Unsymmetrical zinc azaphthalocyanines,peripherally substituted with thiophen-2-yl and 2-functionalized phenoxy groups

Four targeted octasubstituted zinc azaphthalocyanines (ZnAzaPc), substituted with thiophen-2-yl groups and ortho-substituted phenoxy groups, were obtained by cyclotetramerization of 5-aryloxy-6-(thiophen-2-yl)pyrazine-2,3-dicarbonitriles. Thiophen-2-yl substituents are known to extend the macrocyclic conjugation, and thereby cause red-shifted UV–Vis Q-bands. Peripheral phenoxy groups with bulky ortho substituents are expected to suppress aggregation and thereby improve solubility of these compounds. The reagent Zn(quinoline)₂Cl₂ was used for one-step syntheses of these ZnAzaPc. Four tetrasubstituted ZnAzaPc, with phenoxy, (2-isopropyloxy)phenoxy, (2-isopropyl)phenoxy or (2-tert-butyl)phenoxy substituents, were obtained as controls from 5-aryloxypyrazine-2,3-dicarbonitriles. The tetra- and octa-substituted ZnAzaPc, 5 and 6, were obtained in 30–50% yields after purification by chromatography on silica. UV–Vis Q-bands with high molar extinction coefficients (100 000–160 000), were observed at 635 nm for compounds 5, and at 660–665 nm for 6. Grass-green solutions were obtained of compounds 6 in most organic solvents, whereas the less soluble compounds 5 gave blue-green solutions. 2D NMR methods were applied in analyses of DMSO-d₆ solutions of ZnAzaPc 5 and 6. Broad and partly overlapping ¹H NMR signals for some of the compounds indicate some aggregation as well as presence of two or more structural isomers. Molecular ions of ZnAzaPc 5 and 6 were determined by mass spectrometry (MALDI-TOF).     

Temperature‐Programmed Packed Capillary Liquid Chromatography Coupled to Fourier‐Transform Infrared Spectroscopy

Temperature‐programmed packed capillary liquid chromatography has been coupled off‐line to Fourier‐transform infrared spectroscopy, utilizing a commercially available interface with a pneumatic nebulizer rebuilt to handle low flow rates at elevated temperatures. The modified interface showed excellent performance with regard to non‐aqueous reversed phase separations of polymer additives, resulting in constructed Gram‐Schmidt chromatograms comparable to chromatograms obtained using UV detection. The spray of the in‐house constructed nebulizer was not influenced by temperature changes of the column effluent, and hence temperature‐programmed gradient separations could be used successfully. The relative standard deviation of peak height was 4.4% (n = 5) and the mass limit of detection was determined to be about 40 ng, using a polymer antioxidant as model compound. The present instrumental coupling has been used for characterization of the antioxidant Irgafos P‐EPQ.     

Zinc azaphthalocyanines with pyridin-3-yloxy peripheral substituents

Phthalocyanines (Pc), which are peripherally substituted with pyridin-3-yloxy groups, have shown promise as sensitizers for photodynamic cancer therapy (PDT). Some aza-analogues (AzaPc) are reported here. Four monomers were synthesized, i.e. 5,6-di(pyridin-3-yloxy)pyrazine-2,3-dicarbonitrile, and three pyrazine-2,3-dicarbonitriles, substituted with pyridin-3-yloxy- in combination with H, Me and Ph groups. Cyclotetramerizations of these monomers with the reagent Zn(quinoline)₂Cl₂ yielded the targeted ZnAzaPcs in 20–40% yields.The cyclotetramerizations were accompanied, and apparently initiated, by complexation between zinc(II) and the pyridin-3-yloxy groups attached to the pyrazine-dicarbonitriles. Two such zinc(II) complexes were isolated and characterized. Identifications of all new substances were primarily based on NMR spectra, where the pulse techniques COSY, NOESY, HSQC and HMBC were applied. Molecular ions of the ZnAzaPcs were determined by mass spectrometry (MALDI-TOF). The UV–Vis spectra of these macrocycles were as expected, with Q-band absorptions at 630–650 nm and molar extinction coefficients, ε, 70 000–100 000. Eight peripheral pyridin-3-yloxy groups induced a small blue shift of the Q-band, from 636 nm for unsubstituted ZnAzaPc, to 630 nm, whereas a red shifted Q-band at 650 nm resulted from the combination of phenyl and pyridin-3-yloxy substituents. Improved solubilities were observed for the unsymmetrical ZnAzaPcs compared to octa(pyridin-3-yloxy)ZnAzaPc.     

