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Molybdenum coordination complexes are widely applied due to their biological and pharmacological potential, as well as their performance in different catalytic processes. Parent dioxidomolybdenum Schiff base complexes were prepared via the reaction of [MoO2(acac)2] with a hydrazone Schiff-base tetradentate ligand. A new hydrazone-Schiff base (H2L1 and 2) and its corresponding mononuclear and polynuclear dioxidomolybdenum(VI) complex were synthesized and characterized by spectroscopic methods and elemental analyses, and their thermal behavior was investigated by thermogravimetry. The crystal and molecular structures of H2L2 ligands and the complexes [MoO2(L1)(H2O)], [MoO2(L2)(H2O)], [MoO2(L1)(MeOH)]∙MeOH, [MoO2(L1)(EtOH)]∙EtOH, [MoO2(L1)(2-PrOH)]∙2-PrOH, and [MoO2(L1)]n were determined by single-crystal X-ray diffraction. Using the in situ impedance spectroscopy method (IS), the structural transformations of chosen complexes were followed, and their electrical properties were examined in a wide range of temperatures and frequencies.

In this study, the nature of the electrical transport and structural changes resulting from the systematic substitution of Al2O3 with K2O in 40P2O5-(25−x)Al2O3-35Na2O-xK2O, where x = 5.0, 7.5, 10.0, 12.5, and 15.0 mol% (PANxK), is investigated. The impact of the changes in glass structure and its correlation to electrical properties is presented. The mixed alkali effect (MAE) is observed due to the presence of two different alkali oxides, resulting in a non-monotonic trend in the studied glass properties. The infrared spectra show the shift and diminishing of the bands related to the P–O–P/P–O–Al bridges with increasing K2O content and changes in bands related to depolymerization of the glass network, which is confirmed by the trend of the Tg values. The minimum value of DC conductivity is obtained for glass with x = 12.5 mol%. With the overall increase in alkali content, the number of non-bridging oxygens increases, also affecting the conductivity values. Frequency-dependent conductivity spectra analyzed by Summerfield, Baranovskii-Cordes and Sidebottom scaling procedures revealed interesting features and signature of the MAE in the short-range dynamics of the potassium and sodium ions, both for individual glass composition and glass series as a whole. This study showed the impact of MAE and local glass structure on the electrical features and the prevailing of one effect over the other as a function of the glass composition. MAE dominates in a wider range, but with the significant increase in alkali content, MAE is consequently overpowered.

Zinc selenium phosphate glasses added with the traces of Au2O3 were prepared and heat-treated. XRD, TEM, DSC, FT-IR and optical absorption (OA) spectroscopy methods were used for the structural assessment of these samples. Later, diferent dielectric parameters viz., dielectric constant (ε′), electric moduli (M), impedance (Z) and a.c. conductivity (σac) were measured over wide regions of frequency (ω) and temperature (T) as functions of Au2O3 concentration. Dielectric breakdown strength (DBS) of these samples was also measured at ambient conditions. The characterization studies indicated that multiple crystal grains were entrenched in the residual amorphous phase of the samples. The X-ray difraction studies revealed that the bulk glasses consisted of Au2(SeO3)3 crystal phase and Au0 metallic particles (MPs). As Au2O3 content was raised, the intensity of the XRD peak related to Au3+ crystal phase indicated a growing trend, whereas that of Au0 MPs showed a decreasing trend. The results of XPS studies revealed similar inferences. The FT-IR results pointed out an improved degree of augmentation of the glass network as the content of Au2O3 was increased. Optical absorption (OA) - spectra of the glasses indicated a broad absorption band in the spectral range of 500–600 nm due to the surface plasmon resonance (SPR) of Au0 MPs. The intensity of the band was observed to decrease as Au2O3 content was increased and indicated decreasing propor- tion of Au0 metallic particles in the samples. The dielectric parameters exhibited a decreasing trend, whereas the dielectric breakdown strength (DBS) and electrical impedance indicated a substantial hike due to the increasing concentration of Au2O3. Overall, the presence of Au2O3 caused a signifcant improvement in the insulating strength of the ZnO added SeO2- P2O5 glasses and hence such glasses may be considered as insulating layers in the display panel devices.

International audience; This contribution describes the synthesis, characterization, and catalytic implementation of the highly constrained molybdenum(VI) polymers [MoO2(LR)]n (with R = H (1), 3OMe (2), and 4OMe (3)) and cyclic tetramer [MoO2(L4OMe)]4·0.5MeCN (3′·0.5MeCN) with nicotinoyl hydrazonato ligands (LR) derived from salicylaldehyde (LH), 3-methoxy-2-hydroxybenaldehyde (L3OMe), or 4-methoxy-2-hydroxybenzaldehyde (L4OMe). In order to determine the most stable geometries, conformational analysis of the free and coordinated ligands in these assemblies was carried out through the potential energy surface scans using quantum-chemical methods. The mononuclear analogues [MoO2(HLR)(MeOH)]Cl (R = H (1a) and 3OMe (2a)), [MoO2(HLR)Cl] (R = 3OMe (2b) and 4OMe (3b)), and [MoO2(LR)(MeOH)] (R = H (1c), and 4OMe (3c-α and 3c-β)) were also synthesized and evaluated as potential precursors for reactions in the solid state. Vapor induced transformation of 2a quantitatively afforded complex 2b. The chemometric analysis using principal component analysis was applied to provide insight into the reaction profile. Thermally induced solid-state reactions resulted in the transformation of metallocycle 3′·0.5MeCN and monomeric complexes 1c, 2a, 3c-α, and 3c-β into the corresponding coordination polymers. The structural features responsible for these conversions are discussed in detail. Lastly, the metallosupramolecular architectures were tested as catalysts for cyclooctene epoxidation by using tert-butyl hydroperoxide as an oxidant in water or decane. Compound 3′ is shown to be the most effective and selective catalyst.

