Electrochemical synthesis of π-indenyl-π-(3)-1,2-dicarbollyliron(III)

Co-electrolysis of potassium 1,2-dicarbadodecahydroundecaborate and indene in 0.1N sodium bromide solution in dimethylsulfoxide using iron electrodes afforded -indenyl--(3)-1,2-dicarbollyliron(III).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 764–765, April, 1993.     

Pharmacokinetics of ICG and HPPH-car for the detection of normal and tumor tissue using fluorescence, near-infrared reflectance imaging: a case study

We present in vivo fluorescent, near-infrared (NIR), reflectance images of indocyanine green (ICG) and carotene-conjugated 2-devinyl-2-(1-hexyloxyethyl) pyropheophorbide (HPPH-car) to discriminate spontaneous canine adenocarcinoma from normal mammary tissue. Following intravenous administration of 1.0 mg kg-1 ICG or 0.3 mg kg-1 HPPH-car into the canine, a 25 mW, 778 nm or 70 mW, 660 nm laser diode beam, expanded by a diverging lens to approximately 4 cm in diameter, illuminated the surface of the mammary tissue. Successfully propagating to the tissue surface, ICG or HPPH-car fluorescence generated from within the tissue was collected by an image-intensified, charge-coupled device camera fitted with an 830 or 710 nm bandpass interference filter. Upon collecting time-dependent fluorescence images at the tissue surface overlying both normal and diseased tissue volumes, and fitting these images to a pharmacokinetic model describing the uptake (wash-in) and release (wash-out) of fluorescent dye, the pharmacokinetics of fluorescent dye was spatially determined. Mapping the fluorescence intensity owing to ICG indicates that the dye acts as a blood pool or blood persistent agent, for the model parameters show no difference in the ICG uptake rates between normal and diseased tissue regions. The wash-out of ICG was delayed for up to 72 h after intravenous injection in tissue volumes associated with disease, because ICG fluorescence was still detected in the diseased tissue 72 h after injection. In contrast, HPPH-car pharmacokinetics illustrated active uptake into diseased tissues, perhaps owing to the overexpression of LDL receptors associated with the malignant cells. HPPH-car fluorescence was not discernable after 24 h. This work illustrates the ability to monitor the pharmacokinetic delivery of NIR fluorescent dyes within tissue volumes as great as 0.5-1 cm from the tissue surface in order to differentiate normal from diseased tissue volumes on the basis of parameters obtained from the pharmacokinetic models.     

Investigation of Solvatomorphism and Its Photophysical Implications for Archetypal Trinuclear Au3(1-Methylimidazolate)3

A new solvatomorph of [Au₃(1-Methylimidazolate)₃] (Au₃(MeIm)₃)—the simplest congener of imidazolate-based Au(I) cyclic trinuclear complexes (CTCs)—has been identified and structurally characterized. Single-crystal X-ray diffraction revealed a dichloromethane solvate exhibiting remarkably short intermolecular Au⋯Au distances (3.2190(7) Å). This goes along with a dimer formation in the solid state, which is not observed in a previously reported solvent-free crystal structure. Hirshfeld analysis, in combination with density functional theory (DFT) calculations, indicates that the dimerization is generally driven by attractive aurophilic interactions, which are commonly associated with the luminescence properties of CTCs. Since Au₃(MeIm)₃ has previously been reported to be emissive in the solid-state, we conducted a thorough photophysical study combined with phase analysis by means of powder X-ray diffraction (PXRD), to correctly attribute the photophysically active phase of the bulk material. Interestingly, all investigated powder samples accessed via different preparation methods can be assigned to the pristine solvent-free crystal structure, showing no aurophilic interactions. Finally, the observed strong thermochromism of the solid-state material was investigated by means of variable-temperature PXRD, ruling out a significant phase transition being responsible for the drastic change of the emission properties (hypsochromic shift from 710 nm to 510 nm) when lowering the temperature down to 77 K.     