Purity testing of organometallic catalysts by packed capillary supercritical fluid chromatography

A packed capillary column supercritical fluid chromatography system with flame ionization detection has been used for purity testing of candidates for homogeneous catalysis such as methyl tricarbonyl pentamethylcyclopentadienyl tungsten [Cp*W(CO)3Me], methyl tricarbonyl cyclopentadienyl tungsten [CpW(CO)3Me], tetramethyl pentamethylcyclopentadienyl iridium (Cp*IrMe4), trimethyl (1,4,7-trimethyl-1,4,7-triazocyclononane) rhodium (CnRhMe3), trimethylphosphine hydride dicarbonyl cyclopentadienyl molybdenum [eta5-CpMoH(CO)2PMe3] and triphenylphosphine hydride dicarbonyl cyclopentadienyl molybdenum [eta5-CpMoH(CO)2PPh3]. A mass limit of detection of 240 pg was found for eta5-CpMoH(CO)2PMe3 when using a 60-nl injection volume and pure CO2 as mobile phase on a 5 microm Kromasil C18 column. The stability of the catalysts in solution has been examined. After 24 h more than 70% of eta5-CpMoH(CO)2PMe3 and 50% of eta5-CpMoH(CO)2PPh3 had decomposed. Due to the instability of the compounds the purity testing had to take place rapidly after sample dissolution.     

Determination of C(80) tetra-acid content in calcium naphthenate deposits

A method is described which allows to determine the content of the so-called C(80) tetra-acid molecules (TA) in calcium naphthenate deposits. The method consists of four steps. Molecules present in the deposit are dissolved in a mixture of toluene and 2-butanol after an acidic treatment. All acid molecules are then selectively extracted and concentrated by a solid-phase extraction (SPE) method. After derivatization of acids into their naphthacyl esters to increase the sensitivity of the detection, TA is separated and detected by reversed-phase HPLC with UV detection. We have checked that all the steps are quantitative and the method appears selective. The TA content can be determined in presence of other naphthenic acids. Using this methodology we have determined the TA content in three calcium naphthenate deposits from different oil fields. It appears that these deposits have a similar TA concentration between 28 and 41% (w/w).     

Purity testing of organometallic catalysts by micro liquid chromatography-electron ionization mass spectrometry

Summary A micro liquid chromatography-mass spectrometry system utilizing 100 μm i. d. packed capillary columns has been used for purity testing of organometallic catalysts. The total effluent, 1 μLmin⁻¹ from the column, was introduced directly into the ion source of a bench-top quadrupole mass spectrometer and electron ionization mass spectra were acquired. In full scan mode a mass limit of detection of 10–15 ng was achieved for the organometallic compounds investigated. The catalysts dimethyl pentamethylcyclopentadienyl iridium dimethylsulphoxide (Cp^*Ir(DMSO)Me₂) and di(pentamethylcyclopentadienyl dichloro iridium) ((Cp^*IrCl₂)₂) were purity tested and their electron ionization mass spectra recorded. Impurities present down to 1% of the main compound could be determined using large volume injection.     

Temperature-Programmed Packed Capillary Liquid Chromatography Separation with Large Volume On-Column Focusing of Retinyl Esters

A non-aqueous isocratic reversed-phase packed capillary high performance liquid chromatography method for the determination of retinyl esters, utilizing temperature programming and on-column focusing large volume injection, has been developed. The stationary phase material was C₃₀, and the mobile phase consisted of acetonitrile-dichloromethane (70 : 30, v/v). A three-step temperature program, starting at 10°C for 10 min, then 1°/min to 30°C, and finally 2.5°/min to 70°C, was found most appropriate. Compared to an isothermal separation at 25°C, this temperature program provided improved peak resolution, enhanced peak shapes of the last eluting compounds, and a reduction of the overall elution time. A mass limit of detection of 27 pg was found with respect to retinyl palmitate, using UV detection with an “U” shaped flow cell at 327 nm. This corresponds to a concentration limit of detection of 2.7 pg/μL, when utilizing an injection volume of 10 μL. The concentration of retinyl palmitate in arctic seal liver samples was estimated to be 62.6 μg/g liver.