Complexation and Self-Assembling of Sulfonatomethylated Calix[4]resorcinarene with Both Organic and Lanthanide Ions in Aqueous Media

The stoichiometry and binding constant of the paramagnetic lanthanide ion(Gd³⁺) with sulfonatomethylated calix[4]resorcinarene (H₈Xna₄) were evaluated from the NMR relaxation data. Both ¹H NMR spectroscopy and NMR relaxation data indicate that interaction of tetramethylammonium (TEMA) and N-methylpyridinium (MePy) cations with H₈Xna₄ in the presence of Ln³⁺ (Lu³⁺ or Gd³⁺) results in theformation of ternary complexes [Ln(G)H₈X] with lanthanide ions,coordinated via sulfonate groups and organic cation included intothe cavity of H₈Xna₄. The inclusion of long-chainedN-decyl-(DePy) and N-cetylpyridinium (CPy) ions into H₈Xna₄ cavity leads to self-assembling which can be revealed by NMR relaxation method with Gd³⁺ probe ions. The excess of alkylpyridinium or TEMA cations leads to disassembling of (Gd)_n(H₈X)_m(RPy)_maggregates.     

Discriminating bacteria from other atmospheric particles using femtosecond molecular dynamics

We investigated femtosecond pump–repump depletion schemes in biological fluorophors (tryptophan and riboflavin) in order to discriminate bioaerosols from organic interferents emitted by combustion (traffic related urban aerosols). Although fluorescence depletion is significative for riboflavin (Rbf, Vitamin B2), the most striking results have been obtained for the amino acid tryptophan (Trp). By using a 270 nm-pump 810 nm-repump femtosecond excitation, we showed that Trp exhibits fluorescence depletion up to 50%, contrary to naphthalene (<2%), despite almost identical absorption/emission spectra. We demonstrate that this process in Trp is so robust that it still occurs in living bacteria (Bacillus subtilis, Escherechia coli and Enterococcus fæcalis) but is absent for pure diesel fuel. This remarkable difference between biological and organic aerosols can be exploited to discriminate among them.     

Photochemische Reaktionen 94. Mitteilung. Vinyloge β-Spaltung bei Epoxy-enonen der Jonon-Reihe

Photoinduced Vinylogous β-Cleavage of Epoxy-enones of the Ionone Series The photochemistry of the α,β-unsaturated γ,δ-epoxy-enones 1–3 is determined by: (i) C(γ)-O-scission of the epoxide (vinylogous β-cleavage of Type A); (ii) C(γ)-C(δ)-cleavage of the oxirane (vinylogous β-cleavage of Type B); (iii) (E/Z)-isomerization of the enone chromophore. In contrast, 4 with tertiary C(β) shows no Type B cleavage. Type A cleavage is induced both by n,π*- and π,π*-excitation and arises probably from the T₁-state, but Type B cleavage is observed only on π,π*-excitation and represents presumably a S₂-reaction. On Type A cleavage 1–4 undergo 1,2-alkyl-shifts to 1,5-dicarbonyl compounds ( 15–18, 25–28, 34 and 35 ) or rearrange to dihydrofuranes ( 7 and 30 ). The isomerization 1→7 proceeds by a stereoselective [1,3]-sigmatropic shift. On Type B cleavage 1–3 isomerize to a bicyclic enol-ether ( 8, 29 ) or to a monocyclic enol-ether ( 9 ; product of a homosigmatropic [1,5]-shift) or undergo fragmentation to isomers such as allenes 10, 22 and 31 or cyclopropenes 11 and 21 . The non-isolated, unstable (Z)-epoxy-enones 14, 19, 24 and 38 isomerize by fragmentation to the furanes 12, 23, 33 and 39 respectively, on contact with traces of acid or by heating. However, for 19 and 4 , Type B cleavage may lead to the furanes 23 and 39 . On UV. irradiation of the epoxy-enone 4 the initially formed (E/Z)-isomers 34 and 35 yield on π,π*-excitation the enones 37 and 40 by a vinylogous β-fragmentation. In addition, on n,π*-excitation 34 isomerizes to 35 , which decarbonylates exclusively to the enone 37 . The reactions of 1–4 with BF₃ · O(C₂H₅)₂ were also studied (see appendix). The epoxy-enones 1 and 2 isomerize by an 1,2-alkyl shift in good yield to the 1,4-dicarbonyl compounds 79 and 81 , whereas 3 gives the 1,4-diketone 83 , and in small amounts the 1,5-diketone 84 . On the other hand, 4 is converted to the fluorohydroxy-enone 85 and to the 1,5-dicarbonyl product 34 , the only isomer in this series which is identical with one of the photoproducts.     