Molybdenum(VI) catalysts were obtained from methanol or acetonitrile by the reaction of [MoO2(C5H7O2)2] and isonicotinoyl- or nicotinoyl-based aroylhydrazones. Reactions in methanol resulted in the formation of the mononuclear complexes [MoO2(L1–4)(MeOH)] (1a–4a), while the ones in acetonitrile provided polynuclear complexes [MoO2(L1–4)]n (1–4). Crystals of polynuclear compound, [MoO2(L3)]n∙H2O (3∙H2O), suitable for X-ray diffraction analysis were obtained by the solvothermal procedure at 110 °C. Complexes were characterized by infrared spectroscopy (IR-ATR), nuclear magnetic resonance (NMR), elemental analysis (EA), and thermogravimetric analysis (TGA). The prepared catalysts were tested in alcohol oxidation reactions. Carveol, cyclohexanol, and butan-2-ol were investigated substrates. Because the alcohol oxidations are very challenging due to various possible pathways, the idea was to test different oxidants, H2O2, TBHP in water and decane, to optimize the researched catalytic system.

Glasses of the composition (40-x)Li2O-10Pb3O4-50SiO2 doped with different contents of Ag2O were fabricated and were subsequently subjected to heat-treatment. The quantitative analysis of the results of different characterization techniques indicated increasing magnitude of internal connectivity of the glass network with increasing Ag2O content. Several dielectric parameters viz., ε′, M, Z and σacin the frequency (ω) region 0.01 Hz – 1 MHz and in the region of temperature (T) 30 –250 °C of these glasses were measured as functions of Ag2O content. ε′ showed a decreasing tendency with Ag2O content which may be attributed to the decrease in the space charge polarization (scp) due to the increasing order of augmentation of glass network. Such a decrease of scp was attributed to the growing presence of PbO4 units and also Ag0 particles in these samples. The plots of electric modulus vs ω and T indicated relaxation character. Such relaxation phenomena were discussed in detail with the help of Cole-Cole diagrams. Probable dipoles responsible for such effects were recognized and analyzed. σac (conductivity) exhibited a decreasing trend with Ag2O content. The mechanism of conduction was analyzed using polaronic tunneling effect in the intermediate ω and high T ranges, whereas in the low T range it is predicted to follow QMT model. These conclusions were observed to follow the results of various spectroscopic studies. In conclusion, presence of red lead seemed to be an obstruction for the conductivity in the fast ion conducting glasses.

Molybdenum compounds containing benzaldehyde-based hydrazones were obtained. The reaction in MeOH resulted with monomeric Mo complexes, [MoO2(L)(MeOH)], while the reaction in dichloromethane (DCM) provided oligomeric complexes, [MoO2(L)]n. The solid-state structures of the obtained compounds were investigated through Infrared Spectroscopy - Attenuated Total Reflection (IR-ATR), Thermogravimetric analysis (TGA), and via X-ray diffraction. The prepared molybdenum species were employed as cyclooctene epoxidation catalysts. TBHP (tert-butylhydroperoxide) in water and TBHP in decane were employed and compared as oxidants, with 0.25 mol% [Mo]. The catalyst activity and selectivity towards epoxide is &gt, 90% for all the reactions. The results have been linked to theoretical calculations, showing the importance of the first step, i.e., the transformation of [MoO2(L)(MeOH)] into the pentacoordinate [MoO2(L)].

International audience; Self-assembled tetranuclear molybdenum(vi) complexes with hydrazonato ligands, [MoO2L]4, were tested as (pre)catalysts for cyclooctene and cyclohexene epoxidation without extra organic solvent added. Special attention was addressed to the comparison of oxidizing agents, TBHP in water vs. TBHP in decane. The idea was to test the greenness of the complete process. Density Functional Theory calculations were used to support and explain experimental catalytic result for tetranuclear self-assembled systems.

