Functionalization of Dodecaborates by Mild and Efficient Pd-Catalyzed Formation of B-C Bonds with Boronic Acids.

Hybrid organic-inorganic molecules have recently received great interest due to their unique properties, which give access to their implementation in biological and material sciences. Herein, a new synthetic approach for the direct-linkage of the purely inorganic dodecaborate cluster to organic building blocks through B-C bond is established, using boronic acids as functional groups on the organic moiety, reacting under Suzuki-Miyaura coupling conditions with iodo-undecahydridododecaborate. The choices of ligand (DavePhos) and solvent (N-methylpyrrolidone for electron-poor, CD3 CN for electron-rich groups) are essential for the successful coupling. Ultimately, the newly described methodology is found to be functional-group tolerant covering a wide spectrum of substrates including electron-poor arenes.

Organically Functionalized Mixed-Valent Polyoxo-30-molybdate Wheel and Neutral Tetramolybdenum(V) Oxo Cluster.

The first organofunctionalized mixed-valent polyoxo-30-molybdate wheel, [MoVI18MoV12O84{AsO2(CH3)2}18]18- (Mo30), was synthesized in aqueous, mildly acidic conditions, and upon further acidification, the neutral tetramolybdenum(V) oxo cluster [MoV4O8{AsO2(CH3)2}4] (Mo4) was obtained. Single-crystal X-ray diffraction (XRD) revealed that Mo30 comprises 18 MoVI and 12 MoV ions arranged in a cyclic fashion with alternating {MoV2} and {MoVI3} groups, which are capped by 18 dimethylarsinate ligands, resulting in a novel polyoxo-30-molybdate wheel with a central cavity of ∼1.5 nm. On the other hand, Mo4 has a distorted-cubic structure, with the corners of the cube being occupied by alternating MoV ions and oxo ligands. The compounds were characterized in solution by 1H and 13C NMR and UV-vis spectroscopy and in the solid state by X-ray photoelectron spectroscopy and powder XRD. Mo30 represents a novel type of polyanionic cycle with manyfold possibilities regarding host-guest chemistry.

NiII 36 -Containing 54-Tungsto-6-Silicate: Synthesis, Structure, Magnetic and Electrochemical Studies.

The 36-NiII -containing 54-tungsto-6-silicate, [Ni36 (OH)18 (H2 O)36 (SiW9 O34 )6 ]6- (Ni36 ) was synthesized by a simple one-pot reaction of the Ni2 -pivalate complex [Ni2 (µ-OH2 )(O2 CCMe3 )4 (HO2 CCMe3 )4 ] with the trilacunary [SiW9 O34 ]10- polyanion precursor in water and structurally characterized by a multitude of physicochemical techniques including single-crystal XRD, FTIR, TGA, elemental analysis, magnetic and electrochemical studies. Polyanion Ni36 comprises six equivalent {NiII 6 SiW9 } units which are linked by Ni-O-W bridges forming a macrocyclic assembly. Magnetic studies demonstrate that the {Ni6 } building blocks in Ni36 remain magnetically intact while forming a hexagonal ring with antiferromagnetic exchange interactions between adjacent {Ni6 } units. Electrochemical studies indicate that the first reduction is reversible and associated with the WVI/V couple, whereas the second reduction is irreversible attributed to the NiII/0 couple.

Arsenic(III)-Capped 12-Tungsto-2-Arsenates(III) [M2(AsIIIW6O25)2(AsIIIOH)x]n- (M = CrIII, FeIII, ScIII, InIII, TiIV, MnII) and Their Magnetic Properties.

