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A series of bridging linkers such as pyrazine (L1), 4,4′-bipyridine (L2), (E)-1,2-di(pyridin-4-yl)ethene (L3), 1,2-di(pyridin-4-yl)ethane (L4), 1,2-di(pyridin-4-yl)disulfane (L5), 1,2-di(pyridin-4-yl)diazene (L6) and 1,4-di(pyridin-4-yl)benzene (L7) has been used in a Cu(II)-mediated cyano group activation in sodium 2-(2-(dicyanomethylene)hydrazineyl)benzenesulfonate (NaHL), leading to [{Cu(H2O)(La)}2(μ-L1)]n (1) (La = (Z)-2-(1-cyano-2-imino-2-methoxyethylidene)-1-(2-sulfonatophenyl)hydrazin-1-ide), [{Cu(H2O)(La)}2(μ-L2)]·2H2O (2), [{Cu(X)(La)}2(μ-L3)]·3H2O (3) (X = H2O or CH3OH for the two independent units), [{Cu(CH3OH)(La)}2(μ-L4)]·2H2O (4), [{Cu(La)}2(μ-L5)2]n (5), [{Cu(μ-La)}2(μ-L6)Cu(H2O)(La)]2·4H2O (6) and [{Cu(H2O)(La)}2(μ-L7)] (7), respectively. Depending on the length of the respective linkers, the distance between the two copper(II) centres in 1–7 can be expanded/adjusted from 6.762 to 15.138 Å. The catalytic activity of the synthesized compounds in the cyanosilylation reaction of aldehydes with trimethylsilyl cyanide in methanol was performed. No linear correlation among the length of the bridging ligands and the yield of 2-phenyl-2-((trimethylsilyl)oxy)acetonitrile was observed in 1–7 catalysed cyanosilylation of benzaldehyde with trimethylsilyl cyanide, but the copper complexes show a higher catalytic activity in comparison to the monomer [Cu(H2O)2(La)]. The higher catalytic activity exhibited by complex 5 was further investigated evaluating the effects of reaction time, catalyst amount, temperature and the activity with different aldehydes. [ABSTRACT FROM AUTHOR]

Herein, we have isolated new 20-membered macrocycles by the simple condensation of α,α-dihalo-β-oxoaldehydes with diaminofurazan in acetonitrile. The interior and exterior sites of these macrocycles comprise hydrogen and halogen bond donor sites, respectively. Depending on the electron donating or accepting character of the substituents at the exterior sites of macrocyclic scaffolds, the average cavity diameters range from 8.15 to 8.47 Å. [ABSTRACT FROM AUTHOR]

The role of noncovalent interactions (spodium, halogen and hydrogen bonds) in the reaction of [Zn{NH＝C(CCl3)NC(CCl3)＝NH}2] with acetone, pyrazole, 4,4′-bipyridine and Cu(acetylacetonate)2 is reported. Depending on the reactants, different types of organic, coordination and supramolecular compounds were isolated, and various types of noncovalent interactions were disclosed. [ABSTRACT FROM AUTHOR]

A series of coordination compounds [CoIII2{(CoIICl(H4L)(H2O)3}3{(CoII(CH3COO)(H4L)(H2O)2}3]6+(Cl−)6·H2O (1), [Ni(H4L)2] (2), [Cu(H4L)2] (3) and [(H6L)CuCl3]·H2O (4) were synthesized by the reaction of (E)-1-(amino(1H-pyrazol-1-yl)methylene)guanidinium chloride (H5L·HCl) with Co(CH3COO)2·4H2O, Ni(CH3COO)2·4H2O (in the presence of triethylamine), Cu(CH3COO)2·H2O (in the presence of triethylamine) and CuCl2·2H2O in methanol, respectively. 1–4 were fully characterized by infrared spectroscopy, electrospray ionization mass spectrometry, single-crystal X-ray diffraction and elemental analyses. H5L·HCl is potentially a multidentate N-donor ligand, and coordinates to cobalt as a N4 donor in 1, and to nickel or copper as a N2 donor in 2–4. In the structure of 1, the coordination geometry around the CoIII or CoII atoms is distorted octahedral. In 2 and 3, the Ni and Cu atoms have a distorted square planar coordination geometry, whereas Cu in 4 exhibits a square-based pyramidal coordination geometry. In the packing diagrams of 1–4, the N atom 1H-pyrazole moiety and H–N of the 1,3,5-triazopentadienyl ligands act as a H-bond acceptor and donor towards neighbouring molecules, leading to 3D supramolecular networks. All complexes were tested as catalysts for the peroxidative oxidation of styrene to benzaldehyde. The effects of the oxidant type, styrene to catalyst molar ratio, and reaction temperature and time on the catalytic activity were investigated. Under optimized conditions in the presence of 4, high yields (up to 80%) of benzaldehyde can be achieved. [ABSTRACT FROM AUTHOR]

