Reaktionen der Base des Kristallvioletts mit Säuren in organischen Lösungsmitteln

Zusammenfassung Es werden Systeme der Pseudobase des Kristallvioletts mit organischen Säuren in organischen Lösungsmitteln untersucht. Die Kinetik und das Gleichgewicht dieser Systeme werden mit Hilfe von Leitfähigkeits- und Absorptionsmessungen verfolgt. Der Einfluß einer Variation von Konzentration, Temperatur und Wassergehalt, Säurestärke und Lösungsmittel wird untersucht.Das Reaktionsschema ist ein solches erster Ordnung. Als vorläufige reaktionschemische Deutung wird ein Gleichgewicht SalzPseudosalz (Ester) vorgeschlagen.Mit 16 Abbildungen.Herrn Prof. Dr.A. Klemenc zu seinem 70. Geburtstage gewidmet.     

A study of the methanol laser with a 500 MHz tunable CO2 pump laser

The absorption spectrum of CH₃OH is measured optoacoustically over a 500 MHz tuning range in 84 different CO₂ laser lines, and 19 assigned CO-stretch absorptions are used for establishing the linearity of the measurements over two decades of absorption coefficient. 40 new FIR laser lines originating from large offset absorption, are reported in the wavelength range between 40 and 400 m, and their wavelengths are given with a relative accuracy of 5×10^–5. 30 lines are assigned, involving CO-stretch transitions in torsionaln=0, 1, and 2 states, as well as transitions inn=3 of the vibrational ground state, pumped by transitions to Fermi interacting states.Work supported by the Danish National Science Research Council grant No. 11-5375     

Tribrom-methylnitren-Komplexe des Wolframs Die Kristallstruktur von PPh3Me[WBr5(NCBr3)]

Tribromomethylnitrene Complexes of Tungsten. Crystal Structure of PPh₃Me[WBr₅(NCBr₃)] Tungsten hexabromide reacts with BrCN in boiling bromine under formation of the BrCN adduct of tribromomethylnitrene tungsten, [BrCN? WBr₄(NCBr₃)]. This reacts with triphenylmethylphosphonium bromide in dibromomethane forming the tribromomethylnitrene pentabromowolframate, PPh₃Me[WBr₅(NCBr₃)]. Both compounds form brown-black, moisture sensitive crystal powders that were characterized by their IR spectra. The crystal structure of PPh₃Me[WBr₅(NCBr₃)] was determined by X-ray diffraction (3 664 observed reflexions, R = 0.066). Crystal data: a = 1 401.6, b = 1 243.3, c = 884.6 pm, α = 90.82, β = 110.74, γ = 90.67°, space group P1 , Z = 2. The compound consists of PPh₃Me^⊕ cations and [WBr₅(NCBr₃)]^? anions in which the tungsten atoms have a distorted octahedral coordination by five bromine atoms and the N atom of the nitrene ligand. The WN bond length of the nitrene ligand (175 pm) corresponds approximately to a triple bond; the W?N? C group is linear and shows a strong trans effect.     

Squaraine dyes for photodynamic therapy: mechanism of cytotoxicity and DNA damage induced by halogenated squaraine dyes plus light (>600 nm)

Halogenated squaraine dyes 1 and 2 possess favorable photophysical and in vitro photobiological properties that make these new class of molecules interesting for photodynamic therapeutic applications. For a better understanding of the mechanism of their photobiological activity, we have analyzed the DNA damage and the cytotoxicity induced by these photosensitizers in mammalian cells and cell-free systems in the presence and absence of various additives and scavengers. Both photoactivated squaraines were found to be similar efficient in inducing single-strand breaks (SSB) in cell-free DNA when compared with the cellular DNA. Superoxide dismutase and catalase did not show any influence. However, the presence of tert-butanol and glutathione inhibited the formation of the DNA SSB, indicating an indirect (possibly squaraine radical mediated) mechanism under cell-free conditions. Replacing H2O in the buffer by D2O resulted in a five- to six-fold increase in the number of the SSB in cell-free DNA and a significant enhancement of the photocytotoxicity in mouse lymphoma cells. The results demonstrate that singlet oxygen is the major reactive species under cell-free and cellular conditions and confirm that squaraine-based sensitizers 1 and 2 can have potential applications in photodynamic therapy.