Electrochemical dimerization of 2-(2'-thienyl)pyridine adsorbed on Au(111) observed by in situ fluorescence

The study of heterodentate molecules adsorbed on metal electrodes provides an opportunity to expand the functionality of modified surfaces while offering insights into the surface and intramolecular electronic interactions of organic adsorbates. The adsorption of 2-(2'-thienyl)pyridine, a molecule containing both pyridine and thiophene moieties, on a Au(111) electrode is reported. Adsorption was characterized by electrochemistry in neutral and basic aqueous electrolyte and was compared to that of pyridine. The aqueous electrochemistry of thiophene on Au(111) was also characterized for comparison purposes. At negative potentials, in the presence of 2-(2'-thienyl)pyridine, a diffuse, pi-bonded monolayer was formed, and a phase transition to a close-packed N- and/or S-bonded configuration was observed near -0.4 V in a 1 mM solution of adsorbate, similar to that seen in pyridine on Au(111). The thiophene-like oxidative dimerization of the molecule was confirmed at positive potentials using in situ fluorescence microscopy by comparison with the spectrum of the chemically synthesized dimer.     

Conformation of Some Anomeric O-Benzylated D-gluco-, L-Ido-, and Hex-4-enopyranoside derivatives

By use of ¹H-NMR. spectroscopy it is shown that in the anomeric tri-O-benzyl derivatives of D -gluco- and L -idopyranosides the C(5) (aliphatic) substituent has a strong tendency to assume an equatorial position. The conformer (⁴C₁ or ¹C₄) with C(6) in equatorial position is favoured, even if other bulky substituents are forced to occupy an axial position; the same effect is observed in some anomeric O-benzylated 6-deoxy-L -idopyranoside derivatives. If, however, the tetragonal configuration of the saturated C(5) is changed into a trigonal (sp²) configuration, e.g. in the anomers of 1,2,3-tri-O-benzylated L -threo-hex-4-enopyranosiduronates, the C(5)–C(6) bond no longer determines the equilibrium of (distorted) pyranoid conformations; the anomeric (‘Eduard-Lemieux’) effect then becomes important in the stabilization of the corresponding half-chair (¹H₂ or ²H₁) conformations.     

Photochemische Reaktionen. 97 Mitteilung [1]. Zur Photochemie konjugierter Epoxy-diene II. Versuche mit (E)-β-Jonyliden-epoxiden

Photolysis of Conjugated Epoxy-dienes Direct and sensitized excitation of the (E)-β-ionylidene-epoxides 1 and 4 leads to different types of isomerizations. Thus photocycloelimination to the cyclopropene-ketones 2 and 6 is only achieved by ¹(π, π*)-excitation (λ=254 nm), whereas ³(π, π*)-excitation (λ > 280 nm, acetone) gives selective C(1′), O-cleavage of the oxirane ( 1 → 7 – 10 and 4 → 11 – 13 ). In contrast to 1 the twofold methylsubstituted epoxy-diene 4 shows mainly (E/Z)-isomerization ( 4 → 5 ) on both ¹(π, π*)- and ³(π, π*)-excitation while the isomerizations 4 → 6 and 4 → 11 – 13 are minor processes, only.     

