Organotin Complexes of Alizarin and Purpurin

Five novel organotin complexes with the anthraquinone dyes alizarin (1,2-dihydroxyanthraquinone) and purpurin (1,2,4-trihydroxyanthraquinone) were synthesized and characterized by elemental analyses, FTIR and NMR spectroscopy ((1)H, (13)C and (119)Sn). The crystal and Molecular structures Of four complexes were determined by X-ray diffraction on single crystals: [Bu(2)Sn(aliz)(H(2)O)]center dot C(2)H(5)OH (A1 center dot EtO H), [Bu(2)Sn(aliz)(dmso)](2) (A3), [(Bu(2)Sn)(3)O(Hpurp)(2)] (P1) and [Bu(2)Sn(Hpurp)(dmso)](2) (P2), where H(2)aliz = alizarin and H(3)purp = purpurin. The coordination mode of the ligands is identical to that found in their Al/Ca complexes, where they act as dianionic tridentate ligands forming five and six-membered fused chelate rings. The coordination to the tin atoms occurs exclusively via the 1,2- phenolate oxygen and the adjacent quinoid oxygen atoms. The complexes A1, A3 and P1 are dimers with hepta-coordinated tin atoms in form of a slightly distorted pentagonal bipyramid. The trinuclear complex P2 contains two pentacoordinated and one heptacoordinated tin atoms.

ELECTROCHEMICAL REDUCTION PROCESS OF BILIRUBIN IN DIMETHYLFORMAMIDE

The electrochemical reduction behavior of bilirubin (BR) at platinum electrode in DMF was investigated by cyclic voltammetry, in situ electron spin resonance spectroscopy and in situ rapid scanning thin layer spectroelectrochemistry. Experimental results revealed that the reduction of BR firstly undergoes an ECE process: GRAPHICS The generated (BR)(2)(3-). can be re-oxidized to BR and then to purpurin (Pu) by a series of oxidation processes: GRAPHICS However, the re-reduction reactions of Pu are not the reverse processes. The different reduction mechanisms are discussed in detail.

STUDY ON THE REDOX PROCESS OF BILIRUBIN AND BILIVERDIN AT PLATINUM-ELECTRODE BY IN-SITU SPECTROELECTROCHEMISTRY

The electrochemical redox behavior of bilirubin (BR IValpha), biliverdin (BV IValpha) and their oxidized product bile-purpurin (Bi-Pu) have been studied by in situ spectroelectrochemical techniques, which reveals that the transformation of BR IValpha [GRA

INVESTIGATION ON MECHANISMS FOR THE ELECTROOXIDATION OF SOME BILE-PIGMENTS BY SPECTROELECTROCHEMISTRY

The electrooxidation behavior of bilirubin (BR), biliverdin (BV), purpurin (Pu), and choletelin (Ch in dimethylformamide (DMF) have been investigated bv voltammetry, in situ electron spin resonance (ESR) thin-layer spectroelectrochemistry and especially i

A novel sedimentary chlorin: structural evidence for a chlorophyll origin for aetioporphyrins

A novel sedimentary transformation product of chlorophyll, purpurin-7 phytyl ester, has been identified by atmo- spheric pressure chemical ionisation liquid chromatography mass-spectrometry in sediments from Lake Baikal, Russia, Loch Ness and Priest Pot, UK. This product of oxidative transformation is an intermediate on the transformation pathway leading to sedimentary aetioporphyrins and its occurrence lends strong support to the view that aetiopor- phyrins derive mainly from precursor chlorophylls.

Geochemistry of tetrapyrrole, tetraterpenoid, and perylene pigments in sediments from the Gulf of California

Results and discussion cover pigment analyses of 36 sediment samples recovered by Deep Sea Drilling Project Leg 64, and six samples from the Leg 64 site-survey cruise in the Guaymas Basin (Scripps Institution of Oceanography, Leg 3). Pigments investigated were tetrapyrroles, tetraterpenoids, and the PAH compound perylene. Traces of mixed nickel and copper ETIO-porphyrins were ubiquitous in all sediment samples, except for the very surface (i.e., <2 m sub-bottom), and their presence is taken as an indication of minor influxes of previously oxidized allochthonous (terrestrial) organic matter. Phorbides and chlorins isolated from Site 479 sediment samples (i.e., the oxygen-minimum locale, northeast of the Guaymas Basin) well represent the reductive diagenesis ("Treibs Scheme"; see Baker and Palmer, 1978; Treibs, 1936) of chlorophyll derivatives. Three forms of pheophytin-a, plus a variety of phorbides, were found to give rise to freebase porphyrins, nickel phylloerythrin, and nickel porphyrins, with increasing depth of burial (increasing temperature). Sediments from Sites 481, 10G, and 18G yielded chlorophyll derivatives characteristic of early oxidative alterations. Included among these pigments are allomerized pheophytin-a, purpurin-18, and chlorin-p6. The high thermal gradient imposed upon the late Quaternary sediments of Site 477 greatly accelerated chlorophyll diagenesis in the adjacent overlying sediments, that is, the production of large quantities of free-base desoxophylloerythroetioporphyrin (DPEP) occurred in a section (477-7-5) presently only 49.8 meters sub-bottom. Present depth and age of these sediments are such that only chlorins and phorbides would be expected. Carotenoid (i.e., tetraterpenoids) concentrations were found to decrease rapidly with increasing sub-bottom depth. Less deeply buried sediments (e.g., 0-30 m) yielded mixtures of carotenes and oxygen-substituted carotenoids. Oxygencontaining (oxy-, oxo-, epoxy-) carotenoids were found to be lost preferentially with increased depth of burial. Early carotenoid diagenesis is suggested as involving interacting reductions and dehydrations whereby dehydro-, didehydro-, and retro-carotenes are generated. Destruction of carotenoids as pigments may involve oxidative cleavage of the isoprenoid chain through epoxy intermediates, akin to changes in the senescent cells of plants. Perylene was found to be a common component of the extractable organic matter from all sediments investigated. The generation of alkyl perylenes was found to parallel increases in the existing thermal regime at all sites. Igneous sills and sill complexes within the sediment profile of Site 481 altered (i.e., scrambled) the otherwise straightforward thermally induced alkylation of perylene. The degree of perylene alkylation is proposed as an indicator of geothermal stress for non-contemporaneous marine sediments.