Alkyl and dialkylammonium tetrafluoroborate catalyzed cis-trans isomerization of 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane

Alkyl and dialkylammonium tetrafluoroborate promoted cis-trans isomerization of 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane (1) in DMSO-d₆ were studied. The isomerization equilibrium constant K are within the range of 3.74-3.30 from 22 to 47 °C. Thermodynamic parameters of ΔH° and ΔS° for the isomerization were −0.95 kcal/mol and −0.59 cal/mol-K respectively. The isomerization rate is first order in [cis-1] and second order in [R_nNH_4−nBF₄]. Both components of R_nNH_4−n⁺ and BF₄⁻ are essential for the catalytic cis-trans isomerization. The catalytic strength follows the decreasing order of ⁺H₃N(CH₂)₆NH₃⁺>n-C₈H₁₇NH₃⁺>n-C₁₆H₃₃NH₃⁺>Me₃CNH₃⁺>PhCH₂NH₃⁺>Et₂NH₂⁺?Ph₂CHNH₃⁺, Et₃NH⁺. Inversion region was observed in the plot of ln(k_f/T) versus (1/T) with the ceiling located at around 38 °C. The positive activation enthalpy of 9 kcal/mol was estimated at 22-32 °C. The activation enthalpy turns to be slightly negative at T>38 °C.     

Syntheses and structures of zinc and tin(II) compounds with hemilabile N-silyl-tert-butylamido and N-silyl-p-tolylamido ligands that contain pendent tert-butoxy groups

Syntheses and solid-state structures of zinc and tin(II) compounds, containing the N-silyl-amide ligands (O^tBu)(NR)SiMe₂, R = ^tBu (L^tBu), or R = p-tolyl (L^pTol), are reported. The N-silyl amines were synthesized by modified published procedures from commercially available Me₂SiCl₂, ^tBuOH, and ^tBuNH₂, or p-Me-C₆H₄NH₂, respectively. Treatment of SnCl₂ with LiL^pTol furnished Sn(L^pTol)₂, which was X-ray structurally characterized and shown to contain two covalent Sn-N bonds and two asymmetrical O → Sn donor bonds. The single-crystal X-ray structure of Sn(L^tBu)₂ revealed a much more symmetrically-coordinated, pseudo-trigonal-bipyramidal tin atom. Aminolysis of diethylzinc with HL^pTol produced [EtZn(L^pTol)]₂, which crystallized as a centrosymmetric dimer, containing four-coordinate zinc atoms connected by bridging amides. Zinc dichloride, by contrast, reacted with two equivalents of LiL^tBu to produce the homoleptic, pseudo-spirocyclic Zn(L^tBu)₂.     

Visible light-induced magnetization change of the cyano-bridged 3d-4f heterobimetallic

A visible light-induced magnetization change of the 3d-4f heterometallic, [Nd(DMF)₄(H₂O)₃(μ-NC)Co(CN)₅]·H₂O (DMF=N,N-dimethylformamide), is observed and described. The plots of χ_MT versus T of the complex showed that the χ_MT values, after visible light illumination, were enhanced by about 25% as compared to before irradiation in the temperature range of 5-40 K.     

Synthesis, characterization and intercalation property of layered zirconium benzylamino-N,N-dimethylphosphonate phosphate materials

Layered zirconium benzylamino-N,N-dimethylphosphonate phosphate (ZBMPA) was prepared by the reaction of zirconyl chloride with benzylamino-N,N-dimethylphosphonic acid (H₂BMPA) and phosphoric acid in the presence of hydrofluoric acid. The intercalation of n-alkylamines (n-butylamine, n-heptylamine and n-decylamine) into ZBMPA was primarily investigated at room temperature. These materials were characterized by elemental analysis, ICP, XRD, SEM, FT-IR, Raman spectra, TG and DSC. The composition of ZBMPA is Zr(HPO₄)(C₆H₅CH₂N(CH₂PO₃)₂)_0.5 · 2.0H₂O. The interlayer distance of ZBMPA, n-butylamine, n-heptylamine and n-decylamine intercalation compounds is 2.03, 2.58, 2.52 and 3.17 nm, respectively. ZBMPA and the n-alkylamine intercalation compounds are different in the morphology and vibration spectra. Thermogravimetries of all materials obtained reveal three step mass losses at temperatures of up to 1000 °C. These results indicate that n-alkylamines are intercalated into the galleries of host ZBMPA.     

