A multifunctional fluorescent sensor based on a cyclen-appended BINOL derivative (R-1) was synthesized and characterized. It can display on-off-type fluorescence change with high selectivity toward ...Cu(II) among 19 metal ions in 100% aqueous solution. Furthermore, the in situ generated R-1-Cu(II) ensemble could recover the quenched fluorescence upon the addition of sulfide anion resulting in a off-on-type sensing with a detection limit of micromolar range in the same medium. No interference was observed from other biothiols and anions, including GSH, l-Cys, DTT, and sulfates, making it a highly sensitive and selective sulfide probe.
We used iodo-Bodipy derivatives that show strong absorption of visible light and long-lived triplet excited states as organic catalysts for photoredox catalytic organic reactions. Conventionally most ...of the photocatalysts are based on the off-the-shelf compounds, usually showing weak absorption in the visible region and short triplet excited state lifetimes. Herein, the organic catalysts are used for two photocatalyzed reactions mediated by singlet oxygen ((1)O2), that is, the aerobic oxidative coupling of amines and the photooxidation of dihydroxylnaphthalenes, which is coupled to the subsequent addition of amines to the naphthoquinones, via C-H functionalization of 1,4-naphthoquinone, to produce N-aryl-2-amino-1,4-naphthoquinones (one-pot reaction), which are anticancer and antibiotic reagents. The photoreactions were substantially accelerated with these new iodo-Bodipy organic photocatalysts compared to that catalyzed with the conventional Ru(II)/Ir(III) complexes, which show weak absorption in the visible region and short-lived triplet excited states. Our results will inspire the design and application of new organic triplet photosensitizers that show strong absorption of visible light and long-lived triplet excited state and the application of these catalysts in photoredox catalytic organic reactions.
Specific chemical reactions by enzymes acting on a nucleobase are realized by flipping the target base out of the helix. Similarly, artificial oligodeoxynucleotides (ODNs) can also induce the base ...flipping and a specific chemical reaction. We now report an easily prepared and unique structure-providing photo-cross-linking reaction by taking advantage of the base-flipping-out field formed by alkene-type base-flipping-inducing artificial bases. Two 3-arylethenyl-5-methyl-2-pyridone nucleosides with the Ph or An group were synthesized and incorporated into the ODNs. We found that the two Ph derivatives provided the cross-linked product in a high yield only by a 10 s photoirradiation when their alkenes overlap each other in the duplex DNA. The highly efficient reaction enabled forming a cross-linked product even when using the duplex with a low
value.
Supramolecular chemistry provides an effective strategy for the molecular recognition of diverse molecules. Significant efforts to design synthetic hosts have enabled the successful binding of many ...types of guests; however, less is known about how host-guest environments influence binding. Herein, we present a comprehensive study in which we measure the host-guest binding of a bis(arylethynyl phenylurea) host with a chloride guest in eight solvents spanning
(30) values ranging from nonpolar (40.7 kcal mol
) to polar (47.4 kcal mol
). Polar solvents show significantly weaker binding in comparison to nonpolar solvents, and the bulk solvent polarity parameter,
(30), shows a linear free-energy relationship with respect to the free energy of binding in the host-guest complex. These studies provide a better understanding of how host-guest binding in flexible receptors is governed by their environments and highlight the importance of host reorganization contributions in the free energy of binding. In addition, these studies highlight that preorganization may not be as important as previously thought for weak binding in which enthalpic contributions are smaller versus in polar solvents where solvent effects are magnified.
New 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivatives (1 and 2) were synthesized as an "off-on" fluorescent chemosensor and fluorescent chemodosimeter for Cu2+ and Pb2+. Compound 1 ...displayed selective and large chelation enhanced fluorescence effects with Pb2+ and Cu2+ among the metal ions examined. On the other hand, compound 2, a fluorescent chemodosimeter, effectively recognized Cu2+ via a selective hydrolysis of the acetyl group.
A Brønsted acid-promoted arene-ynamide cyclization has been developed to construct the 3H-pyrrolo2,3-cquinolines. This reaction consists of the generation of a highly reactive keteniminium ...intermediate from arene-ynamide activated by a Brønsted acid and electrophilic aromatic substitution reaction to give arene-fused quinolines in high yields. This methodology enabled facile access to marinoquinolines A and C and aplidiopsamine A.
A new and simple fluorescent sensor based on unmodified BINOL was developed. The fluorescence of BINOL could be turned off with high selectivity toward Cu(II) among 27 metal ions. Meanwhile, it was ...found that BINOL was oxidized to dibenzoa,klxanthen-1-ol (A) by Cu(NO3)2. A new peak appeared at ~482 nm upon addition of thiol-containing cysteine (Cys), homocysteine (Hcy), and glutathione (GSH). Thus, a cascade recognition of Cu(II) and Cys, Hcy, and GSH are well presented.
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