Ageing a mixture of sodium molybdate, malonic acid, and tris(ethylenediamine)cobalt(III) chloride using different synthetic routes, namely, solution-based methods at room temperature or 110 °C, and a mechanochemically accelerated vapour-assisted method, yielded the polyoxomolybdate [Co(en)3]5Na[Mo7O24(μ-Mo8O26)Mo7O24]·nH2O (1). The new polyoxomolybdate anion 1 comprised three fragments, namely, two {Mo7O24} units bridged by a {Mo8O26} unit, which were interconnected by the terminal oxygen atoms of MoO6 octahedra and represent a unique structural motif not yet described in the structurally versatile chemistry of polyoxomolybdates (POMos). The ageing reaction was found to occur via a series of intermediates, two of which were isolated and identified as the heptamolybdate coordination polymer [Co(en)3]2[NaMo7O24]Cl·nH2O (2), comprising {Mo7O24} units bridged by a sodium atom, and the heptamolybdate (H3O)[Co(en)3]2[Mo7O24]Cl·9H2O (3). An identical reaction procedure with [Co(C2O4)(en)2]+ instead of [Co(en)3]3+ yielded the orthomolybdate [Co(C2O4)(en)2]2[MoO4]·9H2O (4) and the hydrogen malonate [Co(C2O4)(en)2]C3O4H3 (5). The new polyoxomolybdate [Co(en)3]5Na[Mo7O24(μ-Mo8O26)Mo7O24]·nH2O was also examined as a catalyst for the epoxidation of cyclooctene, and was superior to both heptamolybdate and octamolybdate catalysts over 24 h. The heptamolybdate [Co(NH3)6]2[Mo7O24]·8H2O (6) was isolated as the only reaction product of sodium molybdate and hexaamminecobalt(III) nitrate in the presence of malonic acid using solution-based methods.

Molybdenum(VI) complexes of different nuclearity, mononuclear, [MoO2(L1 or 2) (MeOH)]MeOH (1MeOH and 2MeOH), [MoO2(L1 or 2)(D)] [D = pyridine, (1a and 2a), 3-methylpyridine, (1b and 2b) and 4-methylpyridine, (1c and 2c)], binuclear [{; ; ; ; MoO2(L1 or 2)}; ; ; ; 2(D)] (D = 4, 4'-bipyridine (1d, 1d' and 2d), and polynuclear complexes [MoO2(L1 or 2)]n (3 and 4) were synthesized by solution based reactions of enaminones (H2L1 = 3-(2-hydroxy-4- methylphenylamino)-1-phenylbut-2-en-1-one ; H2L2 = 3-(2- hydroxy-5-methylphenylamino)-1-phenylbut-2-en- 1-one) with the dioxobis(acetylacetonato)molybdenum( VI) complex, [MoO2(acac)2]. Reactions of the mononuclear complexes 1MeOH and 2MeOH with pyridine and its derivatives resulted in corresponding mononuclear [MoO2(L1 or 2)(D)] or binuclear [{; ; ; ; MoO2(L1 or 2)}; ; ; ; 2(D)] complexes. In case of [{; ; ; ; MoO2(L1)}; ; ; ; 2(4, 4-bpy)] two polymorphic forms are obtained (1d and 1d'). The cross-linked transformations of [MoO2(L1 or 2)(D)] complexes in solution or when exposed to vapors of N-heterocyclic bases have been explored. Crystal and molecular structures of ten complexes (1MeOH, 2MeOH, 1a–d, 1d' , 2b–d) were determined by the single-crystal X-ray diffraction analysis. Enaminone ligands and their molybdenum complexes were characterized by elemental and TG analysis, IR and NMR spectroscopy and screened for their in vitro cytotoxic and antibacterial activities. None of the tested compounds showed cytotoxic ability against THP-1 and HepG2 cell lines. Compounds 1MeOH, 1b, 2MeOH, 2a and 3, exhibited weak antibacterial activity on Moraxella catarrhalis strain while other complexes did not show antibacterial properties towards Staphylococcus aureus, Enterococcus faecalis and Escherichia coli bacteria.

As chemists, we are still fascinated by the magic of nature [...]

Synthesis of hydrazones was performed via both conventional and solvent-free routes using the corresponding hydrazide (isonicotinic hydrazide, nicotinic hydrazide, 2- aminobenzhydrazide or 4- aminobenzhydrazide) and appropriate aldehyde (salicylaldehyde, 3- methoxysalicylaldehyde or 4- methoxysalicylaldehyde). A systematic study dedicated to solvatomorphism or polymorphism screening resulted in the formation of twelve novel crystalline forms, and eight of these were characterized via the single crystal X-ray diffraction method. In all studied structures, the molecules were assembled into endless supramolecular chains, discrete rings, chains of rings or nets. The mechanochemical synthesis employing liquid-assisted grinding was also applied and the nicotinic- and isonicotinic- based hydrazones were found to form readily from their corresponding precursors. The chemometric study using principal component analysis for mechanochemical synthesis monitoring was implemented for the first time to provide an insight into the reaction profiles. A thoughtful combination of ex situ powder X-ray diffraction and chemometric analysis was essential to identify a stepwise mechanism for the hydrazone formation via an intermediate phase. In five investigated reactions the first principal component accounted for at least 75% of the total variance, whereas in the case of two reactions this component accounted for 69.72 and 46.23% of the total variance. The hydrazones were also evaluated for cytotoxic activity in vitro. All compounds exhibited weak to moderate cytotoxicity against THP-1 and no cytotoxicity against HepG2 cells. Substantial antibacterial activity was obtained against Moraxella catarrhalis while no growth inhibition of Staphylococcus aureus, Enterococcus faecalis and Escherichia coli was observed.

