Brillouin spectroscopy of induced phonons in x-cut quartz

Triplepass Brillouin spectroscopy was used to detect longitudinal bulk waves generated at a y, z-surface of x-cut quartz. A comparison with Brillouin scattering by thermal phonons shows that Brillouin scattering by induced phonons admit sound attenuation measurements in a dynamic range of almost 80 dB at room temperature. It is also shown that our experimental results agree very well with results obtained at lower frequencies by pulse-echo measurements.     

A New Class of Task-Specific Imidazolium Salts and Ionic Liquids and Their Corresponding Transition-Metal Complexes for Immobilization on Electrochemically Active Surfaces

Adding to the versatile class of ionic liquids, we report the detailed structure and property analysis of a new class of asymmetrically substituted imidazolium salts, offering interesting thermal characteristics, such as liquid crystalline behavior, polymorphism or glass transitions. A scalable general synthetic procedure for N-polyaryl-N’-alkyl-functionalized imidazolium salts with para-substituted linker (L) moieties at the aryl chain, namely [LPh_mIm^HR]⁺ (L=Br, CN, SMe, CO₂Et, OH; m=2, 3; R=C₁₂, PEG_n; n=2, 3, 4), was developed. These imidazolium salts were studied by single-crystal X-ray diffraction (SC-XRD), NMR spectroscopy and thermochemical methods (DSC, TGA). Furthermore, these imidazolium salts were used as N-heterocyclic carbene (NHC) ligand precursors for mononuclear, first-row transition metal complexes (Mn^II, Fe^II, Co^II, Ni^II, Zn^II, Cu^I, Ag^I, Au^I) and for the dinuclear Ti-supported Fe-NHC complex [(OPy)₂Ti(OPh₂ImC₁₂)₂(FeI₂)] (OPy=pyridin-2-ylmethanolate). The complexes were studied concerning their structural and magnetic behavior via multi-nuclear NMR spectroscopy, SC-XRD analyses, variable temperature and field-dependent (VT-VF) SQUID magnetization methods, X-band EPR spectroscopy and, where appropriate, zero-field ⁵⁷Fe Mössbauer spectroscopy.     

Unraveling Complexity: A Strategy for the Characterization of Anisotropic Core Multishell Nanoparticles

In this work, a widely applicable routine to characterize the core, surface, stability, and optical properties of CdSe/CdS/ZnS core–shell–shell nanorods after multiple growth steps is established. First, size, shape, and shell thickness of the nanorods are characterized by transmission electron microscopy (TEM), analytical ultracentrifugation (AUC), and small angle X-ray/neutron scattering (SAXS/SANS). In the next step, Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), and SANS measurements are applied to determine the surface species of nanorods. Then, the colloidal stability of the nanorods is investigated by UV–vis spectroscopy and dynamic light scattering (DLS) after different washing cycles. Finally, photoluminescence quantum yield (PLQY) of the nanorods during washing and sample storage is determined. With this highly complementary routine for particle characterization, the core, surface, stability, and optical properties of nanorods after multiple growth steps are resolved. The results demonstrate the importance of the developed toolbox to characterize such highly complex, anisotropic nanorods for a technical environment. This is of major importance for the handling of colloidal quantum materials and their quality control in industrial applications.     

Synthesis,structures, photophysical properties,and catalytic characteristics of 2,9-dimesityl-1,10-phenanthroline (dmesp) transition metal complexes

The syntheses of the 2,9-dimesityl-1,10-phenanthroline ( dmesp ) metal complexes, [Cu(dmesp)(MeCN)]PF₆ ( 1 ), [Cu(dmesp)₂]PF₆ ( 2 ), Fe(dmesp)Cl₂ ( 3 ), Co(dmesp)Cl₂ ( 4 ), Ni(dmesp)Cl₂ ( 5 ), Zn(dmesp)Cl₂ ( 6 ), Pd(dmesp)MeCl ( 7 ), Cu(dmesp)Cl ( 8 ), and Pd(dmesp)₂Cl₂ ( 9 ), in good to high yields are described. These complexes were characterized by ¹H and ¹³C NMR spectroscopy, HR–MS (ESI and/or APPI), and elemental analysis (CHN). The solid-state structures of complexes 1 – 8 were determined by single-crystal X-ray analysis and their photophysical properties were also characterized. To demonstrate the versatility of this new platform, complexes 3 – 5 , 8 , and 9 were employed in the catalytic oligomerization of ethylene using modified methyl aluminoxane (MMAO) as the cocatalyst, where Co(II) and Ni(II) complexes ( 4 and 5 , respectively) were found to exhibit moderate selectivity for catalytic dimerization of ethylene to butenes over tri- or tetramerization. Complex 8 is an effective catalyst of both the commonly encountered “click” reaction and amine arylation chemistries. Complexes 6 and 9 were found to be excellent catalysts for Friedel-Crafts alkylation and Suzuki-Miyaura coupling, respectively.     