A New Class of Remote N‐Heterocyclic Carbenes with Exceptionally Strong σ‐Donor Properties: Introducing Benzo[c]quinolin‐6‐ylidene

We make the case for benzo[c]quinolin‐6‐ylidene ( 1 ) as a strongly electron‐donating carbene ligand. The facile synthesis of 6‐trifluoromethanesulfonylbenzo[c]quinolizinium trifluoromethanesulfonate ( 2 ) gives straightforward access to a useful precursor for oxidative addition to low‐valent metals, to yield the desired carbene complexes. This concept has been achieved in the case of [Mn(benzo[c]quinolin‐6‐ylidene)(CO)₅]⁺ ( 15 ) and [Pd(benzo[c]quinolin‐6‐ylidene)(PPh₃)₂(L)]²⁺ L=THF ( 21 ), OTf ( 22 ) or pyridine ( 23 ). Attempts to coordinate to nickel result in coupling products from two carbene precursor fragments. The CO IR‐stretching‐frequency data for the manganese compound suggests benzo[c]quinolin‐6‐ylidene is at least as strong a donor as any heteroatom‐stabilised carbene ligand reported.     

Pulsed field gradient NMR on polybutylcyanoacrylate nanocapsules

The applicability of pulsed field gradient nuclear magnetic resonance spectroscopy to nanocapsule systems is demonstrated on dispersed poly-n-butylcyanoacrylate nanocapsules as a model system. Spectroscopic data are presented that allow for the structural characterization of the inner cavities, the observation of Brownian motion of the capsules and the detection of rapid molecular exchange through the capsule walls. An analytical formula is proposed that yields equilibrium populations and average residence times of a given tracer molecule, thus leading to crucial information regarding the permeability of the capsule walls. Based on these analytical methods, two varieties of nanocapsules are compared that derive from two different preparation procedures. It is found that thinner capsule walls obtained under acidic conditions of the organic phase during interfacial polymerization lead to correspondingly higher exchange rates of benzene as a tracer molecule.     

Application of UHPLC for the determination of free amino acids in different cheese varieties

A rapid ultra-high performance liquid chromatography (UHPLC) protocol for the determination of amino acids as their respective 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) derivatives was successfully applied for assessing free amino acid levels in commercial cheese samples representing typical product groups (ripening protocols) in cheesemaking. Based on the Waters AccQ.Tag? method as a high performance liquid chromatography (HPLC) amino acid solution designed for hydrolyzate analyses, method adaptation onto UHPLC was performed, and detection of AQC derivatives was changed from former fluorescence (λ _Ex 250 nm/λ _Em 395 nm) to UV (254 nm). Compared to the original HPLC method, UHPLC proved to be superior by facilitating excellent separations of 18 amino acids within 12 min only, thus demonstrating significantly shortened runtimes (>35 min for HPLC) while retaining the original separation chemistry and amino acid elution pattern. Free amino acid levels of the analyzed cheese samples showed a high extent of variability depending on the cheese type, with highest total amounts found for original Italian extra-hard cheeses (up to 9,000 mg/100 g) and lowest for surface mold- or bacterial smear-ripened soft cheeses (200–600 mg/100 g). Despite the intrinsic variability in both total and specific concentrations, the established UHPLC method enabled reliable and interference-free amino acid profiling throughout all cheese types, thus demonstrating a valuable tool to generate high quality data for the characterization of cheese ripening.     

AFM investigations on the influence of CO2 exposure on Ba0.5Sr0.5Co0.8Fe0.2O3–δ

In this work, fresh and CO₂-exposed specimens of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3–δ (BSCF) are examined by atomic force microscopy (AFM) using amplitude-modulated Kelvin probe force microscopy (KPFM) and also electrostatic force microscopy (EFM) to characterize the early stages of the formation of reaction products due to reaction with gaseous CO₂. A comparison is made with results from electron microscopy on the same samples. BSCF specimens exposed for 24 and 240 h to an atmosphere of 99.9 % CO₂ at 900 °C, respectively, were analyzed and compared with non-exposed specimens. The observation of interconnected carbonate islands on BSCF forming a continuous carbonate layer after some exposure to CO₂ indicates a Stranski–Krastanov or Volmer–Weber growth mechanism of the carbonate layer. Our results demonstrate that the measurement of surface potential variations by means of KPFM and EFM constitutes a very sensitive technique to detect the formation of reaction layers on gas permeation membranes such as BSCF. In contrast to electron microscopy techniques, scanning probe techniques permit the investigation of the topography and of electrochemical characteristics of the sample surface as received and without further preparation.     

