Bright and long-lasting aqueous peroxyoxalate chemiluminescence in cellulose microspheres.

Water decreases the brightness of the peroxyoxalate chemiluminescence partially due to the hydrolysis of the oxalate reagent. Here, we show that encapsulation of an oxalate ester and the fluorescent activator in microspheres of cellulose esters increases the emission intensity 30 times compared to the same reaction in water without encapsulation, whereas the emission intensity decay rate constants are considerably lower. Emission intensities, rate constants and chemiluminescence quantum yields increase with increasing hydrogen peroxide concentrations.

Ex Tenebris Lux: Illuminating Reactive Oxygen and Nitrogen Species with Small Molecule Probes.

Reactive oxygen and nitrogen species are small reactive molecules derived from elements in the air─oxygen and nitrogen. They are produced in biological systems to mediate fundamental aspects of cellular signaling but must be very tightly balanced to prevent indiscriminate damage to biological molecules. Small molecule probes can transmute the specific nature of each reactive oxygen and nitrogen species into an observable luminescent signal (or even an acoustic wave) to offer sensitive and selective imaging in living cells and whole animals.

Development of a solid-supported light-triggered nitric oxide donor.

Nitric Oxide (NO) photocleavable donors are useful tools for interrogating nitric oxide signalling and have potential use in photopharmacological applications. There is currently intensive research into newer methods to improve NO release and kinetic profiles. Herein, we report the design and synthesis of a solid-supported photocleavable NO donor synthesized by ligating an -nitroso photocleavable nitric oxide derivative to a TentaGel polymer resin bead.

The Molecular Basis of Organic Chemiluminescence.

Bioluminescence (BL) and chemiluminescence (CL) are interesting and intriguing phenomena that involve the emission of visible light as a consequence of chemical reactions. The mechanistic basis of BL and CL has been investigated in detail since the 1960s, when the synthesis of several models of cyclic peroxides enabled mechanistic studies on the CL transformations, which led to the formulation of general chemiexcitation mechanisms operating in BL and CL. This review describes these general chemiexcitation mechanisms-the unimolecular decomposition of cyclic peroxides and peroxide decomposition catalyzed by electron/charge transfer from an external (intermolecular) or an internal (intramolecular) electron donor-and discusses recent insights from experimental and theoretical investigation.

An Update on General Chemiexcitation Mechanisms in Cyclic Organic Peroxide Decomposition and the Chemiluminescent Peroxyoxalate Reaction in Aqueous Media.

Four-membered ring peroxides are intimately linked to chemiluminescence and bioluminescence transformations, as high-energy intermediates responsible for electronically excited-state formation. The synthesis of 1,2-dioxetanes and 1,2-dioxetanones enabled mechanistic studies on their decomposition occurring with the formation of electronically excited carbonyl products in the singlet or triplet state. The third member of this family, 1,2-dioxetanedione, has been postulated as the intermediate in the peroxyoxalate reaction, recently confirmed by kinetic studies on peroxalic acid derivatives.

Cyclic Peroxidic Carbon Dioxide Dimer Fuels Peroxyoxalate Chemiluminescence.

Peroxyoxalate chemiluminescence is used in self-contained light sources, such as glow sticks, where oxidation of aromatic oxalate esters produces a high-energy intermediate (HEI) that excites fluorescence dyes via electron transfer chemistry, mimicking bioluminescence for efficient chemical energy-to-light conversion. The identity of the HEI and reasons for the efficiency of the peroxyoxalate reaction remain elusive. We present here unequivocal proof that the HEI of the peroxyoxalate system is a cyclic peroxidic carbon dioxide dimer, namely, 1,2-dioxetanedione.

Water Effect on Peroxyoxalate Kinetics and Mechanism for Oxalic Esters with Distinct Reactivities.

The peroxyoxalate reaction is being widely used for various analytical and bioanalytical applications, and however, few mechanistic studies are performed in aqueous media, important mainly for bioanalytical applications, where low chemiluminescence emission quantum yields are obtained. In this sense, we report here kinetic studies on the peroxyoxalate reaction, using two commercially available and widely utilized esters, bis(2,4-dinitrophenyl) oxalate (DNPO) and bis(2,4,6-trichlorophenyl) oxalate (TCPO), in 1,2-dimethoxyethane:water mixtures. The reaction of the much more reactive DNPO, in anhydrous and aqueous media, occurs by a direct nucleophilic attack of H O to the oxalic ester, not involving nucleophilic catalysis by imidazole.

Mechanistic Studies on the Salicylate-Catalyzed Peroxyoxalate Chemiluminescence in Aqueous Medium.

The peroxyoxalate reaction is one of the most efficient chemiluminescence transformations known and the only system occurring by an intermolecular chemically initiated electron exchange luminescence (CIEEL) mechanism with confirmed high quantum yields. The peroxyoxalate chemiluminescence (PO-CL) is mainly studied in anhydrous organic medium; however, for bioanalytical application, it should be performed in aqueous media. In the present work, we study the peroxyoxalate system in a binary 1,2-dimethoxyethane/water mixture with bis(2,4,6-trichlorophenyl) oxalate (TCPO), bis(4-methylphenyl) oxalate (BMePO) and bis[2-(methoxycarbonyl)phenyl] oxalate (DMO), catalyzed by sodium salicylate, in the presence of rhodamine 6G as activator.