Effect of oxalate test dose size on absolute and percent oxalate absorption

The purpose of this pilot study was to establish the dependence or independence of oxalate absorption on the quantity of the test dose of sodium oxalate over a range of test doses corresponding to physiological dietary oxalate intake values. Gastrointestinal oxalate absorption was measured with the [¹³C₂]oxalate absorption test. Six healthy volunteers were always tested under standardized dietary conditions with 63 mg dietary oxalate and 800 mg dietary calcium per day. The volunteers were tested thrice each with sodium oxalate test doses of 25, 50, 200, and 600 mg. Additionally, 1000 mg sodium oxalate was applied once to three of these volunteers. The oxalate absorption of the six volunteers tested under the standardized conditions with 50 mg sodium [¹³C₂]oxalate was 7.2 ± 2.62 % (mean ± SD), similar to the 120 volunteers tested previously: 8.0 ± 4.4 % (mean ± SD). The tests with sodium [¹³C₂]oxalate doses in the range 25–1000 mg revealed similar percent oxalate absorption values. In conclusion, in healthy volunteers, the amount of oxalate absorbed in the gastrointestinal tract increased proportionally with the higher test doses of oxalate. However, percent oxalate absorption remained unchanged with test doses in the dose range of physiological dietary oxalate intakes.     

Labelling Studies for Structure Elucidation of a New Hydroxymetabolite of Tramadol

Abstract

Tramadol, racemic 1-(3-methoxyphenyl)-2-(dimethylaminomethyl)cyclohexane-1-ol, is an effective analgesic drug. Metabolites of tramadol described so far originate from O- and N-demethylation and are excreted in urine directly or after conjugation. A further metabolite was found in human liver microsome incubations and in the urine of volunteers after ingestion of tramadol. To elucidate the structure of the new metabolite, seven deuterated isotopomers of tramadol have been synthesized and ingested by volunteers. The mass spectra of the metabolites derived showed (i) that it was a hydroxy metabolite, (ii) that the hydroxy group was not located on the aromatic ring, the side chain, or the positions 2 and 6 of the cyclohexane ring, (iii) that the hydroxy-group was introduced to one of the the positions 3, 4 or 5 of the cyclohexane ring. The hydroxy metabolite was formed preferentially from the (-)-enantiomer, (1S,2S)-tramadol.     

Small Molecule Activation with Intramolecular “Inverse” Frustrated Lewis Pairs

The intramolecular “inverse” frustrated Lewis pairs (FLPs) of general formula 1-BR₂-2-[(Me₂N)₂C=N]-C₆H₄ ( 3 – 6 ) [BR₂=BMes₂ ( 3 ), BC₁₂H₈, ( 4 ), BBN ( 5 ), BBNO ( 6 )] were synthesized and structurally characterized by multinuclear NMR spectroscopy and X-ray analysis. These novel types of pre-organized FLPs, featuring strongly basic guanidino units rigidly linked to weakly Lewis acidic boryl moieties via an ortho-phenylene linker, are capable of activating H−H, C−H, N−H, O−H, Si−H, B−H and C=O bonds. 4 and 5 deprotonated terminal alkynes and acetylene to form the zwitterionic borates 1-(RC≡C-BR₂)-2-[(Me₂N)₂C=NH]-C₆H₄ (R=Ph, H) and reacted with ammonia, BnNH₂ and pyrrolidine, to generate the FLP adducts 1-(R₂HN→BR₂)-2-[(Me₂N)₂C=NH]-C₆H₄, where the N-H functionality is activated by intramolecular H-bond interactions. In addition, 5 was found to rapidly add across the double bond of H₂CO, PhCHO and PhNCO to form cyclic zwitterionic guanidinium borates in excellent yields. Likewise, 5 is capable of cleaving H₂, HBPin and PhSiH₃ to form various amino boranes. Collectively, the results demonstrate that these new types of intramolecular FLPs featuring weakly Lewis acidic boryl and strongly basic guanidino moieties are as potent as conventional intramolecular FLPs with strongly Lewis acidic units in activating small molecules.     

The ferroelastic transition of betaine borate

The ferroelastic transition of betaine borate at about 142 K and the nonlinear temperature dependence of the corresponding critical elastic modulus are related to the softening of optical phonons. The transition has to be considered a ferroelastic one of the optic type, i.e. pseudoproper one, therefore. It is shown by Raman spectroscopic results that the transition is induced by a strong bilinear coupling between a homogeneous strain and at least two optic lattice modes which are of the same symmetry as the strain. Optic and dielectric, investigations support the second-order character of and the classical behaviour at this transition, which have been reported in the literature. Differences and similarities to the ferroelastic transition of betaine fumarate are discussed.