One‐Dimensional,Cofacial Porphyrin Polymers Formed by Self‐Assembly of meso‐Tetrakis(ERE Donor) Zinc(II) Porphyrins

A series of meso‐tetrakis‐(ERE donor) zinc(II) porphyrins n Zn (ERE donor=4‐R‐3,5‐bis[(E)‐methyl]phenyl; 1 Zn: E=NMe₂, R=Br; 2 Zn: E=NMe₂, R=H; 3 Zn: E=OMe, R=Br; 4 Zn: E=OMe, R=H) have been synthesized in excellent yields. As a result of the combination of a Lewis acidic site and eight Lewis basic sites within one molecule, monomeric molecules of n Zn self‐assemble to form one‐dimensional porphyrin polymers [ n Zn]_∞ in the solid state, as confirmed for 1 Zn and 3 Zn by X‐ray crystallography. The coordination environment around the zinc(II) ions in these polymers is octahedral. They are ligated by four equatorial nitrogen atoms of the porphyrin and two apical E atoms (E=N, O) provided by the EBrE donor groups of adjacent n Zn molecules. Complexes 2 Zn and 4 Zn did not form single crystals, but solid‐state UV/Vis analysis points to the formation of similar structures. Solution UV/Vis and ¹H NMR spectroscopy indicated that interactions between 1 Zn and 2 Zn monomers in the polymers are stronger than between 3 Zn and 4 Zn monomers. Interestingly, they also revealed that the presence of a neighboring bromine atom in the EBrE donor groups has a considerable influence on the coordination properties of the benzylic N or O atoms. The zinc(II) ions of the porphyrins most likely adopt only hexacoordination in the solid state, owing to the unique predisposition of Lewis acidic and basic sites in the n Zn molecules. Several parameters of the aggregates, for example, the interplanar separation between porphyrins and the zinc–zinc distances, change as a function of the coordinating E groups. The high degree of modularity in their synthesis makes these zinc(II) porphyrins an interesting new entry in noncovalent multiporphyrin assemblies.     

Reversed-phase high-performance liquid chromatography-thermospray mass spectrometry of radiation-induced decomposition products of thymine and thymidine.

High-performance liquid chromatography-thermospray mass spectrometry was applied to the analysis of various radiation-induced decomposition products of thymidine including N-(2-deoxy-beta-D-erythro-pentofuranosyl)formamide and the various diastereomers of 5,6-dihydroxy-5,6-dihydrothymidine, 5-hydroxy-5,6-dihydrothymidine and 5,6-dihydrothymidine. This method combines high sensitivity and product resolution, rendering it particularly useful for monitoring the formation of radiation-induced base damage within DNA.     

Adsorption of the halogens on cerium dioxide

Summary CeO₂, alone or mixed with La₂O₃, is used as halogen adsorbent in the determination of carbon and hydrogen. Quantitative data are given on the adsorption of the single halogens on various samples of pure CeO₂ and La₂O₃. Retention of CO₂ and the influence of several parameters of special interest in the carbon and hydrogen determination, have been examined. It has been found that the conditions for optimum adsorption of the halogens are a large surface and relatively low adsorption temperature. Unfortunately these conditions cannot be applied in the determination of carbon and hydrogen.

---

Zusammenfassung CeO₂ allein oder im Gemisch mit La₂O₃ wurde als Adsorbens für Halogen bei der CH-Bestimmung verwendet. Quantitative Angaben über die Adsorption der einzelnen Halogene an verschiedenen Mustern von reinem CeO₂ und La₂O₃ wurden gebracht. Die Retention von CO₂ und der Einfluß einzelner Parameter, die für die CH-Bestimmung von besonderem Interesse sind, wurden geprüft. Die besten Bedingungen für die Adsorption der Halogene sind große Oberfläche und relativ niedere Temperatur. Beide Bedingungen können leider bei der CH-Bestimmung nicht eingehalten werden.

     

Dipole moments of compounds containing a cobalttin bond

The molecular electric dipole moments are reported for the series of tin-substituted tetracarbonyl cobalt compounds R_nY_m?nSn{Co(CO)₄}_4?m (m = 1–3; n ? m; R = alkyl, phenyl; Y = halogen). The effect of the substituents at the tin atom on the nature of the CoSn bond is established on calculating the (CO)₄CoSn group dipole moments. It is shown that the charge transfer in the CoSn bond is mainly determined by the inductive properties of the ligands attached to tin.     