The chalcogen bond (ChB) is a noncovalent attraction between an electrophilic chalcogen atom and a nucleophilic (Nu) region in the same (intramolecular) or another (intermolecular) molecular entity: R–Ch⋯Nu (Ch = O, S, Se or Te; R = substituents; Nu = nucleophile). ChB is comparable to the hydrogen and halogen bonds both in terms of strengths and directionality. However, in contrast to the monovalent halogen atoms, usually the divalent or tetravalent chalcogen atoms are able to display more than one electrophilic centre (on account of the existence of two or three species bonded to the chalcogen atom), which provides an additional opportunity in the use of this type of noncovalent binding in synthetic operations. In this work, the role of ChB at the secondary coordination sphere of metal complexes through copper(II)-mediated activation of dioxygen or of one nitrile group of a 1,2,5-selenadiazole-3,4-dicarbonitrile ligand to form a carbimidate or an imino-carboxylic acid is demonstrated. DFT calculations allowed evaluation of the strength of the ChBs and proved their relevant structure directing role in the solid state architectures. The effect of metal-coordination on the σ-hole opposite to the coordinated Se＝O bond has been analysed using molecular electrostatic potential (MEP) surfaces and explains the greater ability of the coordinated selenoxide derivatives to form strong ChBs. [ABSTRACT FROM AUTHOR]

A series of water-soluble metal formazanates, [Al2(OH)2(H2O)8](HL)2 (1), [{Fe(H2O)4}(HL)(H2L)]·2H2O (2) and [Cu(en)2(H2O)2][CuL(H2O)2]2 (3), were synthesized by the reaction of sodium 2-(2-((E)-cyano((E)-(2-sulfonatophenyl)diazenyl)methylene)hydrazineyl) benzenesulfonate (Na2HL) with Al(NO3)3·9H2O, FeCl3·6H2O and Cu(NO3)2·3H2O (in the presence of ethylenediamine) in methanol, respectively. The formazan pro-ligand Na2HL and its complexes 1–3 were characterized by ESI-MS, 1H/13C NMR (for Na2HL), IR spectroscopy, elemental and X-ray diffraction analyses (for 1–3). According to the X-ray analysis, the formazanate behaves as an anion or displays a mono- or bidentate coordination mode, for the Al, Fe or Cu centre, respectively. All complexes were tested as catalysts for the peroxidative (with H2O2) oxidation of cyclohexane and cyclohexanol to the coresponding organic products at room temperature. The complexes 2 and 3 are active homogeneous catalysts for the microwave-assisted peroxidative oxidation with aqueous H2O2 of cyclohexane (to cyclohexanol and cyclohexanone) and cyclohexanol to cyclohexanone. [ABSTRACT FROM AUTHOR]

The role of substituents on resonance assisted hydrogen bonding (RAHB) vs. intermolecular hydrogen bonding is highlighted in known arylhydrazones of active methylene compounds (AHAMCs) and in their new representatives – (E/Z)-2-(2-(para-substitutedphenyl)hydrazineylidene)-N,N-diethyl-3-oxobutanamides (–C2H5, –H, –COOH, –CN). The strength of the H-bond depends on the attached functional groups to both the active methylene fragment and the aromatic moiety of the AHAMC. For instance, attachment of the strong electron donor group –N(C2H5)2 (σp = −0.72) to the active methylene fragment of AHAMC allows to isolate this class of compounds without RAHB but with strong intermolecular H-bonds, which are the first examples reported herein. [ABSTRACT FROM AUTHOR]

A series of new (1E,1′E)-2,2′-((perfluoro-1,4-phenylene)bis(2,2-dichloroethene-1,1-diyl))bis(1-(para-substituted phenyl)diazenes) have been synthesized via CuCl catalyzed olefination of the corresponding Schiff bases with CCl4 in the presence of tetramethylethylenediamine (TMEDA) in DMSO. Cl⋯O and Cl⋯F types of halogen bonds were found in these bis-azo dyes, which depend on the electron-donating or -accepting properties of the para-substituent (–OCH3, –CH3, –H, –F) of the azoaromatic ring. DFT calculations demonstrate that noncovalent interactions play a significant role in the stabilization of the intermolecular networks of the structures under study. [ABSTRACT FROM AUTHOR]

