Synthesis, characterization, and spectrophotometric studies of novel fluorescent arachno decaborane and nonaborane clusters containing aza-distyrylbenzene derivatives

Two aza-analogues of distyrylbenzene namely: 1,4-bis[β-(4-quinolyl)vinyl]benzene (PhQ) and 1,4-bis[β-(4-pyridyl)vinyl]benzene (PhPy) containing arachno-decaborane or arachno-nonaborane clusters have been isolated: 6,9-(PhQ)₂-arachno-B₁₀H₁₂ (1), N,N′-bis[9-Me₂S-arachno-B₁₀H₁₂-6-yl]PhQ (2), 6,9-(PhPy)₂-arachno-B₁₀H₁₂ (3), N,N′-bis[(9-Me₂S)-arachno-B₁₀H₁₂-6-yl]PhPy (4), N,N′-bis[arachno-B₉H₁₃-4-yl]PhQ (5), 4-PhQ-arachno-B₉H₁₃ (6), N,N′-bis[arachno-B₉H₁₃-4-yl]PhPy (7), and 4-PhPy-arachno-B₉H₁₃ (8). These boronated compounds were easily prepared from the displacement reactions of weaker ligand (SMe₂) of bis (dimethyl sulfide) arachno-decaborane(14) {6,9-(Me)₂SB₁₀H₁₂}or dimethyl sulfide-arachno-nonaborane {4-(Me)₂SB₉H₁₃} by the stronger bidentate ligands of PhQ or PhPy in ratio (1:2). The electronic interaction between decaborane or nonaborane arachno-type unit and the bonded pyridine units has been investigated by UV-Vis spectroscopy and by AM1 molecular orbital calculations. The resulting compounds undergo trans-cis photoisomerization upon excitation. The connection of boron clusters to PhQ and PhPy led to enhancing of the photoreactivity and decreasing of the fluorescence quantum yield of the products.     

Synthesis of the 1-hydroxy-closo-decaborate anion [1-B10H9OH]

Reactions of the diazonium derivative of closo-decaborate anion with oxygen nucleophiles were studied. The reaction of [1-B₁₀H₉N₂]⁻ with hydroxide ion gives the corresponding hydroxy derivative [1-B₁₀H₉OH]²⁻ in high yield. The reactions with OR (R = Me, Et, i-Pr, Ph) result in mixture of [1-B₁₀H₉OR]²⁻ and [a²-B₂₀H₁₈]⁴⁻.     

Synthesis of 13C4-labelled oxidized metabolites of the carcinogenic polycyclic aromatic hydrocarbon benzo[a]pyrene

Polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (BaP), are ubiquitous environmental contaminants that are implicated in causing lung cancer. BaP is a component of tobacco smoke that is transformed enzymatically to active forms that interact with DNA. We reported previously development of a sensitive stable isotope dilution LC/MS method for analysis of BaP metabolites. We now report efficient syntheses of ¹³C₄-BaP and the complete set of its ¹³C₄-labelled oxidized metabolites needed as internal standards They include the metabolites not involved in carcinogenesis (Group A) and the metabolites implicated in initiation of cancer (Group B). The synthetic approach is novel, entailing use of Pd-catalyzed Suzuki, Sonogashira, and Hartwig cross-coupling reactions combined with PtCl₂-catalyzed cyclization of acetylenic compounds. This synthetic method requires fewer steps, employs milder conditions, and product isolation is simpler than conventional methods of PAH synthesis. The syntheses of ¹³C₄-BaP and ¹³C₄-BaP-8-ol each require only four steps, and the ¹³C-atoms are all introduced in a single step. ¹³C₄-BaP-8-ol serves as the synthetic precursor of all the oxidized metabolites of ¹³C-BaP implicated in initiation of cancer. The isotopic purities of the synthetic ¹³C₄-BaP metabolites were estimated to be ≥99.9%.     

