A quantum chemical study of silsesquioxanes: H8Si8O12, Me8Si8O12, H@Me8Si8O12, He@Me8Si8O 12 + , and He@Me8Si8O12

Quantum chemical PBE0 and B3LYP/cc-pVTZ, PBE0, B3LYP, RHF and MP2/6-31G(d,p) methods are employed to calculate the structural parameters of octa(silsesquioxane) H₈Si₈O₁₂ and octa(methylsilsesquioxane) Me₈Si₈O₁₂. These molecules and complexes H@Me₈Si₈O₁₂, He@Me₈Si₈O ₁₂ ⁺ , and He@Me₈Si₈O₁₂ have highly symmetric (O _h ) equilibrium configurations. With the use of the PBE0 method and a cc-pVTZ multicenter basis set common for the complex and its components coincidence is achieved between the calculated polarizability of a free He atom and the experimental value of 0.21 ų and the polarizability depression of 0.17 ų was found for He@Me₈Si₈O₁₂. In order to avoid the false conclusion about molecular symmetry the calculations of the structure of silsesquioxanes must be performed with sufficiently high accuracy (Int = ultrafine and Opt = tight in the use of the GAUSSIAN program).     

Thermal properties of dimethylgold(III) 8-hydroxyquinolinate and 8-mercaptoquinolinate

Dimethylgold(III) complexes with 8-hydroxyquinoline Me₂Au(Ox) (I) and 8-mercaptoquinoline Me₂Au(Tox) (II) were synthesized and studied. Complex II obtained for the first time was identified from the elemental analysis, IR, ¹H NMR, and mass spectrometry data. The thermal properties of complexes I, II in condensed state were investigated by thermography. The temperature dependences of the saturated vapor pressure over crystals were measured by the Knudsen effusion method with mass spectrometric recording of the gas phase composition and the thermodynamic characteristics of the sublimation process were determined: for I, log P[Torr] = (14.6 ± 0.3) ? (6.34 ± 0.10) × 10³/(T, K), Δ H _subl ^o = 121.2 ± 1.9 kJ^?1, Δ S _subl ^o = 224.1 ± 4.6 J mol^?1 K^?1 (the temperature interval under study 80–115°C); for II, log P [Torr] = (13.3 ± 0.2) ? (6.30 ± 0.09) × 10³/(T, K), Δ H _subl ^o = 120.5 ± 1.7 kJmol^?1, ΔS _subl ^o = 199.3 ± 3.0 J mol^?1 K^?1 (86–145°C).     

Unusual Nitrile–Nitrile and Nitrile–Alkyne Coupling of FcCN and FcCCCN

The reactions of the Group 4 metallocene alkyne complexes, [Cp*₂M(η²‐Me₃SiC₂SiMe₃)] ( 1 a : M=Ti, 1 b : M=Zr, Cp*=η⁵‐pentamethylcyclopentadienyl), with the ferrocenyl nitriles, Fc?C?N and Fc?C?C?C?N (Fc=Fe(η⁵‐C₅H₅)(η⁵‐C₅H₄)), is described. In case of Fc?C?N an unusual nitrile–nitrile C?C homocoupling was observed and 1‐metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes ( 3 a , b ) were obtained. As the first step of the reaction with 1 b , the nitrile was coordinated to give [Cp*₂Zr(η²‐Me₃SiC₂SiMe₃)(N?C‐Fc)] ( 2 b ). The reactions with the 3‐ferrocenyl‐2‐propyne‐nitrile Fc?C?C?C?N lead to an alkyne–nitrile C?C coupling of two substrates and the formation of 1‐metalla‐2‐aza‐cyclopenta‐2,4‐dienes ( 4 a , b ). For M=Zr, the compound is stabilized by dimerization as evidenced by single‐crystal X‐ray structure analysis. The electrochemical behavior of 3 a , b and 4 a , b was investigated, showing decomposition after oxidation, leading to different redox‐active products.     

