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Search for "absorption spectroscopy" in Full Text gives 88 result(s) in Beilstein Journal of Organic Chemistry.

The B & B approach: Ball-milling conjugation of dextran with phenylboronic acid (PBA)-functionalized BODIPY

  • Patrizia Andreozzi,
  • Lorenza Tamberi,
  • Elisamaria Tasca,
  • Gina Elena Giacomazzo,
  • Marta Martinez,
  • Mirko Severi,
  • Marco Marradi,
  • Stefano Cicchi,
  • Sergio Moya,
  • Giacomo Biagiotti and
  • Barbara Richichi

Beilstein J. Org. Chem. 2020, 16, 2272–2281, doi:10.3762/bjoc.16.188

Graphical Abstract
  • recorded on an Inova 400 instrument. Fourier transform infra red absorption spectroscopy (FTIR) was carried out with a Shimadzu IRAffinity-1S spectrometer. Potassium bromide (KBr) pellets were prepared using 100 mg of potassium bromide and 1.0 mg of sample. The spectra were recorded under inert atmosphere
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Published 11 Sep 2020

Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

  • Phil M. Pithan,
  • Sören Steup and
  • Heiko Ihmels

Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82

Graphical Abstract
  • . For 3a, further monitoring by absorption spectroscopy revealed that higher Cu2+ concentrations led to an increase of the reaction rate. However, at a spirooxazine concentration of c = 20 µM, slightly more than 2.0 equiv of Cu2+ were required for a complete conversion (Figure S4, Supporting Information
  • “adjacent-averaging“ (factor of 10). For the reaction monitoring by absorption spectroscopy, an aliquot of the solutions of Cu(BF4)2, Fe(ClO4)3 or Hg(ClO4)2 was added to a solution of 3a (c = 20 µM) in MeCN to achieve a final concentration of the metal ions of c = 20–60 µM. The solutions were mixed
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Published 05 May 2020

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

  • Liliia Moshniaha,
  • Marika Żyła-Karwowska,
  • Joanna Cybińska,
  • Piotr J. Chmielewski,
  • Ludovic Favereau and
  • Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

Graphical Abstract
  • . ΔE values for lactams cRnO are relatively insensitive to the length of the alkylene linker n, in spite of the large changes of the inter-subunit torsion (θ, Supporting Information File 1, Table S1) caused by the increase of n. In line with the absorption spectroscopy data, the ΔE gap is reduced in
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Published 04 May 2020

Direct borylation of terrylene and quaterrylene

  • Haruka Kano,
  • Keiji Uehara,
  • Kyohei Matsuo,
  • Hironobu Hayashi,
  • Hiroko Yamada and
  • Naoki Aratani

Beilstein J. Org. Chem. 2020, 16, 621–627, doi:10.3762/bjoc.16.58

Graphical Abstract
  • QB4 are pretty high among electron-rich compounds. Thus we tested the stability of TB4 and QB4 under air by means of UV–vis absorption spectroscopy. Surprisingly almost no spectral changes for both compounds were observed after 12 h, probably because the most reactive sites are protected by the steric
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Published 06 Apr 2020

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

  • Rafia Siddiqui and
  • Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

Graphical Abstract
  • hydroxylation of arenes (Scheme 18) [157]. They realized that the photoredox catalyst 8 possesses a great oxidizing ability (Ered vs SCE = 2.72 V) at ambient conditions. The mechanism of the reaction was studied by fluorescence quenching and transient absorption spectroscopy. They observed that the one-electron
  • observed that hydroxylation of the fluoro-, chloro-, and bromobenzene derivatives provided low yields. The photocatalytic mechanism for this reaction was inspected by time-resolved transient absorption spectroscopy to detect the triplet–triplet photoredox catalyst spectrum via nanosecond laser flash
  • [163]. They exploited the potent photoredox catalyst 2 for the excitation of the substrate. The mechanism was detected by nanosecond transient absorption spectroscopy. The substrate scope and mechanism are shown in Scheme 22 and Figure 22. Furthermore, König and co-workers synthesized monochlorinated
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Published 26 Feb 2020

Chemical tuning of photoswitchable azobenzenes: a photopharmacological case study using nicotinic transmission

  • Lorenzo Sansalone,
  • Jun Zhao,
  • Matthew T. Richers and
  • Graham C. R. Ellis-Davies

Beilstein J. Org. Chem. 2019, 15, 2812–2821, doi:10.3762/bjoc.15.274

Graphical Abstract
  • Supporting Information File 1. Absorption spectroscopy UV–vis spectra were recorded using a Cary 50 spectrophotometer (Agilent, Santa Clara, CA, USA) at rt in quartz cuvettes with a 1 cm path length in HEPES buffer at pH 7.4. UPLC Chromatography was performed using a Waters Acuity Arc using Cortecs C-18
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Published 21 Nov 2019

