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

Equilibrium constants and protonation site for N-methylbenzenesulfonamides

• José A. Moreira,
• Ana M. Rosa da Costa,
• Luis García-Río and
• Márcia Pessêgo

Beilstein J. Org. Chem. 2011, 7, 1732–1738, doi:10.3762/bjoc.7.203

• -NO2 (3d), in aqueous sulfuric acid were studied at 25 °C by UV–vis spectroscopy. As expected, the values for the acidity constants are highly dependent on the electron-donor character of the substituent (the pKBH+ values are −3.5 ± 0.2, −4.2 ± 0.2, −5.2 ± 0.3 and −6.0 ± 0.3 for 3a, 3b, 3c and 3d

PEG-embedded KBr₃: A recyclable catalyst for multicomponent coupling reaction for the efficient synthesis of functionalized piperidines

• Sanny Verma,
• Suman L. Jain and
• Bir Sain

Beilstein J. Org. Chem. 2011, 7, 1334–1341, doi:10.3762/bjoc.7.157

• reaction mixture by UV–vis spectroscopy at the end of the reaction; no bromine was detected in the reaction mixture, thus establishing the in situ generation of bromine from the reagent during the reaction. Conclusion In summary, we have described the first time use of inexpensive, environmentally benign

• bromine could be detected in the reaction mixture as analyzed by UV−vis spectroscopy; this established the in situ generation of bromine from the reagent during the reaction. Typical experimental procedure Into a stirred mixture of aniline (0.2 g, 2.15 mmol), benzaldehyde (0.2 g, 1.89 mmol), ethyl

Hyperbranched polyethylenimine bearing cyclodextrin moieties showing temperature and pH controlled dye release

• Indra Böhm,
• Susanne Katharina Kreth and
• Helmut Ritter

Beilstein J. Org. Chem. 2011, 7, 1130–1134, doi:10.3762/bjoc.7.130

• -adamantylaminoanthraquinone (AQ-Ada) were encapsulated by the cavity of CD modified PEI. Due to these different types of interaction, the dyes can be controllably released from the CD-cavity (AQ-Ada) by temperature variation or from salt encapsulation by pH variation (AQ-OH), as monitored by UV–vis spectroscopy. Keywords

• the hydrophobic adamantyl moieties are encapsulated by CD. That leads to a purple aqueous solution with λmax at 552 and 668 nm. This complex 5 is not pH sensitive, which was verified by UV–vis spectroscopy (Supporting Information File 1, Figure S7). After 30 min of heating at 60 °C the complexation

• equilibrium shifted towards the free purple colored dye 2. The complete release was monitored by eye and by UV–vis spectroscopy (Figure 2). The absorption plot of complex 6 (a combination of the red and the purple dyes) exhibits maxima at 524, 564 and 656 nm. To show the separate release of dye 2, complex 6

Novel carbazole–pyridine copolymers by an economical method: synthesis, spectroscopic and thermochemical studies

• Aamer Saeed,
• Madiha Irfan and
• Shahid Ameen Samra

Beilstein J. Org. Chem. 2011, 7, 638–647, doi:10.3762/bjoc.7.75

• synthesized by a modified Chichibabin reaction, i.e., by the condensation of diacetylated N-alkylcarbazoles with 3-substituted benzaldehydes in the presence of ammonium acetate in refluxing acetic acid. All the polymers were characterized by FTIR, 1H NMR, 13C NMR, UV–vis spectroscopy, fluorimetry, TGA and DSC

Anion–π interactions influence pK_a values

• Christopher J. Cadman and
• Anna K. Croft

Beilstein J. Org. Chem. 2011, 7, 320–328, doi:10.3762/bjoc.7.42

• out in triplicate for all of the derivatives and the results were averaged out over all three titrations. The action of TBAH was confirmed through UV–vis spectroscopy. First the molar absorption coefficient (ε) for each acid 1–5 was determined by producing standard curves from known acid

Synthesis and self-assembly of 1-deoxyglucose derivatives as low molecular weight organogelators

• Guijun Wang,
• Hao Yang,
• Sherwin Cheuk and
• Sherman Coleman

Beilstein J. Org. Chem. 2011, 7, 234–242, doi:10.3762/bjoc.7.31

• the resulting gel is no longer stable. The concentration prior to formation of the unstable gel was recorded as the minimum gelation concentration (MGC). UV–vis spectroscopy. The UV–vis spectra were recorded on a Bio-Tek PowerWave Microplate Spectrophotometer using a 96-well microplate (Corning’s UV

Self-assembly and semiconductivity of an oligothiophene supergelator

• Pampa Pratihar,
• Suhrit Ghosh,
• Vladimir Stepanenko,
• Sameer Patwardhan,
• Ferdinand C. Grozema,
• Laurens D. A. Siebbeles and
• Frank Würthner