Synthesis, structural and larvicidal studies of some triorganotin 2-(p-chlorophenyl)-3-methylbutyrates

A series of triorganotin 2-(p-chlorophenyl)-3-methylbutyrates, (R₃SnO₂CCH(CH(CH₃)₂)C₆H₄Cl-4), where R = methyl, ethyl, n-propyl, n-butyl, phenyl and cyclo-hexyl, have been synthesized. Elemental analyses, Mössbauer, Infrared and NMR spectroscopies have been used to characterize their structures. Based on the spectroscopic results, all the complexes with the exception of the tricyclohexyl compound were found to be five-coordinated in the solid state while the tricyclohexyltin derivative was determined to be four-coordinated. Structural assignments based on spectroscopic data are supported by the crystallographic results of four of the triorganotin butyrates (trimethyl-, tri-n-propyl-, tri-n-butyl- and tricyclohexyltin 2-(p-chlorophenyl)-3-methylbutyrate). Multinuclear NMR spectroscopy studies indicated that all the complexes were tetrahedral in solution. Larvicidal activities of the complexes were evaluated against the 2nd instar stage of the Anopheles stephensi, Aedes aegypti and Culex pipiens quinquefasciatus mosquitoes. The toxicity data indicate that there does not appear to be any significant differences of the compounds towards the different mosquito species based on their averaged toxicity values. In addition, the toxicity of the triorganotin compounds towards the mosquito larvae was concluded to be dependent on both the compound and the species of mosquito larvae.     

Rhodium(I) complexes with κP coordinated ω-phosphinofunctionalized alkyl phenyl sulfide, sulfoxide and sulfone ligands and their reactions with sodium bis(trimethylsilyl)amide and Ag[BF4]

Reactions of ω-diphenylphosphinofunctionalized alkyl phenyl sulfides Ph₂P(CH₂)_nSPh (n = 1, 1a; 2, 2a; 3, 3a), sulfoxides Ph₂P(CH₂)_nS(O)Ph (n = 1, 1b; 2, 2b; 3, 3b) and sulfones Ph₂P(CH₂)_nS(O)₂Ph (n = 1, 1c; 2, 2c; 3, 3c) with dinuclear chlorido bridged rhodium(I) complexes [(RhL₂)₂(μ-Cl)₂] (L₂ = cycloocta-1.5-diene, cod, 4; bis(diphenylphosphino)ethane, dppe, 5) afforded mononuclear Rh(I) complexes of the type [RhCl{Ph₂P(CH₂)_nS(O)_xPh-κP}(cod)]¹ (n/x = 1/0, 6a; 1/1, 6b; 1/2, 6c; 2/0, 8a; 2/1, 8b; 2/2, 8c; 3/0, 10a; 3/1, 10b; 3/2, 10c) and [RhCl{Ph₂P(CH₂)_nS(O)_xPh-κP}(dppe)] (n/x = 1/0, 7a; 1/1, 7b; 1/2, 7c; 2/0, 9a; 2/1, 9b; 2/2, 9c; 3/0, 11a; 3/1, 11b; 3/2, 11c) having the P^S(O)_x ligands κP coordinated. Addition of Ag[BF₄] to complexes 6-11 in CH₂Cl₂ led with precipitation of AgCl to cationic rhodium complexes of the type [Rh{Ph₂P(CH₂)_nS(O)_xPh-κP,κS/O}L₂][BF₄] having bound the P^S(O)_x ligands bidentately in a κP,κS (13a-18a, 15b-18b) or a κP,κO (13b, 14b, 13c-18c) coordination mode. Unexpectedly, the addition of Ag[BF₄] to 6a in THF afforded the trinuclear cationic rhodium(I) complex [Rh₃(μ-Cl)(μ-Ph₂PCH₂SPh-κP:κS)₄][BF₄]₂·4THF (12·4THF) with a four-membered Rh₃Cl ring as basic framework. Addition of sodium bis(trimethylsilyl)amide to complexes 6-11 led to a selective deprotonation of the carbon atom neighbored to the S(O)_x group (α-C) yielding three different types of organorhodium complexes: a) Organorhodium intramolecular coordination compounds of the type [Rh{CH{S(O)_xPh}CH₂CH₂PPh₂-κC,κP}L₂] (22a-c, 23a-c), b) zwitterionic complexes [Rh{Ph₂PCHS(O)_xPh-κP,κS/O}L₂] having κP,κS (21a, 21b) and κP,κO (20b/c, 21c) coordinated anionic [Ph₂PCHS(O)_xPh] ligands, and c) the dinuclear rhodium(I) complex [{Rh{μ-CH(SPh)PPh₂-κC:κP}(cod)}₂] (19). All complexes were fully characterized spectroscopically and complexes 15b, 15c, 12·4THF and 19·THF additionally by X-ray diffraction analysis. DFT calculations of zwitterionic complexes gave insight into the coordination mode of the [Ph₂PCHS(O)Ph] ligand (κP,κS versus κP,κO).     

