A comparative study of the interactions of cationic hetarenes with quadruplex-DNA forming oligonucleotide sequences of the insulin-linked polymorphic region (ILPR)

• Darinka Dzubiel,
• Heiko Ihmels,
• Mohamed M. A. Mahmoud and
• Laura Thomas

Beilstein J. Org. Chem. 2014, 10, 2963–2974, doi:10.3762/bjoc.10.314

• fluorimetric monitoring of the temperature-dependent Förster resonance energy transfer (FRET) between the dyes [29]. In sodium cacodylate buffer (10 mM Na+, 10 mM K+, 90 mM Li+) the melting curve of the DNA has a weak transition at 50 °C and a more pronounced one at Tm = 71.0 °C (Figure 4). The results of the

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• bromide was introduced as a part of a heterogenic two-chromophore system, to take advantage of very efficient FRET energy transfer process (77%) from fluorescein to the RNA-intercalated phenanthridinium fluorophore (Figure 8, left) [83]. The resulting fluorescent dye exhibited improved ds-RNA-marker

Synthesis and properties of novel star-shaped oligofluorene conjugated systems with BODIPY cores

• Clara Orofino-Pena,
• Diego Cortizo-Lacalle,
• Joseph Cameron,
• Muhammad T. Sajjad,
• Pavlos P. Manousiadis,
• Neil J. Findlay,
• Alexander L. Kanibolotsky,
• Dimali Amarasinghe,
• Peter J. Skabara,
• Tell Tuttle,
• Graham A. Turnbull and
• Ifor D. W. Samuel

Beilstein J. Org. Chem. 2014, 10, 2704–2714, doi:10.3762/bjoc.10.285

• lasing applications. Previously, we have designed star-shaped systems featuring energy transfer by incorporating acceptor chromophore units either within the arms [23], or in the core [24], of parent blue-emissive star-shaped oligofluorene systems. This strategy provides the ability to tune emission and

• T-Bn compounds and 660 nm for the Y-Bn series. The emission originates from the BODIPY core which is an indication of an efficient energy transfer observed in these conjugated systems from the fluorene components to the core. A Stokes shift of around 50 nm was observed in both series, corresponding

• to 1230 cm−1 for Y-Bn and 1560 cm−1 for T-Bn. If one considers the efficient energy transfer from the oligofluorene arms to the BODIPY core, the separation between absorption and emission overall becomes much higher and the materials can therefore be used as efficient down-converters from UV to the

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

• biomolecular interactions [1][2][3]. Traditionally, the biological macromolecules are labeled with two or more dyes which can interact in a conformation/distant-dependent manner via Förster resonance energy transfer (FRET) [4][5][6]. Alternatively, the FRET pairs can be replaced by an environmentally sensitive

• ] or a backbone-tethered label [18][19]. However, in most cases the formation of DNA duplexes does not yield significant fluorescence changes in the Nile red, unless it is used in combination with another dye such as pyrene to form an energy transfer pair [20][21]. A related phenoxazine dye – Nile blue

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

• ) conversion extent of the DAE moiety. A nearly 100% Förster-type resonance energy transfer (FRET) from all three DCM moieties to a single DAE (in its CF) moiety was achieved. Upon visible irradiation, the initial fluorescence intensity was recovered. The observed photoswiching is reversible, with excellent

• photo resistance. Keywords: click chemistry; energy transfer; fluorophore; monosaccharide; photochromism; Introduction The development of functional nanomaterials is nowadays a very attractive field of fundamental and applied research. The chemical functions at the molecular level yield properties

• compound fit well together, the fluorescence can be switched ON and OFF: quenching of the fluorescence through a Förster-type resonance energy transfer (FRET) process from the former to the latter would occur, when the photochromic moiety is in the colored form (state B, Figure 1). At the opposite, in the

Automated solid-phase peptide synthesis to obtain therapeutic peptides

• Veronika Mäde,
• Sylvia Els-Heindl and
• Annette G. Beck-Sickinger

Beilstein J. Org. Chem. 2014, 10, 1197–1212, doi:10.3762/bjoc.10.118

• chain of Dpr (α,β-diaminopropionic acid). These fluorescently labeled conjugates allowed FRET (fluorescence resonance energy transfer) measurements to investigate conformational features of the peptides [132]. With respect to the great potential of NPY ligands as pharmaceuticals for various indications

