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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.

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.

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.

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.

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.

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.

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; 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.

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.