On the conformational characteristics of the O,O,O-trimethyl selenophosphate molecule

Spectroscopic and theoretical studies were carried out for O,O,O-trimethyl selenophosphate molecule. DFT structural and vibrational calculations were performed at 6-311++G^∗∗ level. Ar/matrix-FTIR spectra were recorded. A coexistence of different conformers with C₃ and C₁ symmetries was detected at different temperatures. Spectral evidence of a lower energy C_s conformer was found. These conclusions are consistent with the results from DFT calculations. A tentative assignment of the features observed in the Ar/matrix-FTIR spectra is proposed.     

New N,N-amino-diphosphonate-containing methacrylic derivatives, their syntheses and radical copolymerizations with MMA

Hydroxy-amino-diphosphonates HO-C_n-NH₂, with 2 ? n ? 11, have been successfully synthesized via the Kabachnick-Field reaction at 70 °C with high yields. These hydroxy compounds are then reacted with methacryloyl chloride to lead to novel amino-diphosphonate methacrylates MAC_nNP₂ (with 2 ? n ? 11). These highly pure methacrylate monomers were obtained with yields higher than 75%. Radical copolymerizations of MAC_nNP₂ (with 2 ? n ? 11) with MMA have been conducted and the r₁ values (related to MAC_nNP₂) are in the range of 1.1-1.3, and r₂ values (related to MMA) about 0.8; this shows that the diphosphonate groups are statistically bonded to the methacrylic backbone.     

Phase equilibria and crystal chemistry of the R-Cu-Ti-O systems (R=lanthanides and Y)

As part of the study of interaction of the Ba₂RCu₃O_6+z (R=lanthanides and Y) superconductor with SrTiO₃ buffer, phase equilibria of the subsystem, R₂O₃-TiO₂-CuO (R=Nd, Y, and Yb), have been investigated in air at 960 °C. While the phase relationships of the two phase diagrams with smaller R (Y and Yb) are similar, substantial differences were found in the Nd₂O₃-TiO₂-CuO system, partly due to different phase formation in the binary R₂O₃-TiO₂ and R₂O₃-CuO systems. R₂CuTiO₆ and R₂Cu₉Ti₁₂O₃₆ were the only ternary phases established in all the three diagrams. R₂Cu₉Ti₁₂O₃₆ belongs to the perovskite-related [AC₃](B₄)O₁₂ family which is cubic Im3. Depending on the size of R³⁺, R₂CuTiO₆ crystallizes in two crystal systems: Pnma (R=La-Gd), and P6₃cm (R=Dy-Lu). The structure and crystal chemistry of the Pnma series of R₂CuTiO₆ (R=La, Nd, Sm, Eu, and Gd) are discussed in detail in this paper. Patterns for selected members of R₂CuTiO₆ have also been prepared and submitted for inclusion in the Powder Diffraction File (PDF).     

