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

• conformational changes in polymers. There may also be variations in the organization of large assemblies of molecules in gels or liquid crystals. When polarized light is used, the photoisomerization often induces a reorganization of chromophores that can be reflected in the circular dichroism spectra. The basic

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

• information in a quick fashion have attracted a growing interest within materials science during the last few decades. Although very fast photochromic switching materials working within hundreds of nanoseconds based on other chromophores, such as spiropyranes, have been successfully achieved, reaching such

• to the initial isomer even at elevated temperatures (e.g., fulgides and diarylethenes). ● T-type (thermally reversible type); the photogenerated isomer thermally reverts to the initial form (e.g., azobenzenes, stilbenes or spiropyranes). One of the most used organic chromophores for optical switching

• ultimately within the nanosecond or picosecond range. Even though some chromophores, such as spiropyranes, have been already proved to show very fast thermal back reactions occurring within hundreds of nanoseconds [21][22][23], reaching such fast relaxation times for azobenzene-based photochromic molecular

Synthesis and anion recognition properties of shape-persistent binaphthyl-containing chiral macrocyclic amides

• Marco Caricato,
• Nerea Jordana Leza,
• Claudia Gargiulli,
• Giuseppe Gattuso,
• Daniele Dondi and
• Dario Pasini

Beilstein J. Org. Chem. 2012, 8, 967–976, doi:10.3762/bjoc.8.109

• , centered at 320 nm (quite different from (R,R)-10). The CD spectra (in EtOH) show activity associated with all active UV chromophores and more marked activity for the macrocycle (R,R)-10, with exciton couplet signals greater in intensity than the ones of the other macrocycles. Molecular modeling Molecular

Diarylethene-modified nucleotides for switching optical properties in DNA

• Sebastian Barrois and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2012, 8, 905–914, doi:10.3762/bjoc.8.103

• molecular components represents an increasingly significant goal for the development of new photoreactive nanostructured architectures. Among those architectures, nucleic acids were proven to be an important scaffold for the precise arrangement of all kinds of chromophores inside or along the double helix

• chromophores to oligonucleotides offers potentially interesting optical characteristics, among these being solvatochromism and red-shifted exciplex-type fluorescence [38]. Such absorption and fluorescence readouts are potentially suitable for DNA probing [39][40][41]. On the other hand, with respect to

• reactivity the 5-position of pyrimidines (U/T and C) and the 8-position of purines (A and G) are preferred as chromophore modification sites. The assumption, that these points of attachment allow the chromophores to point into the major groove is only partially true, if at all. In particular, large and

Multistep organic synthesis of modular photosystems

• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2012, 8, 897–904, doi:10.3762/bjoc.8.102

• fill them with functional π-stacks of free choice. Keywords: asparagusic acid; charge-transfer cascades; chromophores; disulfide exchange; hydrazone exchange; molecular switches; naphthalenediimides; π-stacks; surface-initiated polymerization; Introduction The architecture of photosystem 1 is rather

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

• electronic communication between the chromophores [21][22][23][31]. It has also been shown that a 1,2,3-triazole can act as a strong σ-electron donor [26] or as a weak π-electron acceptor [15]. In this study, we aimed at the combination of electron-rich (oligo)thiophenes as donors and electron-deficient

Synthesis of szentiamide, a depsipeptide from entomopathogenic Xenorhabdus szentirmaii with activity against Plasmodium falciparum

• Friederike I. Nollmann,
• Andrea Dowling,
• Marcel Kaiser,
• Klaus Deckmann,
• Sabine Grösch,
• Richard ffrench-Constant and
• Helge B. Bode

Beilstein J. Org. Chem. 2012, 8, 528–533, doi:10.3762/bjoc.8.60

• -weight compounds with UV chromophores (e.g., isopropylstilbenes [4], anthraquinones [4], or xenorhabdines [5]. However, bioactivity-based or MS-based screening of crude extracts and culture supernatants led to the identification of larger compounds, such as the PAX peptides [6], the xenortides [7

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• diimidazoles, benzimidazoles, bis(benzimidazoles), imidazole-4,5-dicarbonitriles, and imidazole-derived chromophores chemically bound to a polymer chain. Keywords: charge transfer; chromophore; conjugation; donor–acceptor system; imidazole; Introduction Over the past three decades, great progress has been

• robustness, possibility for further modification, and facile property tuning. Hence, heteroaromatic push–pull chromophores have been targeted and investigated as active components of optoelectronic devices, organic light-emitting diodes (OLED), photovoltaic cells, semiconductors, switches, data-storage