Studies on the photodegradation of red, green and blue phosphorescent OLED emitters

• Susanna Schmidbauer,
• Andreas Hohenleutner and
• Burkhard König

Beilstein J. Org. Chem. 2013, 9, 2088–2096, doi:10.3762/bjoc.9.245

• atmospheric conditions than under inert atmosphere and show a further increase when performed in benzene-d6. Iridium complexes have been proposed to not only undergo energy transfer to dioxygen but also being capable of electron transfer leading to the formation of superoxide anions. Especially for the blue

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

• stabilities, and tunability of the excited-state energies [9]. Additionally, they can be employed as energy donor or acceptor units in electronic energy transfer processes [10]. In particular, ruthenium(II) polypyridine complexes have been extensively studied and represent an area of widespread interest that

• past years, a large number of luminescent dendrimers based on polynuclear transition-metal complexes have been developed as promising materials for the study of unidirectional energy transfer and multielectron-transfer processes as well as for light-harvesting applications [19]. Among the polypyridine

• nm, which corresponds to the π–π* transition of the ligand. Interestingly, the results show effective quenching of the ligand-based emission and bands centered at the characteristic emission maxima of complexes 1 and 2, indicating efficient photoinduced energy transfer from the oligothiophene to the

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

• rings can rotate with a low activation barrier, and isomerization of the trans form can occur in two different directions, forming two different isomers (enantiomers in the parent system) [4]. Power transmission to neighbouring molecules is inefficient because of energy transfer to internal

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

• (azo-15) may be useful as a molecular switch, because the photoisomerization of azo-fullerene 14 leads to only 8% of the cis-isomer. Although, the quantum yield obtained for cis-14 is not very high, this proportion is significant, given the speed with which energy transfer to the fullerene unit occurs

Sexithiophenes as efficient luminescence quenchers of quantum dots

• Christopher R. Mason,
• Yang Li,
• Paul O’Brien,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2011, 7, 1722–1731, doi:10.3762/bjoc.7.202

• not be a result of Förster energy transfer. The effect of each of the corresponding sexithiophenes with or without a Lewis base group (1 or 2) was then studied by preparing separate stock solutions of quantum dots and sexithiophenes 1b or 2b, of known concentration. A fixed amount of quantum dot

• general trend observed was a decrease in the photoluminescence intensity with increasing sexithiophene concentration, irrespective of the presence (1b) or absence (2b) of a Lewis base (the anomaly at low concentrations of sexithiophenes is explained below). Since energy transfer can be excluded, it may be

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

• an indicator for “over-irradiation”. Mechanistic scenario For ketone-sensitized photodecarboxylations involving phthalimides, energy transfer and electron transfer processes have both been proposed [44][52]. A similar, simplified scenario is depicted in Scheme 8. Due to the comparable triplet

• energies of DMBP (T1 = 69.4 kcal/mol or 290 kJ/mol [53]) and phthalimides (2: T1 = 71 kcal/mol or 297 kJ/mol [39]), energy transfer (Scheme 8, path A) is not very efficient but has been confirmed spectroscopically for a related N-phthalimidocarboxylate/benzophenone pair [52]. Subsequent electron transfer

Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates

• Wang-Yong Yang,
• Samantha A. Marrone,
• Nalisha Minors,
• Diego A. R. Zorio and
• Igor V. Alabugin

Beilstein J. Org. Chem. 2011, 7, 813–823, doi:10.3762/bjoc.7.93

• (Figure 8c). Only glycerol at pH 6 and glycerol and DMSO at pH 8 showed ~10% of protection. Little effect was observed for NaN3, suggesting that the formation of singlet oxygen via triplet energy transfer is inefficient, possibly because of a short triplet lifetime and fast intramolecular photocyclization

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

• temperature and in ethanol at low temperatures are known: Triplet acetone, acetophenone and xanthone in acetonitrile are quenched by 1 via energy transfer; the rate constant is almost diffusion-controlled and somewhat smaller for benzophenone. The sole product from the photolysis of 1 is the double hydrogen

Supramolecular FRET photocyclodimerization of anthracenecarboxylate with naphthalene-capped γ-cyclodextrin

• Qian Wang,
• Cheng Yang,
• Gaku Fukuhara,
• Tadashi Mori,
• Yu Liu and
• Yoshihisa Inoue