Synthesis, characterization and crystal structures of cyclometallated palladium (II) compounds containing difunctional ligands with [P,P], [As,As], [N,N], [P,As], [P,N] and [P,O] donor atoms

Treatment of the chloro-bridged dinuclear complex [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}(μ-Cl)]₂ (1) with homobidentate [P,P], [As,As], [N,N], and heterobidentate [P,As], [P,N] ligands in a 1:1 molar ratio gave the dinuclear complexes [{Pd[3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N](Cl)}₂{μ-L}] (L = Ph₂PC₄H₆(NH)CH₂PPh₂ (2); Ph₂As(CH₂)₂AsPh₂ (3); 1,3-(NH₂CH₂)₂C₆H₄ (4); Ph₂P(CH₂)₂AsPh₂ (5); Ph₂P(CH₂)₂NH₂ (6)), with the bidentate ligands bridging the two cyclometallated fragments.The reaction with the homobidentate ligands in a 1:2 molar ratio in the presence of NaClO₄ afforded the mononuclear compounds [[Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{L-P,P}][ClO₄] (L = Ph₂PC₄H₆(NH)CH₂PPh₂ (7); (o-Tol)₂P(CH₂)₂P(o-Tol)₂ (8)), [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{Ph₂As(CH₂)₂AsPh₂-As,As}][ClO₄] (9) and [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{L-N,N}][ClO₄] (L = NH₂(CH₂)₃NH₂ (10); NH₂(C₆H₈)CH₂(C₆H₈)NH₂ (11); 1,3-(NH₂CH₂)₂C₆H₄ (12); 1,3-(NH₂)₂C₅H₃N (13); NH₂(C₆H₄)O(C₆H₄)NH₂ (14); NMe₂(CH₂)₂NMe₂ (15)), in which the chloro ligands are absent and the bidentate ligands are chelated to the palladium atom.Reaction of 1 with Ph₂P(CH₂)₂AsPh₂ in 1:2 molar ratio in acetone in the presence of NH₄PF₆ afforded the analogous mononuclear compound [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{Ph₂P(CH₂)₂AsPh₂-P,As}][PF₆] (16); whereas reaction with Ph₂P(CH₂)₃NH₂ gave [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{Ph₂P(CH₂)₃N(CMe₂)-P,N}][PF₆] (17), derived from intermolecular condensation between the aminophosphine and acetone. Condensation of the NH₂ group was precluded by change of solvent, using dichloromethane.Iminophoshines also reacted with 1 in 1:2 molar ratio in acetone to give a new series of mononuclear cyclometallated complexes: [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{L-P,N}][ClO₄] (L = Ph₂PC₆H₄C(H)NCy (20); Ph₂PC₆H₄C(H)NC(CH₃)₃ (21); Ph₂PC₆H₄C(H)NNMe₂ (22); Ph₂PC₆H₄C(H)NNHMe (23); Ph₂PC₆H₄C(H)NNHPh (24)). Analogous complexes with a stable P,O-chelate were obtained using bidentate [P,O] donor ligands: [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{L-P,O}][Cl] (L = 2-(Ph₂P)C₆H₄CHO (25); Ph₂PN(Me)C(O)Me (26)).The crystal structures of compounds 1, 5, 15, 16, 18, 20 have been determined by X-ray crystallography.     

Interaction of polyhedral boron hydride anions [B10H10] and [B12H12] with cyclic copper and silver 3,5-bis(trifluoromethyl)pyrazolate complexes

The interactions of cyclic trinuclear copper {[3,5-(CF₃)₂Pz]Cu}₃ and silver {[3,5-(CF₃)₂Pz]Ag}₃ complexes with polyhedral borate anions [B₁₀H₁₀]²⁻ and [B₁₂H₁₂]²⁻ in solvents of low-polarity were studied using IR spectroscopy (190-290 K). Two types of complexes were found in solution: {[((3,5-CF₃)₂PzM)₃][B_nH_n]}²⁻ and {[((3,5-CF₃)₂PzM)₃]₂[B_nH_n]}²⁻ (M = Ag, Cu; n = 10, 12). The stability constants of these complexes were determined from IR-spectra.     