Core Charge Density Dominated Size-Conversion from Au6P8 to Au8P8Cl2

The stimulus-response of metal nanoclusters is crucial to their applications in catalysis and bio-clinics, etc. However, its mechanistic origin has not been well studied. Herein, the mechanism of the Au^IPPh₃Cl-induced size-conversion from [Au₆(DPPP)₄]²⁺ to [Au₈(DPPP)₄Cl₂]²⁺ (DPPP is short for 1,3-bis(diphenylphosphino)propane) is theoretically investigated with density functional theory (DFT) calculations. The optimal size-growth pathway, and the key structural parameters were elucidated. The Au−P bond dissociation steps are key to the size-growth, the easiness of which was determined by the charge density of the metallic core of the cluster precursors (i.e., “core charge density”). This study sheds light on the inherent structure–reactivity relationships during the size-conversion, and will benefit the deep understanding on the kinetics of more complex systems.     

Synthèse de la désamino1-Orn8-vasopressine,de la désamino1-Phe2-Orn8-vasopressine,de la désamino1-Ile3-Orn8-vasopressine (= désamino1-Orn8-oxytocine) et de la désamino1-Phe2-Ile3-Orn8-vasopressine (= désamino1 -Phe2-Orn8-oxytocine)

Four analogues of the vasopressins have been synthesised: Deamino¹-Orn⁸-vasopressin, Deamino¹-Phe²-Orn⁸-vasopressin, Deamino¹-Ile³-Orn⁸-vasopressin (= Deamino¹-Orn⁸-oxytocin) and Deamino¹-Phe²-Ile³-Orn⁸-vasopressin (= Deamino¹-Phe²-Orn⁸-oxytocin). The two former have been prepared by condensation of tripeptide azides with an hexapeptide. The two latter have been obtained from the hexapeptide by the recurring method, using active trichlorophenyl esters.     

Chelate von Chinolin-8-ol — Derivaten. XI. Eigenschaften und Struktur von Nickelchelaten alkyl-substituierter Chinolin-8-ole bzw. Chinolin-8-thiole

Reactions of 1,1,3,3-Tetrakis(dimethylamino)-1λ⁵,3λ⁵-diphosphete with N? H and P? H Acidic Compounds 1,1,3,3-Tetrakis(dimethylamino)-1λ⁵,3λ⁵-diphosphete, 1 , reacts with aniline to give by opening of the ring 2,2,4,4-tetrakis(dimethylamino)-1-phenyl-1,2λ⁵,4λ⁵-azadiphosphapenta-1,3-diene, 2 , with p-CN? C₆F₄? NH₂ the product is 1-(4-cyano-2,3,5,6-tetrafluorophenyl)-2,2,4,4-tetrakis(dimethylamino)-1,2λ⁵,4λ⁵-azadiphosphapenta-1,3-diene, 3 . t-Butylamine or diethylamine do not react with 1 . Mesitylphosphane opens the ring system 1 forming by reduction of one phosphorus atom {[bis(dimethylamino)phosphanyl]methylidene}bis(dimethylamino)methylphosphorane, 4 . The same product 4 is obtained by reaction with phenylphosphane. The reaction products 2–4 are characterized by their nmr, mass, and ir spectra. Their way of formation is discussed. In 4 a ⁵J(PH), in 3 a ⁷J(CF) long range coupling constant could be identified.     

8-Hydroxyquinoline Based Multipodal Systems: Effect of Spatial Placement of 8-Hydroxyquinoline on Metal Ion Recognition

The complexation behaviors of tetrapod 1,2,4,5-tetrakis(8-hydroxyquinolinoxymethyl) benzene (1) and dipod 1,2-bis(8-hydroxyquinolinoxymethyl)benzene (2) have been determined by fluorescence spectroscopy in CH₃CN–H₂O (4:1) buffered at pH 6.9 [HEPES 10 mM] and by ¹H NMR in CD₃CN-CDCl₃ (1:1) mixture. Tetrapod 1 can recognize Ag⁺(10–40 μM) even in the presence of (500 μM) of alkali and alkaline earth metal ions. However, transition metal ions interfere in the estimation of Ag⁺. Dipod 2 shows poor selectivity towards Ag⁺. The ¹H NMR based titrations of podands 1 and 2 against AgNO₃ show characterstic changes in chemical shifts in quinoline, methylene and aromatic protons. The spectral fitting of fluorescence and ¹H NMR titration data has been used to evaluate the stoichiometries of complexes and their complexation constants.     