Comparison between evaporative light scattering detection and charged aerosol detection for the analysis of saikosaponins

Saikosaponins are triterpene saponins derived from the roots of Bupleurum falcatum L. (Umbelliferae), which has been traditionally used to treat fever, inflammation, liver diseases, and nephritis. It is difficult to analyze saikosaponins using HPLC-UV due to the lack of chromophores. Therefore, evaporative light scattering detection (ELSD) is used as a valuable alternative to UV detection. More recently, a charged aerosol detection (CAD) method has been developed to improve the sensitivity and reproducibility of ELSD. In this study, we compared CAD and ELSD methods in the simultaneous analysis of 10 saikosaponins, including saikosaponins-A, -B₁, -B₂, -B₃, -B₄, -C, -D, -G, -H and -I. A mixture of the 10 saikosaponins was injected into the Ascentis^® Express C18 column (100 mm × 4.6 mm, 2.7 μm) with gradient elution and detection with CAD and ELSD by splitting. We examined various factors that could affect the sensitivity of the detectors including various concentrations of additives, pH and flow rate of the mobile phase, purity of nitrogen gas and the CAD range. The sensitivity was determined based on the signal-to-noise ratio. The best sensitivity for CAD was achieved with 0.1 mM ammonium acetate at pH 4.0 in the mobile phase with a flow rate of 1.0 mL/min, and the CAD range at 100 pA, whereas that for ELSD was achieved with 0.01% acetic acid in the mobile phase with a flow rate at 0.8 mL/min. The purity of the nitrogen gas had only minor effects on the sensitivities of both detectors. Finally, the sensitivity for CAD was two to six times better than that of ELSD. Taken together, these results suggest that CAD provides a more sensitive analysis of the 10 saikosaponins than does ELSD.     

Ti functionalized carbon and boron nitride chains: a promising material for hydrogen storage

The geometries, electronic structures, thermochemical properties, polarizabilities, and hyperpolarizabilities of high capacity hydrogen storage media consisting of alkali metal such as Li or transition metal as Ti, that is, functionalized at the end of C and BN chains have been investigated theoretically using density functional theory (DFT). Fundamental aspects such as interaction energy, natural bond orbital (NBO), charge transfer, energy gap, and the projected density of states (PDOS) are elucidated to analyze the adsorption properties of H₂ molecules. Our results revealed that H₂ is introduced sequentially on the Ti-C₇, Ti_(B)-B₄N₃, and Ti_(N)-B₃N₄ complexes and the H₂ uptake capacity are found to be 10.89, 10.80, and 10.58 wt%, respectively. Moreover, two Ti atoms can be adsorbed concomitantly to the ends of C₇, B₄N₃, and B₃N₄ chains where Ti sites can accommodate 16 H₂ molecules, with 8 per Ti center, leading to a storage capacity of up to 26.40, 26.28, and 25.94 wt%, respectively. In addition, two binding mechanisms contribute to the adsorption of hydrogen molecules: polarization of the H₂ under the electric field produced by the Ti–chain dipole and hybridization of the 3d orbitals of Ti with σ orbitals of H₂. These lead to the hydrogen binding energies within the range of 0.22–0.56 eV/H₂, open a prospect of a promising material system for hydrogen storage at ambient temperature. The large difference in charge transfer and interaction between the metal and chains is responsible for the large hyperpolarizability. Moreover, the C and BN chains can be stabilized effectively by C₂₀ fullerene termination and store 8 H₂ with an average binding energy of 0.22 eV/H₂. The hydrogen desorption energies and temperatures indicate that the Ti-C₇,Ti_(B)-B₄N₃, Ti_(N)-B₃N₄, Ti-C₇-Ti, Ti_(B)-B₄N₃-Ti_(B), Ti_(N)-B₃N₄-Ti_(N), Ti-C₇-C₂₀, Ti_(B)-B₄N₃-C₂₀, and Ti_(N)-B₃N₄-C20 complexes are easy to desorb H2 molecules.     