Photoreversible stretching of a BAPTA chelator marshalling Ca2+-binding in aqueous media

  • Aurélien Ducrot,
  • Arnaud Tron,
  • Robin Bofinger,
  • Ingrid Sanz Beguer,
  • Jean-Luc Pozzo and
  • Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

Graphical Abstract
  • restoration of the electronic absorption band attributed to the π–π* transition at 30 °C (Figure 5), the rate constant (k) was estimated at 5.4 × 10−5 s−1. Photoisomerization was also recorded in electron-absorption spectroscopy in the presence of calcium (see Figure S2 in Supporting Information File 1). The
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Published 21 Nov 2019

Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

  • Alessandro Iagatti,
  • Baihao Shao,
  • Alberto Credi,
  • Barbara Ventura,
  • Ivan Aprahamian and
  • Mariangela Di Donato

Beilstein J. Org. Chem. 2019, 15, 2438–2446, doi:10.3762/bjoc.15.236

Graphical Abstract
  • , Supporting Information File 1). Transient absorption spectroscopy To get more insights into the isomerization and fluorescence mechanism of 1, we measured transient absorption spectra of the molecule in different solvents. A fresh solution of the Z-form was excited using 400 nm light, and spectra were
  • the excited state lifetime. Two-photon excitation Earlier experiments revealed that hydrazone 1 is able to isomerize also upon two-photon excitation [29]. In the present study we used transient absorption spectroscopy as an alternative method to determine the two-photon absorption cross section of the
  • -state fluorescence of the E-isomers in most solvents. Transient absorption spectroscopy measurements, repeated in different solvents, allowed us to estimate the timescale of the Z/E isomerization process, which is about 0.5 ps in both toluene and acetonitrile, thus showing a negligible dependence on the
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Published 15 Oct 2019

Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes

  • Andrey G. Lvov,
  • Max Mörtel,
  • Anton V. Yadykov,
  • Frank W. Heinemann,
  • Valerii Z. Shirinian and
  • Marat M. Khusniyarov

Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235

Graphical Abstract
  • located in the wide range 490–563 nm. Photocyclization/cycloreversion of all ligands can be repeated several times without notable fatigue (see inset of Figure 2). Extinction coefficients of closed-ring isomers were determined using 1H NMR and electronic absorption spectroscopy (for representative NMR
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Published 15 Oct 2019

Reversible switching of arylazopyrazole within a metal–organic cage

  • Anton I. Hanopolskyi,
  • Soumen De,
  • Michał J. Białek,
  • Yael Diskin-Posner,
  • Liat Avram,
  • Moran Feller and
  • Rafal Klajn

Beilstein J. Org. Chem. 2019, 15, 2398–2407, doi:10.3762/bjoc.15.232

Graphical Abstract
  • photoisomerization of encapsulated E-1. UV irradiation (365 nm light-emitting diode, LED) of the transparent yellow solution of (E-1)22 in water did not result in any pronounced visual changes. However, UV–vis absorption spectroscopy showed (Figure 4) a dramatic decrease in the intensity of E-1’s absorption at 336
  • excess solid E-1 with a solution of 2 in water (H2O/D2O). Encapsulation of E-1 by 2 was followed by UV–vis absorption spectroscopy; stirring was discontinued when no further coloration of the solution was observed. Excess E-1 was removed by filtration. 1H NMR (500 MHz, D2O) δ 9.26 (s, 8H), 9.17 (s, 4H
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Published 10 Oct 2019

Excited state dynamics for visible-light sensitization of a photochromic benzil-subsituted phenoxyl-imidazolyl radical complex

  • Yoichi Kobayashi,
  • Yukie Mamiya,
  • Katsuya Mutoh,
  • Hikaru Sotome,
  • Masafumi Koga,
  • Hiroshi Miyasaka and
  • Jiro Abe

Beilstein J. Org. Chem. 2019, 15, 2369–2379, doi:10.3762/bjoc.15.229

Graphical Abstract
  • switching speed of PIC opened up various potential applications, no photosensitivity to visible light limits its applications. In this study, we synthesized a visible-light sensitized PIC derivative conjugated with a benzil unit. Femtosecond transient absorption spectroscopy revealed that the benzil unit
  • ; sensitizer; transient absorption spectroscopy; Introduction Photochromism, which is defined as the reversible transformation of a chemical species between two structural isomers by light, has been extensively studied over decades [1][2][3][4]. Recently, visible-light sensitized photochromic materials have
  • femtosecond transient absorption measurements using a 400 nm excitation pulse. The instrumental response function is ≈170 fs. It is noted that the excitation wavelength for femtosecond transient absorption spectroscopy (400 nm) is slightly different from that for nanosecond transient absorption spectroscopy
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Published 04 Oct 2019

