Zum Phosphoreszenz- und Fluoreszenzverhalten von N-Aryl-carbazolen

Am N -(9-phenanthryl)-carbazol (II) und dem Maleinsäureanhydrid-Addukt III des Anthraceno- 2′.3′:2.3-carbazols wird intramolekulare Triplettenergieübertragung beobachtet (Donator: Carbazol- Kern: Akzeptor: Phenanthren- bzw. Naphthalin-Kern). - N-(α-Naphthyl)-carbazol (I) und II zeigen ein für diese Stoffklasse in bezug auf Lösungsmittel- und Temperaturabhängigkeit ungewöhnliches Fluoreszenzverhalten.

On the Fluorescence Quenching of Polycyclic Aromatic Hydrocarbons by Nitromethane

Fluorescence quenching of 22 polycyclic aromatic hydrocarbons by nitromethane in toluene and acetonitrile solutions has been studied. Contrary to Sawicki’s observations that the fluorescence of hydrocarbons with the fluoranthene skeleton is not quenched that of 11.12-and 3.4-benzofluor-anthene and fluoranthene itself is quenched. These compounds have a high energy of the fluorescence transition. The fluorescence quenching of the compounds investigated follows a dynamic quenching mechanism. The bimolecular rate constant of fluorescence quenching increases exponentially with the energy of the fluorescing state of alternant hydrocarbons.

The Intra-annular Internal Heavy-atom Effect on the Fluorescence and Phosphorescence Properties of Oxygen, Sulphur or Selenium Containing Heterocyclic Systems Related to Dibenzo [b,n] perylene

Fluorescence and phosphorescence properties of dibenzo [2,3:10,11] perylo [1,12-bcd] furan (1), dibenzo [2,3:10,11] perylo [1,12-bcd] thiophene (2), and dibenzo [2,3:10,11 ] perylo [1,12-bcd] selenophene (3) have been studied. Fluorescence quantum yields as well as phosphorescence lifetimes correlate linearly with where ck are the Hückel AO coefficients in the HOMO of the parent carbocyclic system dibenzo [b, n] perylene (4) on carbon centres k to which the hetero-atom is bound, and ζ is the spin-orbit coupling constant of the heavy-atom present. The half-value concentration of fluorescence quenching (quencher: methyl iodide) of 1 - 3 increases with increasing strength of the internal heavy-atom effect present

Topological Effect on MO Energies, II

The recently introduced approach of S, T isomers [1] has been applied to aza-benzenes and aza-perylenes. Ab initio and HMO calculations as well as experimental results clearly show that the S.T approach is a suitable means to derive definite predictions concerning the MO patterns and HOMO energies of structurally related aza-arenes.

Heiße Banden im Phosphoreszenzspektrum von Coronen

Two temperature-dependent bands on the short wavelengths side of the phosphorescence spectrum of coronene in a perhydro-coronene matrix are identified as hot bands (from higher vibrational levels of the triplet state T1) by measurement of lifetimes and activation energies.

Photoluminescence of [22]Paracyclophane and p-Xylene in the Presence of Silver Ions

Phosphorescence spectra and phosphorescence lifetimes of [22]paracyclophane (I) and p-xylene have been measured in ethanol glass at 77 K in the presence of silver Perchlorate at various concentrations. From the results it is concluded that the ground state complex formed with AgClO4 is much more stable in the case of the cyclophane than with p-xylene. The results would indicate that under the conditions used [22]paracyclophane forms a 1:1 complex with AgClO4 with the silver ion being located within the cyclophane cage. Fluorescence quenching measurements in fluid solution at room temperature using ethyl bromide and AgClO4 as quenchers support this assumption.

Photochemisches Verhalten und spektroskopische Eigenschaften von Anilino-naphthalinen

From the fluorescence and phosphorescence spectra of several aromatic amines it is concluded that the conjugation between nitrogen and aryl groups in the excited state is restricted. With this result a sterical explanation for the lack of the expected photochemical carbazole ring closure of 1-and 2-anilino naphthalene is given.