LaxSr2−xFeyRu1−yO4±δ: a new family of K2NiF4 type oxides

The phases La_xSr_2−xFe_yRu_1−yO_4±δ (x=0.2-0.8; y=0.6-0.9) have been synthesized by solid-state techniques and yield tetragonal structures with I4/mmm symmetry. The oxygen stoichiometry and high-temperature structures have been examined using diffraction techniques and in situ Mössbauer spectroscopy at temperatures up to ∼600°C. Furthermore, new reduced phases that adopt structures with Immm symmetry have been discovered. Unusual coordination numbers have been determined for the most highly reduced samples with square planar coordination evident for the B site cations. The reduced orthorhombic Immm phases were found to readily reoxidize in air to the tetragonal I4/mmm structure at relatively low temperatures of only ∼500°C.     

Hupermine A,a novel C16N2-type Lycopodium alkaloid from Huperzia phlegmaria

A novel C₁₆N₂-type Lycopodium alkaloid consisting of a quinolizidine with a 6-dimethylaminohexyl side chain, hupermine A (1), was isolated from the club moss of Huperzia phlegmaria, and the structure and relative stereochemistry were elucidated on the basis of spectroscopic data.     

Prediction of molecular weight and density of n-alkanes (C6-C44)

Heavy n-alkanes and their mixtures were characterized by high temperature-simulated distillation using gas chromatography with a capillary column. In this work, the atmospheric boiling point is determined by the HT-SimDis GC method. In this study, molecular weights and density of n-alkanes were evaluated with this method by using retention times and normal boiling points as input data. ASTM D2887 calibration mixture containing 17 n-alkanes in the C₆-C₄₄ range were used for qualitative analyses. Retention times (t_R) of n-alkanes were measured with this method. The other input data that normal boiling points (T_b) and molecular weight (M) had been taken in the literature. Experimental densities (at 20 °C) of n-alkanes were obtained from API Research Projects. Empirical molecular weight and density correlations were developed by using the nonlinear and multiple regressions with correlation coefficients. The results of calculations were compared with experimental data. Normal boiling point predictions were obtained as an average absolute deviation of 1.07%. Molecular weight and density results were evaluated as average absolute deviations of 0.68% and 0.21%, respectively.     

Synthesis of branched tri- to pentasaccharides representative of fragments of Shigella flexneri serotypes 3a and/or X O-antigens

Fragments of the {2)-[α-d-Glcp-(1→3)]-α-l-Rhap-(1→2)-α-l-Rhap-(1→3)-[Ac→2]-α-l-Rhap-(1→3)-β-d-GlcpNAc-(1→}_n ((E)AB_AcCD)_n polymer were synthesized. D(E)A, CD(E)A, _AcCD(E)A were obtained according to a linear strategy, whereas BCD(E)A and B_AcCD(E)A were derived from the condensation of appropriate BC and D(E)A building blocks. Oligosaccharides were synthesized as their propyl glycoside, relying on (i) the efficient trichloroacetimidate chemistry, (ii) a common EA allyl glycoside, and (iii) a 2-trichloroacetamido-d-glucopyranose precursor to residue D. Final Pd/C-mediated deprotection, run under a high pressure of hydrogen, ensured O-acetyl stability. All targets are parts of the O-antigen of Shigella flexneri 3a, a prevalent serotype. Non-O-acetylated oligosaccharides are shared by the S. flexneri serotype X O-antigen.     

Crystallization and melting behaviors of polystyrene-b-poly(ethylene-co-butene) block copolymers

Non-isothermal and isothermal crystallization behaviors of polystyrene-b-poly(ethylene-co-butene) (PSt-b-PEB) block copolymers with different compositions and chain lengths were investigated by differential scanning calorimetry (DSC). The results show that crystallization of PEB block is strongly dependent on the composition. Crystallization temperature (T_c), melting temperature (T_m) and fusion enthalpy (ΔH_f) increase rapidly with PEB volume fraction (V_E) for block copolymers with V_E below 50%, but there is little change when PEB block becomes the major component. Glass transition temperature (T_g) of the PSt block and order-disorder transition temperature (T_ODT) of block copolymers also have a weak effect. The isothermal crystallization kinetics results show that Avrami exponent (n) was strongly dependent on the composition and crystallization temperature. For the block copolymers with V_E below 38.7 vol%, the values of n vary between 0.9 and 1.3, indicating that crystallization is confined. For the PSt-b-PEB block copolymers with V_E higher than 50%, fractionated crystallization behavior is usually observed. A two-step isothermal crystallization procedure is applied to these block copolymers. It is found that breakout crystallization occurs at higher T_c, but confined at lower T_c. Two overlapped melting peaks are observed for the block copolymers with fractionated crystallization behavior after two-step crystallization, and only the higher melting peak corresponding to breakout crystallization can be used to derive equilibrium melting temperature.     

