2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

• Yury A. Sayapin,
• Inna O. Tupaeva,
• Alexandra A. Kolodina,
• Eugeny A. Gusakov,
• Vitaly N. Komissarov,
• Igor V. Dorogan,
• Nadezhda I. Makarova,
• Anatoly V. Metelitsa,
• Valery V. Tkachev,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2015, 11, 2179–2188, doi:10.3762/bjoc.11.236

• which has attracted much attention due to the applications in various molecular probes and luminescent materials because of the remarkable photophysical properties of the ESIPT (excited state intramolecular proton transfer) chromophores [33][34]. UV-irradiation of solutions of these compounds in

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

The chemical behavior of terminally tert-butylated polyolefins

• Dagmar Klein,
• Henning Hopf,
• Peter G. Jones,
• Ina Dix and
• Ralf Hänel

Beilstein J. Org. Chem. 2015, 11, 1246–1258, doi:10.3762/bjoc.11.139

• cases the terminal double bonds survive the cycloaddition process. Photochemical behavior Although oligo- and polyene substructures are present as chromophores in, inter alia, the visual pigments [12], the carotenoid antennae of photosynthesis [13][14], and vitamins A [15] and D [16], relatively little

Chiroptical properties of 1,3-diphenylallene-anchored tetrathiafulvalene and its polymer synthesis

• Masashi Hasegawa,
• Junta Endo,
• Seiya Iwata,
• Toshiaki Shimasaki and
• Yasuhiro Mazaki

Beilstein J. Org. Chem. 2015, 11, 972–979, doi:10.3762/bjoc.11.109

• systems having strong chiroptical properties because they have great potential for use in optical devices involving polarized light [1][2][3]. Chiral response, in electronic circular dichroism (ECD) based on an exciton coupling between two adequate π-chromophores, can express a pronounced chiroptical

• effect over various optical energy regions. Therefore, embedding the chromophores into a chiral rigid framework can be a practical molecular design for ascertaining chiroptical materials [4][5][6][7]. A symmetric allene framework is one of the most reliable chiral resources that can preserve a consistent

• orientation of the chromophores [8][9]. We recently introduced 1,3-bis(tetrathiafulvalenyl)allene derivatives 1, as a new class of chiral electrochromic (EC) materials consisting of redox-active chromophores and a non-centrochiral framework (Figure 1) [10]. The intensive Cotton effect on the ECD spectra is

Discrete multiporphyrin pseudorotaxane assemblies from di- and tetravalent porphyrin building blocks

• Mirko Lohse,
• Larissa K. S. von Krbek,
• Sebastian Radunz,
• Suresh Moorthy,
• Christoph A. Schalley and
• Stefan Hecht

Beilstein J. Org. Chem. 2015, 11, 748–762, doi:10.3762/bjoc.11.85

• interactions, i.e., exciton coupling, between the two porphyrin chromophores seems to be rather weak. For mass spectrometric analysis (ESI-Q-TOF MS) of the desired pseudorotaxanes separate solutions of hosts and guests were prepared (CH2Cl2, A2/C2: 0.6 mM, A4/C4: 0.3 mM). They were mixed in the respective 1:1

Photocatalytic nucleophilic addition of alcohols to styrenes in Markovnikov and anti-Markovnikov orientation

• Martin Weiser,
• Sergej Hermann,
• Alexander Penner and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2015, 11, 568–575, doi:10.3762/bjoc.11.62

• -Markovnikov-type addition of cyanide to styrene [18]. Recently, we showed by a library of different chromophores that 1-(N,N-dimethylamino)pyrene (Py) can be applied as photocatalyst for the nucleophilic addition of methanol to styrene derivatives into the Markovnikov orientation [19]. Most recently, Nicewicz

An improved procedure for the preparation of Ru(bpz)₃(PF₆)₂ via a high-yielding synthesis of 2,2’-bipyrazine

• Danielle M. Schultz,
• James W. Sawicki and
• Tehshik P. Yoon

Beilstein J. Org. Chem. 2015, 11, 61–65, doi:10.3762/bjoc.11.9

• ; palladium; photocatalysis; reductive coupling; Findings Visible light-photoredox catalysis using transition metal chromophores is rapidly becoming recognized as an important strategy in organic synthesis [1][2][3][4][5]. This approach towards reaction design enables the facile generation and exploitation