Einfluß von Chlorsubstitution auf die El ektronenspektren von Biphenyl

Absorption spectra in liquid solution, fluorescence and phosphorescence spectra, phosphores-cence quantum yields, phosphorescence to fluorescence quantum yield ratios, and phosphorescence decay times of 9 chloro substituted biphenyls dissolved in low temperature EPA glass were in-vestigated. The emission spectra of sterically unhindered systems are structured and significantly Stokes-shifted. Ortho substitution shifts the conjugation band in absorption as well as the un-structured fluorescence and phosphorescence bands to shorter wave lengths presumably by pre-venting the system from attaining a planar excited state. Chloro substitution which increases the rate constant of phosphorescence in the order meta < para < ortho, is nearly additive for multiple substituted systems and is correlated to the MO coefficients at the chloro substituted position in the absence of steric hindrance

Fluoreszenzlöschung alternierender und nicht-alternierender polycyclischer aromatischer Kohlenwasserstoffe durch Nitroverbindungen / Fluorescence Quenching of Alternant and Non-alternant Polycyclic Hydrocarbons by Nitro Compounds

Fluorescence Quenching of Alternant and Non-alternant Polycyclic Hydrocarbons by Nitro Compounds Fluorescence quenching of polycyclic aromatic hydro­ carbons by nitromethane or nitrobenzene in fluid solutions is due to an electron transfer mechanism. The non diffusion controlled rate constant of quenching is very much greater for alternant than for non-alternant hydrocarbons with equal singlet excitation energy. This is explained by the known more positive reduction potential of non-alternant compared to alternant hydrocarbons.

Über die Löschung von „Twisted Intramolecular Charge Transfer" (TICT)-Fluoreszenzen durch äußere Schweratom-Störer

The quenching by methyl iodide and ethyl bromide of the TICT fluorescence of N-(p-cyanophenyl)- carbazole (II) and N-(l-naphthyl)-carbazole (III) has been studied in solvents of different polarity. It is found that the heavy atom induced bimolecular fluorescence quenching increases with increasing energy of the TICT fluorescence transition, contrary to the energy-gaprule, and that TICT states are much less readily quenched than locally excited (LE) states. These results are explained by assuming a very small S-T energy gap for TICT states and a solvent polarity dependent distribution function for the intramolecular twist angle.

Löschung der Perylen-Fluoreszenz durch Schweratom-induzierte intermolekulare Singlett Triplett-Energieübertragung

The fluorescence of perylene is quenched by bromonaphthalene but not by bromo-benzene. This is explained with the assumption of an intermolecular energy transfer from the fluorescing state S1 of perylene to the lowest triplet state T1 of the halogen-naphthalene.

Die Bedeutung von Donor-Acceptor-Wechselwirkungen im äußeren Schweratom-Effekt von AgNO3 auf das Lumineszenzverhalten von Aza-aromaten und Carbazolen / The Significance of Donor-Acceptor Interactions in the External Heavy Atom Effect of AgNO3 on the Luminescence Behaviour of Aza-aromatic Systems and Carbazoles

The transition probabilities of spin-forbidden processes become much more enhanced in the case of aza-aromatic systems than for structurally related aromatic hydrocarbons when AgNO3 is used as an external heavy atom perturber. This is explained with the strong electron donor properties of aza-aromatic systems thus causing strong interaction between the π-electronic system and the perturber. Since carbazoles are weaker electron donors than aza-aromatic systems, the enhancement of the phosphorescence/fluorescence quantum yield ratio by AgNO3 is lower than for aza-aromatic systems. The different behaviour of aza-aromatic systems and aromatic hydrocarbons in the heavy atom experiment with AgNO3 can find applications in fluorescence analysis.

Notizen: Some Remarks on the Concept of Molecular Topology

Some general aspects of the concept of molecular topology are delt with. The role of the separability of topological and non-topological factors that determine molecular properties, as well as the "holistic" behaviour of certain classes of compounds are discussed. A suggestion regarding a deeper understanding of the role of molecular topology is made

On the Phosphorescence of Benzologues of Furan , Thiophene , Selenophene , and Tellurophene . A Systematic Study of the Intra -annular Internal Heavy-atom Effect

Phosphorescence in ethanol and n-pentane at 77 K of the benzologues 1-8 of furan, thiophene, selenophene and tellurophene has been investigated. The rate constants of both the radiative (kPT) and non-radiative (kGT) deactivation of the lowest triplet state correlate linearly with where ck denotes the Hückel AO coefficients in the HOMO of the carbon atoms bound to the hetero-atom and ζ is the spin-orbit coupling constant of the hetero-atom present. - The linear correlation observed between kPT and kGT is an example for the Orlandi-Siebrand rule. - The influence of an external heavy-atom perturber (methyl iodide) on phosphorescence lifetimes and the vibrational structure of phosphorescence spectra is the more efficient the less efficient is the internal perturbation caused by the intra-annular heavy-atom.

