Biradical vs singlet oxygen photogeneration in suprofen–cholesterol systems

• Fabrizio Palumbo,
• Francisco Bosca,
• Isabel M. Morera,
• Inmaculada Andreu and
• Miguel A. Miranda

Beilstein J. Org. Chem. 2016, 12, 1196–1202, doi:10.3762/bjoc.12.115

• singlet oxygen was assessed by time-resolved near infrared emission studies in dichloromethane using perinaphthenone as standard. The quantum yields (ΦΔ) were 0.52 for 1 and 2 and 0.56 for 3. In conclusion, SP-α-Ch dyads are unique in the sense that they can be used to photogenerate both biradicals and

Synthesis and fluorosolvatochromism of 3-arylnaphtho[1,2-b]quinolizinium derivatives

• Phil M. Pithan,
• David Decker,
• Manlio Sutero Sardo,
• Giampietro Viola and
• Heiko Ihmels

Beilstein J. Org. Chem. 2016, 12, 854–862, doi:10.3762/bjoc.12.84

• solvent. For the derivatives 6a–d the quantum yields were the highest in MeOH and the lowest in CHCl3. The phenanthrenyl-substituted derivative 6e exhibits the highest fluorescence quantum yields in 2-PrOH and 1-BuOH (ΦF = 0.34) and the lowest in CHCl3 (ΦF = 0.071). Discussion In most of the tested

• quinolizinium derivatives 6a–e. Supporting Information The Supporting Information contains the experimental section (synthesis, determination of fluorescence quantum yields); absorption and emission spectra of 6b; 1H NMR spectra of compounds 6a–e; plots of emission energies of 6e versus selected solvent

Indenopyrans – synthesis and photoluminescence properties

• Andreea Petronela Diac,
• Ana-Maria Ţepeş,
• Albert Soran,
• Ion Grosu,
• Anamaria Terec,
• Jean Roncali and
• Elena Bogdan

Beilstein J. Org. Chem. 2016, 12, 825–834, doi:10.3762/bjoc.12.81

• blue emitters and the trans isomers exhibited significantly higher fluorescence quantum yields (relative to 9,10-diphenylanthracene) as compared to the corresponding cis isomers. The solid-state fluorescence spectra revealed an important red shift of λmax due to intermolecular interactions in the

• groups have been found to exhibit good solvatochromism properties and high quantum yields in the solid state why they are considered as important precursors for the fabrication of fluorescent materials [20]. Owing to their exciting photophysical properties many dicyanomethylene pyran-containing

• process that occurs when an electron is transferred from a singlet energy level into a triplet energy level [36]. The derivatives 2a–d are blue emitters, displaying maximum-emission bands at around 370–393 nm. Remarkably, the fluorescence quantum yields calculated relative to 9,10-diphenylanthracene are

Friedel–Crafts-type reaction of pyrene with diethyl 1-(isothiocyanato)alkylphosphonates. Efficient synthesis of highly fluorescent diethyl 1-(pyrene-1-carboxamido)alkylphosphonates and 1-(pyrene-1-carboxamido)methylphosphonic acid

• Anna Wrona-Piotrowicz,
• Janusz Zakrzewski,
• Anna Gajda,
• Tadeusz Gajda,
• Anna Makal,
• Arnaud Brosseau and
• Rémi Métivier

Beilstein J. Org. Chem. 2015, 11, 2451–2458, doi:10.3762/bjoc.11.266

• photophysical properties of 3a–d and 4 and, for comparison, those of N-alkylamide 5 (Figure 1). The steady-state spectroscopic data for 3a–d, 4 and 5, along with fluorescence quantum yields in chloroform solutions, are presented in Table 1 (although it was recently reported that pyrene undergoes

• practically did not influence the electronic absorption and emission spectra. Structured emission bands were observed showing only a small effect of solvent polarity (Figure 1). However, the fluorescence quantum yields of 3a–d and 4 were significantly higher than that of 5. In order to explain this phenomenon

