End group functionalization of poly(ethylene glycol) with phenolphthalein: towards star-shaped polymers based on supramolecular interactions

• Carolin Fleischmann,
• Hendrik Wöhlk and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 2263–2269, doi:10.3762/bjoc.10.235

• spectroscopy and even the naked eye. Keywords: cyclodextrin; phenolphthalein; poly(ethylene glycol); supramolecular assembly; UV–vis spectroscopy; Introduction Over the past decades, polymers with well-defined and complex architectures gained increasing attention due to a broad variety of applications

• of stable inclusion complexes was observed, representing an interesting approach towards the formation of star shaped polymers. The decolorization of a basic polymer solution caused by the complexation was of great advantage since this behavior enabled following the complex formation by UV–vis

Aryl substitution of pentacenes

• Andreas R. Waterloo,
• Anna-Chiara Sale,
• Dan Lehnherr,
• Frank Hampel and
• Rik R. Tykwinski

Beilstein J. Org. Chem. 2014, 10, 1692–1705, doi:10.3762/bjoc.10.178

• properties of the new pentacene chromophores have been analyzed by UV–vis spectroscopy (solution and thin films), thermoanalytical methods (DSC and TGA), cyclic voltammetry, as well as X-ray crystallography (for 8 derivatives). X-ray crystallography has been specifically used to study the influence of

• acetone. UV–vis spectroscopy Aryl pentacenes 3a–k have been studied by UV–vis absorption spectroscopy in CH2Cl2 solutions and as thin films cast from CH2Cl2 onto quartz. Solution-state UV–vis spectra show characteristic absorptions in the high-energy region with a maximum intensity absorption centered at

• from solid-state films. Pentacene samples 3a–k were drop-cast from a concentrated CH2Cl2 solution onto a quartz surface, and after air-drying, the absorption spectra were measured by UV–vis spectroscopy (Figure 3 and Table 1). While this method sometimes results in rather significant scattering versus

Improving the reactivity of phenylacetylene macrocycles toward topochemical polymerization by side chains modification

• Simon Rondeau-Gagné,
• Jules Roméo Néabo,
• Maxime Daigle,
• Katy Cantin and
• Jean-François Morin

Beilstein J. Org. Chem. 2014, 10, 1613–1619, doi:10.3762/bjoc.10.167

• better solubility of the PDA obtained from PAM2 compared to that obtained from PAM1, although quantitative measurements of the solubility have not been conducted because of the small quantity of materials prepared. Given the observed polymerization of diyne units, UV–vis spectroscopy was performed to

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

• . These novel donor–acceptor dyads are electronically decoupled in the electronic ground state according to UV–vis spectroscopy and cyclic voltammetry. However, in the excited state the inherent donor luminescence is efficiently quenched. Previously performed femtosecond spectroscopic measurements account

• -component reaction represents a rapid and excellent modular and diversity-oriented synthesis of donor-anthraquinone dyads with various phenothiazine and carbazole model donors. Cyclic voltammetry and UV–vis spectroscopy clearly indicate an electronic decoupling of the donor and the acceptor substituents in

Molecular recognition of isomeric protonated amino acid esters monitored by ESI-mass spectrometry

• Andrea Liesenfeld and
• Arne Lützen

Beilstein J. Org. Chem. 2014, 10, 825–831, doi:10.3762/bjoc.10.78

• target compounds 1 and 2 in moderate yields (Scheme 2). Molecular recognition studies With our crown ether derivatives 1 and 2 in hands we studied their recognition behaviour towards the L-leucine isomers. Usually, spectroscopic techniques like NMR or UV–vis spectroscopy are used for this purpose

Charge-transfer interaction mediated organogels from 18β-glycyrrhetinic acid appended pyrene

• Jun Hu,
• Jindan Wu,
• Qian Wang and
• Yong Ju

Beilstein J. Org. Chem. 2013, 9, 2877–2885, doi:10.3762/bjoc.9.324

• and 4 (1:1, molar ratio) in DMSO/water (3:1, v/v) was studied by UV–vis spectroscopy (Figure 7a). The absorbance at 547 nm (CT absorption band) decreased with increasing temperature (35 °C to 75 °C), and the colour changed from dark red to light yellow (inset of Figure 7b), indicating the dissociation

