Far-infrared spectrum of the internal rotation in methylamine

The far-infrared spectra of the Q branches of hindered rotation of CH₃NH₂ were studied in the 80 to 280 cm^?1 spectral region with resolutions up to 0.12 cm^?1. Through the theoretical analysis 11 of the 12 b-type parameters I_a1, I_a2, V₃, V₆, k₁, k₂, k₃, k₄, k₅, k₆, k₇, D_KK are determined using a nonlinear least-squares fit. The agreement between the observed and the final theoretical spectrum is satisfactory considering that only Q-branch lines were studied. Experimentally more lines, especially at low frequencies, were observed which probably belong to P- and R-branch lines of clusters thereof.     

White phosphorus as single source of "P" in the synthesis of nickel phosphide

White phosphorus, P4, was reacted in a stoichiometric manner with Ni(0) complexes or particles to produce nanoparticles of nickel phosphide.     

Production of malachite green oxalate and leucomalachite green reference materials certified for purity

Malachite green oxalate (MG oxalate) and leucomalachite green (LMG) have been prepared and certified as pure reference materials. The purities of MG oxalate and LMG were assessed by high-performance liquid chromatography–diode array detection (HPLC–DAD), nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), Karl Fischer titration, ashing and thermogravimetric analysis (TGA). MG oxalate was purified by supercritical fluid extraction (SFE). Prior to purification, commercial MG oxalate purity was estimated to be about 90%. The main impurities present in SFE-purified MG oxalate were identified and quantified using HPLC–DAD. The main impurities were found to be monode-MG (monodemethylated MG oxalate synthesis impurity), 4-(dimethylamino)benzophenone (4-DMABP), MG-carbinol and LMG. The homogeneity of both reference materials was also determined. Issues associated with the stability of LMG and MG oxalate in solution forced an extensive study investigating different parameters i.e. solvent, acid, analyte concentration and temperature. MG oxalate (100 μg/mL) was found to be stable in acetonitrile containing 1% v/v glacial acetic acid for at least 155 days and LMG (100 μg/mL) was stable in acetonitrile for at least 133 days. The final purity value for MG oxalate was 94.3 ± 1.4% m/m at the 95% confidence interval (or 67% m/m if MG cation is reported). For LMG, the certified purity was found to be 98.8 ± 0.8% m/m at the 95% confidence interval. Figure Calibration reference materials for malachite green and leucomalachite green, certified for purity, are essential in characterising these key analytes in a fish matrix reference material     

A new approach to synthesis of layered fluorites containing molecular anions: synthesis of Ln2O2CO3, K(LnO)CO3, and Ln2O2CrO4 via metathesis reactions

A new synthetic approach is suggested for preparation of layered rare-earth oxide compounds containing [Ln2O2] slices and molecular anion sheets (CO32-, SO42-, and CrO42-). It is based on exchange reactions of rare-earth oxychlorides, [Ln2O2]Cl2, and alkali carbonates, sulfates, or chromates. Five new rare-earth oxychromates [Ln2O2]CrO4 (Ln=Pr-Gd) have been prepared which adopt a new, probably layered, structure type. In addition, significantly easier and more efficient synthetic pathways were found to the known compounds [Ln2O2]K2(CO3)2 and [La2O2]CrO4. The structure of the latter compound has been determined from neutron powder diffraction data. Factors affecting reaction pathways and products are discussed, as well as prospects for applying the approach to more complex layered compounds.     

Gold(I)-catalyzed cycloisomerization of 1,7- and 1,8-enynes: application to the synthesis of a new allocolchicinoid

Gold(I)-catalyzed cycloisomerization of 1,7- and 1,8-enyne propargylic acetates afforded cyclopropyl derivatives containing seven- and eight-membered rings, respectively. This reaction was used for the synthesis of a new allocolchicinoid having a cyclopropane ring fused to the B seven-membered ring at the C6-C7 positions.     

