanol used as model substrate). At 120°C and in the presence of the nitroxyl radical 2,2,6,6-tetramethylpiperydil-1-oxyl (TEMPO), the complete conversion of 1-phenylethanol into acetophenone occurs with TOFs up to 1,200 h⁻¹.

Ferraria A, M. Botelho do Rego A, Correia LMM, Saraiva MS, Pombeiro AJL. Ultrasound and Radiation-Induced Catalytic Oxidation of 1-Phenylethanol to Acetophenone with Iron-Containing Particulate Catalysts

Iron-containing particulate catalysts of 0.1–1 µm size were prepared by wet and ball-milling procedures from common salts and characterized by FTIR, TGA, UV-Vis, PXRD, FEG-SEM, and XPS analyses. It was found that when the wet method was used, semi-spherical magnetic nanoparticles were formed, whereas the mechanochemical method resulted in the formation of nonmagnetic microscale needles and rectangles. Catalytic activity of the prepared materials in the oxidation of 1-phenylethanol to acetophenone was assessed under conventional heating, microwave (MW) irradiation, ultrasound (US), and oscillating magnetic field of high frequency (induction heating). In general, the catalysts obtained by wet methods exhibit lower activities, whereas the materials prepared by ball milling afford better acetophenone yields (up to 83%). A significant increase in yield (up to 4 times) was observed under the induction heating if compared to conventional heating. The study demonstrated that MW, US irradiations, and induction heating may have great potential as alternative ways to activate the catalytic system for alcohol oxidation. The possibility of the synthesized material to be magnetically recoverable has been also verified.

Cd(ii) coordination compounds as heterogeneous catalysts for microwave-assisted peroxidative oxidation of toluene and 1-phenylethanol

Cd(ii) compounds as catalysts towards microwave assisted peroxidative oxidation (with tert-butylhydroperoxide, TBHP) of toluene and 1-phenylethanol under heterogeneous conditions are explored.

Cu(II) and Fe(III) Complexes Derived from N-Acetylpyrazine-2-Carbohydrazide as Efficient Catalysts Towards Neat Microwave Assisted Oxidation of Alcohols

The mononuclear Cu(II) complex [Cu((kNN′O-HL)(H2O)2] (1) was synthesized using N-acetylpyrazine-2-carbohydrazide (H2L) and characterized by elemental analysis, IR spectroscopy, ESI-MS and single crystal X-ray crystallography. Two Fe(III) complexes derived from the same ligand viz, mononuclear [Fe((kNN′O-HL)Cl2] (2) and the binuclear [Fe(kNN′O-HL)Cl(μ-OMe)]2 (3) (synthesized as reported earlier), were also used in this study. The catalytic activity of these three complexes (1–3) was examined towards the oxidation of alcohols using tert-butyl hydroperoxide (TBHP) as oxidising agent under solvent-free microwave irradiation conditions. Primary and secondary benzyl alcohols (benzyl alcohol and 1-phenylethanol), and secondary aliphatic alcohols (cyclohexanol) were used as model substrates for this study. A comparison of their catalytic efficiency was performed. Complex 1 exhibited the highest activity in the presence of TEMPO as promoter for the oxidation of 1-phenylethanol with a maximum yield of 91.3% of acetophenone.

Ni(II)-Aroylhydrazone Complexes as Catalyst Precursors Towards Efficient Solvent-Free Nitroaldol Condensation Reaction

The aroylhydrazone Schiff bases 2-hydroxy-(2-hydroxybenzylidene)benzohydrazide and (2,3-dihydroxybenzylidene)-2-hydroxybenzohydrazide have been used to synthesize the bi- and tri-nuclear Ni(II) complexes [Ni2(L1)2(MeOH)4] (1) and [Ni3(HL2)2(CH3OH)8]· (NO3)2 (2). Both complexes have been characterized by elemental analysis, spectroscopic techniques [IR spectroscopy and electrospray ionization-mass spectrometry (ESI-MS)], and single-crystal X-ray crystallography. The coordination behavior of the two ligands is different in the complexes: The ligand exhibits the keto form in 2, while coordination through enol form was found in 1. Herein, the catalytic activity of 1 and 2 has been compared with the nitroaldol condensation reaction under various conditions. Complex 2 exhibits the highest activity towards solvent-free conditions.