Synthesis, characterization and luminescence studies of gold(I)–NHC amide complexes

• Adrián Gómez-Suárez,
• David J. Nelson,
• David G. Thompson,
• David B. Cordes,
• Duncan Graham,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2013, 9, 2216–2223, doi:10.3762/bjoc.9.260

• yellow. The excitation and emission maxima were then determined. These measurements were conducted on more concentrated (ca. 4 mmol/L) CH2Cl2 solutions, compared to those used for UV–vis spectroscopy. In each case, the relevant maxima could be identified. An example dataset is presented in Figure 3

Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor

• Rajesh Munirathinam,
• Roberto Ricciardi,
• Richard J. M. Egberink,
• Jurriaan Huskens,
• Michael Holtkamp,
• Herbert Wormeester,
• Uwe Karst and
• Willem Verboom

Beilstein J. Org. Chem. 2013, 9, 1698–1704, doi:10.3762/bjoc.9.194

• of 13 min. A substrate concentration of 25 µM was used for all the substrates. The conversions were determined using online UV–vis spectroscopy by following the change in the extinction of a substrate specific wavelength. In case of 2-hydroxy-1-naphthaldehyde oxime (6, Table 2, entry 4) and

Simple and rapid hydrogenation of p-nitrophenol with aqueous formic acid in catalytic flow reactors

• Rahat Javaid,
• Shin-ichiro Kawasaki,
• Akira Suzuki and
• Toshishige M. Suzuki

Beilstein J. Org. Chem. 2013, 9, 1156–1163, doi:10.3762/bjoc.9.129

• –vis spectroscopy. The analytical UV–vis peaks of p-nitrophenol and p-aminophenol are sufficiently separated both under acidic and basic conditions (Supporting Information File 1). The spectral difference between acidic and basic solutions is responsible for the association and dissociation of phenolic

• the pressure drop and plugging. The evolution of gas bubbles was observed during the reaction forming an alternate gas–liquid slug flow. GC analysis of the gas phase evidenced the evolution of CO2 as a sole product and H2 was not found. The hydrogenation reaction of p-nitrophenol was followed by UV

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

• , MALDI–TOF-mass spectrometry and elemental analysis as well as by cyclic voltammetry and UV–vis spectroscopy. Electronic absorption and emission properties. One of our goals was to study electronic communication between the core metal complex and the attached oligothiophene dendron as a function of

Superstructures of fluorescent cyclodextrin via click-reaction

• Arkadius Maciollek,
• Helmut Ritter and
• Rainer Beckert

Beilstein J. Org. Chem. 2013, 9, 827–831, doi:10.3762/bjoc.9.94

• )-interactions. The supramolecular structures were characterized by 1H NMR-ROESY spectroscopy, dynamic light scattering, UV–vis spectroscopy, fluorescence spectroscopy, and asymmetric flow field-flow fractionation. By adding potassium adamantane-1-carboxylate, the thiazol dye is displaced from the CD-cavity and

• NOE interaction between protons of the methyl group of the thiazole and the triazole proton itself with CD is noticed. This indicates that only the inclusion of the pyridine moiety in the hydrophobic cavity of the CD takes place. The formation of supramolecular structures was also proven by UV–vis

• spectroscopy and fluorescence spectroscopy. Figure 2 shows the UV–vis absorption spectra of 3 in water with the characteristic band at λmax= 340 nm. The addition of a 10-fold excess of potassium adamantane-1-carboxylate, as competitive guest for CD leads to a hypsochromic shift with λmax = 336 nm, through the

End-labeled amino terminated monotelechelic glycopolymers generated by ROMP and Cu(I)-catalyzed azide–alkyne cycloaddition