Selenoketene (H2CCSe)+• and selenoketyl cumulene (HCCSe)+ ions and their neutral counterparts: a tandem mass spectrometric and computational study

Dissociative electron ionization (70eV) of selenophene (C₄H₄Se) generates m/z 106 ions of composition [H₂, C₂, ⁸⁰Se]^+? and m/z 105 ions of [H, C₂, ⁸⁰Se]⁺. From tandem mass spectrometric experiments, Density Functional Theory (DFT) and ab initio calculations, it is concluded that these ions have the structure of selenoketene H₂C?C?Se^+? (1a^+? )and selenoketyl HC?C?Se⁺ (2a⁺) ions respectively. The calculations predict that selenoketene ion 1a^+? is separated by high energy barriers from its isomers selenirene (H e)^+? 1b^+?, ethyne selenol (HCCSeH)^+? 1c^+?, (CCHSeH)^+? 1d^+? and (CCSeH₂)^+? 1e^+?. The selenoketyl ion 2a⁺ is separated by high barriers from its isomers (CCHSe)⁺ 2b⁺, and (CCSeH)⁺ 2c⁺. Neutralization‐reionization mass spectra (NRMS) of these structurally characterized ions confirmed that the corresponding neutral analogues, selenoketene H₂CCSe 1a and selenoketyl radical HCCSe 2a^? are stable in the rarefied gas phase. The relative, dissociation, and isomerization energies for selenoketene and selenoketyl ions and neutrals studied at B3LYP/6–31G(d,p) and G2/G2(MP2) levels are used to support and interpret the experimental results. Copyright © 2005 John Wiley & Sons, Ltd.     

13C NMR spectra of 8-mercaptoquinoline and 8-hydroxyquinoline

The signals in the¹³C NMR spectra of quinoline and its 8-substituted derivatives (SH, SCH₃, OH, OCH₃, NH₂, I, and CH₃), 8,8-diquinolyl disulfide, the 8-hydroxy-N-methylquinolinium ion, and the protonated and anionic forms of 8-hydroxy- and 8-mercaptoquinoline were assigned. The increments of the substituents in the neutral forms of these compounds correlate satisfactorily with those in substituted benzenes and the Swain-Lupton parameters (r = 0.94–0.99). The differences in the ortho increments of the substituents are due to a change in the electron densities on the carbon atoms and also to steric hindrance. The effect of an intramolecular hydrogen bond on the¹³C chemical shift of the quinoline ring of 8-hydroxy- and 8-mercaptoquinoline was examined. The¹³C chemical shifts correlate satisfactorily with the total charges (q) on the carbon atoms in the neutral forms of these compounds. A similar correlation is satisfied to a lesser extent for the protonated and anionic forms because of a change in the bond orders.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 657–662, May, 1980.     

Syntheses of substituted 8-(aminobenzyl)dinaphthodioxaphosphocine 8-oxides

Substituted (8-aminobenzyl)dinaphthodioxaphosphocine 8-oxides were prepared in a two-step process. The first step of the reaction is one-pot synthesis of α-aminophosphonates by the reaction of aldehydes, amines, and trialkyl phosphite in the presence of ceric ammonium nitrate. The second step is cyclization of α-aminophosphonates with bis(2-hydroxy-1-naphthyl)methane in the presence of a catalytic amount of p toluenesulphonic acid under reflux conditions. Their structures were established by elemental analyses, IR, ¹H, ¹³C, ³¹P NMR, and mass spectral data. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, 1574–1580, September, 2007.     

