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

• for the 5,8-BQA phosphate 24 occurs at 321 nm in 10% aq MeCN. For the 2,6-HNA series, a strong fluorescence emission is observed at 470 nm as shown here for the more aqueous soluble GABA ester derivative. The 2,6-HNA GABA had better aqueous solubility for fluorescence studies. (See Supporting

• protecting groups (PPGs) for phosphates depicted as diethyl phosphate (DEP) esters. A. UV–vis spectrum of 14a (1,4-HNA DEP) in 1% aq MeCN. B. Fluorescence emission/excitation spectra of 2,6-HNA GABA (0.042 mM) in pH 7.3 TRIS buffer containing 1% MeCN. Naphthyl and quinolin-5-yl caged phosphate esters 10, 14

Synthesis of new, highly luminescent bis(2,2’-bithiophen-5-yl) substituted 1,3,4-oxadiazole, 1,3,4-thiadiazole and 1,2,4-triazole

• Anastasia S. Kostyuchenko,
• Vyacheslav L.Yurpalov,
• Aleksandra Kurowska,
• Wojciech Domagala,
• Adam Pron and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2014, 10, 1596–1602, doi:10.3762/bjoc.10.165

• dichloromethane. Optimum fluorescence excitation wavelengths (given in the legends) have been selected based on fluorescence emission profiles. Photoluminescence quantum yields measured for 13, 15 and 18 together with their formulae. Synthesis of ethyl 3-decyl-2,2'-bithiophene-5-carboxylate (3). Synthesis of

Pyrene-modified PNAs: Stacking interactions and selective excimer emission in PNA₂DNA triplexes

• Alex Manicardi,
• Lucia Guidi,
• Alice Ghidini and
• Roberto Corradini

Beilstein J. Org. Chem. 2014, 10, 1495–1503, doi:10.3762/bjoc.10.154

• units in the PNA:DNA complexes. In Figure 2 the fluorescence emission spectra of the PNA probes in the absence or in the presence of complementary DNA1 or mismatched DNA2 are reported. For PNA1, having only one pyrene unit, a typical pyrene excimer band was observed in the presence of DNA1 (Figure 2a

• , but of the entire triplex, leading to high mismatch recognition. This induces the very high selectivity in the switch-on of the excimer fluorescence emission (Figures 2, 3 and 4). All the other tested dispositions are not so effective in terms of stabilization, fluorescence response and selectivity

• incubated at 90 °C for 5 min, and then slowly cooled to the temperature of analysis. Fluorescence emission spectra were recorded with an excitation wavelength of 347 nm (slit excitation: 5.0 nm), scanning from 370 nm to 550 nm (slit emission: 10.0 nm), a scan speed of 200 nm/min was used with 3 spectra

Multichromophoric sugar for fluorescence photoswitching

• Stéphane Maisonneuve,
• Rémi Métivier,
• Pei Yu,
• Keitaro Nakatani and
• Juan Xie

Beilstein J. Org. Chem. 2014, 10, 1471–1481, doi:10.3762/bjoc.10.151

• and b show that upon increasing irradiation times at 335 nm, an absorption band at 600 nm emerges, corresponding to the photochromic moiety in its thermally stable closed form, and the fluorescence emission is concomitantly quenched by 51%. As displayed in Figure 3, the emission band of the

• conversion yield (53%) corresponds almost to the fluorescence quenching (51%), the FRET process appears to be extremely efficient: under irradiation at 335 nm, half of the multichromophoric system is still in its initial open form 2-OF, associated with a strong fluorescence emission, and another half are

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

• exhibited only an incremental red shift of absorption maxima similar to that observed in the case of 3, in aqueous DMSO (see Supporting Information File 1). In addition, the fluorescence emission for 1, 2 and 3 was found to be quenched in DMSO and NMP as well as in their aqueous medium (Figure 2b

• DMSO for various percentages of water in DMSO. Excitation at 345 nm. For comparison fluorescence emission spectra of pyrenemethylamine hydrochloride is shown (black trace, pyrene) in (b). (c) UV–vis spectra of 1 mM solutions of 1, 2 and 3 in 40% aqueous DMSO/NMP show the charge-transfer bands. The

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

• recorded on a Perkin Elmer Lambda 19 spectrometer and fluorescence emission spectra on a Perkin Elmer LS 55 spectrometer. Emission quantum yields of ligands and complexes were measured using 9,10-diphenylanthracene (Φf = 0.9 in cyclohexane) [54] and [Ru(bpy)3][PF6]2 (Φf = 0.062 in acetonitrile) [55] by