Determination of oxaliplatin in human plasma and plasma ultrafiltrate by graphite-furnace atomic-absorption spectrometry

A method for sensitive determination of the anti-cancer agent oxaliplatin in human plasma and human plasma ultrafiltrate (pUF) is presented. The method is based on the quantification of platinum by graphite-furnace atomic-absorption spectrometry, with Zeeman correction and an atomisation temperature of 2,700°C. Sample pretreatment involves dilution of the samples with a solution containing 0.15 mol L^–1 NaCl and 0.20 mol L^–1 HCl in water. Validation was performed in accordance with the most recent FDA guidelines for bioanalytical method validation. All results were within requirements. The validated ranges of quantification were 0.10–400 mol L^–1 for human pUF and 0.50–400 mol L^–1 for plasma. The assay is now successfully used to support pharmacokinetic studies of cancer patients treated with oxaliplatin.     

Base- and light-assisted synthesis of anthracenes from 3-allylnaphthalene-2-carbaldehydes

The synthesis of substituted anthracenes from naphthalene precursors is described. The key step involved heating ortho-allyl substituted naphthalene-2-carbaldehydes and potassium t-butoxide in DMF with concomitant irradiation from a high pressure mercury lamp to afford anthracenes in yields of 76-98%.     

Zur direkten ma?analytischen Bestimmung von Carbamaten als sehr schwache S?uren

Zusammenfassung Eine direkte maßanalytische Methode zur Bestimmung diverser Carbamate wird beschrieben. Die potentiometrische Titration mit käuflicher Tetra-n-butylammoniumhydroxid-Lösung, verdünnt mit Propanol-(2), ist bequem durchzuführen, und die erhaltenen Titrationskurven gestatten eine korrekte Auswertung.

---

Direct volumetric determination of carbamates as very weak acids

Summary A volumetric procedure for the determination of some carbamates is described. The potentiometric titration with commercial tetra-n-butylammonium hydroxide solution diluted with propanol-(2) is convenient and the obtained titration curves permit a correct calculation.

     

Light dosimetry: status and prospects

This paper is a report on the state of the art of light dosimetry in photomedicine and photobiology. The basic quantity of interest is the radiant energy fluence rate, which can either be measured using a suitable probe, or calculated theoretically from measured optical constants. First, theoretical models used to analyse experimental transmission and reflection data are briefly discussed. It is shown that a two-flux model derived from the transport equation in the diffusion approximation resembles the Kubelka-Munk and other heuristic models. This illustrates the limitations of these models and suggests their abandonment in favour of transport theory. For theoretical energy fluence rate calculations at least three optical constants are needed, namely the absorption coefficient, the scattering coefficient and the average cosine of the scattering angle. These three constants have been measured for very few tissues. In principle only two of the three constants can be measured directly on thin samples, independent of a theoretical model. The energy fluence rate can be measured quantitatively with a miniature fibre optic probe with isotropic response. Such measurements allow indirect determination of the three optical constants. It appears that we are just beginning to understand the distribution of light energy fluence rate in tissues. Tasks for the near future are comparison of methods to measure optical constants, quantitative checks of calculated and measured energy fluence rates in model tissues and optical phantoms and further development of theoretical models. Particular attention is required for boundary conditions, with and without refractive index matching.     

Kinetics and mechanism of the Co(II)-assisted oxidation of thioureas by dioxygen

Catalytic oxidation of N,N'-dimethylthiourea and thiourea by dioxygen in water using a new cobalt(II) complex of octasulfophenyltetrapyrazinoporphyrazine was performed under mild conditions. The reaction is shown to include the formation of an intermediate anionic five-coordinate complex followed by an unusual two-electron oxidation to produce the corresponding urea and elemental sulfur (S8). Kinetic and thermodynamic parameters for the different reaction steps of the process were determined. Drastic differences in catalytic activity of cobalt and iron octasulfophenyltetrapyrazinoporphyrazines were observed.