Synthesis of electronically and coordinatively unsaturated complexes [Ru2(CO)4(μ-H)(μ-PBu2)(μ-L2)] (L2 = biphosphanes)

A convenient synthesis and the characterization of six new electronically and coordinatively unsaturated complexes of the formula [Ru₂(CO)₄(μ-H)(μ-P^tBu₂)(μ-L₂)] (2b-g) (RuRu) is described exhibiting a close relation to the known [Ru₂(CO)₄(μ-H)(μ-P^tBu₂)(μ-dppm)] (2a). The complexes 2b-g were obtained in a kind of one-pot synthesis starting from [Ru₃(CO)₁₂] and P^tBu₂H in the first step followed by the reaction with the bidentate bridging ligand in the second step. The method was developed for the following bridging ligands (μ-L₂): dmpm (2b, dmpm = Me₂PCH₂PMe₂), dcypm (2c, dcypm = Cy₂PCH₂PCy₂), dppen (2d, dppen = Ph₂PC(=CH₂)PPh₂), dpppha (2e, dpppha = Ph₂PN(Ph)PPh₂), dpppra (2f, dpppra = Ph₂PN(Pr)PPh₂), and dppbza (2g, dppbza = Ph₂PN(CH₂Ph)PPh₂). The molecular structures of all new complexes 2b−g were determined by X-ray diffraction.     

Electron Impact Induced Fragmentation of Aromatic Alkoxyimines II [5]. Formation and Transformation of Heterocyclic Radical Cations in the Gas Phasea

 The molecular ion 1 of N-(n-propoxy)benzaldimine I rearranges by an 1,5-H-shift to the δ-distonic ion 2 which subsequently cyclizes to the α-distonic ion 3. Homolytic cleavage of the N–O bond in 3 results in the δ-distonic ion 4 which expels CH₂O leading to the β-distonic ion 5. Ion 5 is also formed from the molecular ions of tetrahydrooxazines II and III and from M^+• of phenylazetidine IVa. In a subsequent step, ion 5 cyclizes to the N-protonated 3,4-dihydroisoquinolinium ion 6. The syntheses of II–IV and their derivatives are described.     

A 50% n-octylmethyl, 50% diphenyl-polysiloxane as stationary phase with unique selectivity for gas chromatography

An n-octylmethyl, diphenyl-polysiloxane called SOP-50-Octyl was prepared by a condensation reaction of bis(dimethylamino) n-octylmethylsilane with diphenylsilanediol. The resulting copolymer was a gum with high molecular weight and was obtained with a yield of 80%. 1H and 29Si NMR spectroscopy revealed that the copolymer was a 52% octylmethyl, 48% diphenyl-polysiloxane with random microstructure. Small cyclic impurities could be almost quantitatively removed via a purification step. SOP-50-Octyl was used as stationary phase for the preparation of wall coated open tubular fused silica capillary columns for gas-liquid chromatography. The capillary columns exhibited high separation efficiency and high inertness. The stationary phase offered a unique selectivity due to its unique composition. The Rohrschneider-McReynolds constants indicated a low overall polarity in spite of the high phenyl content, as the polarity was distinctly decreased by the octyl substituent. Furthermore, the octyl substituent was responsible for a high column bleed, reducing the maximum allowable operating temperature to 280 degrees C. The elution temperatures of apolar compounds were increased due to increased interaction of the octyl substituent with the analytes. Some applications with volatile and semi-volatile organic compounds illustrate that SOP-50-Octyl is an excellent choice for confirmational analyses.