• into the corresponding fluorescent amidoalkylphosphonates. It is worthy to note that this class of compounds offers numerous possibilities of chemical transformations [35][36]. The pyrenyl amidoalkylphosphonates emit fluorescence with quantum yields ca. 2 times higher than simple N-substituted pyrene-1

2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

• Yury A. Sayapin,
• Inna O. Tupaeva,
• Alexandra A. Kolodina,
• Eugeny A. Gusakov,
• Vitaly N. Komissarov,
• Igor V. Dorogan,
• Nadezhda I. Makarova,
• Anatoly V. Metelitsa,
• Valery V. Tkachev,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2015, 11, 2179–2188, doi:10.3762/bjoc.11.236

• –f, which indicates that irradiation of solutions of 11a–f in heptane at 293 K initiates the ESIPT O−H···N → O···H−N responsible for the ASS-fluorescence. It should be noted that the quantum yields of the ASS-fluorescence of compounds 11a,c,e (R1 = H) (0.15–0.18) and 11b,d,f (R1 = Cl) (0.19–0.22) are

Effective ascorbate-free and photolatent click reactions in water using a photoreducible copper(II)-ethylenediamine precatalyst

• Redouane Beniazza,
• Natalia Bayo,
• Florian Molton,
• Carole Duboc,
• Stéphane Massip,
• Nathan McClenaghan,
• Dominique Lastécouères and
• Jean-Marc Vincent

Beilstein J. Org. Chem. 2015, 11, 1950–1959, doi:10.3762/bjoc.11.211

• efficient photoinduced electron transfer process leading to a fast Cu(II) to Cu(I) reduction, the final electron source being the solvent. The photoreduction process was extremely efficient, photoreduction quantum yields (Фred) ranging from 0.17 up to around 1 being measured in good H-atom donating solvents

Design, synthesis and photochemical properties of the first examples of iminosugar clusters based on fluorescent cores

• Mathieu L. Lepage,
• Antoine Mirloup,
• Manon Ripoll,
• Fabien Stauffert,
• Anne Bodlenner,
• Raymond Ziessel and
• Philippe Compain

Beilstein J. Org. Chem. 2015, 11, 659–667, doi:10.3762/bjoc.11.74

• . Difluoroboradiaza-s-indacenes, commonly named boron-dipyrromethene dyes (F-BODIPY), were logically selected for the construction of the probes. These compounds indeed combine high fluorescence quantum yields and high molar extinction coefficients, strong chemical and photochemical stability in solution and in solid

• properties of those multivalent dyes in aqueous media (glycine buffer at pH 10.7), are interesting, providing high quantum yields, 24% for 13a and 43% for 15a, and well-defined spectroscopic features. Altogether, these results augur well for a new class of molecular tools dedicated to rationalize the mode of

A facile synthesis of functionalized 7,8-diaza[5]helicenes through an oxidative ring-closure of 1,1’-binaphthalene-2,2’-diamines (BINAMs)

• Youhei Takeda,
• Masato Okazaki,
• Yoshiaki Maruoka and
• Satoshi Minakata

Beilstein J. Org. Chem. 2015, 11, 9–15, doi:10.3762/bjoc.11.2

• –430 nm), while π–π* transitions (300–340 nm) were red-shifted. On the other hand, diluted dichloromethane solutions (10−5 M) of diazahelicenes 2 did not show photoluminescence (Φf < 0.02, for the detailed values of quantum yields, see the Supporting Information File 1). Due to the presence of the

A small azide-modified thiazole-based reporter molecule for fluorescence and mass spectrometric detection

• Stefanie Wolfram,
• Hendryk Würfel,
• Stefanie H. Habenicht,
• Christine Lembke,
• Phillipp Richter,
• Eckhard Birckner,
• Rainer Beckert and
• Georg Pohnert

Beilstein J. Org. Chem. 2014, 10, 2470–2479, doi:10.3762/bjoc.10.258

• transilluminator whereas BPT (1) offers a very good absorbance at 365 nm, a standard UV excitation wavelength. We then recorded fluorescence spectra of all fluorophores and determined fluorescence quantum yields Φ (Table 1). To characterize BPT (1) in a non-interacting solvent we used cyclohexane resulting in an