Transition-metal-like bonding behaviors of a boron atom in a boron-cluster boronyl complex [(η7-B7)-B-BO]−

Boron displays many unusual structural and bonding properties due to its electron deficiency. Here we show that a boron atom in a boron monoxide cluster (B₉O⁻) exhibits transition-metal-like properties. Temperature-dependent photoelectron spectroscopy provided evidence of the existence of two isomers for B₉O⁻: the main isomer has an adiabatic detachment energy (ADE) of 4.19 eV and a higher energy isomer with an ADE of 3.59 eV. The global minimum of B₉O⁻ is found surprisingly to be an umbrella-like structure (C_6v, ¹A₁) and its simulated spectrum agrees well with that of the main isomer observed. A low-lying isomer (C_s, ¹A′) consisting of a BO unit bonded to a disk-like B₈ cluster agrees well with the 3.59 eV ADE species. The unexpected umbrella-like global minimum of B₉O⁻ can be viewed as a central boron atom coordinated by a η⁷-B₇ ligand on one side and a BO ligand on the other side, [(η⁷-B₇)-B-BO]⁻. The central B atom is found to share its valence electrons with the B₇ unit to fulfill double aromaticity, similar to that in half-sandwich [(η⁷-B₇)-Zn-CO]⁻ or [(η⁷-B₇)-Fe(CO)₃]⁻ transition-metal complexes. The ability of boron to form a half-sandwich complex with an aromatic ligand, a prototypical property of transition metals, brings out new metallomimetic properties of boron.

The global minimum of the B₉O⁻ cluster is found to have an umbrella-like structure, where the central B atom exhibits transition-metal-like bonding properties, coordinated by a η⁷-B₇ ligand on one side and a BO ligand on the other.     

Nucleophilic addition of alcohols to the C-N multiple bonds of the nitrilium substituent in the anion [2-B10H9(N≡CMe)]−

The reactions of salts of the anion [2-B₁₀H₉(N≡CMe)]⁻ with aliphatic alcohols ROH (R = C _n H_2n+1 (n = 1–6) CH₂CH₂(OEt), Prⁱ, Buⁱ, Bu^t, i-C₅H₁₁) are studied. These reactions result in hydrolytically stable imidates [2-B₁₀H₉{NH=C(OR)Me}]⁻. Their structures were confirmed by the data from mass spectrometry, IR, ¹H, ¹¹B, and ¹³C NMR spectroscopy. The molecular geometry of [2(Z)-B₁₀H₉{NH=C(OBu)Me}]⁻, which formed in nucleophilic addition reaction of n-butyl alcohol to [2-B₁₀H₉(N≡CMe)]⁻, was established by X-ray diffraction analysis.     

[2,6(9)-B10H8>(O)2CCH3]− and [2,7(8)-B10H8(OC(O)CH3)2]2− derivatives in synthesis of position isomers of the [B10H8(OC(O)CH3)(OH)]2− anion with the 2,6(9)- and 2,7(8)-arrangement of functional groups

The interaction of Cat₂B₁₀H₁₀ (Cat = Ph₄P⁺, Ph₄As⁺) with acetic acid has been studied. Disubstituted closo-decaborate derivatives with a bidentately bound acetate group, Cat[2,6(9)-B₁₀H₈>(O)₂CCH₃], or two monodentate acetate groups, Cat₂[2,7(8)-B₁₀H₈(OC(O)CH₃)₂], have been isolated (Cat = Ph₄P⁺, Ph₄As⁺). Hydrolysis of these compounds has led to the position isomers of the [B₁₀H₈(OC(O)CH₃)(OH)]^2? anion with the hydroxo and acetate groups in the 2,6(9)- and 2,7(8)-positions. The structures of {Pb(Bipy)₂[2,6(9)-B₁₀H₈(OC(O)CH₃)(OH)]}₂ · 3H₂O, (Ph₄As)₂[2,6(9)-B₁₀H₈(OC(O)CH₃)(OH)] · 0.4C₂H₅OH · 0.25H₂O, and (Ph₄As)₂[2,7(8)-B₁₀H₈(OC(O)CH₃)(OH)], as well as of the product of the reaction of the B₁₀H ₁₀ ^2? anion with formic acid (Ph₄P)₂[2-B₁₀H₉OC(O)H] · CH₃CN, have been determined by X-ray crystallography.     