International audience; Symmetrical disubstituted carbohydrazides (H4L1–6) when reacted with [MoO2(acac)2] (in 1 : 2 molar ratio) afford the corresponding discrete complexes, [(MoO2)2L1,5,6(MeOH)2], [(MoO2)2L1,5,6(Im)2] (Im = imidazole), and/or polymeric ensembles, [(MoO2)2L1–6]n, depending on the reaction solvent, the ligand framework and the presence of ancillary coordinating species. In these assemblies, asymmetrical dimolybdenum(vi) entities, [(MoO2)2L1–6], wherein the corresponding carbohydrazide acts as an adaptable two-compartment ligand offering ONO and ONN coordination environments, serve as the main building blocks. The solid-state structures of the obtained materials were elucidated via X-ray diffraction and infrared spectroscopy, whereas the behaviour of polymeric ensembles in DMSO-d6 solution was investigated by nuclear magnetic resonance. Thermal studies revealed that the discrete species transform to the corresponding polymeric ensembles upon heating, whereas upon grinding they either remain intact or afford their reactive and coordinatively unsaturated (pentacoordinated) counterparts. While the discrete methanol-based complexes have a comparable spatial arrangement of ancillary ligands, imidazole-based ones offer substantially different scenario which was addressed in detail via density functional theory calculations. Finally, the polymeric ensembles were shown to be efficient catalysts for cyclooctene epoxidation under eco-friendly conditions while employing aqueous tert-butyl hydroperoxide as an oxidant.

Unsymmetrically substituted carbohydrazides, containing chelating o-hydroxyaryl and non- chelating pyridyl subunits were synthesized via two-step functionalization of carbohydrazide. Anion binding and coordinative propensities of the compounds were tested in reactions with appropriate Mo(VI) species. Such procedures yielded four types of products: monomeric dioxomolybdenum(VI) complexes, dimeric and oligomeric/polymeric dioxomolybdenum(VI)- containing ensembles, hybrid hexamolybdate systems where the protonated ligand acts as cation and the hybrid hexamolybdate salts where the cation is the protonated form of the monomeric dioxomolybdenum(VI) complex. The solid-state structures of the compounds were elucidated by X-ray diffraction and infrared spectroscopy, while their thermal stability was inspected via thermogravimetric analysis and differential scanning calorimetry experiments. The behaviour of the ligands, monomeric, dimeric, and oligomeric/polymeric ensembles in DMSO solution was investigated by nuclear magnetic resonance. In the isolated materials, carbohydrazide ligands adopt altogether four distinctive protonation forms: neutral, monoprotonated in the corresponding hexamolybdate salt, doubly deprotonated while forming {; ; ; ; MoO2}; ; ; ; 2+ complexes, and neutral zwitterionic when shaping the hybrid salt. In all these structures the unsymmetrical carbohydrazide framework retains robust conformation and geometry.

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- ihydroxybenzaldehyde) 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 4b4py. 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.

Ageing a mixture of sodium molybdate, malonic acid, and tris(ethylenediamine)cobalt(iii) chloride using different synthetic routes, namely, solution-based methods at room temperature or 110 °C, and a mechanochemically accelerated vapour-assisted method, yielded the polyoxomolybdate [Co(en)

Adipic acid (AA) was obtained by catalyzed oxidation of cyclohexene, epoxycyclohexane, or cyclohexanediol under organic solvent-free conditions using aqueous hydrogen peroxide (30%) as an oxidizing agent and molybdenum- or tungsten-based Keggin polyoxometalates (POMs) surrounded by organic cations or ionically supported on functionalized Merrifield resins. Operating under these environmentally friendly, greener conditions and with low catalyst loading (0.025% for the molecular salts and 0.001&ndash, 0.007% for the supported POMs), AA could be produced in interesting yields.

International audience; Cyclic dinuclear molybdenum(vi) complexes [MoO2(L1–3)]2 (1, 2-α, 2-β and 3) were synthesized through the use of coordination-driven self-assembly of a MoO22+ core and 4-aminobenzoylhydrazone ligands (salicylaldehyde (H2L1), 3-methoxysalicylaldehyde (H2L2) or 4-methoxysalicylaldehyde 4-aminobenzoylhydrazone (H2L3)). Their X-ray diffraction (XRD) analysis revealed that these types of ligands could serve as organic linkers for cis-octahedral complexes containing a MoO22+ core. Mononuclear complexes [MoO2(L1–3)(MeOH)] (1a–3a) and [MoO2(L1–3)(EtOH)] (1b, 2b-α, 2b-β and 3b) were also obtained. In the presence of strong donors, such as dmf, ligand substitution occurred and the structures of 1–3 changed into [MoO2(L1)(dmf)] (1c), [MoO2(L2)(dmf)] (2c) and [MoO2(L3)(H2O)]·dmf (3c·dmf), respectively. The dioxidomolybdenum(vi) complexes were tested for catalytic epoxidation of cyclooctene under eco-friendly reaction conditions by using aqueous tert-butyl hydroperoxide (TBHP) as an oxidant without the addition of an organic solvent. The present study showed much better activity of the dinuclear catalysts than the mononuclear ones due to the weak donor properties of the amino group and high geometric constraints occurring in such small sized self-assembled systems as confirmed by density functional theory calculations.

