Articulated rods – a novel class of molecular rods based on oligospiroketals (OSK)

• Pablo Wessig,
• Roswitha Merkel and
• Peter Müller

Beilstein J. Org. Chem. 2015, 11, 74–84, doi:10.3762/bjoc.11.11

• functionalizations in terminal positions. First applications were presented with pyrene, cinnamoyl and anthracenyl labelled ARs. Keywords: articulated rods; click chemistry; molecular rods; oligospiroketals; pyrene excimer; Introduction One of the basic principles in living nature is based on shape-persistent and

• and structureless excimer emission at ca. 477 nm is red-shifted by more than 100 nm against the structured monomer emission at ca. 377 nm. This conspicuous change in the fluorescence spectra permits the investigation of the equilibrium between 32a-STR and 32a-FOL (Scheme 11). At first we investigated

• the influence of temperature and solvent viscosity on the STR–FOL equilibrium. At room temperature a ratio between the monomer and excimer emission IM/IEX of about 100:60 is observed (Figure 4, red curve). The ratio does not change on dilution (1.5·10−5 mol/L → 1.1·10−6 mol/L) indicating that excimer

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

• position of the DNA-active chromophore in the peptide backbone as well as the structural characteristics of the linker between them can easily be modified. In the first series of peptide-bridged bis-phenanthridine derivatives, derivative 11 with the shortest linker formed an intramolecular excimer

• phenanthridine–thymine conjugates [77], intercalated into ds-DNA whereby binding was marginally influenced by attached thymine and the peptide backbone. More intriguing was the observed excimer fluorescence emission and the very specific CD spectrum of pentapeptide confirming the very efficient phenanthridine

Influence of perylenediimide–pyrene supramolecular interactions on the stability of DNA-based hybrids: Importance of electrostatic complementarity

• Christian B. Winiger,
• Simon M. Langenegger,
• Oleg Khorev and
• Robert Häner

Beilstein J. Org. Chem. 2014, 10, 1589–1595, doi:10.3762/bjoc.10.164

• dialkynylpyrenes (Y) results in a pronounced excimer fluorescence [53]. Hybridization of single strands 1 and 2 increases the intensity of the excimer (Figure 6), whereas hybridization of single strands 1 and 6 results in an extinction of excimer fluorescence. Such behaviour was also observed in previous work and

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

• sequence with prevalence of pyrimidine bases, complementary to cystic fibrosis W1282X point mutation were synthesized. These compounds showed sequence-selective switch-on of pyrene excimer emission in the presence of target DNA, due to PNA2DNA triplex formation, with stability depending on the number and

• positioning of the pyrene units along the chain. An increase in triplex stability and a very high mismatch-selectivity, derived from combined stacking and base-pairing interactions, were found for PNA2, bearing two distant pyrene units. Keywords: modified nucleobase; nucleic acids; PNA; pyrene excimer; SNP

• [9][10]. Among the possible reporter groups, pyrene has been proposed in several in vitro detection systems, due to the sensitivity of its fluorescence properties to microenvironment and due to its ability to produce stabilizing stacking interactions and to show excimer fluorescence [11][12][13][14

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

• emission with high quantum yield (0.82) was observed for pyrenylsumanene in solution, while excimer-type red-shifted emission was evident in the crystalline phase. Keywords: carbon nanomaterials; columnar crystal packing; fluorescence; herringbone; pyrenylsumanene; Introduction Buckybowls – bowl-shaped

• -shifted relative to those of 3 and pyrene, again owing to the π-extension. The emission of pyrene at 395 nm in solution is considered to result from the monomer form because of the low concentration, since pyrene is known to generate excimer emission at 480 nm at high concentrations (>10−5 M) [26][27

• ]. The emission of 1 at 422 nm is also assigned to monomer emission. Compound 1 did not generate excimer emission in solution concentrations over the range of 10−4–10−7 M and, due to the poor solubility of this compound, spectra at concentrations above 10−4 M could not be acquired. The emissions of 1 and

Molecular assembly of amino acid interlinked, topologically symmetric, π-complementary donor–acceptor–donor triads

• M. B. Avinash,
• K. V. Sandeepa and
• T. Govindaraju

Beilstein J. Org. Chem. 2013, 9, 1565–1571, doi:10.3762/bjoc.9.178

• ). Interestingly, in the case of 2, (both in aqueous DMSO as well as in aqueous NMP) a new weak emission band at ~460 nm was observed, which was attributed to the excimer of pyrene (see Supporting Information File 1). In addition, UV–vis spectra clearly show a new broad absorption band in the range of 450 nm to

Electron self-exchange activation parameters of diethyl sulfide and tetrahydrothiophene

• Martin Goez and
• Martin Vogtherr

Beilstein J. Org. Chem. 2013, 9, 1448–1454, doi:10.3762/bjoc.9.164

• was done with a Lambda Physik EMG 101 excimer laser (medium, XeCl; wavelength, 308 nm; pulse width, 15 ns) triggered by the computer of the spectrometer. The probe was thermostated to ±0.3 K. Quantum mechanical calculations were carried out with the Gaussian 09 package [53] using the AM1 Hamiltonian