Photoluminescent behavior of SrB4O7:RE (RE=Sm and Eu) prepared by Pechini, combustion and ceramic methods

This work reports the preparation of system containing RE²⁺ ions (RE=Sm and Eu)-doped in SrB₄O₇ matrix by ceramic, Pechini and combustion methods. These compounds were prepared by reduction of RE³⁺ to RE²⁺ in air, which exhibit some different features according to the preparation method. Photoluminescent properties of these systems were investigated based on the emission and excitation spectral data. The emission spectra of SrB₄O₇:Eu²⁺ system prepared by combustion and Pechini methods are characterized by a broad band assigned to interconfigurational 4f⁶5d→4f⁷ transition, while SrB₄O₇:Sm²⁺ compound exhibit narrow emission bands arising from intraconfigurational-4f⁶ also shows ⁴G_5/2→⁶H_J′ transitions ( and ) arising from Sm³⁺ ion, transitions. SrB₄O₇:RE system prepared by combustion method presents emission bands from RE³⁺ ions as intense as that arising from RE²⁺, suggesting that the preparation route is not efficient for the reduction RE³⁺→RE²⁺ process. Emission quantum efficiency and radiative emission rates of Sm²⁺ ion are determined and discussed.     

Synthesis of Closo-1,7-Carboranyl Alkyl Amines

Of the three closo-carborane isomers (C₂B₁₀H₁₂), closo-1,2-carborane has been used most widely in the synthesis of carboranyl amines. However, closo-1,2-carboranes are prone to deboronation to nido-7,8-carborane under various conditions including attack by basic amino groups. In order to overcome this problem, closo-1,7-carboranyl ethyl-, propyl-, and butylamine were synthesized, which should be more stable towards basic deboronation than their closo-1,2-carboranyl counterparts. These closo-1,7-carboranyl amines (5, 18 and 19) were synthesized using two different methods, both starting from the corresponding closo-1,7-carboranyl alkyl iodides (3, 14 and 15). One of the carboranyl alkyl amine (5) was conjugated with folic acid to form a closo-1,7-carborane-folic acid bioconjugate (20).     

Revised phase diagram of Li2MoO4-ZnMoO4 system, crystal structure and crystal growth of lithium zinc molybdate

Orthorhombic lithium zinc molybdate was first chosen and explored as a candidate for double beta decay experiments with ¹⁰⁰Mo. The phase equilibria in the system Li₂MoO₄-ZnMoO₄ were reinvestigated, the intermediate compound Li₂Zn₂(MoO₄)₃ of the α-Cu₃Fe₄(VO₄)₆ (lyonsite) type was found to be nonstoichiometric: Li_2−2xZn_2+x(MoO₄)₃ (0≤x≤0.28) at 600 °C. The eutectic point corresponds to 650 °C and 23 mol% ZnMoO₄, the peritectic point is at 885 °C and 67 mol% ZnMoO₄. Single crystals of the compound were prepared by spontaneous crystallization from the melts and fluxes. In the structures of four Li_2−2xZn_2+x(MoO₄)₃ crystals (x=0; 0.03; 0.21; 0.23), the cationic sites in the face-shared octahedral columns were found to be partially filled and responsible for the compound nonstoichiometry. It was first showed that with increasing the x value and the number of vacancies in M3 site, the average M3-O distance grows and the lithium content in this site decreases almost linearly. Using the low-thermal-gradient Czochralski technique, optically homogeneous large crystals of lithium zinc molybdate were grown and their optical, luminescent and scintillating properties were explored.