Activation of propargylic alcohols by dimolybdenum tris(μ-thiolate) complexes: Influence of the substituents R in HCCCR2(OH)-vinylidene/allenylidene transformation. Reactivity of allenylidene complexes

Reaction of the bis(nitrile) complex [Mo₂Cp₂(μ-SMe)₃(NCMe)₂](BF₄) (1) with dimethylpropargylic alcohol, HCCCMe₂(OH), at room temperature in dichloromethane produced good yields of the μ-alkynol species [Mo₂Cp₂(μ-SMe)₃{μ-CHCCMe₂(OH)}](BF₄) (2a) through replacement of the two acetonitrile ligands in 1 by the alkynol. The NMR spectra of 2a indicate a μ-η¹:η¹ coordination mode for the alkyne which is thereby incorporated into a dimetallacyclobutene ring like that found here by X-ray diffraction (XRD) analysis of the related complex [Mo₂Cp₂(μ-SMe)₃(μ-η¹:η¹-CHCCO₂Me)](BPh₄) (2b). When 2a was stirred with Et₃N at room temperature in dichloromethane, deprotonation gave high yields of the μ-3-hydroxyalkynyl derivative [Mo₂Cp₂(μ-SMe)₃{μ-η¹:η²-CCCMe₂(OH)}] (3), together with small amounts of the already-known vinylacetylide [Mo₂Cp₂(μ-SMe)₃{μ-η¹:η²-CCC(Me)CH₂}] (4) resulting from dehydration of 3. Treatment of 3 with 1 equiv. of HBF₄ · OEt₂ in diethyl ether at room temperature gave the 3-hydroxyvinylidene derivative [Mo₂Cp₂(μ-SMe)₃{μ-η¹:η²-CCHCMe₂(OH)}](BF₄) (5) as the major product, together with other minor products [Mo₂Cp₂(μ-SMe)₃{μ-η¹:η²-CCHC(Me)CH₂}](BF₄) (6), [Mo₂Cp₂(μ-SMe)₃(μ-η¹:η²-CCCMe₂)](BF₄) (7), [Mo₂Cp₂(μ-SMe)₃(μ-η¹:η²-CCH₂)](BF₄) (8), [Mo₂Cp₂(μ-SMe)₃{μ-η¹:η²-CCH(CHMe₂)}](BF₄) (9) and [Mo₂Cp₂(μ-SMe)₃(μ-O)](BF₄) (10). The vinylidene (6) and allenylidene (7) species resulted from dehydration of the 3-hydroxyvinylidene complex 5 whereas the vinylidene derivative 8 was formed by deketonisation of 5. When 3 reacted with a large excess of HBF₄ · OEt₂ in dichloromethane, the 3-isopropylvinylidene complex 9 was obtained nearly quantatively via a H radical process. When left for several days CD₂Cl₂ solutions of 5 afforded mainly the vinylidene species 8 by deketonisation and the side-oxoproduct [Mo₂Cp₂(μ-SMe)₃(μ-O)](BF₄) (10) by hydrolysis or reaction with oxygen. Addition of nucleophiles (H⁻, OMe⁻, OH⁻, SMe⁻) to the allenylidene complex [Mo₂Cp₂(μ-SMe)₃(μ-η¹:η²-CCCPh₂)](BF₄) (11) resulted in the formation of the corresponding μ-acetylide derivatives [Mo₂Cp₂(μ-SMe)₃(μ-η¹:η²-CCCRPh₂)] [R = H (12), OMe (16a), OH (17), SMe (16b)], which by further reaction with tetrafluoroboric acid afforded either the vinylidene species [Mo₂Cp₂(μ-SMe)₃{μ-η¹:η²-CCH(CRPh₂)}](BF₄) when R = H (13), or the starting complex 11 when R is a leaving group (OMe). Reaction of 13 with Na(BH₄) gave the μ-alkylidyne complex [Mo₂Cp₂(μ-SMe)₃(μ-η¹-CCH₂CPh₂H)] (14) by nucleophilic attack of H⁻ at the C_β carbon atom of the vinylidene chain. Proton addition at C_α in 14 led to the formation of a μ-vinylidene compound 15 containing an agostic C-H bond. New complexes have been characterised by elemental analyses and spectroscopic methods, supplemented for 2b and 3 by X-ray diffraction studies.     