A new synthetic protocol for coumarin amino acid

• Xinyi Xu,
• Xiaosong Hu and
• Jiangyun Wang

Beilstein J. Org. Chem. 2013, 9, 254–259, doi:10.3762/bjoc.9.30

• mM sodium phosphate buffer (pH 5.8–8.0) or sodium acetate buffer (pH 3.7–5.6). Effect of the pH value of the solution on the fluorescence emission spectra of compounds 1b and 1c. (A) Fluorescence emission spectrum of compound 1b. (B) Fluorescence emission spectrum of compound 1c. Synthetic route to

Hydrophobic analogues of rhodamine B and rhodamine 101: potent fluorescent probes of mitochondria in living C. elegans

• Laurie F. Mottram,
• Safiyyah Forbes,
• Brian D. Ackley and
• Blake R. Peterson

Beilstein J. Org. Chem. 2012, 8, 2156–2165, doi:10.3762/bjoc.8.243

• ]. Photophysical and physicochemical properties The absorbance (panel A) and fluorescence emission (panel B) spectra of fluorophores 4, 5, and 8–10 are shown in Figure 2. The red-shifted spectra of HR101 10 compared with HRB 9 can be explained by greater delocalization of the lone pairs on nitrogen due to

• ). The ratio of fluorescence emission at λmax was used to calculate log D. Biological evaluation The N2 strain of C. elegans was cultured as described [47] and maintained at 20–22.5 °C. Fluorophores were added to normal growth media (NMG) liquid (at 45–55 °C), poured into Petri dishes (60 mm), and

• rhodamine (HRB, 9, and HR101, 10). Normalized absorbance (Panel A) and fluorescence emission (Panel B) spectra. Fluorophores were analyzed at 10 µM (absorbance) or 5 nM (fluorescence) in MeOH. The spectra for rhodamine 123 (4) in MeOH were downloaded from a publically accessible database [41]. Maximum

The effect of the formyl group position upon asymmetric isomeric diarylethenes bearing a naphthalene moiety

• Renjie Wang,
• Shouzhi Pu,
• Gang Liu and
• Shiqiang Cui

Beilstein J. Org. Chem. 2012, 8, 1018–1026, doi:10.3762/bjoc.8.114

• nm respectively. In comparison with those of 1o–3o in hexane, the fluorescence emission peaks of 1o–3o in PMMA films consistently exhibited a remarkable bathochromic shift. The emission intensity of the ortho-substituted derivative 3o was the strongest, while that of the para-substituted derivative

• 1o was the weakest in both hexane and PMMA films. Compared to the unsubstituted parent diarylethene, 1-(2-methylnaphth-1-yl)-2-[2-methyl-5-phenylthien-3-yl]perfluorocyclopentene (Φf = 0.011) [37], the fluorescence emission intensities of diarylethenes 1o and 2o were decreased, but that of 3o was

• the fluorescence emission intensity of diarylethenes with a naphthalene moiety. Diarylethenes 1–3 exhibited an evident fluorescence switching capability upon changing from the open-ring to the closed-ring isomers by photoirradiation in both hexane and PMMA films. When irradiated by UV light, the

Synthesis, solid-state fluorescence properties, and computational analysis of novel 2-aminobenzo[4,5]thieno[3,2-d]pyrimidine 5,5-dioxides

• Kenichirou Yokota,
• Masayori Hagimori,
• Naoko Mizuyama,
• Yasuhisa Nishimura,
• Hiroshi Fujito,
• Yasuhiro Shigemitsu and
• Yoshinori Tominaga

Beilstein J. Org. Chem. 2012, 8, 266–274, doi:10.3762/bjoc.8.28

• )aluminium (Alq3) was used as the standard for fluorescence spectrum measurements [17]. We analyzed the solid-state fluorescence emission spectra of 3a–g, 6 and 7 at room temperature. The fluorescence maxima (λem,max) and relative fluorescence intensities (RI) of these compounds are listed in Table 2. The

Fluorescent hexaaryl- and hexa-heteroaryl[3]radialenes: Synthesis, structures, and properties

• Antonio Avellaneda,
• Courtney A. Hollis,
• Xin He and
• Christopher J. Sumby

Beilstein J. Org. Chem. 2012, 8, 71–80, doi:10.3762/bjoc.8.7

• calculations that show intramolecular charge transfer character in the lowest excited states for hexaaryl[3]radialene derivatives [42]. In the excited state, rotation about the exocyclic bonds of the cyclopropane ring is also possible. The fluorescence emission of the hexaaryl[3]radialenes, coupled with the