A group of symmetrical disubstituted carbohydrazides, namely 1, 5-bis(2, 3- dihydroxybenzylidene)carbohydrazide, H4L1 ; 1, 5-bis(2, 4-dihydroxybenzylidene)carbohydrazide, H4L2, and 1, 5-bis(2-hydroxy-1- naphtalidene)carbohydrazide, H4L3, were synthesized by combining conventional solution and mechanochemical approach. In the solid- state all three compounds possess the same tautomeric form ; keto one with respect to the central carbamide fragment and the enol-imino form when considering their aldehyde residues, as established by single-crystal X-ray diffraction and IR spectroscopy. Similar situation is observed in DMSO solution, where compounds were investigated by NMR spectroscopy. In addition, divergent and complicated thermal behavior was established for all three compounds, as found by combined DSC and TG measurements. Finally, the obtained compounds (H4L1-H4L3) along with the previously published 1, 5-bis(2- hydroxybenzylidene)carbohydrazide (H4L4) and their parent carbohydrazide (1, 3-diaminourea ; CH) were evaluated in vitro for their cytotoxic and antibacterial activity. All compounds proved to be noncytotoxic against HepG2 cells, while some of the examined carbohydrazides showed only very weak activity against THP-1 cell line. None of the tested compounds showed antibacterial properties towards S. aureus, E. faecalis, E. coli and M. catarrhalis strain.

International audience; The focus of this work was on the synthesis, characterization and catalytic activity of Mo(vi) complexes with hemilabile polydentate ligands that show a high tendency to form discrete small-sized self-assembled structures. A series of mononuclear, [MoO2(L1 or 3)(MeOH)] (1a and 3a) and [MoO2(L1)(EtOH)] (1b), and dinuclear, [MoO2(L1–3)]2 (1–3), complexes was synthesised by using 2-aminobenzoylhydrazone ligands derived from salicylaldehyde (H2L1), 3-methoxy-2-hydroxybenzaldehyde (H2L2) and 4-methoxy-2-hydroxybenzaldehyde (H2L3). Different reaction conditions led to the formation of several crystalline forms of the dinuclear cyclic species [MoO2(L1 or 3)]2 (1-α, 1-β, 1-γ, 1·CH3CN, 3-α, 3-β and 3·2CH3CN), a feature which is observed for the first time in the case of the metallosupramolecular compounds incorporating cis-MoO22+ subunits. These complexes were tested as catalysts for cyclooctene epoxidation under eco-friendly reaction conditions by using aqueous tert-butyl hydroperoxide as an oxidant without the addition of an organic solvent. The use of the hemilabile ligands provided the opportunity to employ relatively stable coordinatively saturated dinuclear Mo(vi) complexes, which in turn offered access to highly reactive pentacoordinated species in the presence of olefins. Lastly, the hemilabile ligand induced catalytic enhancement was addressed by using density functional theory calculations.

Six non−symmetric enaminones 4-[(2-hydroxy-5-methylphenyl)amino]pent-3-en-2-one ( H 2 L 1 ), 4-[(2-hydroxy-4-methylphenyl)amino]pent-3-en-2-one ( H 2 L 2 ), 4-[(4-hydroxy-2-methylphenyl)amino)]pent-3-en-2-one ( H 2 L 3 ), 3-[(2-hydroxy-5-methylphenyl)amino]-1-phenylbut-2-en-1-one ( H 2 L 4 ), 3-[(2-hydroxy-4-methylphenyl)amino]-1-phenylbut-2-en-1-one ( H 2 L 5 ) and 3-[(4-hydroxy-2-methylphenyl)amino]-1-phenylbut-2-en-1-one ( H 2 L 6 ) have been prepared by solution based method. The enaminones were characterized by elemental and DSC analysis, NMR and IR spectroscopy. Crystal and molecular structures of H 2 L 1 , H 2 L 2 , H 2 L 4 and H 2 L 6 were determined via single crystal X−ray analysis. The prepared enaminones were screened against THP-1 and HepG2 cells, and Staphylococcus aureus , Enterococcus faecalis , Escherichia coli and Moraxella catarrhalis bacteria to assess their cytotoxic and antibacterial activity, respectively. All compounds proved to be non-cytotoxic and showed mild or no antibacterial activity. Quantum mechanical calculations suggest that the presence of hydroxy group in ortho position, combined with the methyl group on the same aromatic ring, has a significant impact on the biological activities.