Synthesis and Structure of Copper Complexes of a N6O4 Macrocyclic Ligand and Catalytic Application in Alcohol Oxidation

Reactions between N6O4 macrocyclic 1,4,19,22,25,40-hexaaza-10,13,31,34-tetraoxa-6,14,27,35(1,4)-tetrabenzenacyclopentacontane (L) and several copper salts (viz. trifuoromethane and toluene sulfonates, nitrate, perchlorate, benzoate, and acetate) led to the formation of dinuclear compounds [Cu2(OSO2CF3)2(DMF)2L](SO3CF3)2 (1), [Cu2(p-OSO2C6H4Me)2L(DMF)2](SO3C6H4Me)2 (2), [Cu2(ONO2)2L(DMF)2](NO3)2 (3), [Cu2(OClO3)2(DMF)2L](ClO4)2 (4), [Cu2(OOCPh)2L(H2O)2](O2CPh)2 (5), and [Cu2(OOCMe)4L] (6), which were characterized by IR, elemental analysis and TG-DTA (thermogravimetric-differential thermal analysis), as well as by single-crystal X-ray diffraction, EPR (electron paramagnetic resonance) spectroscopy, and electrochemical techniques (cyclic voltammetry and controlled potential electrolysis). The molecular structures of compounds 1–6 reveal a considerable conformational flexibility of the ligand L, which allowed its readjustment for the formation of the metal compounds and confirmed the presence of dinuclear endo macrocyclic species. In every case, the L ligand coordinates to each copper cation via three nitrogen atoms, with the remaining coordination positions of the metal square pyramid environment being accomplished by neutral or anionic ligands. The macrocyclic cavities appear to be adequate for the enclosure of a neutral species as proved by compound 6 with 1,4-dioxane. The compounds, in combination with the TEMPO (2,2,6,6-tetramethyl-piperidinyloxyl) radical and in alkaline aqueous solution, act as efficient catalysts in the aerobic oxidation of different alcohols to the corresponding aldehydes (yields up to 99% and TON up 232) after 20 h at 70 °C. In addition, the microwave-assisted solvent-free peroxidative oxidation (by tert-butylhydroperoxide, TBHP) of 1-phenylethanol led to acetophenone yields up to 99% and TOF of 1.1 × 103 after 0.5 h, without any additive.

Vanadium complexes of different nuclearities in the catalytic oxidation of cyclohexane and cyclohexanol – an experimental and theoretical investigation

Catalytic activities of oxidovanadium(v) complexes towards microwave-assisted peroxidative oxidation of cyclohexane and cyclohexanol are explored by experimental and DFT calculations.

Peroxidative Oxidation of Alkanes and Alcohols under Mild Conditions by Di- and Tetranuclear Copper (II) Complexes of Bis (2-Hydroxybenzylidene) Isophthalohydrazide

Bis(2-hydroxybenzylidene)isophthalohydrazide (H₄L) has been used to synthesize the dinuclear [Cu₂(1κNO²:2κN′O′²-H₂L)(NO₃)₂(H₂O)₂] (1) and the tetranuclear [Cu₄(μ-1κNO²:2κN′O²-H₂L)₂(μ-NO₃)₂(H₂O)₄]·2C₂H₅OH (2) complexes. The solvent plays an important role in determining the ligand behaviour in the syntheses of the complexes. An ethanol-acetonitrile mixture of solvents favours partials enolization in the case of 2. Both complexes have been characterized by elemental analysis, infrared radiation (IR), single crystal X-ray crystallography and electrochemical methods. The variable temperature magnetic susceptibility measurements of 2 show strong antiferromagnetic coupling between the central nitrato-bridged Cu (II) ions. The catalytic activity of both 1 and 2 has been screened toward the solvent-free microwave-assisted oxidation of alcohols and the peroxidative oxidation of alkanes under mild conditions. Complex 1 exhibits the highest activity for both oxidation reactions, leading selectively to a maximum product yield of 99% (for the 1-phenylethanol oxidation after 1 h without any additive) and 13% (for the cyclohexane oxidation to cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone after 3 h).