• )[3]radialene in acetone. Synthesis of (a) hexakis(3-cyanophenyl)[3]radialene (2) and (b) hexakis(3,4-dicyanophenyl)[3]radialene (3). Electrochemical potentials for the synthesised [3]radialenes 1–3 and related compounds. Visible absorption maxima, molar extinction coefficient ε and fluorescence

• emission maxima for various hexaaryl[3]radialene compounds. Supporting Information Supporting Information File 9: 1H and 13C NMR spectra of all compounds, cyclic voltammograms of hexaaryl[3]radialenes, crystal data and structure refinement for 3. Supporting Information File 10: Crystallographic

Synthesis of dye/fluorescent functionalized dendrons based on cyclotriphosphazene

• Aurélien Hameau,
• Sabine Fuchs,
• Régis Laurent,
• Jean-Pierre Majoral and
• Anne-Marie Caminade

Beilstein J. Org. Chem. 2011, 7, 1577–1583, doi:10.3762/bjoc.7.186

• ), fluorescence emission (excitation wavelength 347 nm) (λem), and quantum yield (Φ) (reference: quinine sulfate) of compound 10 in mixtures of water/dioxane with different molar fractions (x) of water in 1,4-dioxane. Supporting Information Supporting Information File 289: Experimental details. Supporting

Ratiometric fluorescent probe for enantioselective detection of D-cysteine in aqueous solution

• Xiao-bo Zhou,
• Wing-Hong Chan,
• Albert W. M. Lee and
• Chi-Chung Yeung

Beilstein J. Org. Chem. 2011, 7, 1508–1515, doi:10.3762/bjoc.7.176

• enantioselectivity on Cys for the first time. Experimental Proton NMR spectra were recorded on a Bruker Avance-III 400 spectrometer at 400 MHz in DMSO-d6. Fluorescence emission spectra and UV–vis spectra were collected on a PE LS50B and a Cary UV-100 spectrometer, respectively. All inorganic reagents and amino acid

Fluorometric recognition of both dihydrogen phosphate and iodide by a new flexible anthracene linked benzimidazolium-based receptor

• Kumaresh Ghosh and
• Debasis Kar

Beilstein J. Org. Chem. 2011, 7, 254–264, doi:10.3762/bjoc.7.34

• optimized geometry of 1 with H2PO4− (E = 92.14 kcal/mol, a = 2.45 Å, b = 1.94 Å, c = 2.34 Å, d = 2.82 Å). Change in fluorescence emission of 1 (c = 5.78 × 10−5 M) in the presence of 2 equiv of tetrabutylammonium salts of different guests in CH3CN. Change in emission spectra of 1 (c = 5.78 × 10−5 M) in

• with H2PO4−. Change in fluorescence emission of 2 (c = 3.93 × 10−5 M) in the presence of 1 equiv of tetrabutylammonium salts of different guests in CH3CN. Stern–Volmer plots for 1 (c = 5.78 × 10−5 M) with H2PO4−, F−, Br− and I− at 420 nm (up to the addition of 2 equiv of guest) in CH3CN. Change in UV

• –vis spectra of 1 (c = 5.78 × 10−5 M) in presence of increasing amounts of H2PO4− in CH3CN. Change in fluorescence emission of 1 (c = 5.78 × 10−5 M) in the presence of 2 equiv of tetrabutylammonium salts of different guests in CHCl3 containing 0.1% CH3CN. Stern–Volmer plots for 1 (c = 5.78 × 10−5 M

An easy assembled fluorescent sensor for dicarboxylates and acidic amino acids

• Xiao-bo Zhou,
• Yuk-Wang Yip,
• Wing-Hong Chan and
• Albert W. M. Lee

Beilstein J. Org. Chem. 2011, 7, 75–81, doi:10.3762/bjoc.7.11

• intensity limit on adding excess anion, CA is the concentration of the anion added, and CH is the concentration of the host molecule. The changes in the fluorescence emission spectra of sensor 1 (5.0 × 10−6 M) upon addition of isophthalate in acetonitrile. λex = 366 nm. (Inset) Quenching ratio of sensor 1

A new fluorescent chemosensor for fluoride anion based on a pyrrole–isoxazole derivative

• Zhipei Yang,
• Kai Zhang,
• Fangbin Gong,
• Shayu Li,
• Jun Chen,
• Jin Shi Ma,
• Lyubov N. Sobenina,
• Albina I. Mikhaleva,
• Guoqiang Yang and
• Boris A. Trofimov

Beilstein J. Org. Chem. 2011, 7, 46–52, doi:10.3762/bjoc.7.8

• deprotonation rather than the formation of hydrogen bond. Figure 6 shows the changes of fluorescence emission of 1 upon addition of F− in CH3CN where the emission maximum was red-shifted to 432 nm. With increasing F− concentration, the emission intensity was quenched by about 90% when 50 equiv of F− was added