Photochemische Reaktionen. 85. Mitteilung [1]. Zur Photochemie von α, β-Epoxy-eucarvon

Photochemistry of α,β-epoxy-eucarvone . On π,π^*-excitation (λ = 254 nm) 4 isomerizes to the bicyclic ketoaldehyde 5 ; on n,π^*-excitation (λ ? 280 nm) 4 gives 5 , the β,γ-unsaturated ketone 6 , the enone 7 and the cyclobutanone 8 . Scission of the (C—C)-bond of the oxirane 4 would give the dihydrofurane e , which could isomerize to the ketoaldehyde 5 . On the other hand, 4 is assumed to isomerize to the β,γ-unsaturated aldehyde c , which could yield 6 and 7 by photodecarbonylation. The cyclo-butanone 8 is shown to be a photoisomer of the ketone 6 . Furthermore, eucarvol ( 18 ) rearranges by a thermal [1,5]-H-shift to dihydro-eucarvone ( 20 ); on UV.-irradiation 18 gives the bicyclic isomers 27 and 28 .     

Structural and electronic properties of phosphino(oligothiophene) gold(I) complexes

A series of gold(I) complexes containing phosphino(oligothiophene) ligands of varying conjugation length has been prepared. Solid state crystal structures of (PT3)AuCl (PT3 = 5-diphenylphosphino-2,2':5',2' '-terthiophene) and AuCl(PTP)AuCl (PTP = 2,5-diphenylphosphinothiophene) have been obtained. The complex AuCl(PTP)AuCl crystallizes as a dimer with two intermolecular Au-Au contacts. Variable temperature NMR spectroscopy is used to demonstrate the presence of aurophilic interactions in solution for AuI(PTP)AuI. Dual emission is observed for AuCl(PTP)AuCl in solution and is attributed to emission from both monomer and dimer. In the solid state, dimer emission is dominant. The iodo analogue, AuI(PTP)AuI, shows only low energy dimer emission in both solution and the solid state. Compounds in which the ligands contain longer bridges (either bithienyl or terthienyl) show absorption and emission bands due to the pi-pi* transition only, both in solution and the solid state.     

Topical 5-aminolevulinic acid-photodynamic therapy of hairless mouse skin using two-fold illumination schemes: PpIX fluorescence kinetics, photobleaching and biological effect

Light fractionation with dark periods of the order of hours has been shown to considerably increase the efficacy of 5-aminolevulinic acid-photodynamic therapy (ALA-PDT). Recent investigations have suggested that this increase may be due to the resynthesis of protoporphyrin IX (PpIX) during the dark period following the first illumination that is then utilized in the second light fraction. We have investigated the kinetics of PpIX fluorescence and PDT-induced damage during PDT in the normal skin of the SKH1 HR hairless mouse. A single illumination (514 nm), with light fluences of 5, 10 and 50 J cm-2 was performed 4 h after the application of 20% ALA, to determine the effect of PDT on the synthesis of PpIX. Results show that the kinetics of PpIX fluorescence after illumination are dependent on the fluence delivered; the resynthesis of PpIX is progressively inhibited following fluences above 10 J cm-2. In order to determine the influence of the PpIX fluorescence intensity at the time of the second illumination on the visual skin damage, 5 + 95 and 50 + 50 J cm-2 (when significantly less PpIX fluorescence is present before the second illumination), were delivered with a dark interval of 2 h between light fractions. Each scheme was compared to illumination with 100 J cm-2 in a single fraction delivered 4 or 6 h after the application of ALA. As we have shown previously greater skin damage results when an equal light fluence is delivered in two fractions. However, significantly more damage results when 5 J cm-2 is delivered in the first light fraction. Also, delivering 5 J cm-2 at 5 mW cm-2 + 95 J cm-2 at 50 mW cm-2 results in a reduction in visual skin damage from that obtained with 5 + 95 J cm-2 at 50 mW cm-2. A similar reduction in damage is observed if 5 + 45 J cm-2 are delivered at 50 mW cm-2. PpIX photoproducts are formed during illumination and subsequently photobleached. PpIX photoproducts do not dissipate in the 2 h dark interval between illuminations.