Six arsenic(III)-capped 12-tungsto-2-arsenates(III) of the type [M2(AsIIIW6O25)2(AsIIIOH)x]n- (M = CrIII, 1; FeIII, 2; ScIII, 3; InIII, 4; TiIV, 5; MnII, 6) have been synthesized in aqueous medium by direct reaction of the elements using a one-pot strategy and structurally characterized by FT-IR spectroscopy, single-crystal XRD, and elemental analysis. Polyanions 1-6 are comprised of two octahedrally coordinated guest metal ions M sandwiched between two {AsW6} units, resulting in a structure with C2h point-group symmetry. Polyanions 1-5 contain tri- and tetravalent metal ion guests M (M = CrIII, FeIII, ScIII, InIII, and TiIV, respectively), and they have one {AsIIIOH} group grafted on each {AsW6} unit, whereas the divalent MnII-containing derivative 6 has two such {AsIIIOH} groups grafted on each {AsW6} unit. Magnetic studies on polyanions 3-5 over the temperature range 1.8-295 K and magnetic fields of 0-7 T confirmed that they are diamagnetic. On the other hand, polyanions 1, 2, and 6 are strongly magnetic and follow the Curie-Weiss law above 30 K. The susceptibility plots of 1 and 6 exhibit broad peaks suggesting short-range antiferromagnetic ordering, while the very weak antiferromagnetic ordering of 2 is overshadowed by traces of a paramagnetic impurity. The magnetization data of 1, 2, and 6 at 1.8 K over 0-7 T were analyzed by using the Heisenberg exchange procedure. Small (negative) values of the obtained J values help in understanding the absence of long-range antiferromagnetic ordering.

Synthesis, structure, electrochemistry and magnetism of cobalt-, nickel- and zinc-containing [M4(OH)3(H2O)2(α-SiW10O36.5)2]13- (M = Co2+, Ni2+, and Zn2+).

Interaction of the trilacunary 9-tungstosilicate [A-α-SiW9O34]10- with cobalt(ii), nickel(ii) and zinc(ii) ions in pH 9 aqueous medium at room temperature led to the formation of the respective M4-containing heteropolytungstates [M4(OH)3(H2O)2(α-SiW10O36.5)2]13- (M = Co2+ (1), Ni2+ (2), and Zn2+ (3)). Polyanions 1-3 were characterized in the solid state by single-crystal XRD, FT-IR spectroscopy, and thermogravimetric and elemental analyses. Electrochemical studies showed that the Co2+ ions in 1 can be oxidized to Co3+ and the CVs of the WVI centers of the polyanions feature well-defined and chemically reversible reduction waves. Magnetic measurements on 1 and 2 showed paramagnetism with complex ferromagnetic and antiferromagnetic interactions. A model was presented for extracting the exchange constants for the magnetic exchange interaction.

Peroxouranyl-Containing W48 Wheel: Synthesis, Structure, and Detailed Infrared and Raman Spectroscopy Study.

We report on the first example of a peroxouranium-containing {P8W48} wheel, [{(UO2)4(O2)4}2(P8W48O184)]40- (1), which was synthesized by a one-pot reaction of UO2(NO3)2·6H2O with the 48-tungsto-8-phosphate wheel [H7P8W48O184]33- and aqueous hydrogen peroxide in a pH 6 lithium acetate solution at 50 °C. Polyanion 1 comprises two tetrauranyl squares with side-on peroxo bridging ligands in the cavity of the {P8W48} wheel, and was isolated as the hydrated potassium-lithium salt K18Li22[{(UO2)4(O2)4}2(P8W48O184)]·133H2O (KLi-1), which was characterized in the solid state by single-crystal X-ray diffraction, as well as thermogravimetric and elemental analyses. A detailed Fourier transform infrared and Raman spectroscopy study was also performed.

FeIII 48 -Containing 96-Tungsto-16-Phosphate: Synthesis, Structure, Magnetism and Electrochemistry.

The 48-FeIII -containing 96-tungsto-16-phosphate, [FeIII 48 (OH)76 (H2 O)16 (HP2 W12 O48 )8 ]36- (Fe48 ), has been synthesized and structurally characterized. This polyanion comprises eight equivalent {FeIII 6 P2 W12 } units that are linked in an end-on fashion forming a macrocyclic assembly that contains more iron centers than any other polyoxometalate (POM) known to date. The novel Fe48 was synthesized by a simple one-pot reaction of an {Fe22 } coordination complex with the hexalacunary {P2 W12 } POM precursor in water. The title polyanion was characterized by single-crystal XRD, FTIR, TGA, magnetic and electrochemical studies.

Lanthanide-Containing 22-Tungsto-2-germanates [Ln(GeW11O39)2]13-: Synthesis, Structure, and Magnetic Properties.