The hydrazone functional group is a universal building block incorporated in a wide spectrum of organic and inorganic compounds [1]. Its stability, modularity and subsequent structural versatility along with the acid-base properties makes hydrazones applicable as e.g. molecular switches, sensors or as anion receptors. Moreover, the adaptability of hydrazones via E/Z isomerisation, designates them as pervasive ligands for the construction of extended metal-organic assemblies, like metal-organic grids or hybrid metal-organic systems. In this family, especially stimulating are bis-hydrazones, as they extend the scope of the (mono)hydrazone counterparts. Carbohydrazones, in particular offer, besides increment in a number of hydrazone linkages, a possibility of asymmetric design, while providing systems with two different subunits varying in coordinating behaviour and acid-base properties. Here we unveil an interesting coordination and anion receptor scenarios offered by asymmetric carbohydrazones bearing hydroxyaryl and pyridyl moieties. It was established that under appropriate conditions, such carbohydrazones can act as cations, as multifunctional ligands or as a combination thereof. While the first scenario led to corresponding polyoxomolybdate (POM) salts, in the second case discrete dinuclear complexes formed. The last option refers to hybrid POMs, where charged dioxomolybdenum(VI) complexes adopted a role of cations. Whereas dioxomolybdenum(VI) complexes have their structures determined by chelating hydroxyaryl subunit, structures of POM salts are shaped by competition between the relevant hydrogen bonds involving both ligand subunits.

A range of dioxidomolybdenum(VI) complexes has displayed very high catalytic activities and exquisite selectivity. The dioxidomolybdenum(VI) mononuclear complexes with 4-aminobenzoylhydrazone ligands (salicylaldehyde (H2L1), 3- methoxysalicylaldehyde (H2L2), or 4- methoxysalicylaldehyde 4-aminobenzoylhydrazone (H2L3) being of the type cis-[MoO2L1-3(D)] ; D = MeOH, EtOH, H2O, dmf] have been prepared and structurally characterized. The crystal structure analysis of mononuclear complexes (Fig.1.) reveals distorted octahedral Mo(VI) coordination by ONO donor atoms from dianionic tridentate 4- aminobenzoylhydrazone ligands, two oxido oxygen atoms from the MoO22+ moiety and the oxygen atom from coordinated alcohol molecules (D = MeOH, EtOH).The molybdenum oxido groups of the MoO22+ moiety show the expected mutual cis configuration and are located trans to the imine nitrogen atom and coordinated alcohol molecule. The bond distances range around Mo follows trend: Mo-Ot < Mo-O(phenolate) < Mo- O(hydrazone part) < Mo-N< MoO(ROH ; R=Me, Et). The bicyclic system of two chelate rings is slightly folded along the axis of molybdenum- imino bond and by the offset of metal centre apart from chelate planes towards the terminal oxygen atom. The most deviation from chelate rings coplanarity is shown by the phenolate oxygen atom due to its participation in intermolecular interactions. The complexes were tested for catalytic epoxidation of cyclooctene under eco-friendly reaction conditions by using aqueous tert-butyl hydroperoxide (TBHP) as an oxidant. Due to trans effect of oxido oxygen atom, Mo-O(D) bond is the longest bond distance within molybdenum coordination sphere and it expected to be the point of maximum catalytic reactivity of the complexes. It is previously shown that pentacoordinated molybdenum systems activate oxidizing agent TBHP through adduct formation assisted by the O–H…O hydrogen bond. Another explanation of the substituent influence is p-π conjunctive effect with methoxy group due to increasing electron density of the phenyl ring.

New molybdenum complexes were prepared by the reaction of [MoVIO2(acac)2] or (NH4)2[MoVOCl5] with different N-substituted pyridoxal thiosemicarbazone ligands (H2L1 = pyridoxal 4-phenylthiosemicarbazone; H2L2 = pyridoxal 4-methylthiosemicarbazone, H2L3 = pyridoxal thiosemicarbazone). The investigation of monomeric [MoO2L1(CH3OH)] or polymeric [MoO2L1–3] molybdenum(VI) complexes revealed that molybdenum is coordinated with a tridentate doubly-deprotonated ligand. In the oxomolybdenum(V) complexes [MoOCl2(HL1–3)] the pyridoxal thiosemicarbazonato ligands are tridentate mono-deprotonated. Crystal and molecular structures of molybdenum(VI) [MoO2L1(CH3OH)]·CH3OH, and molybdenum(V) complexes [MoOCl2(HL1)]·C2H5OH, as well as of the pyridoxal thiosemicarbazone ligand methanol solvate H2L3·MeOH, were determined by the single crystal X-ray diffraction method.

New dinuclear pentacoordinate molybdenum(V) complexes, [Mo2VO3L2] [L = thiosemicarbazonato ligand: C6H4(O)CH:NN:C(S)NHR' and C10H6(O)CH:NN:C(S)NHR' ; R' = H, CH3, C6H5) were obtained either by oxygen atom abstraction from MoVIO2L with triphenylphosphine or by using [Mo2O3(acac)4] in the reaction with the corresponding ligands H2L. Crystal and molecular structure of [Mo2O3{; ; ; ; ; C6H4(O)CH:NN:C(S)NHC6H5}; ; ; ; ; 2]· CH3CN has been determined by the single-crystal X-ray diffraction method.