A series of water soluble copper(ii) complexes, [Cu(κO1O2N-H2L1)(H2O)2]·2H2O (2), [Cu(κO-H3L1)2(H2O)4] (3), [Cu(κO-H4L2)2(H2O)4] (5) and [Cu(H2O)6]·2H2L3·2(CH3)2NCHO (7), were prepared by the reaction of Cu(NO3)2·3H2O with sodium (Z)-2-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)benzenesulfonate, [Na(μ4-1:2κO1,2κO2,3κO3,4κO4-H3L1)]n (1; for 2 and 3), sodium (Z)-3-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)-4-hydroxybenzene-sulfonate, [Na(μ-1κO1,2κO2-H4L2)]2 (4; for 5) or sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazineyl)naphthalene-1-sulfonate, [Na(μ-1κO1O2,2κO3-H2L3)(CH3OH)2]2 (6; for 7). Compounds 1–7 were fully characterized, also by single-crystal X-ray diffraction analysis, and applied as homogeneous catalysts for the azide–alkyne cycloaddition (AAC) reaction to afford 1,4-disubstituted 1,2,3-triazoles. A structure–catalytic activity relationship has been recognized for the first time on the basis of the occurrence of resonance- and charge-assisted hydrogen bond interactions (RAHB and CAHB), in charge and ligand binding modes, enabling the catalytic activity of the compounds to be ordered as follows: Cu(NO3)2<7 (complex salt with RAHB and CAHB) ＜ 3 (with RAHB and CAHB) ＜ 5 (with RAHB) ＜ 2 (neither RAHB nor CAHB). Complex 2, without such non-covalent interactions, was found to be the most efficient catalyst for the AAC reaction, affording up to 98% product yield after being placed for 15 min, at 125 °C, in a water/acetonitrile mixture under low power (10 W) MW irradiation. [ABSTRACT FROM AUTHOR]

Chalcogen bonding is a type of noncovalent interaction in which a covalently bonded chalcogen atom (O, S, Se or Te) acts as an electrophilic species towards a nucleophilic (negative) region(s) in another or in the same molecule. In general, this interaction is strengthened by the presence of an electron-withdrawing group on the electron-acceptor chalcogen atom and upon moving down in the periodic table of elements, from O to Te. Following a short discussion of the phenomenon of chalcogen bonding, this Perspective presents some demonstrative experimental observations in which this bonding is crucial for synthetic transformations, crystal engineering, catalysis and design of materials as synthons/tectons. [ABSTRACT FROM AUTHOR]

Five isostructural lanthanide MOFs, [Ln(1κOO′,2κO′′,3κO′′′,4κO′′′′-μ4-L)(NO3)(DMF)2]n·n(DMF) {Ln = La3+ (1), Ce3+ (2), Nd3+ (3), Sm3+ (4) and Dy3+ (5); L = 5-[2-{2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene}hydrazinyl]isophthalate; DMF = N,N′-dimethyl formamide}, based on dicarboxyl-functionalized arylhydrazone of barbituric acid were synthesized under solvothermal conditions. They were characterized by elemental analysis, FT-IR spectroscopy, thermogravimetric and X-ray diffraction analyses. Crystal structure analysis revealed that these frameworks possess a similar type of two dimensional (2D) structure with a dinuclear {Ln2(COO−)2} unit acting as a secondary building block. Topological analysis shows that these frameworks display a 3,6-connected kgd; Shubnikov plane (3.6.3.6)/dual net. They exhibit excellent heterogeneous catalytic activities (compound 2 is the most active one) towards the cyanosilylation of aldehydes under solvent-free conditions. These catalysts can be recycled at least up to five cycles without a loss of activity. Compounds 1–5 exhibit luminescence properties in the solid state at room temperature. [ABSTRACT FROM AUTHOR]

Several known water soluble [Cu(1κN,O2:2κO-HL1)(S)]2 [S = CH3OH (1), (CH3)2NCHO (2)] and [Cu(κN-HL1)(en)2]·CH3OH·H2O (3) CuII complexes were prepared by reaction of CuII nitrate hydrate with the new (E/Z)-4-(2-(1-cyano-2-ethoxy-2-oxoethylidene)hydrazinyl)-3-hydroxybenzoic acid (H3L1), in the presence (for 3) or absence (for 1 and 2) of ethylenediamine (en), while the FeIII complex [Fe(κN3-HL2)2] (4) was synthesized by treatment of iron(iii) chloride hexahydrate with the new (1E,1E)-N′,2-di(1H-1,2,4-triazol-3-yl)diazenecarbohydrazonoyl cyanide (H3L2). The interaction of calf thymus DNA (CT DNA) and bovine serum albumin (BSA protein) with complexes 1–4 has been investigated by absorption and fluorescence titration methods. The observed DNA binding constants, number of DNA binding sites (s≤ 1) for the complexes and viscosity data suggest the intercalative mode of binding to CT DNA. All the complexes show good binding propensity to the BSA protein, giving KBSA values of 0.97(±0.10) × 106 (1), 1.19(±0.09) × 106 (2), 0.50(±0.01) × 106 (3) and 1.06(±0.08) × 106 M−1 (4). An in vitro anti-proliferative study establishes the anticancer potency of complexes 1–4 and cisplatin against the human cervical (HeLa) and breast (MCF7) cancer cell lines; noncancer breast epithelial (MCF10) cells were also investigated. The observed IC50 values of complexes 1 (8.3, 11.9 and 44.8 μM), 2 (7.0, 7.1 and 35.6 μM), 3 (18.1, 20.4 and 58.8 μM), 4 (13.2, 15.1 and 79.4 μM) and cisplatin (4.02, 3.42 and 89.5 μM) against the HeLa, MCF7 and MCF-10a cells, respectively, suggest that 2 can be explored further as a potential anticancer drug. [ABSTRACT FROM AUTHOR]

