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

Expeditious, mechanochemical synthesis of BODIPY dyes

• Laramie P. Jameson and
• Sergei V. Dzyuba

Beilstein J. Org. Chem. 2013, 9, 786–790, doi:10.3762/bjoc.9.89

• have received a lot of attention in recent years due to their favorable chemical and physical characteristics, including high quantum yields and tunable fluorescent properties as well as high thermal and chemical stabilities [1][2][3]. As such, BODIPY and their derivatives have found widespread utility

A new synthetic protocol for coumarin amino acid

• Xinyi Xu,
• Xiaosong Hu and
• Jiangyun Wang

Beilstein J. Org. Chem. 2013, 9, 254–259, doi:10.3762/bjoc.9.30

• similar extinction coefficients and quantum yields as compound 1a, according to the literature [20][21]. However, their pKa values are significantly different from those of 1a, as shown in Table 3. The pKa values are calculated from the absorbance at 360 nm at different pH values illustrated in Figure 3

Amino-substituted diazocines as pincer-type photochromic switches

• Hanno Sell,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2013, 9, 1–7, doi:10.3762/bjoc.9.1

• ]diazocine (1), has been known for more than a hundred years [5]. However, only recently we discovered that the photophysical properties of 1 (quantum yields, photostationary states) are superior to those of parent azobenzene, and most of its derivatives [6][7][8]. In contrast to azobenzene, diazocine 1 is

Hydrophobic analogues of rhodamine B and rhodamine 101: potent fluorescent probes of mitochondria in living C. elegans

• Laurie F. Mottram,
• Safiyyah Forbes,
• Brian D. Ackley and
• Blake R. Peterson

Beilstein J. Org. Chem. 2012, 8, 2156–2165, doi:10.3762/bjoc.8.243

• ) are renowned for their red-shifted fluorescence, photostability, and high quantum yields over a wide range of pH values (i.e., pH 4–10). These fluorophores penetrate cells more readily than analogous fluorescein derivatives, because the negative plasma membrane potential within the cytoplasm of cells

• restricted rotation about C–N bonds conferred by the fused rings of 10. By using the method of Williams [42], the quantum yields of 9 and 10 were determined relative to rhodamine B (5) and rhodamine 6G (7, Figure 3, panels A and B), and the extinction coefficients of these compounds were quantified (Figure 3

• absorbance and emission wavelengths are indicated with arrows. Linear regression used to determine spectroscopic parameters of HRB 9 and HR101 10 in MeOH. Panels A and B: Determination of quantum yields relative to rhodamine B (5) [44] and rhodamine 6G (7) [45]. Panel C: Quantification of molar extinction

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• and S2←S0 excitations and cis–trans isomerization by exciting into the S1 or S2 state [21]. The sum of the quantum yields is different to unity, which indicates multiple pathways for isomerization. In stilbene, the isomerization occurs exclusively by rotation and the quantum yield equals unity [22

• structural forms should be easily detectable. An efficient interrupt process. High quantum yields have to be achieved by using short irradiation periods. The response times have to be quick to be also fast interrupting cycles. It is necessary that all properties remain unchanged when the compound used as the

Synthesis of new pyrrole–pyridine-based ligands using an in situ Suzuki coupling method

• Matthias Böttger,
• Björn Wiegmann,
• Steffen Schaumburg,
• Peter G. Jones,
• Wolfgang Kowalsky and
• Hans-Hermann Johannes

Beilstein J. Org. Chem. 2012, 8, 1037–1047, doi:10.3762/bjoc.8.116

• their triple positive charge, this coordination sphere must be saturated to achieve high quantum yields when the target is to optimize its luminescent properties [6]. In the “classic” complexes, i.e., the β-diketonates [6][7], this is often achieved by combining three “saturating ligands” that consist

The effect of the formyl group position upon asymmetric isomeric diarylethenes bearing a naphthalene moiety

• Renjie Wang,
• Shouzhi Pu,
• Gang Liu and
• Shiqiang Cui

Beilstein J. Org. Chem. 2012, 8, 1018–1026, doi:10.3762/bjoc.8.114

• fluorescence quantum yield. The cyclization quantum yields of these compounds increased in the order of para < ortho < meta, whereas their cycloreversion quantum yields decreased in the order of meta > para > ortho. Additionally, all of these diarylethenes functioned as effective fluorescent switches in both

• coefficients, and quantum yields of cyclization and cycloreversion. For the isomeric diarylethenes 1–3, the absorption maxima of both the open-ring and closed-ring isomers exhibited a remarkable hypochromatic shift when the formyl group was moved from the para to the meta, then to the ortho position in both

• different from those with an electron-donating methoxy group [14][50][51]. The cycloreversion quantum yields of diarylethenes 1–3 increased in the order of ortho (Φc-o = 0.11) < para (Φc-o = 0.12) < meta substitution (Φc-o = 0.15) by the formyl group. However, the cyclization quantum yield of the para

Thiophene-based donor–acceptor co-oligomers by copper-catalyzed 1,3-dipolar cycloaddition