• of odd-electron intermediates such as radicals and radical ions under exceptionally mild reaction conditions. A large number of transition metal chromophores with well-characterized photophysical and electrochemical properties are known, and the influence of ligand modification on the photoredox

• properties of these complexes is well understood [6][7][8]. As a result, a variety of Ru and Ir based chromophores spanning a range of redox potentials have recently become widely utilized in the design of new photocatalytic transformations [9]. In particular, the homoleptic tris(bipyrazyl) complex 2 (Ru(bpz

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

• . The obtained results [92][93][94] stress the importance of DNA-basepair dynamics for the electronic transfer processes in DNA-stacks. The efficiency of transfer is rather more controlled by motions of chromophores involved in aromatic stacking of DNA-reporter complex than with rigid aryl-stacking

Molecular recognition of AT-DNA sequences by the induced CD pattern of dibenzotetraaza[14]annulene (DBTAA)–adenine derivatives

• Marijana Radić Stojković,
• Marko Škugor,
• Łukasz Dudek,
• Jarosław Grolik,
• Julita Eilmes and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2175–2185, doi:10.3762/bjoc.10.225

• intercalator). There are several possible explanations for the observed hypochromic effect, including the intramolecular stacking of DBTAA with adenine or the intermolecular stacking of two DBTAA chromophores within DNA/RNA grooves, a solvatochromic effect in the DNA/RNA binding site, and even a weak partial

• polynucleotides. Such an unspecific binding mode (possible locations are minor/major groove, not excluding weak partial intercalation of the DBTAA moiety) results in DBTAA chromophores characterized by a variety of orientations oriented variously in respect to the DNA/RNA chiral axis, which can yield the observed

Photorelease of phosphates: Mild methods for protecting phosphate derivatives

• Sanjeewa N. Senadheera,
• Abraham L. Yousef and
• Richard S. Givens

Beilstein J. Org. Chem. 2014, 10, 2038–2054, doi:10.3762/bjoc.10.212

• studies substantiated the generality of the meta effect for phosphate leaving groups in heterolytic photoreactions. Over the past four decades, additional examples of phosphate esters attached to reactive chromophores other than phenyl and benzyl [6][7][8][9][10][11] have been investigated for their

• propensity to undergo heterolytic photosolvolysis reactions, most notably o-nitrobenzyl (o-NB) [12], benzyl phenyl ketone (benzoin) [13][14], coumarin-4-ylmethyl [15], and, more recently, p-hydroxyphenacyl (pHP) [15] phosphate esters (Figure 1). While these chromophores exhibit a range of photophysical

• properties, all share a conjugated aromatic structural motif that facilitates UV–vis absorption and serves as a traceless reagents, orthogonal to common ground state deprotection processes and essentially independent of pH effects. Thus, the chromophores are particularly useful at neutral pH and no added

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

• stability, processability, and semiconductor device performance. Intermolecular π–π-interactions between chromophores can be dramatically improved upon functionalization at the 6- and 13-positions of pentacene, as demonstrated by the two-dimensional (2D) bricklayer-packing motif for TIPSPc [13][14]. A

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

• aedamers (aromatic electron donor acceptor oligomers) pioneered by Iverson and coworkers [18][36][37]. They consist of face-to-face stacked electron-rich naphthalene and electron-poor naphthalenediimide (NDI) chromophores and belong to the broader area of foldamers [38]. DNA has been described as a

• molecular scaffold for arranging various types of chromophores [39][40][41][42][43][44]. Recently, we reported that oligoarenotides (oligomers with an alternating phosphodiester-aromatic hydrocarbon motif) exhibit similar structural properties as nucleic acids, and although the aromatic hydrocarbons cannot

• (PDI, E). PDIs (Figure 1A) are some of the most widely studied organic chromophores [49][50][51][52]. Moreover, we have reported on the aggregation and stacking properties of 1,8- and 1,6-dialkynylpyrene [53][54]. Figure 1B shows the electrostatic potential surface of 1,8-diprop-1-ynylpyrene and N,N

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

• approximation. Keywords: absorption spectroscopy; cyclic voltammetry; chromophores; fluorescence; multicomponent reactions; photo-induced electron transfer; Introduction Chromophores, fluorophores, and electrophores, are functional organic materials [1] and constitute active components in molecular

• diversity-oriented syntheses of chromophores [62][63][64][65][66][67][68][69] we have established accesses to chromophores in a one-pot fashion based upon transition metal catalysis as an entry to consecutive multicomponent [70][71] and domino reactions [72]. The highly convergent synthetic approach by