The aquasoluble [Cu(1κN,O2:2κO-HL1)(S)]2 [S = CH3OH (1), (CH3)2NCHO (2)] and [Cu(κN-HL1)(en)2]·CH3OH·H2O (3) CuII complexes were prepared by the reaction of CuII nitrate hydrate with the new ligand (E/Z)-4-(2-(1-cyano-2-ethoxy-2-oxoethylidene)hydrazinyl)-3-hydroxybenzoic acid (H3L1), in the presence (for 3) or absence (for 1 and 2) of ethylenediamine (en), while the FeIII complex [Fe(κN3-HL2)2] (4) was isolated by treatment of iron(III) chloride hexahydrate with the new ligand (1E,1E)-N′,2-di(1H-1,2,4-triazol-3-yl)diazenecarbohydrazonoyl cyanide (H3L2), and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. Cooperative E,Z→E isomerization of H3L1, induced by coordination and ionic interactions, occurs upon interaction with CuII in the presence of en. Complexes 1–4 act as catalyst precursors for the solvent-free microwave (MW) assisted selective oxidation of primary or secondary alcohols and diols to the corresponding aldehydes, ketones and diketones, respectively, with yields in the 5–99% range (TONs up to 4.96 × 102) after 60 min of MW irradiation at 120 °C. The influence of temperature, time and organic radicals was studied and also the regioselective oxidation of the catalytic systems involving the primary and secondary alcohols. [ABSTRACT FROM AUTHOR]

Four novel Zn(ii) and Cd(ii) compounds based on a dicarboxyl-functionalized arylhydrazone of barbituric acid ligand, 5-[2-{2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene}hydrazinyl]isophthalic acid (H5L), namely [Zn(1κO:2κO′:3κO′′-H3L)(H2O)2]n (1), [Cd(1κO,O’:2κO′:3κO′′,O′′′-H3L)(H2O)2]n (2), [Zn(κN-H3L)(H2O)3]·3H2O (3) and [Cd(1κO,O′:2κN-H3L)(H2O)3]n·4nH2O (4), have been synthesized at different pHs under hydrothermal conditions and characterized by elemental and thermogravimetric, FT-IR, and X-ray single-crystal diffraction analyses. Compounds 1 and 2 prepared in acidic medium are coordination polymers exhibiting double chain type one-dimensional (1D) structures, whereas 3 and 4 are obtained in basic medium. Compound 3 is a mononuclear Zn(ii) complex containing three lattice water molecules, but in 4, Cd(ii) cations are bridged by H3L2− ligands to form an interesting zig-zag type 1D coordination polymer. The crystal structures of these compounds are stabilized by strong hydrogen bonding interactions, forming two and three-dimensional networks. The pH value of the reaction system plays a crucial role in the ligand deprotonation and in the assembly of the metal–organic polymers. These compounds act as effective heterogeneous catalysts, under mild conditions, for the Knoevenagel condensation reaction of different aldehydes with malononitrile and can be recycled at least five times without losing activity. Further, compounds 1–4 exhibit luminescence properties in the solid state at room temperature. [ABSTRACT FROM AUTHOR]

Two complexes [KLa(HL1)2{(CH3)2NCHO}2(H2O)3] (1) and [Sm(H2O)9](E-H2L2)3·2H2O (2) were synthesized by the reaction of lanthanum(iii) and samarium(iii) nitrates with potassium 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonate (KH2L1) and potassium (E,Z)-5-chloro-3-(2-(1,3-dioxo-1-phenylbutan-2-ylidene)hydrazinyl)-2-hydroxybenzenesulfonate (KH2L2), respectively. Both complexes were fully characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy, ESI-MS and single-crystal X-ray diffraction. Cooperative E,Z→E isomerization of KH2L2, induced by resonance assisted hydrogen bonding and ionic interactions, occurs upon the interaction with Sm(iii). Catalytic activities of KH2L1,2 and their lanthanide derivatives were evaluated in the Henry reaction of nitroethane with a variety of aromatic and aliphatic aldehydes. Good yields (up to 91%) and diastereoselectivities (syn/anti 3 : 1) were observed in the reactions catalyzed by 1 in water. [ABSTRACT FROM AUTHOR]