• Stefanie Potratz,
• Amaresh Mishra and
• Peter Bäuerle

Beilstein J. Org. Chem. 2012, 8, 683–692, doi:10.3762/bjoc.8.76

• showed structured bands due to vibronic splitting. The red-shift of the emission maximum of 14 in comparison to 12 and 13 confirmed the facts assumed from UV–vis spectra that there should be weak electronic communication in the oligomers going through the 1,2,3-triazole ring. Fluorescence quantum yields

• micrOTOF-Q 43 with electron spray ionization (ESI) and atmospheric-pressure chemical ionization (APCI). UV–vis spectra were taken on a Perkin-Elmer Lambda 19 in 1 cm cuvettes. Fluorescence spectra were measured with a Perkin-Elmer LS 55 in 1 cm cuvettes. Fluorescence quantum yields were determined with

Enaminones in a multicomponent synthesis of 4-aryldihydropyridines for potential applications in photoinduced intramolecular electron-transfer systems

• Nouria A. Al-Awadi,
• Maher R. Ibrahim,
• Mohamed H. Elnagdi,
• Elizabeth John and
• Yehia A. Ibrahim

Beilstein J. Org. Chem. 2012, 8, 441–447, doi:10.3762/bjoc.8.50

• ) upon excitation in the 400 nm ranges. Relative fluorescence quantum yields (Table 2) were measured at 25 °C, taking quinine bisulfate (in 0.1 M H2SO4, 22 °C) as standard (Φf = 0.58 at λex = 350 nm, Φf = 0.55 at λex = 365 nm). This synthesis of dihydropyridines was extended to enamino aldehyde 9

• coefficient. The emission spectra were measured at the same concentration after excitation at the specified λ shown in Figure 2, by using a Horiba-Jobin Vyon Fluromax-4 instrument. Relative fluorescence quantum yields were measured at 25 °C taking quinine bisulfate (in 0.1 M H2SO4, 22 °C) as standard (Φf

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• be very efficient pH-triggered NLO switches. The fluorescent and photophysical properties of chromophores 88–93 were further studied [110][111]. The fluorescence was studied in various solvents and polymer matrices and at various temperatures. Intense fluorescence with quantum yields of 0.05 to 0.98

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• were identified with a two- and three-fold Stokes shift as compared to their DPO (diphenyloxazole) and POPOP (phenyloxazolephenyloxazolephenyl) references, and with high quantum yields (Scheme 11) [53]. Daugulis used the bulky butyldi-1-adamantylphosphine associated with the potassium phosphate base to

Microphotochemistry: 4,4'-Dimethoxybenzophenone mediated photodecarboxylation reactions involving phthalimides

• Oksana Shvydkiv,
• Kieran Nolan and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2011, 7, 1055–1063, doi:10.3762/bjoc.7.121

• phthalimides and its analogues has been intensively studied over the last decades [28][29][30][31][32]. Among the various transformations developed, photodecarboxylation reactions have emerged as efficient and powerful alkylation procedures with high quantum yields of up to 60% [33][34]. Selected

Photoinduced electron-transfer chemistry of the bielectrophoric N-phthaloyl derivatives of the amino acids tyrosine, histidine and tryptophan

• Axel G. Griesbeck,
• Jörg Neudörfl and
• Alan de Kiff

Beilstein J. Org. Chem. 2011, 7, 518–524, doi:10.3762/bjoc.7.60

• photoinduced electron-transfer (PET) reactions. N-Alkylated phthalimides typically absorb in the 295 nm region with extinction coefficients around 103. The quantum yields for intersystem crossing ФISC significantly change with the substitution on the imide nitrogen, e.g., ФISC = 0.5 for N-isobutylphthalimide

Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 278–289, doi:10.3762/bjoc.7.37

• substituents within the complex. Specifically, the deactivation of the excited-state by conformational relaxation is suppressed upon complex formation leading to increased quantum yields of the photoreaction. Nevertheless, in the case of the thioureido-substituted derivative 1i additional effects need to be

Photoinduced homolytic C–H activation in N-(4-homoadamantyl)phthalimide

• Nikola Cindro,
• Margareta Horvat,
• Kata Mlinarić-Majerski,
• Axel G. Griesbeck and
• Nikola Basarić

Beilstein J. Org. Chem. 2011, 7, 270–277, doi:10.3762/bjoc.7.36

• protic solvent, undergoes H-abstraction to give products with ten times higher quantum yields than in an aprotic solvent. Such a finding is in accordance with previous reports for phthalimides and is probably due to a switching of the relative order of the singlet and the triplet excited states of the

A new fluorescent chemosensor for fluoride anion based on a pyrrole–isoxazole derivative

• Zhipei Yang,
• Kai Zhang,
• Fangbin Gong,
• Shayu Li,
• Jun Chen,
• Jin Shi Ma,
• Lyubov N. Sobenina,
• Albina I. Mikhaleva,
• Guoqiang Yang and
• Boris A. Trofimov

Beilstein J. Org. Chem. 2011, 7, 46–52, doi:10.3762/bjoc.7.8

• recorded on a Hitachi F-4500 fluorescence spectrophotometer. Fluorescence quantum yields (ФF) were determined by the comparative method using 1,4-bis(5-phenyl-2-oxazolyl)benzene (ФF = 0.97) as reference standard [12]. 1H NMR spectra were recorded on a Bruker dmx 400 MHz NMR spectrometer at room temperature