• was emitted by NBD/DDY/catalase, which is probably due to very low fluorescence quantum yields reported for NBD derivatives of primary amines in water [39]. Furthermore, NBD (9) is not suitable for standard SDS-PAGE (12% gels) as the dye smears and therefore potentially covers fluorescent signals of

• with a GENESYS™ 10 S spectrophotometer (Thermo Fischer Scientific Inc., Waltham, MA, USA) with 10 mm quartz cells. Quantum yields were obtained as described in [43] using quinine sulfate in 0.05 M sulfuric acid as fluorescent standard with a Varian Cary 500 spectrophotometer (Varian Inc., Palo Alto, CA

Synthesis and optical properties of pyrrolidinyl peptide nucleic acid carrying a clicked Nile red label

• Nattawut Yotapan,
• Chayan Charoenpakdee,
• Pawinee Wathanathavorn,
• Boonsong Ditmangklo,
• Hans-Achim Wagenknecht and
• Tirayut Vilaivan

Beilstein J. Org. Chem. 2014, 10, 2166–2174, doi:10.3762/bjoc.10.224

• the fluorescence quantum yields (50% MeCN: λabs 564 nm, λem 641 nm, ΦF 0.29; 20% MeCN: λabs 587 nm, λem 651 nm; ΦF 0.14). In aqueous phosphate buffer (10 mM, pH 7.0), the Nile red-labeled acpcPNA 10mer-Nr exhibited a broad absorption peak centered at 575 nm and a fluorescence emission at 656 nm

• maxima (647 nm) compared to the single-stranded PNA (656 nm) as well as a small fluorescence increase (1.36 fold at 643 nm) (Figure 3a,b). The blue-shifted fluorescence maxima and increased quantum yields of Nile red suggest that the Nile red chromophore in complementary PNA–DNA duplexes was placed in a

• , 11merCC-Nr, 11merGG-Nr, 11merTT-Nr) were synthesized. These four Nile red-labeled acpcPNA sequence exhibited differences only at the bases flanking the Nile red label, For single-stranded PNA, the order of fluorescence quantum yields was AA > TT ~ CC > GG. This suggests a more efficient quenching of the

Photorelease of phosphates: Mild methods for protecting phosphate derivatives

• Sanjeewa N. Senadheera,
• Abraham L. Yousef and
• Richard S. Givens

Beilstein J. Org. Chem. 2014, 10, 2038–2054, doi:10.3762/bjoc.10.212

• bioactivity. The desirable properties of any new PPG candidate are 1) absorption at wavelengths near or above 400 nm, 2) enhanced chemical and photochemical quantum yields and 3) improved rate of release, ideally in the range of ps to ns time constants; all three are useful properties for applications in

• ) and comparison with an independently synthesized sample obtained from Friedel–Crafts alkylation of 1-methoxynaphthalene (11) with methyl bromoacetate and ferric oxide [27]. Quantum yields for disappearance and percentage conversions for 14a are higher than that of 14b as indicated in Table 1. After

• aq MeOH (Φdis = 0.028, Table 1 and Table 2) but the product mixture was more complex (vide infra). Interestingly, quantum yields for the disappearance for 14a are enhanced three-fold (Φdis = 0.067) when the photolysis solution was purged free of oxygen (Table 2). The quantum yield of 14a for the

Synthesis of new, highly luminescent bis(2,2’-bithiophen-5-yl) substituted 1,3,4-oxadiazole, 1,3,4-thiadiazole and 1,2,4-triazole

• Anastasia S. Kostyuchenko,
• Vyacheslav L.Yurpalov,
• Aleksandra Kurowska,
• Wojciech Domagala,
• Adam Pron and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2014, 10, 1596–1602, doi:10.3762/bjoc.10.165

• synthesis, efficient ring closure reaction affording a 4H-1,2,4-triazole unit is presented. All target ambipolar compounds display strong photoluminescence with measured quantum yields up to 0.59. Modification of the demonstrated synthetic routes may be exploited for the preparation of longer, specifically