• Ronald Okoth and
• Amit Basu

Beilstein J. Org. Chem. 2013, 9, 608–612, doi:10.3762/bjoc.9.66

• from the NHS ester of pyrene butyric acid 13 via intermediate 14, afforded the pyrene-end-labeled glycopolymers 16. The extent of pyrene labeling was determined by UV–vis spectroscopy and found to be essentially quantitative for the galactosyl and mannosyl polymers. The SGal polymer 12c only underwent

Polymerization of novel methacrylated anthraquinone dyes

• Christian Dollendorf,
• Susanne Katharina Kreth,
• Soo Whan Choi and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 453–459, doi:10.3762/bjoc.9.48

• of monomeric dyes out of the network was observed, as examined by UV–vis spectroscopy. This proves the covalent emplacement of the monomeric dyes in the polymer network. Figure 3 shows polymers containing 9 and 10 after sharpening for further application as iris implants. For use in medical

Synthesis and testing of the first azobenzene mannobioside as photoswitchable ligand for the bacterial lectin FimH

• Vijayanand Chandrasekaran,
• Katharina Kolbe,
• Femke Beiroth and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2013, 9, 223–233, doi:10.3762/bjoc.9.26

• . Photoirradiation was carried out in the dark at room temperature by employing a 365 nm LED. Photostationary states (PSS) were reached after 10 minutes of irradiation for both compounds. E→Z isomerisation was observed by both 1H NMR and UV–vis spectroscopy. The E/Z ratios of the ground state (GS) as well as of the

Inclusion of the insecticide fenitrothion in dimethylated-β-cyclodextrin: unusual guest disorder in the solid state and efficient retardation of the hydrolysis rate of the complexed guest in alkaline solution

• Dyanne L. Cruickshank,
• Natalia M. Rougier,
• Raquel V. Vico,
• Susan A. Bourne,
• Elba I. Buján,
• Mino R. Caira and
• Rita H. de Rossi

Beilstein J. Org. Chem. 2013, 9, 106–117, doi:10.3762/bjoc.9.14

• Spectroscopic methods are frequently used to determine association constants between cyclodextrins and different guests [16]. We attempted to determine the binding constant of 1 with DIMEB by UV–vis spectroscopy; however, when we recorded the spectra of 1 in the presence of DIMEB, only a small hypsochromic

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

• the cis isomer is quantitative within the error limits of 1H NMR and UV–vis spectroscopy (Figure 4). Thermal stability of the trans isomers Amino and alkylamino substituents in para position to the azo group reduce the lifetime of the cis states of azobenzenes [15][16]. A dramatically shortened half

Self-assembled organic–inorganic magnetic hybrid adsorbent ferrite based on cyclodextrin nanoparticles

• Ângelo M. L. Denadai,
• Frederico B. De Sousa,
• Joel J. Passos,
• Fernando C. Guatimosim,
• Kirla D. Barbosa,
• Ana E. Burgos,
• Fernando Castro de Oliveira,
• Jeann C. da Silva,
• Bernardo R. A. Neves,
• Nelcy D. S. Mohallem and
• Rubén D. Sinisterra

Beilstein J. Org. Chem. 2012, 8, 1867–1876, doi:10.3762/bjoc.8.215

• microscopy (AFM). Size distribution and colloidal suspension stability were characterized by dynamic light scattering (DLS) and sedimentation kinetic studies by using UV–vis spectroscopy. Ferrite binding sites were characterized by zeta potential (ZP) and potentiometric titration. The free volume for both

Design and synthesis of a photoswitchable guanidine catalyst

• Philipp Viehmann and
• Stefan Hecht

Beilstein J. Org. Chem. 2012, 8, 1825–1830, doi:10.3762/bjoc.8.209

• the validity of our concept, illustrating the azobenzene’s utilization as a spacer by spatial separation of the guanidine core and carbonyl function. In order to utilize the incorporated light-sensitive azobenzene functionality, the photochromic behavior of guanidine 2 was investigated by UV–vis

• spectroscopy (Figure 2). The UV–vis spectrum of guanidine 2E in acetonitrile exhibits the expected behavior, similar to the unsubstituted parent azobenzene, i.e., a low intensity n→π* band in the visible region and a much stronger π→π* band in the UV region of the spectrum. Note that the n→π* band partially