International audience; The mononuclear dioxotungsten(VI) complexes [WO2(L-3OMe)(D)] (1a and 1b), [WO2(L-4OMe)(D)] (2a and 2b) and [WO2(L-H)(D)] (3a and 3b) (D = EtOH (1a-3a) or MeOH (1b-3b); L-3OMe = 3-methoxy-2-oxybenzaldehyde isonicotinoyl hydrazonato, L-4OMe = 4-methoxy-2-oxybenzaldehyde isonicotinoyl hydrazonato, L-H = 2-oxybenzaldehyde isonicotinoyl hydrazonato) were synthesized by the reaction of [WO2(acac)(2)]center dot 0.5C(6)H(5)Me with the respective isoniazid-related hydrazone. The compounds were characterized by microanalysis, FT-IR and NMR spectroscopy, thermogravimetric analysis, and powder X-ray diffraction method. The crystal and molecular structures of 1a, 1b, 3a and [WO2(acac)(2)]center dot 0.5C(6)H(5)Me were determined by single crystal X-ray diffraction. The structures of 1a, 1b, 3a are mononuclear and form hydrogen bonded centrosymmetric dimers. In all three complexes, the dimers are also held together by pi center dot center dot center dot pi interactions between aromatic rings. The catalytic performances (activity and selectivity) of 1a-3a and 1b-3b towards alkene epoxidation by tert-butyl hydroperoxide (TBHP) were investigated under different conditions.

International audience; A series of dinuclear and mononuclear oxovanadium(V) complexes containing tridentate Schiff base ligands derived from pyridoxal and appropriate thiosemicarbazide or hydrazide are reported. The compounds were characterised by elemental analysis, thermogravimetric analysis, IR and NMR spectroscopy. The molecular structure of the dioxido-vanadium(V) complex [VO2(HL5)]center dot MeOH center dot H2O (H2L5 = pyridoxal benzhydrazido ligand), determined by X-ray crystallography, reveals an unexpected distorted trigonal bipyramidal arrangement of the VO2 moiety. A DFT study of this molecule and of the related [VO2(H2L5)] complex of V-IV reveals a moderate effect of the oxidation state change on the bond distances and angles, pointing to solvation as the cause of the structural distortion. All complexes were tested as (pre) catalysts for olefin epoxidation by aqueous tert-butylhydroxyperoxide (TBHP) under solvent-free conditions. Low vanadium loadings (0.05% vs. olefin) resulted in good cyclooctene conversions and TOFs. The lifetime of one catalyst was explored through repeated runs with recovery/recycling. DFT calculations have also addressed the olefin epoxidation mechanism, which reveals the possible direct O atom transfer from the activated tert-butoxido (tBuOO(-)) ligand, without the need to generate a peroxido (022) ligand.

International audience; Synthesis of the dioxomolybdenum(vi) complexes [MoO2(L-3OMe)(EtOH)) (1), (MoO2(L-4OMe)(EtOH)] (2) and [MoO2(L-H)(EtOH)] (3) and dioxotungsten(VI) complexes [WO2(L-3OMe)(EtOH)] (4), [WO2(L-4OMe)(EtOH)] (5) and [WO2(L-H)](n) (6a) was carried out using [MO2(C5H7O2)(2)] = Mo or W) and the corresponding aroythydrazone ligand H2LR (3-methoxysalicylaldehyde 4-hydroxybenzhydrazone (H2L3OMe), 4-methoxysalicylaldehyde 4-hydroxybenzhydrazone (H2L4OMe), or salicylaldehyde 4-hydroxybenzhydrazone (H2LH) in ethanol. Compounds obtained upon heating of the mononuclear complexes in acetonitrile or dichtoromethane, [MO2(L-R)](n) (1a-6a) or [MoO2(L-3OMe)](2) (1b), respectively, were also investigated. Crystal and molecular structures of the mononuclear 1, 2 and 3, polynuclear 1a.MeCN and dinuclear 1b complexes were determined by the single crystal X-ray diffraction method. Powder X-ray diffraction showed isostructurality of 1 and 4, and 2 and 5. The complexes were further characterized by elemental analysis, IR spectroscopy, TO and DSC analyses, and one- and two-dimensional NMR spectroscopy. The catalytic performances of 1-5 and 6a were investigated for epoxidation of cyclooctene using aqueous tert-butyl hydroperoxide (TBHP) as the oxidant.