One-pot template condensation of CCl3C≡N with ammonia on a metal source [MnCl2·4H2O, FeCl3·6H2O or Co(CH3COO)2·4H2O] in DMSO led to the formation of tris{2,4-bis(trichloromethyl)-1,3,5-triazapentadienato}-M(iii) complexes, [M{NH=C(CCl3)NC(CCl3)=NH}3]·n(CH3)2SO [M = Mn, n = 1 (1); M = Fe, n = 2 (2); M = Co, n = 2 (3)], which were characterized using elemental analysis, and IR, ESI-MS and single-crystal X-ray analysis. The role of inter- and intramolecular non-covalent halogen and hydrogen bonds in the synthesis of 1–3 is discussed. It is shown that the crystal ionic radii of the metal ions [68.5 (Co) ＜ 69 (Fe) ＜ 72 (Mn), pm] are related to the corresponding Cl…Cl distances [3.178 (3) ＞ 3.155 (2) ＞ 3.133 (1) Å]. Compounds 1–3 and the related di(triazapentadienato)-Cu(ii) complex [Cu{NH=C(CCl3)NC(CCl3)=NH}2]·2(CH3)2SO (4) act as catalyst precursors for the additive-free microwave (MW) assisted homogeneous oxidation of 1-phenylethanol with tert-butylhydroperoxide (TBHP), leading to the formation of acetophenone with yields up to 99% and TONs up to 5.0 × 103 after 1 h of low power (10 W) MW irradiation. [ABSTRACT FROM AUTHOR]

Metal-free regioselective activation of a carbon–carbon bond in 1,3,5-triazine derivatives of β-diketones is easily achieved, in the absence of a catalyst, with the assistance of intramolecular hydrogen bonding. [ABSTRACT FROM AUTHOR]

The aquasoluble [Cu(H2O)((CH3)2NCHO)(HL)] (2) and [Cu2(CH3OH)2(μ-HL)2] (3) CuII complexes were prepared by reaction of CuII nitrate hydrate with the new 3-(2-hydroxy-4-carboxyphenylhydrazone)pentane-2,4-dione (H3L, 1), in the presence (for 2) or absence (for 3) of (n-C4H9)2SnO, and characterized by elemental analysis, IR spectroscopy and X-ray single crystal diffraction. Magnetic susceptibility measurements, in compound 3, reveal strong antiferromagnetic coupling between the CuII ions through the μ2-phenoxido-O atoms, J = −203(1) cm−1. Complexes 2 and 3 act as catalyst precursors for the acid-free peroxidative oxidation of cyclohexane to the mixture of cyclohexyl hydroperoxide (primary product), cyclohexanol and cyclohexanone (TONs and yields up to 163 and 14.4%, respectively), as well as for the selective aerobic oxidation of benzyl alcohols to benzaldehydes in aqueous solution, mediated by a TEMPO radical, under mild conditions (TONs and yields up to 390 and 94%, respectively). In the alkane oxidations, 2 and 3 appear to behave as “dual role catalysts” combining, in one molecule, an active metal centre and an acidic promoting group, to provide a high activity of the system even without any acid promoter. [ABSTRACT FROM AUTHOR]

A novel parato metashift of a nitro group at the phenyl ring of 3-(2-hydroxy-4-nitrophenylhydrazo)pentane-2,4-dione (H2L1, 1), with formation of the new 3-(2-hydroxy-3,5-dinitrophenylhydrazo)pentane-2,4-dione (H2L2, 2), occurs upon nitration of 1with an equimolar amount of NaNO2, under basic conditions. 2acts as a polydentate ligand for the synthesis of the polymeric potassium [K(μ5-HL2)]n(3) and monomeric nickel(ii) [Ni(H2O)3(L2)]·H2O (4) compounds. They have been fully characterized, including single crystal X-ray analysis, and the complexes feature metal–organic (in 3) or supramolecular (in 4) 3D networks. The topological analysis of 3reveals a uninodal 5-connected underlying net with the point symbol of (46.64) and a very rare 5/4/t5 topology, which had not yet been observed in coordination polymers. [ABSTRACT FROM AUTHOR]

The zinc(ii) complexes with ortho-hydroxy substituted arylhydrazo-β-diketonates [Zn2(CH3OH)2(μ-L1)2] (5), [Zn{(CH3)2SO}(H2O)(L2)] (6), [Zn2(H2O)2(μ-L3)2] (7) and [Zn(H2O)2(L4)]·H2O (8) were synthesized by reaction of a zinc(ii) salt with the appropriate hydrazo-β-diketone, HO-2-C6H4-NHNC{C(O)CH3}2(H2L1, 1), HO-2-O2N-4-C6H3-NHNC{C(O)CH3}2(H2L2, 2), HO-2-C6H4-NHNCC(O)CH2C(CH3)2CH2C(O) (H2L3, 3) or HO-2-O2N-4-C6H3-NHNCC(O)CH2C(CH3)2CH2C(O) (H2L4, 4). They were fully characterized, namely by X-ray diffraction analysis that disclosed the formation of extensive H-bonds leading to 1D chains (5and 6), 2D layers (7) or 3D networks (8). The thermodynamic parameters of the Zn(ii) reaction with H2L2in solution, as well as of the thermal decomposition of 1–8were determined. Complexes 5–8act as diastereoselective catalysts for the nitroaldol (Henry) reaction. The threo/erythrodiastereoselectivity of the β-nitroalkanol products ranges from 8 : 1 to 1 : 10 with typical yields of 80–99%, depending on the catalyst and substrate used. [ABSTRACT FROM AUTHOR]