The chemistry of isomers of icosaborane(26): Crystal and molecular structure of 1,2′-bi(nido-decaboranyl)

The crystal and molecular structure of 1,2′-(nido-B₁₀H₁₃)₂ has been determined by single-crystal X-ray diffraction analysis, thus con     

Regioselective hydrogen-deuterium exchange in the [B10H10]2– anion. Syntheses of [1,10-B10H8D2]2– and [2,3,4,5,6,7,8,9-B10H2D8]2–

Decahydro-closo-decaborate anion, [B₁₀H₁₀]^2–, undergoes regioselective deuterio-exchange in methanol-d₄. Selectively deuterated derivatives [1,10-B₁₀H₈D₂]^2– and [2,3,4,5,6,7,8,9-B₁₀H₂D₈]^2– were synthesized.     

Reactions of nucleophilic addition of primary amines to the nitrilium derivative of the <Emphasis Type="Italic">closo</Emphasis>-decaborate anion [2-B<Subscript>10</Subscript>H<Subscript>9</Subscript>(N≡CCH<Subscript>3</Subscript>)]<Superscript>−</Superscript>

Compounds (Bu₄N)[2-B₁₀H₉{NH=C(NHR)CH₃}]⁻ are obtained by reactions of the tetrabutylammonium salt of the [2-B₁₀H₉(N≡CCH₃)]⁻ anion with aliphatic and aromatic primary amines RNH₂ (R = n-C₃H₇, n-C₄H₉, cyclo-C₅H₉, C₆H₅, cyclo-C₆H₁₁, n-C₆H₁₃, C₇H₇, C₈H₈NH₂, C₆H₄NO₂, and C₁₈H₃₇) and identified by IR, ESI/MS, and NMR (¹H, ¹¹B, and ¹³C) spectroscopy. The structures of the amidine-type derivatives [2-B₁₀H₉{Z-NH=C(NH-cyclo-C₅H₉)CH₃}]⁻ and [2-B₁₀H₉{Z-NH=C(NH-C₇H₇)CH₃}]⁻ are determined by X-ray diffraction.     

Experimental and Theoretical Study of the Features of Zinc(II) and Cadmium(II) Complexation with the Substituted closo-Hydridoborate Anion [2-B10H9(OH)]2−

Herein, we studied the experimental and theoretical foundations of the process of zinc(II) and cadmium(II) complexation with 2-hydroxido-nonahydrido-closo-decaborate(2−) anion [2-B₁₀H₉(OH)]²⁻ in the presence of azaheterocyclic ligands L (L=2,2′-bipyridyl (bipy), 1,10-phenanthroline (phen), and 2,2′-bipyridylamine (bpa)), which can be used as model system for obtaining complexes with the required composition and structure. The first examples of mixed-ligand Zn(II) and Cd(II) complexes with [2-B₁₀H₉(OH)]²⁻ coordinated by the metal atom were isolated selectively. The structures of zinc(II) complexes [Zn(bipy)₂(2-B₁₀H₉(OH)-κ²H¹,O)] ⋅ 2CH₃CN ( 1 ⋅ 2CH₃CN) and [Zn(phen)₂(2-B₁₀H₉(OH)-κ²H⁹,O)] ⋅ 2CH₃CN ( 2 ⋅ 2CH₃CN), as well as two cadmium(II) bond isomers [Cd(bipy)₂(2-B₁₀H₉(OH)-κ²H¹,O)] ( 4 a ) and [Cd(bipy)₂(2-B₁₀H₉(OH)-κ²H⁹,H¹⁰)] ( 4 b ) bound into a dimeric pair in the complex [Cd(bipy)₂(2-B₁₀H₉(OH))] ( 4 ), and cadmium(II) complex [Cd(bpa)₂(2-B₁₀H₉(OH)-κ²H⁷,H¹⁰)] ( 7 ) were solved by single-crystal X-ray diffraction (XRD). Density functional theory (DFT) calculations show that for cadmium(II) the formation of both multicenter BH−Cd−HB and BO(H)−Cd−HB bonds is equally probable. The affinity of zinc(II) for oxygen leads to preferential formation of complexes via BO(H)−Zn−HB bonds than BH−Zn−HB bonds. The M−B(H) bonding was found to be presumably electrostatic in nature, which could be the reason of topological isomerism of zinc(II) and cadmium(II) decaborates.     