We report on the synthesis and structural characterization of two series of lanthanide-containing 22-tungsto-2-germanates. The first series corresponds to a family of polyanions with the formula [Ln(ß2-GeW11O39)2]13- (LnIII = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Gd (6), Dy (7)), and the second series corresponds to a family with the formula [Ln(ß2-GeW11O39)(α-GeW11O39)]13- (LnIII = Ho (8), Er (9), Tm (10)). All compounds were characterized in the solid state by single-crystal and powder XRD, IR, TGA, and SQUID magnetometry. The polyanions were synthesized in aqueous medium by direct reaction of the monolacunary [ß2-GeW11O39]8- POM precursor with the corresponding lanthanide salts. The structure of the polyanions consists of an 8-coordinated lanthanide ion in a square-antiprismatic geometry, which is sandwiched either between two [ß2-GeW11O39]8- units for 1-7 or between a [ß2-GeW11O39]8- and a [α-GeW11O39]8- unit for 8-10. Furthermore, the effect of the central paramagnetic lanthanide ion on the magnetic behavior of the polyanions was investigated, with the erbium-derivative [Er(ß2-GeW11O39)(α-GeW11O39)]13- (9) showing single-molecule magnet (SMM) behavior.

In Vitro and In Vivo Evaluation of the Anticancer and Anti-inflammatory Activities of 2-Himachelen-7-ol isolated from Cedrus Libani.

Cedrus libani is a majestic evergreen tree native to the Mediterranean mountains of Lebanon, Syria and Turkey. In this study, the tree heart wood was extracted using hexane to produce C. libani oil extract (CLOE) as a dark oil. GCMS analysis of CLOE identified up to 30 compounds whereby 2-himachalen-7-ol (7-HC) was the most abundant (40%). 7-HC was isolated using column chromatography and the identity of the white crystalline solid was confirmed via NMR spectroscopy and X-Ray Crystallography. 7-HC demonstrated potent cytotoxic activity against several human cancer cell lines including brain (SF-268, IC50 8.1 µg/mL) and colon (HT-29, IC50 10.1 µg/mL; Caco-2, IC50 9.9 µg/mL) with ovarian (Sk-OV-3, IC50 > 50 µg/mL) cells being the most resistant. However, while HT-29 displayed resistance to Cisplatin, 7-HC was 8-10 folds more potent. Co-treatment with 7-HC and Cisplatin showed a significant synergistic anti-proliferative effect against SF-268, HT-29 and Caco-2 cells. 7-HC also exhibited significant anti-inflammatory effect in formalin-induced paw edema in rats. Western blot analysis revealed that 7-HC displayed dose dependent inhibition of LPS-induced COX-2 protein expression in isolated rat monocytes. The present study demonstrates that 7-HC possesses promising anticancer and anti-inflammatory activities, and may serve as a lead molecule in cancer therapy.

Peroxo-Cerium(IV)-Containing Polyoxometalates: [CeIV6(O2)9(GeW10O37)3]24-, a Recyclable Homogeneous Oxidation Catalyst.

The class of peroxo-cerium-containing polyoxometalates has been discovered via the synthesis of the 9-peroxo-6-cerium(IV)-containing 30-tungsto-3-germanate, [CeIV6(O2)9(GeW10O37)3]24- (1). Polyanion 1 consists of a cyclic [Ce6(O2)9]6+ assembly that is stabilized by three dilacunary [GeW10O37]10- Keggin fragments. The title polyanion 1 is solution-stable, on the basis of 183W nuclear magnetic resonance, and was shown to act as a recyclable homogeneous catalyst for the selective, microwave-activated sulfoxidation of the model substrate methionine to the sulfoxide in the absence and to the sulfone in the presence of hydrogen peroxide. Solution and solid-state Raman as well as solid-state infrared studies of 1 demonstrated the complete loss (and regain) of the nine peroxo groups in situ during the catalytic cycle, suggesting that the peroxo-free {Ce6(GeW10)3} skeleton remains most likely intact during the catalytic cycle. Solid-state X-ray photoelectron spectroscopy measurements showed that peroxo loss is accompanied by reduction of the cerium ions from +4 to +3, which is fully reversible. Density functional theory calculations are in complete agreement with all of these observations and furthermore suggest that the reduction of the six cerium(IV) ions is accompanied by the formation of molecular dioxygen.