Reactions of copper(ii) with 3-phenylhydrazopentane-2,4-diones X-2-C6H4–NHNC{C(O)CH3}2bearing a substituent in the ortho-position [X = OH (H2L1) 1, AsO3H2(H3L2) 2, Cl (HL3) 3, SO3H (H2L4) 4, COOCH3(HL5) 5, COOH (H2L6) 6, NO2(HL7) 7or H (HL8) 8] lead to a variety of complexes including the monomeric [CuL4(H2O)2]·H2O 10, [CuL4(H2O)2] 11and [Cu(HL4)2(H2O)4] 12, the dimeric [Cu2(H2O)2(μ-HL2)2] 9and the polymeric [Cu(μ-L6)]n] 13ones, often bearing two fused six-membered metallacycles. Complexes 10–12can interconvert, depending on pH and temperature, whereas the Cu(ii) reactions with 4in the presence of cyanoguanidine or imidazole (im) afford the monomeric compound [Cu(H2O)4{NCNC(NH2)2}2](HL4)2·6H2O 14and the heteroligand polymer [Cu(μ-L4)(im)]n15, respectively. The compounds were characterized by single crystal X-ray diffraction (complexes), electrochemical and thermogravimetric studies, as well as elemental analysis, IR, 1H and 13C NMR spectroscopies (diones) and ESI-MS. The effects of the substituents in 1–8on the HOMO–LUMO gap and the relative stability of the model compounds [Cu(OH)(L8)(H2O)]·H2O, [Cu(L1)(H2O)2]·H2O and [Cu(L4)(H2O)2]·H2O are discussed on the basis of DFT calculations that show the stabilization follows the order: two fused 6-membered > two fused 6-membered/5-membered > one 6-membered metallacycles. Complexes 9, 10, 12and 13act as catalyst precursors for the peroxidative oxidation (with H2O2) of cyclohexane to cyclohexanol and cyclohexanone, in MeCN/H2O (total yields of ca. 20% with TONs up to 566), under mild conditions. [ABSTRACT FROM AUTHOR]

The possibility of tunable regioselective activation of a dinitrile towards nucleophilic attack was demonstrated. For that, a sulfo-arylhydrazone unit was introduced into malononitrile and the thus formed intramolecular hydrogen bond systems assisted specific nucleophilic attacks to the cyano moieties leading to a variety of amidines, carboxamides and iminoesters depending on the nucleophiles and conditions used. [ABSTRACT FROM AUTHOR]

A solvothermal reaction of Cd(II) with the dicarboxyl-functionalized arylhydrazone pro-ligands, 5-(2-(2,4,6-trioxotetrahydro-pyrimidin-5(2 H )-ylidene)hydrazineyl)isophthalic acid (H 5 L 1 ) and 5-(2-(2,4-dioxopentan-3-ylidene)hydrazineyl)isophthalic acid (H 3 L 2 ), or their halogen bond donor centre(s) decorated analogs 2,4,6-triiodo-5-(2-(2,4,6-trioxotetrahydropyrimidin-5(2 H )-ylidene)hydrazineyl)isophthalic acid (H 5 L 3 ) and 5-(2-(2,4-dioxopentan-3-ylidene)hydrazineyl)-2,4,6-triiodoisophthalic acid (H 3 L 4 ), leads to the formation of known [Cd(H 3 L 1 )(H 2 O) 2 ] n (1) and new {[Cd(HL 2 )(H 2 O) 2 (DMF)]·H 2 O} n (2), [Cd(H 3 L 3 )] n (3) and {[Cd 2 (μ-H 2 O) 2 (μ-H 2 L 4 ) 2 (H 2 L 4 ) 2 ]·2H 2 O} n (4) coordination compounds, respectively. The aggregation of mononuclear units via Cd-OC and Cd-OH 2 coordination and C Ar -I⋯I types of intramolecular halogen bonds lead to a dinuclear tecton 4. Both C Ar -I⋯O and C Ar -I⋯I types of intermolecular halogen bonds play a fundamental role in the supramolecular architectures of the obtained metal-organic frameworks 3 and 4. Theoretical (DFT) calculations confirmed the presence of the C Ar -I⋯O and C Ar -I⋯I halogen bonds in 3 and 4 and allowed their characterisation. The formation of intermolecular noncovalent interactions between the attached iodine substituents to the hydrazone ligands and polar solvent (water or methanol) molecules promoted, at least in part, the solubility of the corresponding complexes (3 and 4), which act as homogeneous catalyst precursors in the Henry reaction between aldehydes and nitroethane. The corresponding β-nitroalkanol products were obtained in good yields (66-79%) and with good diastereoselectivity ( threo / erythro ca. 72 : 28) in water at room temperature.