• C5 in addition to N1. On the imidazole backbone, two principal orientations of the substituents are possible, and these are most frequently used to generate Y-shaped chromophores as shown in Figure 2. The donor appended through an additional π-linker to the imidazole C2, completed with two peripheral

Photochemical and thermal intramolecular 1,3-dipolar cycloaddition reactions of new o-stilbene-methylene-3-sydnones and their synthesis

• Kristina Butković,
• Željko Marinić,
• Krešimir Molčanov,
• Biserka Kojić-Prodić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2011, 7, 1663–1670, doi:10.3762/bjoc.7.196

• such a system, where two chromophores, stilbene and sydnone, are divided by a methylene bridge, an intramolecular 1,3-dipolar cycloaddition and the formation of diverse polycyclic compounds could be expected. Herein we describe, for the first time, the synthesis of cis- and trans-3-(stilbenylmethyl

One-pot four-component synthesis of pyrimidyl and pyrazolyl substituted azulenes by glyoxylation–decarbonylative alkynylation–cyclocondensation sequences

• Charlotte F. Gers,
• Julia Rosellen,
• Eugen Merkul and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2011, 7, 1173–1181, doi:10.3762/bjoc.7.136

• these intermediates into many classes of heterocycles [12][13][14][15]. These novel MCRs nicely correspond with diversity-oriented strategies towards functional organic chromophores [1][2]. The striking blue color of azulene (1a) (from the Spanish word “azul” = blue) has aroused scientific attention for

• -component approach to heterocyclic derivatives of azulene is well suited for the development of functional chromophores with extended π-conjugation. Selected resonance structures of azulene (1a) and structure of the sesquiterpene guaiazulene (1b). Synthesis of ynones by glyoxylation–decarbonylative

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

• of 7, where the included naphthalene chromophores are arranged in a right-handed screw [24]. As can be seen from Figure 3, naphthalene-capped γ-CD 6 gave only weak induced circular dichroism signals at the 1La and 1Bb bands of the naphthalene chromophore, the intensity of which was not concentration

Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 278–289, doi:10.3762/bjoc.7.37

• (trifluoromethyl)phenyl substituents. Notably, not even the commonly employed sensitizer acetone is capable of inducing the DPM rearrangement of 1i. Considering the different photophysical and photochemical properties of the carbonyl and thiocarbonyl chromophores [49], it may be that a similar difference exists

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

• on bisurea derivatives of bithiophene chromophores and demonstrated a significant charge carrier mobility as a result of self-assembly (Σμmin = 5 × 10−3 cm2 V−1 s−1) [18]. However, the building blocks were made only from mono and bithiophene units. Later, Shinkai and co-workers reported the gelation

• -type aggregate to monomeric building blocks at elevated temperature. The self-assembly of T1 at such low concentrations can be attributed to the synergistic effect of π-π-stacking among the oligothiophene chromophores and intermolecular hydrogen bonding between the amide groups of the neighbouring

• 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

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

• ; photoluminescence; solar cell; Introduction A useful strategy in the design of new polymers for electronic applications is to incorporate chromophores which are highly absorbing and emitting in the visible and near infrared region into π-conjugated polymers chains. Potentially useful chromophores for electronic

• . Strong hydrogen bonding between the lactam units favors the chromophores forming physically cross-linked chain structures in the solid state, which is the origin for the poor solubility [7][8]. Short distances between the chromophore planes (0.336 nm) and phenyl ring planes (0.354 nm) enable π-π

• , and the chromophore requires to be functionalized with polymerizable groups. The solubility can be increased by N-alkylation [10], arylation [11] or acylation [12] of the lactam units thus preventing hydrogen bond formation between the chromophores. Polymerizable groups can be attached to the aryl

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

• of the two contacting phases). This approach was developed to carry out functionalization reactions between the water-soluble PVAm and suitable chromophores [30] or fluorophores. In these reactions, silica can be considered as ‘solubilizer’ because PVAm, as well as the reactants, are consecutively

• NH2 groups of the PVAm on the UV–vis absorption maxima of the chromophore. Probably, the chains of the polymer are able to insulate the chromophores from the solvent molecules. Hence, the chromophores interact more strongly with the polymer chains than they do with the solvents. The HBD ability of the