Eine PMO-theoretische Untersuchung der benzogenen Diels-Alder-Reaktion polycyclischer aromatischer Kohlenwasserstoffe / APMO-theoretical Treatment of the Benzogenic Diels-Alder Reaction of Polycyclic Arom atic Hydrocarbons

Experimental reaction rates of the benzogenic Diels- Alder reaction of polycyclic aromatic hydrocarbons with maleic anhydride are correlated with the corresponding bislocalization energies calculated by the PMO method. The observed relations between the localization energies of the reacting centres and the topology of the hydrocarbons can be qualitatively understood on the basis of Clar’s π-sextet model of polycyclic systems and Polansky’s pars orbital method.

Note on the Influence of External Heavy-Atom Perturbers on the Phosphorescence Spectrum of Triphenylene

Spectral changes in symmetry-forbidden phosphorescence spectra observed in the presence of external heavyatom perturbers may have quite different causes depending on the chemical nature of the perturber. This is exemplified using triphenylene as the phosphorescent compound and methyl iodide and silver Perchlorate respectively as the perturber. Intensification of the 0-0 band of the symmetry-forbidden phosphorescence spectrum of triphenylene by silver Perchlorate is assumed to result from symmetry-reduction of the hydrocarbon by ground-state complex formation with silver Perchlorate.

Notizen: E-Typ-verzögerte Fluoreszenz von 1,1′-Dicoronyl in einer Kunststoffmatrix / E-type Delayed Fluorescence of 1,1′-dycoronyl in a Plastic Matrix

E-type delayed fluorescence of 1,1′-dicoronyl (III) has been established by measurement of luminescence lifetimes and activation energy.

On the Role of Microcrystal Formation in Intermolecular Triplet-Triplet Energy Transfer in Rigid Glasses

The intermolecular triplet-triplet energy transfer system benzophenone (donor)/naphthalene (acceptor) was studied in various rigid glasses at 77 K. It is shown that energy transfer is much more efficient if the donor is present in the form of microcrystals than in the case where both donor and acceptor compound are in true solution.

Long-term analysis of health status and preventive behavior in music students across an entire university program

OBJECTIVES

The aim of this investigation was to analyze longitudinal data concerning physical and psychological health, playing-related problems, and preventive behavior among music students across their complete 4- to 5-year study period.

METHODS

In a longitudinal, observational study, we followed students during their university training and measured their psychological and physical health status and preventive behavior using standardized questionnaires at four different times.

RESULTS

The data were in accordance with previous findings. They demonstrated three groups of health characteristics observed in beginners of music study: healthy students (cluster 1), students with preclinical symptoms (cluster 2), and students who are clinically symptomatic (cluster 3). In total, 64% of all students remained in the same cluster group during their whole university training. About 10% of the students showed considerable health problems and belonged to the third cluster group.

CONCLUSION

The three clusters of health characteristics found in this longitudinal study with music students necessitate that prevention programs for musicians must be adapted to the target audience.

Arabidopsis basic helix-loop-helix transcription factors MYC2, MYC3, and MYC4 regulate glucosinolate biosynthesis, insect performance, and feeding behavior

Arabidopsis thaliana plants fend off insect attack by constitutive and inducible production of toxic metabolites, such as glucosinolates (GSs). A triple mutant lacking MYC2, MYC3, and MYC4, three basic helix-loop-helix transcription factors that are known to additively control jasmonate-related defense responses, was shown to have a highly reduced expression of GS biosynthesis genes. The myc2 myc3 myc4 (myc234) triple mutant was almost completely devoid of GS and was extremely susceptible to the generalist herbivore Spodoptera littoralis. On the contrary, the specialist Pieris brassicae was unaffected by the presence of GS and preferred to feed on wild-type plants. In addition, lack of GS in myc234 drastically modified S. littoralis feeding behavior. Surprisingly, the expression of MYB factors known to regulate GS biosynthesis genes was not altered in myc234, suggesting that MYC2/MYC3/MYC4 are necessary for direct transcriptional activation of GS biosynthesis genes. To support this, chromatin immunoprecipitation analysis showed that MYC2 binds directly to the promoter of several GS biosynthesis genes in vivo. Furthermore, yeast two-hybrid and pull-down experiments indicated that MYC2/MYC3/MYC4 interact directly with GS-related MYBs. This specific MYC-MYB interaction plays a crucial role in the regulation of defense secondary metabolite production and underlines the importance of GS in shaping plant interactions with adapted and nonadapted herbivores.