• photoluminescence quantum yields are indicated together with the formulae of the corresponding compounds. In the case of 18 (4-phenyl-4H-1,2,4-triazole ring) the photoluminescence quantum yield is almost three times higher than that measured for 15 (1,3,4-thiadiazole ring). The obtained results clearly demonstrate

• dichloromethane. Optimum fluorescence excitation wavelengths (given in the legends) have been selected based on fluorescence emission profiles. Photoluminescence quantum yields measured for 13, 15 and 18 together with their formulae. Synthesis of ethyl 3-decyl-2,2'-bithiophene-5-carboxylate (3). Synthesis of

Pyrene-modified PNAs: Stacking interactions and selective excimer emission in PNA₂DNA triplexes

• Alex Manicardi,
• Lucia Guidi,
• Alice Ghidini and
• Roberto Corradini

Beilstein J. Org. Chem. 2014, 10, 1495–1503, doi:10.3762/bjoc.10.154

• fluorescence properties of these PNA in the absence and in the presence of DNA. The evaluation of the pyrene quantum yields showed that these probes are much less fluorescent than the 1-pyreneacetic acid precursor in water (23 times lower quantum yield for PNA2, see Supporting Information File 1, Figure S16

Multichromophoric sugar for fluorescence photoswitching

• Stéphane Maisonneuve,
• Rémi Métivier,
• Pei Yu,
• Keitaro Nakatani and
• Juan Xie

Beilstein J. Org. Chem. 2014, 10, 1471–1481, doi:10.3762/bjoc.10.151

• fluorescence quantum yields were determined by using quinine sulfate dihydrate in sulfuric acid (0.5 N) as a standard at λexc = 325 nm (ΦF = 0.546) and coumarin 540A in ethanol as a standard at λexc = 450 nm (ΦF = 0.544). Photochromic reactions were induced in situ by a continuous irradiation Hg–Xe lamp

Synthesis, characterization and DNA interaction studies of new triptycene derivatives

• Sourav Chakraborty,
• Snehasish Mondal,
• Rina Kumari,
• Sourav Bhowmick,
• Prolay Das and
• Neeladri Das

Beilstein J. Org. Chem. 2014, 10, 1290–1298, doi:10.3762/bjoc.10.130

• quantum yields (Φ) of pure 1 and 2 were found to be 0.016 and 0.022 respectively (aqueous solution of L-tryptophan was used as the reference, Φ = 0.15). Conclusion In conclusion, synthesis and structural characterization of trisubstituted ethynyl and azide triptycenes have been reported. The facile

The Ugi four-component reaction as a concise modular synthetic tool for photo-induced electron transfer donor-anthraquinone dyads

• Sarah Bay,
• Gamall Makhloufi,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 1006–1016, doi:10.3762/bjoc.10.100

• recorded (Figure 8). For the donor–anthraquinone dyads 8 the emission is significantly quenched in comparison to the corresponding donor-only model systems 2 and 10 at the same concentrations according to relative fluorescence quantum yields Φf,rel (Table 3) and only residual weak emission traces from the

• donor and/or the anthraquinone excitations can be detected (for spectra of the residual emissions of the dyads 8 see Supporting Information File 1). Since the relative fluorescence quantum yields Φf,rel are attenuated by 95–99% in comparison to the donors’ fluorescence an efficient and rapid

• quantum yields Φf,rel of Do-anthraquinone dyads 8 in comparison to their donor-only reference systems 2 and 10. Calculation of the Gibbs free energies for the simple electron transfer ΔGET,simpl, for the solvation, and the electron transfer according to the Weller approximation of the dyads 8

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• discussed on the basis of pH, solvent polarity, lamp type, absorption properties, and quantum yields. Determination of the latter proved to be an especially valuable tool for the distinction between radical chain and photocatalytic reactions. Keywords: mechanism; organocatalysis; photocatalysis; photoredox