1,2,3-Triazolium macrocycles in supramolecular chemistry

  • Mastaneh Safarnejad Shad,
  • Pulikkal Veettil Santhini and
  • Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

Graphical Abstract
  • (DB24C8) are capable of a reversible pH-controlled movement of the crown ether between two stations. UV–vis absorption spectroscopy experiments and 1H NMR spectroscopy have shown that the electron-rich crown ether rings and the electron-deficient N-methyl-1,2,3-triazolium can interact with each other
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Published 12 Sep 2019

Synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles: Cs2CO3-mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium

  • Mio Matsumura,
  • Yuki Kitamura,
  • Arisa Yamauchi,
  • Yoshitaka Kanazawa,
  • Yuki Murata,
  • Tadashi Hyodo,
  • Kentaro Yamaguchi and
  • Shuji Yasuike

Beilstein J. Org. Chem. 2019, 15, 2029–2035, doi:10.3762/bjoc.15.199

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  • tetracyclic heterocycles are all novel compounds. Single-crystal X-ray analysis of the parent benzimidazo[2,1-b]benzoselenoazole revealed that the tetracyclic ring is almost planar. Absorption spectroscopy data of the benzimidazo[2,1-b]benzoselenoazoles showed the λmax was dependent on the number of rings
  • parent tetracyclic compound 2a features a nearly coplanar ring. Absorption spectroscopy data revealed the λmax was dependent on the number of rings. Detailed mechanistic studies of this cyclization and the applications of this reaction to other heterocycles are currently underway in our laboratory
  • . Cyclization of 1-(2-bromophenyl)benzimidazoles with chalcogen elements.a Absorption spectroscopy dataa. Supporting Information Supporting Information File 401: Experimental details and analytical data, copies of absorption and NMR spectra. Supporting Information File 402: X-ray crystal structure of 2a
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Published 26 Aug 2019

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

  • Gagandeep Kour Reen,
  • Ashok Kumar and
  • Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Graphical Abstract
  • EDGs at p- and m-positions gave a higher yield than sterically hindered o-substituents and EWGs. Moreover, the absence of metal leaching as tested by atomic absorption spectroscopy (AAS) demonstrated the heterogeneous nature of the used catalyst. Recently, a robust, ligand and additive-free
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Published 19 Jul 2019

Introduction of an isoxazoline unit to the β-position of porphyrin via regioselective 1,3-dipolar cycloaddition reaction

  • Xiujun Liu,
  • Xiang Ma and
  • Yaqing Feng

Beilstein J. Org. Chem. 2019, 15, 1434–1440, doi:10.3762/bjoc.15.143

Graphical Abstract
  • ]. However, only one fraction was isolated in this reaction besides the unconsumed starting material 2. The structure of 1,3-dipole cycloaddition products 3a,b were firstly characterized by absorption spectroscopy (Figure 1). The two compounds 3a,b showed approximately overlapped traces with typical intense
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Published 28 Jun 2019

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

  • Jennifer Klose,
  • Tobias Severin,
  • Peter Hahn,
  • Alexander Jeremies,
  • Jens Bergmann,
  • Daniel Fuhrmann,
  • Jan Griebel,
  • Bernd Abel and
  • Berthold Kersting

Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

Graphical Abstract
  • = |2.59| cm−1 were determined [13]. UV–vis spectroscopy All new compounds were further investigated by electronic absorption spectroscopy. The electronic absorption spectra were recorded in acetonitrile (1, 2 and 5–9) or dimethyl sulfoxide (3, 4) solution in the 190 to 1200 nm spectral range. Figure 11
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Published 03 Apr 2019

Azologization of serotonin 5-HT3 receptor antagonists

  • Karin Rustler,
  • Galyna Maleeva,
  • Piotr Bregestovski and
  • Burkhard König

Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74

Graphical Abstract
  • performed in DMSO and depending on their solubility in phosphate buffer + 0.1% DMSO (16a–d) by UV–vis absorption spectroscopy. The compounds were dissolved at 50 µM in the respective solvent and irradiated with the indicated wavelengths to generate a substantial amount of their cis-isomer. This process can
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Published 25 Mar 2019

Degenerative xanthate transfer to olefins under visible-light photocatalysis

  • Atsushi Kaga,
  • Xiangyang Wu,
  • Joel Yi Jie Lim,
  • Hirohito Hayashi,
  • Yunpeng Lu,
  • Edwin K. L. Yeow and
  • Shunsuke Chiba