Enantiomeric Resolution of Asymmetric-Carbon-Free Binuclear Double-Stranded Cobalt(III) Helicates and Their Application as Catalysts in Asymmetric Reactions

A series of double-stranded binuclear helicates [Co₂(H1)₂]⁴⁺, [Co₂(H2)₂]⁴⁺, and [Co₂(H3)₂]⁴⁺, derived from monodeprotonated bis-pyridyl hydrazine-based ligands of H₂1, H₂2, and H₂3 with one, two, and three -CH₂ spacers, were obtained. These asymmetric-carbon-free racemic helicates were separated into their ΔΔ and ΛΛ enantiomers. The resolved helicates were examined for the first time as enantioselective catalysts in asymmetric benzoylation and nitroaldol reactions.

The crystal structure of 4-tert-butyl-N′-[(E)-(4-fluoro-3-methoxyphenyl)methylidene]benzohydrazide, C19H21F1N2O2

C19H21F1N2O2, monoclinic,Cc(no. 9),a= 14.337(3) Å,b= 15.549(3) Å,c= 8.0212(16) Å,β= 103.33(3)°,V= 1740.0(6) Å3,Z= 4,Rgt(F) = 0.0796,wRref(F2) = 0.2192, T = 170 K.

Selective Oxidation of Lignin Model Compounds

Lignin, the planet's most abundant renewable source of aromatic compounds, is difficult to degrade efficiently to welldefined aromatics. We developed a microwave-assisted catalytic Swern oxidation system using an easily prepared catalyst, MoO₂ Cl₂ (DMSO)₂ , and DMSO as the solvent and oxidant. It demonstrated high efficiency in transforming lignin model compounds containing the units and functional groups found in native lignins. The aromatic ring substituents strongly influenced the selectivity of β-ether phenolic dimer cleavage to generate sinapaldehyde and coniferaldehyde, monomers not usually produced by oxidative methods. Time-course studies on two key intermediates provided insight into the reaction pathway. Owing to the broad scope of this oxidation system and the insight gleaned with regard to its mechanism, this strategy could be adapted and applied in a general sense to the production of useful aromatic chemicals from phenolics and lignin.

Novel chelators based on adamantane-derived semicarbazones and hydrazones that target multiple hallmarks of Alzheimer's disease

Novel adamantane-derived semicarbazones and hydrazones show multi-functional activity as potential therapeutics for Alzheimer's disease.

Aroylhydrazone Cu(II) Complexes in keto Form: Structural Characterization and Catalytic Activity towards Cyclohexane Oxidation

The reaction of the Schiff base (3,5-di-tert-butyl-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H3L) with a copper(II) salt of a base of a strong acid, i.e., nitrate, chloride or sulphate, yielded the mononuclear complexes [Cu(H2L)(NO3)(H2O)] (1), [Cu(H2L)Cl]·2MeOH (2) and the binuclear complex [{Cu(H2L)}2(µ-SO4)]·2MeOH (3), respectively, with H2L(-) in the keto form. Compounds 1-3 were characterized by elemental analysis, Infrared (IR) spectroscopy, Electrospray Ionisation Mass Spectrometry (ESI-MS) and single crystal X-ray crystallography. All compounds act as efficient catalysts towards the peroxidative oxidation of cyclohexane to cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone, under mild conditions. In the presence of an acid promoter, overall yields (based on the alkane) up to 25% and a turnover number (TON) of 250 (TOF of 42 h(-1)) after 6 h, were achieved.

Mononuclear copper(ii) complexes of an arylhydrazone of 1H-indene-1,3(2H)-dione as catalysts for the oxidation of 1-phenylethanol in ionic liquid medium

Cu^II complexes of an arylhydrazone of 1H-indene-1,3(2H)-dione act as homogeneous catalysts for the microwave-assisted peroxidative oxidation of alcohols in ionic liquid medium.