Beilstein J. Org. Chem. 2010, 6, 1070–1078, doi:10.3762/bjoc.6.122

• were characterized by 1H NMR and UV-vis spectroscopy, HRMS (ESI) and elemental analysis, while those synthetic intermediates already reported in the literature were characterized by 1H NMR and UV-vis spectroscopy. Gelation tests The gelation properties of T1 were examined in various organic solvents

• spectroscopy Self-assembly of T1 in solution was examined by UV-vis spectroscopy. Chloroform is known to be an excellent solvent for the study of rigid π-systems [20][21], and the oligothiophene chromophore T1 has good solubility in this solvent. However, as noted above, in nonpolar solvents such as n-heptane

• chromophores (Scheme 3). To ascertain the involvement of hydrogen bonding in the self-assembly, we examined the effect of a protic solvent, e.g. MeOH, on the self-assembly process by UV-vis spectroscopy. MeOH itself can be involved in H-bonding interaction with the amide groups, and thus expected to interfere

Hybrid biofunctional nanostructures as stimuli-responsive catalytic systems

• Gernot U. Marten,
• Thorsten Gelbrich and
• Annette M. Schmidt

Beilstein J. Org. Chem. 2010, 6, 922–931, doi:10.3762/bjoc.6.98

• investigated by the classical BAPNA method [57] and is compared to the native protein. Trypsin-catalyzed hydrolysis of benzoyl-Arg p-nitroanilide (BAPNA) results in the formation of p-nitroaniline that can be quantified by UV–vis spectroscopy at 410 nm (Scheme 2) [58]. The increase of relative absorption A410

• at 410 nm was detected over a period of up to 20 min by UV–vis spectroscopy. Analytic methods and instrumentation: ATR-IR spectra were measured on a Nicolet 6700 spectrometer. Elemental analyses were performed on a Perkin-Elmer 2400 CHN analyzer. The organic content was calculated through C content

• to the oscillating magnetic field. Via a fiber-optical sensor the fluid temperature T was measured against time t. For UV–vis spectroscopy, a Nicolet UV 540 spectroscope, a Unicam UV 500 or a Perkin Elmer Lambda19 with a thermostat Colora NBDS was used. Differential scanning calorimetry thermograms

Chromo- and fluorophoric water-soluble polymers and silica particles by nucleophilic substitution reaction of poly(vinyl amine)

• Katja Hofmann,
• Ingolf Kahle,
• Frank Simon and
• Stefan Spange

Beilstein J. Org. Chem. 2010, 6, No. 79, doi:10.3762/bjoc.6.79

• , β and π*, respectively. corresponds to a standard process, referenced to a nonpolar medium. a, b and s represent solvent-independent regression coefficients which reflect the relative influence of each of the three parameters. UV–vis spectroscopy The solvatochromism of 1-M and 1-P was investigated

RAFT polymers for protein recognition

• Alan F. Tominey,
• Julia Liese,
• Sun Wei,
• Klaus Kowski,
• Thomas Schrader and
• Arno Kraft

Beilstein J. Org. Chem. 2010, 6, No. 66, doi:10.3762/bjoc.6.66

• produced slightly higher polydispersities (1.56). For comparison, some copolymers such as S20CH15 were also prepared with a molecular weight of ~3000 g mol−1. Titrations were first carried out by UV–vis spectroscopy with cytochrome C, a protein carrying a chromophore. Second derivative spectra were

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

• chiral (R)-(−)-2-amino-1-butanol [160] (Figure 15). The association constants, measured by UV–vis spectroscopy in methanol/chloroform solvent mixture, revealed for S-, R-Ala-OMe hydrochloride the highest value for both macrocycles (Ka = 1.5 × 104 dm3 mol−1) as calculated by a modified Benesi–Hildebrand

• investigated and published in 1998 by the group of Naemura [179]. This system displayed, on investigation by UV–vis spectroscopy in chloroform, a good enantiodiscrimination ability in favor of (R)-phenylalaninol with an ΔR-SΔG = 6.4 kJ mol−1. In succession, Steensma et al. investigated thermodynamic data and

Synthesis of mesogenic phthalocyanine-C₆₀ donor–acceptor dyads designed for molecular heterojunction photovoltaic devices

• Yves Henri Geerts,
• Olivier Debever,
• Claire Amato and
• Sergey Sergeyev

Beilstein J. Org. Chem. 2009, 5, No. 49, doi:10.3762/bjoc.5.49

• group. Structural characterization of the molecules in solution was performed by NMR spectroscopy, UV–vis spectroscopy and cyclic voltammetry. Preliminary studies suggest formation of liquid crystalline (LC) mesophases for some of the prepared dyads. To the best of our knowledge, this is the first