Donor-acceptor substituted phenylethynyltriphenylenes – excited state intramolecular charge transfer, solvatochromic absorption and fluorescence emission

• Ritesh Nandy and
• Sethuraman Sankararaman

Beilstein J. Org. Chem. 2010, 6, 992–1001, doi:10.3762/bjoc.6.112

• 1e, the quantum yield of fluorescence was measured in ethanol. The fluorescence quantum yields for these derivatives in ethanol were low, presumably due to facile electron transfer and hydrogen bonding interaction with the solvent which enhances the non-radiative processes. In polar solvents electron

Conjugated polymers containing diketopyrrolopyrrole units in the main chain

• Bernd Tieke,
• A. Raman Rabindranath,
• Kai Zhang and
• Yu Zhu

Beilstein J. Org. Chem. 2010, 6, 830–845, doi:10.3762/bjoc.6.92

• soluble polymers P-2 to P-8 exhibiting yellow to red absorption and emission colours, and fluorescence quantum yields of up to 86% were obtained. Characteristic properties are compiled in Table 1. Compared with the DPP monomers, the absorption of most of the polymers was bathochromically shifted by 24 to

• P-11 exhibited a maximum absorption at 560 nm, and a solution-cast film of the same polymer had a λmax-value of 581 nm. The band gaps were between 1.5 and 1.7 eV, i.e., considerably smaller than for the previously reported DPP-based polymers. The fluorescence quantum yields Φ of the copolymers were

• copolymerized with primary or secondary arylamines to yield DPP-containing polyiminoarylenes. The solutions of the polymers in chloroform exhibited a purple red colour with absorption maxima between 530 and 550 nm, and emission maxima from 610 to 630 nm. Fluorescence quantum yields were moderate (20 to 60

Synthetic incorporation of Nile Blue into DNA using 2′-deoxyriboside substitutes: Representative comparison of (R)- and (S)-aminopropanediol as an acyclic linker

• Daniel Lachmann,
• Sina Berndl,
• Otto S. Wolfbeis and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2010, 6, No. 13, doi:10.3762/bjoc.6.13

• protocol, worked up and purified according to literature [17]. The two Nile Blue-modified oligonucleotides DNA1 and DNA2 were identified by ESI mass spectrometry, quantified by UV–vis absorption and characterized by fluorescence spectroscopy (including quantum yields) and measurement of melting

• contrast to the absorption properties that were pretty similar for all Nile Blue-modified duplexes, fluorescence spectra show the influence of the sequential neighborhood. The quantum yields of the Nile Blue-modified single strands are reduced from 33% for the isolated dye in ethanol to 15% in the single

• the chromophore has been attached via the R-configured linker (this study) or the S-configured one [17]. The comparison of quantum yields (Table 1) reflects only very minor differences that are within the experimental error. It was quite surprising to observe that in contrast to experiments with D

Functional properties of metallomesogens modulated by molecular and supramolecular exotic arrangements

• Alessandra Crispini,
• Mauro Ghedini and
• Daniela Pucci

Beilstein J. Org. Chem. 2009, 5, No. 54, doi:10.3762/bjoc.5.54

• in solution), in the red region of the Vis spectrum (λ = 610 nm), with emission quantum yields in the range of 6–23%, depending on the solvent. However, the 3,4,5-trialkoxy-substituted benzoato fragment of the curcumin ligand imposes an overall hemi-disc structure to the resulting palladium

Reversible intramolecular photocycloaddition of a bis(9-anthrylbutadienyl)paracyclophane – an inverse photochromic system. (Photoactive cyclophanes 5)

• Henning Hopf,
• Christian Beck,
• Jean-Pierre Desvergne,
• Henri Bouas-Laurent,
• Peter G. Jones and
• Ludger Ernst

Beilstein J. Org. Chem. 2009, 5, No. 20, doi:10.3762/bjoc.5.20

• concentration, no intermolecular reaction could compete with an intramolecular process [12]. Disappearance quantum yields at 394 nm were found to be low in methylcyclohexane (1.5 × 10−4) and in acetonitrile (4.2 × 10−2). The weakness of the cyclophotoaddition probably reflects a preference for internal

• balance (sensitivity 10−7 g). Quantum yields Reaction quantum yields were determined as described elsewhere [29], using the Parker iron trioxalate actinometer. The monochromatic beams were obtained from a cooled 1000 W Xenon lamp, using a Bausch and Lomb monochromator. The samples were previously purged

Synthesis of coumarin or ferrocene labeled nucleosides via Staudinger ligation

• Ivana Kosiova,
• Andrea Janicova and
• Pavol Kois

Beilstein J. Org. Chem. 2006, 2, No. 23, doi:10.1186/1860-5397-2-23

• ), which were synthesised in our department as part of studies into new ligands. Coumarins as fluorescent probes or labels [28][29][30] have extensive and diverse applications, they exhibit extended spectral range, are photostable and have high emission quantum yields. Ferrocene derivatives are often used