Studies on clathrasils VIII. Nonasils-[4158], 88SiO2 · 8M8 · 8M9 · 4M20: Synthesis,thermal properties,and crystal structure

Nonasils-[4¹5⁸], 88SiO₂·8M⁸·8M⁹·4M²⁰, have been synthesized with 2-methylpyrrolidine, hexamethyleneimine, 2-(aminomethyl)-tetrahydrofuran, 1,2-diaminocyclohexane, 2-methylpiperidine, 2-methylpiperazine, 1-aminobutane, 2-aminobutane, and 2-aminopentane as guest molecules, M²⁰. The samples have been prepared from aqueous silicate solutions which were sealed in silica tubes and heated at about 200°C for several weeks. These clathrasils crystallize in space groupFmmm. For the nonasil with 2-aminopentane as the guest molecule and the unit cell dimensionsa _o=22.232(6) Å,b ₀=15.058(4) Å, andc _o=13.627(4) Å, the structure has been refined using 550 non-equivalent single crystal reflexions to a reliability factorR _w =0.125. The 3-dimensional 4-connected silica host framework has three types of cage-like voids, [5⁴6⁴], [4¹5⁸], and [5⁸6¹²], the latter housing the structure-controlling guest molecules, M²⁰. The non-spherical shape of the guest molecules is the most important factor for the formation of nonasils-[4¹5⁸]. On heating nonasils-[4¹5⁸] up to 950°C the organic guest species are driven out and the pure silica form of nonasil is obtained.Part of this study was presented at the 24th Jahrestagung der AGKr, Cologne, 1985 [1]. For part VII see [4].     

Ein Beitrag über CuPrMo2O8 und CuTbMo2O8

A Contribution on CuPrMo₂O₈ and CuTbMo₂O₈ Single crystals of (I): CuPrMo₂O₈ and (II): CuTbMo₂O₈ were prepared by solid state reactions in closed copper tubes. They crystallize with orthorhombic symmetry, space group D-Pbca, (I): a = 10.4114, b = 9.8917, c = 14.8287 Å, (II): a = 10.2243, b = 9.7385, c = 14.6000, Z = 8. Both compounds are isotypic to CuYMo₂O₈, showing isolated MoO₄ tetrahedra, square antiprismatic coordination of Ln³⁺ and Cu⁺ besides one edge of an O^2? triangle. Calculations of the coulombterm of lattice energy support the oxidation state Cu²⁺ in combination with mixed valences of Mo⁶⁺ and Mo⁵⁺ on the molybdenum point positions.     

Mass spectrometry of 8-hydroxyquinoline derivatives

In contrast to the fragmentation of the corresponding alkyl aryl ethers, characteristic [M-H]⁺ and [M-H, -CO]⁺ fragments were observed in the fragmentation of 5-nitro(halo)-substituted 8-alkoxyquinolines. It was found by means of deuterium labeling that a hydrogen atom is split out primarily from the alkoxy group. It was demonstrated that an [M-H, -CO]⁺ fragment was formed from the [M-H]⁺ ion, which has a three-ring structure and a quaternary nitrogen atom. The formation of an [M-CO]⁺ fragment is characteristic for the fragmentation of 5(7)-nitro(halo)-substituted 8-hydroxyquinolines. The interrelationship between the intensities of the [M-H]⁺, [M-H, -CO]⁺, and [M-CO]⁺ ion peaks and the protonation constants (pK_a) of the investigated compounds is discussed.Communication 4 from the series Mass spectrometry of biologically active substances, See [1] for communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 786–791, June, 1984.     

Isomerisation of hydrocarbon ions III–[C8H8]+·, [C8H8]2+, [C6H6]+· AND [C6H5]+ IONS

Collisional activation spectra of [C₈H₈]⁺·, [C₈H₈]²⁺, [C₆H₆]⁺· and [C₆H₅]⁺ ions from fifteen different sources are reported. Decomposing [C₈H₈]⁺· ions of ten of these precursors isomerise to a mixture of mainly the cyclooctatetraene and, to a smaller extent, the styrene structure. Three additional structures are observed with [C₈H₈]⁺· ions from the remaining precursors. [C₈H₈]^2+., [C₈H₈]⁺·, [C₆H₆]⁺· and [C₆H₅]⁺· ions mostly decompose from common structures although some exceptions are reported.     