Repression of the Arabidopsis thaliana jasmonic acid/ethylene-induced defense pathway by TGA-interacting glutaredoxins depends on their C-terminal ALWL motif

Glutaredoxins are small heat-stable oxidoreductases that transfer electrons from glutathione (GSH) to oxidized cysteine residues, thereby contributing to protein integrity and regulation. In Arabidopsis thaliana, floral glutaredoxins ROXY1 and ROXY2 and pathogen-induced ROXY19/GRX480 interact with bZIP transcription factors of the TGACG (TGA) motif-binding family. ROXY1, ROXY2, and TGA factors PERIANTHIA, TGA9, and TGA10 play essential roles in floral development. In contrast, ectopically expressed ROXY19/GRX480 negatively regulates expression of jasmonic acid (JA)/ethylene (ET)-induced defense genes through an unknown mechanism that requires clade II transcription factors TGA2, TGA5, and/or TGA6. Here, we report that at least 17 of the 21 land plant-specific glutaredoxins encoded in the Arabidopsis genome interact with TGA2 in a yeast-two-hybrid system. To investigate their capacity to interfere with the expression of JA/ET-induced genes, we developed a transient expression system. Activation of the ORA59 (OCTADECANOID-RESPONSIVE ARABIDOPSIS AP2/ERF-domain protein 59) promoter by transcription factor EIN3 (ETHYLENE INSENSITVE 3) was suppressed by co-expressed ROXY19/GRX480. Suppression depended on the L**LL motif in the C-terminus of ROXY19/GRX480. This putative protein interaction domain was recently described as being essential for the TGA/ROXY interaction. Ten of the 17 tested ROXY proteins suppressed ORA59 promoter activity, which correlated with the presence of the C-terminal ALWL motif, which is essential for ROXY1 function in flower development. ROXY19/GRX480-mediated repression depended on the GSH binding site, suggesting that redox modification of either TGA factors or as yet unknown target proteins is important for the suppression of ORA59 promoter activity.

Physical and mental health of different types of orchestra musicians compared to other professions

OBEJECTS: This study examined the physical and mental health of orchestra musicians of different types of orchestras compared to a reference sample of the general population and of two other professions.

METHODS

Professional musicians (n = 429) from nine opera and/or concert orchestras were surveyed with the Short Form-12 general health questionnaire (SF-12). Data were compared with a reference sample (n = 2805) with a sample of physicians (n = 549) and aircraft manufacturers (n = 822).

RESULTS

Compared to the reference sample and the two other professional groups, the musicians had a higher physical health score: 53.07 (SD 5.89) vs 49.03 (SD 9.35) reference, 51.26 (SD 7.53) physicians, and 49.31 (SD 7.99) aircraft manufacturers. The musicians' mental health score was lower compared to the reference sample but did not differ from the other professional groups: 48.33 (SD 9.52) for musicians vs 52.24 (SD 8.10) reference, 48.26 (SD 10.06) physicians, and 48.54 (SD 9.59) aircraft manufacturers. Physical health but not mental health decreased with age in all groups. In physical and mental health, women scored lower than men. There was no significant difference in physical and mental health scores between musicians of concert and opera orchestras. Age and gender accounted for 3.6% of the variance of the physical health score, but none of the demographic characteristics or orchestral roles and functions was predictive for mental health scores.

CONCLUSIONS

Musicians report better physical but poorer mental health than the general population, but they did not differ in mental health scores from physicians or aircraft manufacturers.

The glutaredoxin ATGRXS13 is required to facilitate Botrytis cinerea infection of Arabidopsis thaliana plants

Botrytis cinerea is a major pre- and post-harvest necrotrophic pathogen with a broad host range that causes substantial crop losses. The plant hormone jasmonic acid (JA) is involved in the basal resistance against this fungus. Despite basal resistance, virulent strains of B. cinerea can cause disease on Arabidopsis thaliana and virulent pathogens can interfere with the metabolism of the host in a way to facilitate infection of the plant. However, plant genes that are required by the pathogen for infection remain poorly described. To find such genes, we have compared the changes in gene expression induced in A. thaliana by JA with those induced after B. cinerea using genome-wide microarrays. We have identified genes that are repressed by JA but that are induced by B. cinerea. In this study, we describe one candidate gene, ATGRXS13, that encodes for a putative glutaredoxin and that exhibits such a crossed expression. In plants that are infected by this necrotrophic fungus, ATGRXS13 expression was negatively controlled by JA and TGA transcription factors but also through a JA-salicylic acid (SA) cross-talk mechanism as B. cinerea induced SA production that positively controlled ATGRXS13 expression. Furthermore, plants impaired in ATGRXS13 exhibited resistance to B. cinerea. Finally, we present a model whereby B. cinerea takes advantage of defence signalling pathways of the plant to help the colonization of its host.