• catalysis; quantum yields; visible light; Introduction The ability of natural systems to harness solar energy for the genesis of matter has been fascinating mankind since time immemorial and has stimulated numerous reproduction attempts in the context of chemical synthesis over the last two centuries. The

• radiation events of several recent literature protocols by recording the quantum yields Φ [15][16][17][19][20][21]. Furthermore, we have learned along the way that the reactions appear to be strongly dependent on the pH of the solution and the type of lamp used for irradiation. Here, we present a detailed

Tailoring of organic dyes with oxidoreductive compounds to obtain photocyclic radical generator systems exhibiting photocatalytic behavior

• Christian Ley,
• Julien Christmann,
• Ahmad Ibrahim,
• Luciano H. Di Stefano and
• Xavier Allonas

Beilstein J. Org. Chem. 2014, 10, 936–947, doi:10.3762/bjoc.10.92

• handle. ΔGBET is given by . This reaction is generally quite exergonic and the rate compete with the dissociation rate kdiss of the contact ion pair into free solvated species. In practice BET reduce the overall radical generation quantum yields. Some new approaches allow to trigger this reaction [57][58

• -initiator of lowest concentration, in the present case the acceptor TA. All this phenomena explain the synergistic effect observed in some free radical polymerization. Radical and photolysis quantum yields As for the Type II systems, in order to quantify the catalytic behavior of the dye, the quantum yield

• RB/TA/EDB are given in Table 3. In Type II PIS both quantum yields are equal because the amount of radicals formed is equal to the amount of dye photolysed: as a consequence, only about two photons are needed to bleach one dye molecule, corresponding to a very low turnover number. Moreover we can see

Columnar/herringbone dual crystal packing of pyrenylsumanene and its photophysical properties

• Binod Babu Shrestha,
• Shuhei Higashibayashi and
• Hidehiro Sakurai

Beilstein J. Org. Chem. 2014, 10, 841–847, doi:10.3762/bjoc.10.80

• distance of 3.0 Å (Figure 1f). The π–π stacking of pyrene moieties, however, is not evident in the arrangement. The UV–vis absorption and emission spectra and maxima as well as the quantum yields of 1, 3 and pyrene in CH2Cl2 or in the solid state are summarized in Figure 3 and Table 1. The absorption

• in the crystal is also assigned to the excimer state. The quantum yields of pyrene in solution and in the solid state are almost equal (0.64 and 0.68). In contrast, the quantum yield of 1 in the solid state (0.10) is decreased significantly from that in solution (0.82). This exciton quenching may be

Rapid pseudo five-component synthesis of intensively blue luminescent 2,5-di(hetero)arylfurans via a Sonogashira–Glaser cyclization sequence

• Fabian Klukas,
• Alexander Grunwald,
• Franziska Menschel and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 672–679, doi:10.3762/bjoc.10.60

• interesting due to their bright blue luminescence with remarkably high quantum yields. The electronic structure of the title compounds is additionally studied with DFT computations. Keywords: C–C coupling; copper; DFT; fluorescence; furans; mircowave-assisted synthesis; multicomponent reactions; palladium

• recorded in dichloromethane and the fluorescence quantum yields Φf were determined with coumarin 1 or p-terphenyl as references (Table 2). The most furans display intense, broad absorption bands between 321 and 358 nm with molar extinction coefficients between 21000 to 35000 L/mol cm−1. In addition

• redshifted shoulders appear between 336 and 377 nm. Likewise the emission maxima are found between 367 and 439 nm and blueshifted shoulders appear between 351 and 424 nm. The Stokes shifts determined from the absorption and emission maxima range from 3500 to 6400 cm−1 and the quantum yields are quite large

Topochemical control of the photodimerization of aromatic compounds by γ-cyclodextrin thioethers in aqueous solution

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2013, 9, 1858–1866, doi:10.3762/bjoc.9.217

• aromatic guests under controlled, homogenous reaction conditions. The quantum yields for unsubstituted anthracene, acenaphthylene, and coumarin complexed in these γ-CD thioethers were found to be up to 10 times higher than in the non-complexed state. The configuration of the photoproduct reflected the