Beilstein J. Org. Chem. 2018, 14, 3047–3058, doi:10.3762/bjoc.14.283

Graphical Abstract
  • absorption spectroscopy study of xanthate 1a was conducted (Figure 3). The UV–vis absorption spectrum of 1a (1 mM in DMSO) showed absorption bands at 340–390 nm assigned to the n→π* electronic transition of the C=S bond as a characteristic peak of thiocarbonyl containing compounds [56]. In fact, the reaction
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Published 13 Dec 2018

Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

  • Amrita Das,
  • Mitasree Maity,
  • Simon Malcherek,
  • Burkhard König and
  • Julia Rehbein

Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

Graphical Abstract
  • (1,3,5-TMB•+) is formed indeed during the quenching process of the catalyst by 1,3,5-TMB (Scheme 5) ns-time-resolved transient absorption spectroscopy was used [50]. To allow for a decomposition of the multicomponent spectra we conducted laser flash photolysis (LFP) experiments on the single components
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Published 27 Sep 2018

A self-assembled photoresponsive gel consisting of chiral nanofibers

  • Lei Zou,
  • Dan Han,
  • Zhiyi Yuan,
  • Dongdong Chang and
  • Xiang Ma

Beilstein J. Org. Chem. 2018, 14, 1994–2001, doi:10.3762/bjoc.14.174

Graphical Abstract
  • absorption spectroscopy, circular dichroism, scanning electron microscopy and rheological techniques. This work provides a new method for facile synthesis of chiro-optical gels. Keywords: chirality; nanostructure; organogel; photoresponse; self-assembly; Introduction Supramolecular gels [1][2] immobilized
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Published 01 Aug 2018

An overview of recent advances in duplex DNA recognition by small molecules

  • Sayantan Bhaduri,
  • Nihar Ranjan and
  • Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

Graphical Abstract
  • absorption spectroscopy, viscosity measurement, cyclic voltammetry and molecular modeling (Figure 9) [93]. Docking results confirmed that these complexes have the ability to interact with the minor groove of the ct-DNA. In addition, the authors confirmed that in presence of ascorbic acid, these complexes
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Published 16 May 2018

Polarization spectroscopy methods in the determination of interactions of small molecules with nucleic acids – tutorial

  • Tamara Šmidlehner,
  • Ivo Piantanida and
  • Gennaro Pescitelli

Beilstein J. Org. Chem. 2018, 14, 84–105, doi:10.3762/bjoc.14.5

Graphical Abstract
  • ligand as a function of concentration and/or mixing ratios [3][5][6][9][18]. However, ECD relies on the difference in absorption between left and right circularly polarized light which makes it at least two orders of magnitude less sensitive than absorption spectroscopy [1][9]. ECD spectroscopy can give
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Published 08 Jan 2018

Photocatalytic formation of carbon–sulfur bonds

  • Alexander Wimmer and
  • Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

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  • from alkyl and aryl thiosulfates and aryl diazonium salts (Scheme 39) [74]. They confirmed by transient absorption spectroscopy that a single-electron transfer occurs between [Ru(bpy)3]Cl2 and the aryl diazonium salt. Additionally, electron paramagnetic resonance studies showed that K2CO3 interacts
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Published 05 Jan 2018

Pyrene–nucleobase conjugates: synthesis, oligonucleotide binding and confocal bioimaging studies

  • Artur Jabłoński,
  • Yannic Fritz,
  • Hans-Achim Wagenknecht,
  • Rafał Czerwieniec,
  • Tytus Bernaś,
  • Damian Trzybiński,
  • Krzysztof Woźniak and
  • Konrad Kowalski

Beilstein J. Org. Chem. 2017, 13, 2521–2534, doi:10.3762/bjoc.13.249

Graphical Abstract
  • , or oligothymidine, T10, respectively, as template strands were investigated in water. Due to the nearly complete insolubility of the chromophore–nucleobase conjugates in water it is possible to follow this self-assembly simply by UV–vis absorption spectroscopy (Figure 5). Only those chromophore
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Published 28 Nov 2017

New electroactive asymmetrical chalcones and therefrom derived 2-amino- / 2-(1H-pyrrol-1-yl)pyrimidines, containing an N-[ω-(4-methoxyphenoxy)alkyl]carbazole fragment: synthesis, optical and electrochemical properties

  • Daria G. Selivanova,
  • Alexei A. Gorbunov,
  • Olga A. Mayorova,
  • Alexander N. Vasyanin,
  • Igor V. Lunegov,
  • Elena V. Shklyaeva and
  • Georgii G. Abashev

Beilstein J. Org. Chem. 2017, 13, 1583–1595, doi:10.3762/bjoc.13.158

Graphical Abstract
  • properties of the prepared compounds were investigated by UV–vis absorption spectroscopy and cyclic voltammetry. Electrochemical oxidation of these heterocycles resulted in the formation of thin films on the surface of an ITO working electrode. The morphology of grown films has been investigated by means of
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Published 10 Aug 2017
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