A series of water soluble copper(ii) complexes, [Cu(κO 1 O 2 N-H 2 L 1 )(H 2 O) 2 ]·2H 2 O (2), [Cu(κO-H 3 L 1 ) 2 (H 2 O) 4 ] (3), [Cu(κO-H 4 L 2 ) 2 (H 2 O) 4 ] (5) and [Cu(H 2 O) 6 ]·2H 2 L 3 ·2(CH 3 ) 2 NCHO (7), were prepared by the reaction of Cu(NO 3 ) 2 ·3H 2 O with sodium (Z)-2-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)benzenesulfonate, [Na(μ 4 -1:2κO 1 ,2κO 2 ,3κO 3 ,4κO 4 -H 3 L 1 )] n (1; for 2 and 3), sodium (Z)-3-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)-4-hydroxybenzene-sulfonate, [Na(μ-1κO 1 ,2κO 2 -H 4 L 2 )] 2 (4; for 5) or sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazineyl)naphthalene-1-sulfonate, [Na(μ-1κO 1 O 2 ,2κO 3 -H 2 L 3 )(CH 3 OH) 2 ] 2 (6; for 7). Compounds 1-7 were fully characterized, also by single-crystal X-ray diffraction analysis, and applied as homogeneous catalysts for the azide-alkyne cycloaddition (AAC) reaction to afford 1,4-disubstituted 1,2,3-triazoles. A structure-catalytic activity relationship has been recognized for the first time on the basis of the occurrence of resonance- and charge-assisted hydrogen bond interactions (RAHB and CAHB), in charge and ligand binding modes, enabling the catalytic activity of the compounds to be ordered as follows: Cu(NO 3 ) 2 ≪7 (complex salt with RAHB and CAHB) < 3 (with RAHB and CAHB) < 5 (with RAHB) < 2 (neither RAHB nor CAHB). Complex 2, without such non-covalent interactions, was found to be the most efficient catalyst for the AAC reaction, affording up to 98% product yield after being placed for 15 min, at 125 °C, in a water/acetonitrile mixture under low power (10 W) MW irradiation.

Five isostructural lanthanide MOFs, [Ln(1κOO',2κO'',3κO''',4κO''''-μ 4 -L)(NO 3 )(DMF) 2 ] n ·n(DMF) {Ln = La 3+ (1), Ce 3+ (2), Nd 3+ (3), Sm 3+ (4) and Dy 3+ (5); L = 5-[2-{2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene}hydrazinyl]isophthalate; DMF = N,N'-dimethyl formamide}, based on dicarboxyl-functionalized arylhydrazone of barbituric acid were synthesized under solvothermal conditions. They were characterized by elemental analysis, FT-IR spectroscopy, thermogravimetric and X-ray diffraction analyses. Crystal structure analysis revealed that these frameworks possess a similar type of two dimensional (2D) structure with a dinuclear {Ln 2 (COO - ) 2 } unit acting as a secondary building block. Topological analysis shows that these frameworks display a 3,6-connected kgd; Shubnikov plane (3.6.3.6)/dual net. They exhibit excellent heterogeneous catalytic activities (compound 2 is the most active one) towards the cyanosilylation of aldehydes under solvent-free conditions. These catalysts can be recycled at least up to five cycles without a loss of activity. Compounds 1-5 exhibit luminescence properties in the solid state at room temperature.

A series of double dihydromethylpiperazinediium metallic sulfates 1-7 [H(2)mpz]M(II)(SO(4))(2)·nH(2)O (mpz = 2-methylpiperazine, C(5)H(12)N(2)) are prepared by slow evaporation using a racemic (R/S)-mpz (for 1, 2) or enantiopure R-mpz (for 3), S-mpz (for 4-7) and sulfates of Cu(II) (for 5), Fe(II) (for 1, 4), Co(II) (for 7) and Zn(II) (for 2, 3, 6), and characterized by infrared spectroscopy, elemental analysis and single crystal X-ray diffraction. The [M(II)(H(2)O)(6)](2+), [(R/S)-H(2)mpz](2+), [(R)-H(2)mpz](2+) or [(S)-H(2)mpz](2+) cations and 2SO(4)(2-) anions are linked together via two types of hydrogen bonds, Ow-Hw···O and N-H···O, leading to supramolecular arrangements. The use of the racemic 2-mpz provides alternatives in crystallization: a centrosymmetric structure where the enantiomers are related by an appropriate crystallographic symmetry operation or one where the enantiomers occupy the same crystallographic position, generating disorder. Compounds 1-7 act as diastereoselective catalysts for the nitroaldol (Henry) reaction. The diastereoselectivity can be regulated from exclusive threo to exclusive erythro isomer preparation with typical yields of 50-99%, depending on the catalyst and the substrate used.