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

• ion binding processes are direct absorption and emission measurements utilizing chromophores in the receptor or analyte molecule, displacement assays with suitable dyes, NMR titration experiments, isothermal titration calorimetry and transport through an organic phase monitored by HPLC, NMR [37][38

Synthetic incorporation of Nile Blue into DNA using 2′-deoxyriboside substitutes: Representative comparison of (R)- and (S)-aminopropanediol as an acyclic linker

• Daniel Lachmann,
• Sina Berndl,
• Otto S. Wolfbeis and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2010, 6, No. 13, doi:10.3762/bjoc.6.13

• similar within each duplex set, DNA1Y or DNA2Y. This is typical for chromophores as base surrogates [26][27][28][29][30][31][32][33][34][35][36] since they do not exhibit any preferential base pairing properties. The UV–vis absorption properties of all Nile Blue-modified duplexes are remarkably different

• experimental result can be imaged by geometrically optimized DNA models. Our result is remarkable regarding opposite results with the L-/D-threoninol linkers [37][38][39][40] that revealed strong differences in stacking and also in function of attached chromophores depending on the chirality of the linker. We

Synthesis of rigidified flavin–guanidinium ion conjugates and investigation of their photocatalytic properties

• Harald Schmaderer,
• Mouchumi Bhuyan and
• Burkhard König

Beilstein J. Org. Chem. 2009, 5, No. 26, doi:10.3762/bjoc.5.26

• Harald Schmaderer Mouchumi Bhuyan Burkhard Konig Institute of Organic Chemisty, University of Regensburg, Universitätsstr. 31, D-93040 Regensburg, Germany 10.3762/bjoc.5.26 Abstract Flavin chromophores can mediate redox reactions upon irradiation by blue light. In an attempt to increase their

• ; Introduction Flavins are redox-active chromophores [1][2][3][4][5][6] and represent one of the most abundant classes of natural enzyme co-factors [7][8][9]. Recently, the photo redox properties of flavins have been used to catalyze chemical reactions [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24

Synthesis of novel photochromic pyrans via palladium- mediated reactions

• Christoph Böttcher,
• Gehad Zeyat,
• Saleh A. Ahmed,
• Elisabeth Irran,
• Thorben Cordes,
• Cord Elsner,
• Wolfgang Zinth and
• Karola Rueck-Braun

Beilstein J. Org. Chem. 2009, 5, No. 25, doi:10.3762/bjoc.5.25

• was investigated by time-resolved absorption spectroscopy in the picosecond time domain. Keywords: benzopyrans; chromenes; naphthopyrans; palladium-mediated coupling reactions; photochromism; Introduction Interest in photoswitchable chromophores for the material and life sciences has increased

• dramatically over the past decade [1]. In the past, naphthopyrans were primarily commercialized as components for photochromic ophthalmic eyeware [2][3][4][5]. Nowadays, basic research in material sciences tries to implement photoswitchable pyrans and related chromophores as functional parts in organo

Reversible intramolecular photocycloaddition of a bis(9-anthrylbutadienyl)paracyclophane – an inverse photochromic system. (Photoactive cyclophanes 5)

• Henning Hopf,
• Christian Beck,
• Jean-Pierre Desvergne,
• Henri Bouas-Laurent,
• Peter G. Jones and
• Ludger Ernst

Beilstein J. Org. Chem. 2009, 5, No. 20, doi:10.3762/bjoc.5.20

• the cyclophane acting as a convenient scaffold, as demonstrated previously [18][19]. To avoid steric crowding and excessive distance between the chromophores, it seemed reasonable to select the rigid all-trans butadienyl tether as represented in compound 2 (see Figure 3). The synthesis, molecular

Convenient methods for preparing π-conjugated linkers as building blocks for modular chemistry

• Jiří Kulhánek,
• Filip Bureš and
• Miroslav Ludwig

Beilstein J. Org. Chem. 2009, 5, No. 11, doi:10.3762/bjoc.5.11

• most important goals of modern material chemistry. Organic chemists steadily attempt to design and synthesize novel and well-defined organic push-pull systems with prospective applications as chromophores for nonlinear optics (NLO) [1][2][3][4][5], dyes [6], electronic and photonic devices [7][8

• ) between the donor (D = NR2, OR groups etc.) and the acceptor (A = NO2, CN groups etc.) is most commonly comprised of double and triple bonds, aromatic and heteroaromatic rings as well as their combinations [14][15][16][17][18][19]. A typical synthetic approach to CT chromophores involves either a stepwise