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• has to be recirculated, leading to the possibility of side reactions. Nonetheless, this has proved to be a valuable device in the right circumstances. For example, Griesbeck [11] reported the design of a particularly useful version in conjunction with a high power 308 nm XeCl excimer source. Why then

Interaction of cyclodextrins with pyrene-modified polyacrylamide in a mixed solvent of water and dimethyl sulfoxide as studied by steady-state fluorescence

• Akihito Hashidzume,
• Yongtai Zheng and
• Akira Harada

Beilstein J. Org. Chem. 2012, 8, 1312–1317, doi:10.3762/bjoc.8.150

• and excimer states [32][33]. Since pyrene is very hydrophobic, it may tend to form aggregates, e.g., dimers, in aqueous solutions. It is also known that pyrene forms inclusion complexes with β-CD and γ-CD in different manners; β-CD includes monomeric pyrene whereas γ-CD includes dimeric pyrene [34][35

• assignable to a Py excimer around 480 nm, indicating that Py residues tend to form dimers because of the hydrophobicity. It is likely that Py residues associate intramolecularly under the dilute conditions (0.04 g L−1) in this study. These spectra indicate that the intensity of excimer fluorescence decreases

• predominantly due to the Py excimer and monomer, respectively, were calculated and plotted in Figure 1b against xDMSO. I480/I376 decreases monotonously from 0.125 to 0.025 with increasing xDMSO from 0 to 1. The interaction of β-CD and γ-CD with pAAmPy was also investigated at varying xDMSO by steady-state

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• lower-rim pyrene groups apart. The same cation had a much higher affinity for cone-54 through its complementary binding sites, but approached these from the upper rim, leaving the excimer fluorescence unaffected. Yamato also pursued this path, preparing a tris(pyrenyl) derivative 55 in the cone

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

• transformations have also been realized on a semi-technical scale using an advanced falling-film batch reactor equipped with a 308 nm excimer light source [35][36]. However, the established PDC protocol utilizes UVB light for the activation step (direct or acetone sensitized), thus limiting the desired future

Fluorometric recognition of both dihydrogen phosphate and iodide by a new flexible anthracene linked benzimidazolium-based receptor

• Kumaresh Ghosh and
• Debasis Kar

Beilstein J. Org. Chem. 2011, 7, 254–264, doi:10.3762/bjoc.7.34

• tetrabutylammonium salts of H2PO4−, F−, Br− and I−, the emission of 1 was quenched by 72, 18, 14 and 30%, respectively. During titration experiments, no other changes such as excimer or exciplex formation were observed. The large quenching in emission of 1 upon increasing H2PO4− concentration is illustrated in

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

• and also by substituting donor-acceptor groups along the conjugation [23][24][25]. In addition, pyrene also exhibits excimer emission at a longer wavelength compared to monomer emission which can be used in sensing applications [26][27][28][29][30]. The pyrene chromophore can act as a donor or as an

• studied. In contrast to pyrene, triphenylene does not form an excimer in the excited state – emission from the excimer state is very rare for triphenylene chromophore [37][38][39]. The fluorescence of triphenylene occurs around 348 nm, which is more blue shifted than pyrene monomer emission. Only a few

Anthracene coupled adenine for the selective sensing of copper ions

• Kumaresh Ghosh and
• Tanushree Sen

Beilstein J. Org. Chem. 2010, 6, No. 44, doi:10.3762/bjoc.6.44

• between Cu2+ ion and the other metal ions investigated. During interaction of 1 with metal ions no additional peak at higher wavelengths either for excimer or exciplex formation should be observed. Figure 4 shows the spectral change of 1 upon titration with Cu2+ metal ions. A similar trend in emission

Quinoline based receptor in fluorometric discrimination of carboxylic acids

• Kumaresh Ghosh,
• Suman Adhikari,
• Asoke P. Chattopadhyay and
• Purnendu Roy Chowdhury

Beilstein J. Org. Chem. 2008, 4, No. 52, doi:10.3762/bjoc.4.52

• fluororeceptors 1 and 2 have been designed and synthesized for detection of hydroxy carboxylic acids in less polar solvents. The receptor 1 shows monomer emission quenching followed by excimer emission upon hydrogen bond-mediated complexation of carboxylic acids. The excimer emission distinguishes aromatic

• dicarboxylic acids from aliphatic dicarboxylic acids and even long chain aliphatic dicarboxylic acids from short chain aliphatic dicarboxylic acids. The receptor 1 is found to be selective for citric acid with a strong excimer emission in CHCl3. On the contrary, the receptor 2 exhibited less binding constant

• value and did not form any excimer upon complexation with the same acids under similar conditions. This established the role of quinoline ring nitrogen in binding with the acids. Keywords: carboxylic acid recognition; excimer emission; naphthalene; quinoline; Introduction The sensing and monitoring of