• ) compounds. Plotting the extinction coefficient against the wavelength it becomes evident that the Do–anthraquinone dyads behave additively with respect to the constituent reference chromophores (Figure 6). Absorption spectroscopy as a probe for the electronic ground state also supports that in Do

Rapid pseudo five-component synthesis of intensively blue luminescent 2,5-di(hetero)arylfurans via a Sonogashira–Glaser cyclization sequence

• Fabian Klukas,
• Alexander Grunwald,
• Franziska Menschel and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 672–679, doi:10.3762/bjoc.10.60

• reaction efficiency and atom economy. Besides lead finding in pharmaceutical and medicinal chemistry [8][9][10] MCRs have also been recognized as a DOS tool for approaching functional π-systems [11] such as luminescent chromophores [6]. Interestingly, multicomponent syntheses of symmetrically substituted

• African trypanosomiasis [18][19][20], and against human renal cancer cells [21][22][23]. Furthermore, 2,5-di(hetero)arylfurans have been reported as photonic chromophores [24]. However, the electronic and photophysical properties of 2,5-di(hetero)aryl furans have only been occasionally studied [25][26][27

One-pot three-component synthesis and photophysical characteristics of novel triene merocyanines

• Christian Muschelknautz,
• Robin Visse,
• Jan Nordmann and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 599–612, doi:10.3762/bjoc.10.51

• reactions; Introduction Functional organic materials [1], such as chromophores, fluorophores, and electrophores, constitute the active components in molecular electronics [2], photonics [3], and bioanalytics [4][5][6]. Among many chromophores the class of merocyanines [7][8][9], i.e. α-donor-ω-acceptor

• -substituted polyenes, has become increasingly interesting due to their fine-tunable electronic distribution [10]. For instance, merocyanines are perfectly suited for developing molecule-based non-linear optical materials and photovoltaic chromophores [11]. Classically, these push–pull chromophores always have

• , and photophysics. Inspired by the concept of a diversity-oriented synthetic approach to chromophores [19][20][21][22][23][24][25][26] we have launched a program to apply transition metal-catalyzed processes as an entry to consecutive multicomponent [27][28] and domino reactions [29]. These highly

Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

• Dae Won Cho,
• Patrick S. Mariano and
• Ung Chan Yoon

Beilstein J. Org. Chem. 2014, 10, 514–527, doi:10.3762/bjoc.10.47

• , each as a mixture of diastereomers. In these processes, SET from the terminal α-silyl ether donor sites to the excited phthlaimide chromophores produces zwitterionic biradicals 50, which then undergo methanol-assisted desilylation to form biradicals 52, whose cyclization by C–C bond formation produced

Self-assembly of 2,3-dihydroxycholestane steroids into supramolecular organogels as a soft template for the in-situ generation of silicate nanomaterials

• Valeria C. Edelsztein,
• Andrea S. Mac Cormack,
• Matías Ciarlantini and
• Pablo H. Di Chenna

Beilstein J. Org. Chem. 2013, 9, 1826–1836, doi:10.3762/bjoc.9.213

• a self-supporting gel. There are several types of cholesterol-based LMOGs grafted on hydrophilic heads such as saccharides, chromophores, ligands, peptides, etc. The first study on rational syntheses of cholesterol derived organogels was made by Weiss et al. [23] on a family of molecules containing

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

• excitonic cotton effects (Figure 3c–f). In DMSO, 2 (Figure 3c) and 3 (Figure 3e) exhibit a weak CD signal above 350 nm suggesting minimal excitonic coupling of NDI chromophores. However, CD studies for 2 (Figure 3d) and 3 (Figure 3f) in NMP show positive excitonic cotton effects indicating P-type helicity

• . In aqueous DMSO as well as in aqueous NMP both 2 and 3 tend to approach towards CD silencing. The relatively bulkier side chain functionality of the interlinking amino acids in 2 and 3 is believed to inhibit the effective excitonic coupling of the chromophores in lower percentages (≤ 60%) of the

• aqueous solution. However, at higher percentages of the aqueous solution the enhanced hydrophobic forces render transition of the angles between transition dipole moments of the stacked chromophores towards zero, resulting in CD silencing. Moreover, the relative differences between the CD features of 2

New core-pyrene π structure organophotocatalysts usable as highly efficient photoinitiators