Crystal growth and structure of a new manganese vanado-antimonate MnVSbO6

Single crystals of a new compound of formula MnVSbO₆ were grown by slow cooling from a V₂O₅-B₂O3₃ flux at 900°C. The compound crystallizes in the orthorhombic space group Pbcn (No. 60), with cell parameters (in the Pcnb setting) a=4.6604(3) Å, b=4.9603(3) Å, c=17.1433(9)Å, Z=4. The crystal structure was solved from 1188 independent reflections to R_w=3.20% and goodness-of-fit 1.5 for 44 refined parameters. The structure can be described as a superstructure of the α-PbO₂ type with a cation ordering similar to that found in Fe₂WO₆. Cations occupy octahedral sites in the PbO₂-like layers. Zigzag chains of edge-sharing MnO₆ octahedra alternate with mixed Sb/V chains following a -Mn-Sb/V-Sb/V- sequence. The magnetic susceptibility of MnVSbO₆ follows the Curie-Weiss law down to ca. 15 K, where it orders antiferromagnetically. The bond lengths and Curie constant are consistent with the expected charge distribution Mn²⁺V⁵⁺Sb⁵⁺O₆.     

Synthesis of Schiff bases and benzylamino derivatives containing [1-B<Subscript>10</Subscript>H<Subscript>9</Subscript>NH<Subscript>3</Subscript>]<Superscript>−</Superscript> anion

Reactions of an amino derivative of the closo-decaborate anion [1-B₁₀H₉NH₃]^– with aromatic aldehydes afforded Schiff bases [1-B₁₀H₉NH=CHAr]^– (Ar=Ph, C₆H₄-2-OMe, or C₆H₄-4-NHCOMe). The reduction of the latter with sodium borohydride gave the corresponding benzylamino derivatives [1-B₁₀H₉NH₂CH₂Ar]^–.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2004–2007, September, 2004.     

Isomerization [trans-B20H18]2– → [iso-B20H18]2– during silver(I) complexation with triphenylphosphine

The trans–iso isomerization of the dimeric borohydride cluster anion [B₂₀H₁₈]^2– in the course of the silver(I) complexation reaction with triphenylphosphine has been described for the first time. The isomeric complexes [Ag₂(Ph₃P)₆[trans-B₂₀H₁₈]] and [Ag₂(Ph₃P)₆[iso-B₂₀H₁₈]] have been isolated and characterized by physicochemical methods. The structures of the compounds have been determined by X-ray crystallography.     

Barrier of rotation around C-N bond in 1-(N,N-dimethylcarbamoyl)-π-cyclopentadienyl-π-(3)-1, 2-dicarbollylcobalt

Conclusions The barriers of rotation around the C-N bond in the amides C₅H₅CoB₉H₉C₂HCON(CH₃)₂, 1-(CH₃)₂NCO-1, 2-B₁₀C₂H₁₁ and 1-(CH₃)₂NCO-1,7-B₁₀C₂H₁₁ are substantially lower than in ordinary amides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2119–2120, September, 1977.     