• log K2 = 6.38 ± 0.15, respectively [17][18] (Figure 7). Studies on reaction with hydroxide (OH−) Tetrabutylammonium hydroxide was added to the solution of 1 in CH3CN to investigate the above process. Changes in fluorescence emission of 1 upon addition of F− and OH− in CH3CN were almost the same

• , except for the degree of quenching, as shown in Figure 8. Upon the addition of 5 equiv of OH− the fluorescence emission of receptor 1 displayed λmax at 408 nm and the intensity was quenched by about 51%. On the other hand, upon addition of F− the emission displayed λmax at 405 nm but the intensity was

Donor-acceptor substituted phenylethynyltriphenylenes – excited state intramolecular charge transfer, solvatochromic absorption and fluorescence emission

• Ritesh Nandy and
• Sethuraman Sankararaman

Beilstein J. Org. Chem. 2010, 6, 992–1001, doi:10.3762/bjoc.6.112

• absorption and fluorescence emission properties of these molecules have been studied in solvents of different polarity. For a given derivative, solvent polarity had minimal effect on the absorption maxima. However, for a given solvent the absorption maxima red shifted with increasing conjugation of the

• substituent. The fluorescence emission of these derivatives was very sensitive to solvent polarity. In the presence of strongly electron withdrawing (–CN) and strongly electron donating (–NMe2) substituents large Stokes shifts (up to 130 nm, 7828 cm−1) were observed in DMSO. In the presence of carbonyl

• . These results indicate that the fluorescence emission arises from excited state intramolecular charge transfer in these molecules where the triphenylene chromophore acts either as a donor or as an acceptor depending upon the nature of the substituent on the phenyl ring. HOMO–LUMO energy gaps have been

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

• -dimethylcyclodextrin or by pre-adsorption onto silica particles. Furthermore, 1 was converted with isopropylamine into the model compound 1-M. All new compounds were characterized by NMR, FTIR, UV–vis and fluorescence spectroscopy. The solvent-dependent UV–vis absorption and fluorescence emission band positions of the

• possible [32]. The fluorescence emission maxima of 1-M and 1-P are shown in Table 4. Figure 5 shows an UV–vis absorption spectrum and a fluorescence emission spectrum of 1-M and 1-P measured in methanol as well as a photograph of solutions of these compounds. Similar to the UV–vis measurements, 1-M shows

• the longest-wavelength emission maximum in DMSO at λmax = 595 nm and 1-P in ethanol at λmax = 586 nm. The longest hypsochromic shifts of the fluorescence emission maximum were observed at λmax(1-M) = 577 nm in HFIP and λmax(1-P) = 561 nm in DMMA. These band shifts correspond to a small solvatochromic

Synthesis of indolo[3,2-b]carbazole-based new colorimetric receptor for anions: A unique color change for fluoride ions

• Ajit Kumar Mahapatra,
• Giridhari Hazra and
• Prithidipa Sahoo

Beilstein J. Org. Chem. 2010, 6, No. 12, doi:10.3762/bjoc.6.12

• a quenching results from a hydrogen bond interaction of phenolic OH with anions, which leads to the stabilization of the nπ* state with respect to the ππ* state and a subsequent decrease in the fluorescence emission intensity [51]. Analogous investigation of fluorescence was carried out with other

Quinoline based receptor in fluorometric discrimination of carboxylic acids

• Kumaresh Ghosh,
• Suman Adhikari,
• Asoke P. Chattopadhyay and
• Purnendu Roy Chowdhury

Beilstein J. Org. Chem. 2008, 4, No. 52, doi:10.3762/bjoc.4.52

• compounds were characterized using 1H NMR, 13C, mass, IR and UV spectroscopic methods. Interaction studies UV-vis study The sensitivity and selectivity of the receptors 1 and 2 were evaluated by observing the changes in 1H NMR, UV-vis and fluorescence emission in CHCl3. Initially, the photophysical

Synthesis of deep- cavity fluorous calix[4]arenes as molecular recognition scaffolds

• Maksim Osipov,
• Qianli Chu,
• Steven J. Geib,
• Dennis P. Curran and
• Stephen G. Weber

Beilstein J. Org. Chem. 2008, 4, No. 36, doi:10.3762/bjoc.4.36

• fluorescence emission (as observed qualitatively on TLC). An increase in fluorescence emission was observed with 7, 8, and 9 as compared to the single aryl ring analogs, and allows for better applications of the scaffold as a sensor [8][37]. Conclusion Deep-cavity functionalized fluorous calix[4]arenes that