Applications of Hybrid Polymers Generated from Living Anionic Ring Opening Polymerization

Increasingly precise control of polymer architectures generated by “Living” Anionic Ring-Opening Polymerization (Living AROP) is leading to a broad range of commercial advanced material applications, particularly in the area of siloxane macromers. While academic reports on such materials remain sparse, a significant portion of the global population interacts with them on a daily basis—in applications including medical devices, microelectronics, food packaging, synthetic leather, release coatings, and pigment dispersions. The primary driver of this increased utilization of siloxane macromers is their ability to incorporate the properties of silicones into organic structures in a balanced manner. Compared to organic polymers, the differentiating properties of silicones—low T_g, hydrophobicity, low surface energy, and high free molal space—logically lend themselves to applications in which low modulus, release, permeability to oxygen and moisture, and tactile interaction are desired. However, their mechanical, structural and processing properties have until recently precluded practical applications. This review presents applications of “Living” AROP derived polymers from the perspective of historical technology development. Applications in which products are produced on a commercial scale—defined as not only offered for sale, but sold on a recurrent basis—are emphasized. Hybrid polymers with intriguing nanoscale morphology and potential applications in photoresist, microcontact printing, biomimetic soft materials, and liquid crystals are also discussed. Previously unreported work by the authors is provided in the context of this review.     

Extremal Betti Numbers of Vietoris–Rips Complexes

Upper bounds on the Betti numbers over an arbitrary field of Vietoris–Rips complexes are established, and examples of such complexes with large Betti numbers are given.     

Thermochromic luminescence of copper iodide clusters: the case of phosphine ligands

Three copper(I) iodide clusters coordinated by different phosphine ligands formulated [Cu(4)I(4)(PPh(3))(4)] (1), [Cu(4)I(4)(Pcpent(3))(4)] (2), and [Cu(4)I(4)(PPh(2)Pr)(4)] (3) (PPh(3) = triphenylphosphine, Pcpent(3) = tricyclopentylphosphine, and PPh(2)Pr = diphenylpropylphosphine) have been synthesized and characterized by (1)H and (31)P NMR, elemental analysis and single crystal X-ray diffraction analysis. They crystallize in different space groups, namely, monoclinic P21/c, cubic Pa ?3, and tetragonal I ?42m for 1, 2, and 3, respectively. The photoluminescence properties of clusters 1 and 3 show reversible luminescence thermochromism with two highly intense emission bands whose intensities are temperature dependent. In accordance to Density Functional Theory (DFT) calculations, these two emission bands have been attributed to two different transitions, a cluster centered (CC) one and a mixed XMCT/XLCT one. Cluster 2 does not exhibit luminescence variation in temperature because of the lack of the latter transition. The absorption spectra of the three clusters have been also rationalized by time dependent DFT (TDDFT) calculations. A simplified model is suggested to represent the luminescence thermochromism attributed to the two different excited states in thermal equilibrium. In contrast with the pyridine derivatives, similar excitation profiles and low activation energy for these phosphine-based clusters reflect high coupling of the two emissive states. The effect of the Cu-Cu interactions on the emission properties of these clusters is also discussed. Especially, cluster 3 with long Cu-Cu contacts exhibits a controlled thermochromic luminescence which is to our knowledge, unknown for this family of copper iodide clusters. These phosphine-based clusters appear particularly interesting for the synthesis of original emissive materials.     

Reaction of perfluoroalkyl grignard reagents with phosphorus trihalides: a new route to perfluoroalkyl-phosphonous and -phosphonic acids

The reaction of perfluoroalkyl Grignard reagents with phosphorus(III) halides was explored. In the process a new convenient, one-pot, high yield method for the synthesis of (perfluoroalkyl)phosphonic acids has been developed. Perfluoroalkyl Grignard reagents react with phosphorus trichloride or phosphorus tribromide to form (perfluoroalkyl)phosphonous dihalides. Hydrolysis gives the corresponding (perfluoroalkyl)phosphonous acids. Oxidation of the phosphonous acids with H(2)O(2) produces (perfluoroalkyl)phosphonic acids in 60-78% overall yields, based on the corresponding perfluoroalkyl iodide. The X-ray crystal structures of the toluidinium salts, [MeC(6)H(4)NH(3)](2)[C(2)F(5)PO(3)] and [MeC(6)H(4)NH(3)][C(8)F(17)P(O)(2)OH], are reported.