The nuclear quadrupole double resonance spectrum of decaborane

The boron nuclear quadrupole double resonance spectrum of decaborane, B₁₀H₁₄, was taken at 77 K. The assignment of its ¹¹B lines to the various boron atoms of the molecule is based on the spectrum of μ,1,2,3,4,5,7,8,10-B₁₀H₂D₁₂, the theoretically verified intensity relations, and the transition frequencies calculated from a SCF study.     

Thermochemical study of gaseous salts of oxygen-containing acids: XXVIII. Gallium borates

Reactions of the gas-phase synthesis of gallium borate from oxides and its dimerization were studied. It was found that the molecules Ga₂O, B₂O₃, GaBO₂, and (GaBO₂)2 are present in the vapor above the Ga₂O₃-B₂O₃ system. Enthalpies of formation and atomization of gaseous gallium borates were determined.     

Synthesis of Bu4NB11H14 by the Reaction of Tetrabutylammonium Octahydrotriborate with Diborane in Diglyme

The method for synthesis of Bu₄NB₁₁H₁₄ by dehydrocondensation of Bu₄NB₃H₈ with diborane in diglyme in the temperature range of 70–90°C was developed. The product is formed in 75–85% yield. The conditions that ensure complete conversion of the anions, namely, initial B₃H₈ ^– and intermediate arachno-B₉H₁₄ ^–, into nido-B₁₁H₁₄ ^– and prevent further dehydrocondensation of B₁₁H₁₄ ^– to closo-B₁₂H₁₂ ^2– were established.     

Reaktionen von [B12H12–n(OH)n]2–, n = 1, 2 mit Säuredichloriden und Kristallstruktur von Cs2[1,2-B12H10(ox)] · CH3OH

Reactions of [B₁₂H_12–n(OH)_n]^2–, n = 1, 2 with Acid Dichlorides and Crystal Structure of Cs₂[1,2-B₁₂H₁₀(ox)] · CH₃OH By treatment of [B₁₂H₁₁(OH)]^2– with organic and inorganic acid dichlorides in acetonitrile the bridged dicluster compounds [B₁₂H₁₁(ox)B₁₂H₁₁)]^4– ( 1 ), [B₁₂H₁₁(p-OOCC₆H₄COO)B₁₂H₁₁]^4– ( 2 ), [B₁₂H₁₁(m-OOCC₆H₄COO)B₁₂H₁₁]^4– ( 3 ), [B₁₂H₁₁(SO₃)B₁₂H₁₁]^4– ( 4 ), [B₁₂H₁₁(SO₄)B₁₂H₁₁]^4– ( 5 ) are obtained in good yields. The dihydroxododecaborates [1,2-B₁₂H₁₀(OH)₂]^2– and [1,7-B₁₂H₁₀(OH)₂]^2– afford clusters with an anellated ring: [1,2-B₁₂H₁₀(ox)]^2– ( 6 ), [1,2-B₁₂H₁₀(SO₄)]^2– ( 7 ) and [1,7-B₁₂H₁₀(OOC(CH₂)₈COO)]^2– ( 8 ). Isomerically pure [1,7-B₁₂H₁₀(OH)₂]^2– ( 9 ) is formed by reaction of (H₃O)₂[B₁₂H₁₂] with ethylene glycol. All new compounds are characterized by vibrational, ¹¹B, ¹³C and ¹H NMR spectra. The crystal structure of Cs₂[1,2-B₁₂H₁₀(ox)] · CH₃OH (monoclinic, space group P 2₁/c, a = 9.616(2), b = 10.817(1), c = 15.875(6) Å, β = 95.84(8)°, Z = 4) reveals a distortion of the B₁₂ icosahedron caused by the anellated six-membered heteroring.