Beilstein J. Org. Chem. 2011, 7, 290–297, doi:10.3762/bjoc.7.38

• .7.38 Abstract γ-Cyclodextrin (CD) derivatives with a naphthalene moiety anchored to one or two of the glucose units of the CD were synthesized in order to investigate the effects of flexible and rigid capping upon complexation, as well as Förster resonance energy transfer (FRET) and photochirogenic

• Förster resonance energy transfer (FRET) sensitization. Results and Discussion Naphthalene-capped γ-CD 6 was synthesized by the reaction of 6A,6C-ditosyl-γ-CD [23] with disodium 2,6-naphthalenedicarboxylate in DMSO. An attempt to synthesize the regioisomeric 6A,6D-(2,6-naphthalenedicarboxyl)-γ-CD by

• wavelength (296 nm) and the internal filter effect of AC at 350–400 nm is negligible (absorbance <0.1). Considering the nice spectral overlap of the naphthalene fluorescence with the AC absorption (Figure 4), we conclude that Förster resonance energy transfer (FRET) is operating from naphthalene-appended 7

Photocycloaddition of aromatic and aliphatic aldehydes to isoxazoles: Cycloaddition reactivity and stability studies

• Axel G. Griesbeck,
• Marco Franke,
• Jörg Neudörfl and
• Hidehiro Kotaka

Beilstein J. Org. Chem. 2011, 7, 127–134, doi:10.3762/bjoc.7.18

• ]. Surprisingly, in the absence of aldehydes as the potential reaction partners, the conversions of 7f–h were significantly lower, suggesting the possibility of an energy transfer from the excited singlet or triplet aldehyde to the isoxazole. Since the photolysis of 7d and 7e in presence of benzaldehyde showed

Photocycloadditions and photorearrangements

• Axel G. Griesbeck

Beilstein J. Org. Chem. 2011, 7, 111–112, doi:10.3762/bjoc.7.15

• excited state is generated either by direct light absorption or by energy transfer sensitization. This excited state has to be sufficiently well characterized in order to understand its chemical and physical behaviour. Organic molecules can react either as triplet or singlet excited states, often showing

Gelation or molecular recognition; is the bis-(α,β-dihydroxy ester)s motif an omnigelator?

• Peter C. Griffiths,
• David W. Knight,
• Ian R. Morgan,
• Amy Ford,
• James Brown,
• Ben Davies,
• Richard K. Heenan,
• Stephen M. King,
• Robert M. Dalgliesh,
• John Tomkinson,
• Stuart Prescott,
• Ralf Schweins and
• Alison Paul

Beilstein J. Org. Chem. 2010, 6, 1079–1088, doi:10.3762/bjoc.6.123

• collected for about 8 h and transformed into the conventional scattering law, S(Q,ω) (arbitrary units), vs. energy transfer, Et (cm-1), using standard programs. Schröder–van Laar analysis for the melting of toluene (open symbols) and ethanol/water (filled symbols) gels formed from G6 (circles) and G8

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

• absorption of visible light by the DPP chromophore, and a rapid one arising from additional absorption of UV-light by the phenylene comonomer unit followed by energy transfer to the DPP chromophore. The actual mechanism of photodecomposition remains unclear. Comparative studies indicated that conjugated DPP

A perfluorocyclopentene based diarylethene bearing two terpyridine moieties – synthesis, photochemical properties and influence of transition metal ions

• Falk Wehmeier and
• Jochen Mattay

Beilstein J. Org. Chem. 2010, 6, No. 53, doi:10.3762/bjoc.6.53

• processes between the ruthenium nuclei. On the other hand the closed isomer 10aC might act as an acceptor; a similar effect has been observed with a spiropyran moiety bridging two terpyridine units, whose (closed) merocyanine form inhibits the energy transfer between metal centres and thus acts as a T

N-acylation of ethanolamine using lipase: a chemoselective catalyst

• Mazaahir Kidwai,
• Roona Poddar and
• Poonam Mothsra

Beilstein J. Org. Chem. 2009, 5, No. 10, doi:10.3762/bjoc.5.10

• less reaction time, taking only 4–5 min on solid support and 40–50 min in solution phase while low yields were obtained conventionally even after 4–5 h (Figure 1). In the microwave, the heating is homogenous whereas conventional energy transfer through contact, is comparatively slow and not so