Kompleksni spojevi molibdena (VI), [MoO2L(CH3OH)] (L = nesimetrične Schiffove baze), su priređeni sa svrhom proučavanja izmjena liganada u trans položaju odnosu na okso kisik MoO22+ skupine budući da su pogodni modelni sustavi za proučavanje katalitičkih reakcija. U literaturi je opisano katalitičko djelovanje ovog tipa kompleksa ali i njihova biokemijska svojstva pa se posljednjih godina intenzivno istražuje njihova potencijalna farmakološka primjena.1 U okviru ovog istraživanju priređeni su i indentificirani kompleksi s derivatima Schiffovih baza, dobivenih reakcijama 2-amino-4-metilfenola odnosno 2-amino-5-metilfenola i 1-benzil-1, 3-butadiona u etanolu (L1 = Bzac-4Me odnosno L2 = Bzac-5Me). Kompleksi molibdena(VI) su priređeni reakcijom bis(2, 4-pentandionato)dioksomolibdena(VI) i odgovarajuće Schiffove baze u metanolu. Molekulska i kristalna struktura kompleksa [MoO2L1(CH3OH)] i [MoO2L2(CH3OH)] su određene na temelju podataka rentgenske strukturne analize, infracrvene spektroskopije, elementne i termičke analize. Ispitivanja svojstava priređenih kompleksa su pokazala da je moguća izmjena koordiniranog metanola s drugim ligandima kao što su piridin, 4-metilpiridin, 4, 4-bipiridin i imidazol u otopini i u čvrstom stanju. Ustanovljeno je također da u odsutnosti koordinirajućeg liganda kao što je alkohol ili neka N-baza dolazi do polimerizacije i nastanka [MoO2L]n kompleksa. Izmjena O- i N-donorskih liganada kao i polimerizacija su popraćene promjenom boje.

The reaction of [MoO2(acac)2] (where acac = acetylacetonate ligand) with the salicylaldehyde isonicotinyl hydrazonate ligand (SIH2−) yielded a zigzag chain polymer [MoO2(SIH)]n (1), an interwoven hexagon [MoO2(SIH)]6 (2), or the mononuclear complexes [MoO2(SIH)(C2H5OH)] (3EtOH) and [MoO2(SIH)(C3H7OH)] (3PrOH). Diversity in the formation of dioxomolybdenum(VI) compounds illustrates their sensitivity to the reaction conditions. Crystal and molecular structures of all of the investigated molybdenum(VI) compounds were determined by the single crystal X-ray diffraction method. Solid-state reactions lead to the transformation of the supramolecular hexagon or the mononuclear complexes into the chain coordination polymer. These thermally induced conversions were characterized by the X-ray powder diffraction method. All of the investigated compounds were further characterized by elemental analysis, thermogravimetric analyses, Fourier transform infrared (FT-IR), and NMR spectroscopy.

International audience; Molybdenum(VI) pyridoxal thiosemicarbazonato complexes have proved to be efficient catalysts in the olefinic epoxidation of cyclooctene by aqueous TBHP in the absence of an organic solvent. High activity and selectivity have been obtained with a catalyst loading of just 0.05% molybdenum in the case of one mononuclear (pre)catalyst (TOF 3360 h−1) under solvent‐free conditions. The influence of methanol on the activity and selectivity has been studied.

International audience; Pyridoxal hydrazonato molybdenum(VI) complexes were prepared by the reaction of the corresponding hydrazone (H2L1 = pyridoxal isonicotinic acid hydrazone, H2L2 = pyridoxal benzhydrazone, H2L3 = pyridoxal 4-hydroxy benzhydrazone) and [MoO2(acac)(2)] under appropriate conditions. The complexes can be classified into three categories: mononuclear [MoO2(L1-3)(MeOH)], polynuclear [MoO2(L1-3)](n) and hybrid organic-inorganic compounds with the Lindqvist polyoxomolybdate [MoO2(HL1-3)](2)Mo6O19. A unique example of a cationic polymer assembly with Lindqvist anions is reported herein for the first time. The compounds were characterised by elemental, TG and DSC analyses and by spectroscopic (IR, UV-Vis, H-1, C-13 NMR) techniques. The crystal and molecular structure of the pyridoxal benzhydrazone H2L2, three mononuclear complexes [MoO2(L1-3)(MeOH)], and the Lindqvist-containing compounds [MoO2(HL2)](2)Mo6O19 center dot 2MeCN and (H4L1)Mo6O19 were determined by single crystal X-ray diffraction. All complexes were tested as (pre)catalysts for the epoxidation of cyclooctene under solvent-free conditions with the use of aqueous TBHP (TBHP tert-butylhydroperoxyde) as an oxidant. Optimal results in terms of conversion, selectivity, TOF and TON were obtained at very low (pre)catalyst loadings (0.05% [Mo] vs. substrate). The influence of the Linqvist anion on catalytic performance is discussed.

Organic-inorganic hybrids, based on the Lindqvist-type polyoxometalate (POM) and dioxomolybdenum(VI) complexes, have been synthesized by hydrolysis of [MoO2(acac)2] (acac = acetylacetonate) in the presence of aroylhydrazone ligands in weak donor solvents. This provides an efficient route to materials that contain open coordination sites or sites occupied by labile ligands. Removal upon grinding or heating of the labile acetonitrile and acetone molecules on the dioxomolybdenum centres and the reaction in the solid-state represents a way for designing structures with the Lindqvist Mo6O192- anion coordinated to the metal centres of two complex cations. The compounds were characterised by the single crystal and powder X-ray diffraction methods, elemental analysis, IR spectroscopy, TG and DSC analyses.