9-Cobalt(II)-Containing 27-Tungsto-3-germanate(IV): Synthesis, Structure, Computational Modeling, and Heterogeneous Water Oxidation Catalysis.

The 9-cobalt(II)-containing trimeric, cyclic polyanion [Co9(OH)3(H2O)6(PO4)2(B-α-GeW9O34)3]21- (1) was synthesized in an aqueous phosphate solution at pH 8 and isolated as a hydrated mixed sodium-cesium salt. Polyanion 1 was structurally and compositionally characterized in the solid state by single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, as well as thermogravimetric and elemental analyses. The magnetic and electrochemical properties of 1 were also studied and compared with those of its phosphorus analogue, [Co9(OH)3(H2O)6(HPO4)2(B-α-PW9O34)3]16- (Co9-P). The electrochemical water oxidation activity of the cesium salt of 1 under heterogeneous conditions was also studied and shown to be superior to that of Co9-P. The experimental results were supported by computational studies.

The mixed-valent 10-manganese(III/IV)-containing 36-tungsto-4-arsenate(V), [MnIII6MnIV4O4(OH)12(H2O)12(A-ß-AsW9O34)4]22.

Interaction of the mixed-valent 12-manganese coordination complex [MnIII8MnIV4O12(CH3COO)16(H2O)4] with the lacunary 9-tungstoarsenate(V) [A-α-AsW9O34]9- resulted in the 10-manganese(III/IV)-containing 36-tungsto-4-arsenate(V), [MnIII6MnIV4O4(OH)12(H2O)12(A-ß-AsW9O34)4]22- (1). Polyanion 1 was isolated as a hydrated mixed potassium-sodium salt, K14Na8[MnIII6MnIV4O4(OH)12(H2O)12(A-ß-AsW9O34)4]·104H2O, which crystallizes in the orthorhombic space group Pbcn and was characterized by FT-IR spectroscopy and single-crystal X-ray diffraction, as well as elemental and thermogravimetric analyses. The title polyanion contains a unique [MnIII6MnIV4O4(OH)12(H2O)12]14+ core stabilized within the 36-tungsto-4-arsenate(V) framework.

15-Copper(ii)-containing 36-tungsto-4-silicates(iv) [Cu15O2(OH)10X(A-α-SiW9O34)4]25- (X = Cl, Br): synthesis, structure, magnetic properties, and electrocatalytic CO2 reduction.

The 15-copper(ii)-containing 36-tungsto-4-silicates [Cu15O2(OH)10X(A-α-SiW9O34)4]25- (X = Cl, 1; Br, 2) have been prepared in 70% yield by reaction of the trilacunary 9-tungstosilicate precursor [A-α-SiW9O34]10- with Cu2+ ions in aqueous pH 8 medium. Both polyanions 1 and 2 were isolated as hydrated mixed potassium/sodium salts and characterized in the solid state by FT-IR, TGA, single-crystal XRD, and elemental analysis. DC magnetic susceptibility measurements from 1.8-300 K established the ground state to be paramagnetic with a magnetic moment corresponding to 15 uncoupled Cu2+ (S = 1/2) ions. EPR measurements and simulations were consistent with this analysis. Electrochemical studies were performed for polyanions 1 and 2 dissolved in solution to elucidate the electroactivity of both copper and tungstate sites. Using 2 as a representative example, the electrocatalytic activity towards CO2 reduction upon deposition on a glassy carbon electrode surface, while retaining selectivity relative to hydrogen evolution, was demonstrated.

CrIII-Substituted Heteropoly-16-Tungstates [CrIII2(B-ß-XIVW8O31)2]14- (X = Si, Ge): Magnetic, Biological, and Electrochemical Studies.

The dichromium(III)-containing heteropoly-16-tungstates [CrIII2(B-ß-SiIVW8O31)2]14- (1) and [CrIII2(B-ß-GeIVW8O31)2]14- (2) were prepared via a one-pot reaction of the composing elements in aqueous, basic medium. Polyanions 1 and 2 represent the first examples of CrIII-containing heteropolytungstates comprising the octatungstate unit {XW8O31} (X = Si, Ge). Magnetic studies demonstrated that, in the solid state, the two polyanions exhibit a weak antiferromagnetic interaction between the two CrIII centers with J = -3.5 ± 0.5 cm-1, with no long-range ordering down to 1.8 K. The ground-state spin of polyanions 1 and 2 was thus deduced to be 0, but the detection of a complex set of EPR signals implies that there are thermally accessible excited states containing unpaired spins resulting from the two S = 3/2 CrIII ions. A comprehensive electrochemistry study on 1 and 2 in solution was performed, and biological tests showed that both polyanions display significant antidiabetic and anticancer activities.