• Sofia Telitel,
• Frédéric Dumur,
• Thomas Faury,
• Bernadette Graff,
• Mohamad-Ali Tehfe,
• Didier Gigmes,
• Jean-Pierre Fouassier and
• Jacques Lalevée

Beilstein J. Org. Chem. 2013, 9, 877–890, doi:10.3762/bjoc.9.101

• -performance PIs and PICs are continuously being developed [1][2][3][4][5][6][7][8][9][10] through the design of novel structures (e.g., novel chromophores, novel cleavable bonds) and the modification ofexisting structures by using the classical introduction of electron-donating or -withdrawing substituents

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

• photophysical properties studied [33][34][35][36][37][38]. However, to our knowledge, tpy-functionalized dendritic oligothiophenes have not been synthesized so far. The complexation of these dendrons could lead to interesting nanosized materials containing different chromophores to study electronic energy

• -ethynylene moieties [26]. In comparison with the absorption spectra of dendrons 6 and 7 [42], a significant spectral broadening was observed for these ligands, indicative of extended conjugation and more delocalized electronic distribution between tpy and ethynylene-thienylene chromophores. The results were

A chemist and biologist talk to each other about caged neurotransmitters

• Graham C.R. Ellis-Davies

Beilstein J. Org. Chem. 2013, 9, 64–73, doi:10.3762/bjoc.9.8

• fully understood. What is known is that similarly caged Glu and GABA probes (e.g., CDNI-Glu and -GABA) both block GABA-A receptors with the same efficacy, implying that the amino acid is not crucial. Furthermore, the diversity of the structures of caging chromophores (Figure 1) implies that one specific

• rings to produce photosensitivity. The simplest type of caging chromophores are quite water soluble (Table 1), but even modest derivatives can lose water solubility precipitously! With drugs this is often counteracted by adding betacyclodextrin to the formulation, and with caged compounds, a small

• of an issue. It is important for chemists to know that we usually make up stock solutions that are at least 10 times higher than those used, therefore we would look for water solubility in the 50–100 mM range. Chemist: This can easily be achieved for caged transmitters with simple chromophores such

A bisazobenzene crosslinker that isomerizes with visible light

• Subhas Samanta,
• Harris I. Qureshi and
• G. Andrew Woolley

Beilstein J. Org. Chem. 2012, 8, 2184–2190, doi:10.3762/bjoc.8.246

• of a new crosslinker in which a central piperazine unit links two azobenzene chromophores. Molecular modeling indicates that this crosslinker can undergo a large change in end-to-end distance upon trans,trans to cis,cis isomerization. Photochemical characterization indicates that it does isomerize

• chromophores completely, while providing N-centered lone pairs to extend the π-system of each independent azo unit. In this manner, independent photoswitching behavior of the two units at wavelengths shifted towards the visible range was expected to occur. Results and Discussion The p-diacetamido piperazine

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

• lifetimes of a few hundred hours, which can be extended considerably if left on. They can be used for general-purpose photochemistry and are particularly suited for chromophores absorbing strongly in the 290–400 nm region. The glassware used for the immersion-well is particularly important as it functions

Palladium-catalyzed dual C–H or N–H functionalization of unfunctionalized indole derivatives with alkenes and arenes

• Gianluigi Broggini,
• Egle M. Beccalli,
• Andrea Fasana and
• Silvia Gazzola

Beilstein J. Org. Chem. 2012, 8, 1730–1746, doi:10.3762/bjoc.8.198

• role in the discovery of active antitumor drugs [29][30][31]. Carbazole derivatives also find applications in organic materials as chromophores and photoconductors [32]. For several years, the development of methodologies concerning indole synthesis and functionalization has been one of the most

Partial thioamide scan on the lipopeptaibiotic trichogin GA IV. Effects on folding and bioactivity

• Marta De Zotti,
• Barbara Biondi,
• Cristina Peggion,
• Matteo De Poli,
• Haleh Fathi,
• Simona Oancea,
• Claudio Toniolo and
• Fernando Formaggio

Beilstein J. Org. Chem. 2012, 8, 1161–1171, doi:10.3762/bjoc.8.129

• of these three isomeric peptides between 195 and 250 nm because, in addition to the expected Cotton effects of the peptide chromophores [57][58], the thioamide chromophore [34][35] is also known to contribute heavily in this spectral region. However, we can safely state that the shape of the CD