• only improves the quantum yields of photodimerizations but also gives rise to high regio- and stereo-selectivities [15][16][17][18] However, the application of native CDs for fully hydrophobic reactants is hampered by the fact that their inclusion compounds are nearly insoluble in water leading to

• paid to both the quantum yields Φ and stereoselectivities of the photodimerizations. Results and Discussion Photodimerization of anthracene Due to the fact that the inclusion compounds of ANT in native β-CD or γ-CD are completely insoluble in water, only the aqueous photochemistry of hydrophilic ANT

Synthesis and spectroscopic properties of 4-amino-1,8-naphthalimide derivatives involving the carboxylic group: a new molecular probe for ZnO nanoparticles with unusual fluorescence features

• Laura Bekere,
• David Gachet,
• Vladimir Lokshin,
• Wladimir Marine and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2013, 9, 1311–1318, doi:10.3762/bjoc.9.147

• dyes for natural and synthetic fibers [1], optical brighteners in detergents, textiles, polymeric materials [1][2][3] and chemiluminiscent agents [4]. Owing to the high fluorescence quantum yields 1,8-naphthalimides are used as laser dyes [5][6]. Some naphthalimide derivatives have also been reported

Substituent effect on the energy barrier for σ-bond formation from π-single-bonded species, singlet 2,2-dialkoxycyclopentane-1,3-diyls

• Jianhuai Ye,
• Yoshihisa Fujiwara and
• Manabu Abe

Beilstein J. Org. Chem. 2013, 9, 925–933, doi:10.3762/bjoc.9.106

• crystallographic analysis as well as by NOE measurements. The steady-state photolyses of AZc–g in benzene solution were performed with a Xenon lamp (500 W) through a Pyrex filter (hν > 300 nm). The ring-closed compounds CPc–g were quantitatively obtained in the denitrogenation reaction (Scheme 2). The quantum

• yields of the denitrogenation of AZc–g were determined to be ≈0.90 by comparison with those reported for similar azoalkanes [33]. The quantitative formation of CPc–g and the high quantum yield of the denitrogenation process suggest the clean generation of DRc–g in the photoirradiation reaction of AZc–g

New core-pyrene π structure organophotocatalysts usable as highly efficient photoinitiators

• Sofia Telitel,
• Frédéric Dumur,
• Thomas Faury,
• Bernadette Graff,
• Mohamad-Ali Tehfe,
• Didier Gigmes,
• Jean-Pierre Fouassier and
• Jacques Lalevée

Beilstein J. Org. Chem. 2013, 9, 877–890, doi:10.3762/bjoc.9.101

• of these Co_Py/Iod (or TH) combinations will be affected by different parameters: (i) their relative light absorption properties, (ii) the quantum yields of radical or radical cation formation in the singlet state (the singlet state is predominant, see above), (iii) the rate constants for reactions

Synthesis, photophysical and electrochemical characterization of terpyridine-functionalized dendritic oligothiophenes and their Ru(II) complexes

• Amaresh Mishra,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2013, 9, 866–876, doi:10.3762/bjoc.9.100

• at 465 and 541 nm, respectively. As shown in Figure 1b the band maximum undergoes a marked bathochromic shift with increasing size and also compared to the parent dendrons 6 and 7, which further ascribed to the extended conjugation. The fluorescence quantum yields (Φf) of the ligands were found to be

• 0.15 and 0.24, respectively. Excitation of complexes 1 and 2 at their respective 1MLCT band in deaerated acetonitrile resulted in weak emissions at 693 nm and 755 nm and extended to the near-infrared region. For complexes on the basis of their structureless emission and low fluorescence quantum yields

• recorded on a Perkin Elmer Lambda 19 spectrometer and fluorescence emission spectra on a Perkin Elmer LS 55 spectrometer. Emission quantum yields of ligands and complexes were measured using 9,10-diphenylanthracene (Φf = 0.9 in cyclohexane) [54] and [Ru(bpy)3][PF6]2 (Φf = 0.062 in acetonitrile) [55] by