Coordination and Activation of AlH and GaH Bonds

The modes of interaction of donor‐stabilized Group 13 hydrides (E=Al, Ga) were investigated towards 14‐ and 16‐electron transition‐metal fragments. More electron‐rich N‐heterocyclic carbene‐stabilized alanes/gallanes of the type NHC?EH₃ (E=Al or Ga) exclusively generate κ² complexes of the type [M(CO)₄(κ²‐H₃E?NHC)] with [M(CO)₄(COD)] (M=Cr, Mo), including the first κ² σ‐gallane complexes. β‐Diketiminato (′nacnac′)‐stabilized systems, {HC(MeCNDipp)₂}EH₂, show more diverse reactivity towards Group 6 carbonyl reagents. For {HC(MeCNDipp)₂}AlH₂, both κ¹ and κ² complexes were isolated, while [Cr(CO)₄(κ²‐H₂Ga{(NDippCMe)₂CH})] is the only simple κ² adduct of the nacnac‐stabilized gallane which can be trapped, albeit as a co‐crystallite with the (dehydrogenated) gallylene system [Cr(CO)₅(Ga{(NDippCMe)₂CH})]. Reaction of [Co₂(CO)₈] with {HC(MeCDippN)₂}AlH₂ generates [(OC)₃Co(μ‐H)₂Al{(NdippCme)₂CH}][Co(CO)₄] ( 12 ), which while retaining direct Al?H interactions, features a hitherto unprecedented degree of bond activation in a σ‐alane complex.     

Polychalcone derived from 8-acetoxyquinoline-5-aldehyde

Fries rearrangement of 8-acetoxyquinoline-5-aldehyde (aqa) in nitrobenzene using AlCl₃ as catalyst affords the polychalcone poly(8-hydroxy-5,7-quinolinylenecarbonylvinylene) (phqcv). Thephqcv samples were characterized by elemental analysis,ir spectroscopy, molecular weight, intrinsic viscosity andtga. Polymeric metal chelates of Cu²⁺, Fe³⁺, Co²⁺, Ni²⁺, Mn²⁺, Zn²⁺ and UO ₂ ²⁺ withphqcv polychalcone were prepared and characterized.     

The Mixed Gold–Palladium Polyoxo‐Noble‐Metalate [NaAuIII4PdII8O8(AsO4)8]11−

The first fully inorganic, discrete gold–palladium–oxo complex [NaAu^III₄Pd^II₈O₈(AsO₄)₈]^11? has been synthesized in aqueous medium. The combination of single‐crystal XRD, elemental analysis, mass spectrometry, and DFT calculations allowed establishing the structure and composition of the novel polyanion, and UV/Vis studies suggest that it is stable in neutral aqueous media.     

[Pd8(CH3COO)8(NO)8]: solution from X‐ray powder diffraction data

The water‐insoluble title compound, octakis(μ‐acetato‐κ²O:O)­octakis(μ‐nitro­so‐κ²N:O)­octapalladium(II), [Pd₈(CH₃COO)₈(NO)₈], was precipitated as a yellow powder from a solution of palladium nitrate in nitric acid by adding acetic acid. Ab initio crystal structure determination was carried out using X‐ray powder diffraction techniques. Patterson and Fourier syntheses were used for atom locations, and the Rietveld technique was used for the final structure refinement. The crystal structure is of a molecular type. The skeleton of the [Pd₈(CH₃COO)₈(NO)₈] mol­ecule is con­structed as a tetragonal prism with Pd atoms at the vertices. The eight NO⁻ groups are in bridging positions along the horizontal edges of the prism. The N and O atoms of each nitro­so group coordinate two different Pd atoms. The vertical edges present Pd⋯Pd contacts with a short distance of 2.865 (1) Å. These Pd atoms are bridged by a pair of acetate groups in a cis orientation with respect to each other. The complex has crystallographically imposed 4/m symmetry; all C atoms of the acetate groups are on mirror planes. The unique Pd atom lies in a general position and has square‐planar coordination, consisting of three O and one N atom.     

8-Methoxyquinoline based turn-on metal fluoroionophores

Novel turn-on fluoroionophores 2 and 3 based on highly fluorescent 8-methoxyquinoline were developed in which a sequential singlet-singlet energy transfer, ISC, and triplet-triplet energy transfer occurred leading to a fluorescence ‘off’ state. They showed substantially enhanced fluorescence in the presence of transition metal ions such as Zn²⁺, Cu²⁺, Pb²⁺, and Hg²⁺ and an extremely high selectivity toward Zn²⁺ by 3.