A novel para to meta shift of a nitro group at the phenyl ring of 3-(2-hydroxy-4-nitrophenylhydrazo)pentane-2,4-dione (H(2)L(1), 1), with formation of the new 3-(2-hydroxy-3,5-dinitrophenylhydrazo)pentane-2,4-dione (H(2)L(2), 2), occurs upon nitration of 1 with an equimolar amount of NaNO(2), under basic conditions. 2 acts as a polydentate ligand for the synthesis of the polymeric potassium [K(μ(5)-HL(2))](n) (3) and monomeric nickel(II) [Ni(H(2)O)(3)(L(2))]·H(2)O (4) compounds. They have been fully characterized, including single crystal X-ray analysis, and the complexes feature metal-organic (in 3) or supramolecular (in 4) 3D networks. The topological analysis of 3 reveals a uninodal 5-connected underlying net with the point symbol of (4(6).6(4)) and a very rare 5/4/t5 topology, which had not yet been observed in coordination polymers.

The zinc(II) complexes with ortho-hydroxy substituted arylhydrazo-β-diketonates [Zn(2)(CH(3)OH)(2)(μ-L(1))(2)] (5), [Zn{(CH(3))(2)SO}(H(2)O)(L(2))] (6), [Zn(2)(H(2)O)(2)(μ-L(3))(2)] (7) and [Zn(H(2)O)(2)(L(4))]·H(2)O (8) were synthesized by reaction of a zinc(II) salt with the appropriate hydrazo-β-diketone, HO-2-C(6)H(4)-NHN=C{C(=O)CH(3)}(2) (H(2)L(1), 1), HO-2-O(2)N-4-C(6)H(3)-NHN=C{C(=O)CH(3)}(2) (H(2)L(2), 2), HO-2-C(6)H(4)-NHN=CC(=O)CH(2)C(CH(3))(2)CH(2)C(=O) (H(2)L(3), 3) or HO-2-O(2)N-4-C(6)H(3)-NHN=[CC(=O)CH(2)C(CH(3))(2)CH(2)C(=O) (H(2)L(4), 4). They were fully characterized, namely by X-ray diffraction analysis that disclosed the formation of extensive H-bonds leading to 1D chains (5 and 6), 2D layers (7) or 3D networks (8). The thermodynamic parameters of the Zn(II) reaction with H(2)L(2) in solution, as well as of the thermal decomposition of 1-8 were determined. Complexes 5-8 act as diastereoselective catalysts for the nitroaldol (Henry) reaction. The threo/erythro diastereoselectivity of the β-nitroalkanol products ranges from 8:1 to 1:10 with typical yields of 80-99%, depending on the catalyst and substrate used.

Reactions of copper(II) with 3-phenylhydrazopentane-2,4-diones X-2-C(6)H(4)-NHN=C{C(=O)CH(3)}(2) bearing a substituent in the ortho-position [X = OH (H(2)L(1)) 1, AsO(3)H(2) (H(3)L(2)) 2, Cl (HL(3)) 3, SO(3)H (H(2)L(4)) 4, COOCH(3) (HL(5)) 5, COOH (H(2)L(6)) 6, NO(2) (HL(7)) 7 or H (HL(8)) 8] lead to a variety of complexes including the monomeric [CuL(4)(H(2)O)(2)]·H(2)O 10, [CuL(4)(H(2)O)(2)] 11 and [Cu(HL(4))(2)(H(2)O)(4)] 12, the dimeric [Cu(2)(H(2)O)(2)(μ-HL(2))(2)] 9 and the polymeric [Cu(μ-L(6))](n)] 13 ones, often bearing two fused six-membered metallacycles. Complexes 10-12 can interconvert, depending on pH and temperature, whereas the Cu(II) reactions with 4 in the presence of cyanoguanidine or imidazole (im) afford the monomeric compound [Cu(H(2)O)(4){NCNC(NH(2))(2)}(2)](HL(4))(2)·6H(2)O 14 and the heteroligand polymer [Cu(μ-L(4))(im)](n)15, respectively. The compounds were characterized by single crystal X-ray diffraction (complexes), electrochemical and thermogravimetric studies, as well as elemental analysis, IR, (1)H and (13)C NMR spectroscopies (diones) and ESI-MS. The effects of the substituents in 1-8 on the HOMO-LUMO gap and the relative stability of the model compounds [Cu(OH)(L(8))(H(2)O)]·H(2)O, [Cu(L(1))(H(2)O)(2)]·H(2)O and [Cu(L(4))(H(2)O)(2)]·H(2)O are discussed on the basis of DFT calculations that show the stabilization follows the order: two fused 6-membered > two fused 6-membered/5-membered > one 6-membered metallacycles. Complexes 9, 10, 12 and 13 act as catalyst precursors for the peroxidative oxidation (with H(2)O(2)) of cyclohexane to cyclohexanol and cyclohexanone, in MeCN/H(2)O (total yields of ca. 20% with TONs up to 566), under mild conditions.