Gallium(III)-Containing, Sandwich-Type Heteropolytungstates: Synthesis, Solution Characterization, and Hydrolytic Studies toward Phosphoester and Phosphoanhydride Bond Cleavage.

The gallium(III)-containing heteropolytungstates [Ga4(H2O)10(ß-XW9O33)2](6-) (X = As(III), 1; Sb(III), 2) were synthesized in aqueous acidic medium by reaction of Ga(3+) ions with the trilacunary, lone-pair-containing [XW9O33](9-). Polyanions 1 and 2 are isostructural and crystallized as the hydrated sodium salts Na6[Ga4(H2O)10(ß-AsW9O33)2]·28H2O (Na-1) and Na6[Ga4(H2O)10(ß-SbW9O33)2]·30H2O (Na-2) in the monoclinic space group P21/c, with unit cell parameters a = 16.0218(12) Å, b = 15.2044(10) Å, c = 20.0821(12) Å, and ß = 95.82(0)°, as well as a = 16.0912(5) Å, b = 15.2178(5) Å, c = 20.1047(5) Å, and ß = 96.2(0)°, respectively. The corresponding tellurium(IV) derivative [Ga4(H2O)10(ß-TeW9O33)2](4-) (3) was also prepared, by direct reaction of sodium tungstate, tellurium(IV) oxide, and gallium nitrate. Polyanion 3 crystallized as the mixed rubidium/sodium salt Rb2Na2[Ga4(H2O)10(ß-TeW9O33)2]·28H2O (RbNa-3) in the triclinic space group P1̅ with unit cell parameters a = 12.5629(15) Å, b = 13.2208(18) Å, c = 15.474(2) Å, α = 80.52(1)°, ß = 84.37(1)°, and γ = 65.83(1)°. All polyanions 1-3 were characterized in the solid state by single-crystal XRD, FT-IR, TGA, and elemental analysis, and polyanion 2 was also characterized in solution by (183)W NMR and UV-vis spectroscopy. Polyanion 2 was used as a homogeneous catalyst toward adenosine triphosphate (ATP) and the DNA model substrate 4-nitrophenylphosphate, monitored by (1)H and (31)P NMR spectroscopy. The encapsulated gallium(III) centers in 2 promote the Lewis acidic synergistic activation of the hydrolysis of ATP and DNA model substrates at a higher rate in near-physiological conditions. A strong interaction of 2 with the P-O bond of ATP was evidenced by changes in chemical shift values and line broadening of the (31)P nucleus in ATP upon addition of the polyanion.

Synthesis, Structure, and Tandem Mass Spectrometric Characterization of the Diastereomers of Quinic Acid.

(-)-Quinic acid possess eight possible stereoisomers, which occur both naturally and as products of thermal food processing. In this contribution, we have selectively synthesized four isomers, namely, epi-quinic acid, muco-quinic acid, cis-quinic acid, and scyllo-quinic acid, to develop a tandem LC-MS method identifying all stereoisomeric quinic acids. Four derivatives have been unambiguously characterized by single-crystal X-ray crystallography. The missing diastereomers of quinic acid were obtained by nonselective isomerization of (-)-quinic acid using acetic acid/concentrated H2SO4 allowing chromatographic separation and assignment of all diastereomers of quinic acid. We report for the first time that a full set of stereoisomers are reliably distinguishable on the basis of their tandem mass spectrometric fragment spectra as well as their elution order. A rationale for characteristic fragmentation mechanisms is proposed. In this study, we also observed that muco-quinic acid, scyllo-quinic acid, and epi-quinic acid are present in hydrolyzed Guatemalan roasted coffee sample as possible products of roasting.

Tetra-Antimony(III)-Bridged 18-Tungsto-2-Arsenates(V), [(LSb(III))4(A-α-As(V)W9O34)2](10-) (L = Ph, OH): Turning Bioactivity On and Off by Ligand Substitution.