Molecular solubilization of fullerene C₆₀ in water by γ-cyclodextrin thioethers

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2012, 8, 1644–1651, doi:10.3762/bjoc.8.188

• to the aqueous solutions of γ-CD and γ-CD thioether 5, in the hope of accelerating and improving the dissolution of C60 as reported by Murphy et al. [42]. The resulting solutions were characterized by UV–vis spectroscopy. The saturation concentrations of C60 are listed in Table 2. Indeed, for native

Recent advances towards azobenzene-based light-driven real-time information-transmitting materials

• Jaume García-Amorós and
• Dolores Velasco

Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113

• kinetics of the thermal cis-to-trans isomerisation process for azo-dyes 1–6 were analysed by conventional UV–vis spectroscopy. Since these azoderivatives are not water-soluble, ethanol was used as a solvent instead of water. The unimolecular thermal cis-to-trans isomerisation process in the dark obeys

Synthesis and characterization of a novel carboxyl group containing (co)polyimide with sulfur in the polymer backbone

• Miroslav Mrsevic,
• David Düsselberg and
• Claudia Staudt

Beilstein J. Org. Chem. 2012, 8, 776–786, doi:10.3762/bjoc.8.88

• components for high-temperature applications, such as light emitting diodes (LEDs) [34]. UV–vis spectroscopy In order to characterize the optical properties of the (co)polyimides with respect to their color and transparency, UV–vis spectra of free standing films were recorded. The previously described

• procedure to prepare free-standing films for moisture uptake measurements was also applied for UV–vis spectroscopy. Spectra were recorded in the range of 250 to 800 nm with average film thicknesses of 140 μm. To ensure sufficient comparability, transparency is defined as the transmittance value at the

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

• -triazole co-oligomers were investigated by UV–vis spectroscopy and cyclic voltammetry. Several co-oligomers were electropolymerized to the corresponding conjugated polymers. Keywords: acetylene; azide; click chemistry; thiophene; triazole; Introduction Oligo- and polythiophenes are among the most

Synthesis of mesomeric betaine compounds with imidazolium-enolate structure

• Nina Gonsior,
• Fabian Mohr and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 390–397, doi:10.3762/bjoc.8.42

• mesomeric betaine with randomly methylated (1.8) β-cyclodextrin were investigated by UV–vis spectroscopy. Furthermore, the reaction conditions were applied to poly(vinylimidazole) and 1,4-bis(1H-imidazol-1-yl)butane to obtain functionalized polymer networks and condensate polymers, respectively. Keywords

• ). Regarding our interest in supramolecular chemistry and the enhancement of water solubility, the ability of 3 to form inclusion complexes with randomly methylated (1.8) β-cyclodextrin (m-β-CD) was investigated by means of UV–vis spectroscopy. Therefore, the type of inclusion complex and the complex formation

• mesomeric betaine. Inclusion complexes of 3 with m-β-CD were investigated by UV–vis spectroscopy. The Higuchi–Connors phase diagram indicated the formation of weak 1:1 and 1:2 complexes. In addition, the reaction conditions were applied to poly(vinylimidazole) and 1,4-bis(1H-imidazol-1-yl)butane to obtain

Synthesis and photooxidation of styrene copolymer bearing camphorquinone pendant groups

• Branislav Husár,
• Norbert Moszner and
• Ivan Lukáč

Beilstein J. Org. Chem. 2012, 8, 337–343, doi:10.3762/bjoc.8.37

• calibration curve consisting of five different concentrations of MCQ in CCl4 solution. UV–vis spectroscopy was used in a similar way by interpolation of the n→π* peak area (390–510 nm) using a calibration curve. The content of MCQ units in MCQ/S copolymer was determined to be 0.72 mol % from FTIR and 0.62 mol

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

• 3a in 1997 by UV–vis spectroscopy [74]. In a later full paper, UV–vis absorption spectra of C60 were recorded with calix[n]arenes and oxacalix[3]arenes. The interaction of fullerenes with calixarenes affected the spectra between 420 and 450 nm [75]. By using the Benesi–Hildebrand method, 3a was shown