Two tetra-antimony(III)-bridged, sandwich-type 18-tungsto-2-arsenates(V), [(LSb(III))4(A-α-As(V)W9O34)2](10-) (L = Ph (1), OH (2)), were prepared and fully characterized in the solid state and in solution. Both polyanions are stable in aqueous physiological medium for at least 24 h (at concentrations ≥2.5 × 10(-6) M). Despite the presence of an isostructural tetra-antimony(III) motif in 1 and 2, distinctly different antibacterial activity was observed for both polyanions. The minimum inhibitory concentrations (MIC) of 1 (7.8-62.5 µg/mL) is lower than for any other organoantimony(III)-containing polyoxometalate reported to date.

Mixed-Valent Mn16-Containing Heteropolyanions: Tuning of Oxidation State and Associated Physicochemical Properties.

The two 16-manganese-containing, Keggin-based 36-tungsto-4-silicates [Mn(III)10Mn(II)6O6(OH)6(PO4)4(A-α-SiW9O34)4](28-) (1) and [Mn(III)4Mn(II)12(OH)12(PO4)4(A-α-SiW9O34)4](28-) (2) have been prepared by reaction of the trilacunary Keggin precursor [A-α-SiW9O34](10-) with either Mn(OOCCH3)3·2H2O (for 1) or MnCl2·4H2O (for 2), in aqueous phosphate solution at pH 9. Polyanions 1 and 2 comprise mixed-valent, cationic {Mn(III)10Mn(II)6O6(OH)6}(24+) and {Mn(III)4Mn(II)12(OH)12}(24+) cores, respectively, encapsulated by four phosphate groups and four {SiW9} units in a tetrahedral fashion. Both polyanions were structurally and compositionally characterized by single-crystal XRD, IR, thermogravimetric analysis, and X-ray absorption spectroscopy. Furthermore, studies were performed probing the magnetic, electrochemical, oxidation catalytic, and Li-ion battery performance of 1 and 2.

Heptanickel(ii) double-cubane core in wells-dawson heteropolytungstate, [Ni7(OH)6(H2O)6(P2W15O56)2](16-).

The hepta-Ni(2+)-containing 30-tungsto-4-phosphate(v) [Ni7(OH)6(H2O)6(P2W15O56)2](16-) (1) has been synthesized in aqueous, slightly basic medium under conventional reaction conditions, and charactarized via different physical methods. Single-crystal XRD showed that 1 consists of a corner-fused double-cubane {Ni7(OH)6(H2O)6}(8+) fragment sandwiched by two trilacunary [P2W15O56](12-) units. Polyanion 1 is solution-stable as shown by (31)P NMR. Ferromagnetic coupling interaction between the 7 paramagnetic centers of the double-cubane core in 1 with a S = 7 ground state was demonstrated. Electrochemical studies were also performed on 1.

Ln12 -Containing 60-Tungstogermanates: Synthesis, Structure, Luminescence, and Magnetic Studies.

A new class of hexameric Ln12 -containing 60-tungstogermanates, [Na(H2 O)6 ⊂Eu12 (OH)12 (H2 O)18 Ge2 (GeW10 O38 )6 ](39-) (Eu12 ), [Na(H2 O)6 ⊂Gd12 (OH)6 (H2 O)24 Ge(GeW10 O38 )6 ](37-) (Gd12 ), and [(H2 O)6 ⊂Dy12 (H2 O)24 (GeW10 O38 )6 ](36-) (Dy12 ), comprising six di-Ln-embedded {ß(4,11)-GeW10 } subunits was prepared by reaction of [α-GeW9 O34 ](10-) with Ln(III) ions in weakly acidic (pH 5) aqueous medium. Depending on the size of the Ln(III) ion, the assemblies feature selective capture of two (for Eu12 ), one (for Gd12 ), or zero (for Dy12 ) extra Ge(IV) ions. The selective encapsulation of a cationic sodium hexaaqua complex [Na(H2 O)6 ](+) was observed for Eu12 and Gd12 , whereas Dy12 incorporates a neutral, distorted-octahedral (H2 O)6 cluster. The three compounds were characterized by single-crystal XRD, ESI-MS, photoluminescence, and magnetic studies. Dy12 was shown to be a single-molecule magnet.