Chemiluminescence efficiency of catalyzed 1,2-dioxetanone decomposition determined by steric effects.

The chemiluminescent decomposition of 1,2-dioxetanones (α-peroxylactones), catalyzed by an appropriate fluorescent activator, is an important simple model for efficient bioluminescent transformations. In this work, we report experimental data on the catalyzed decomposition of two spiro-substituted 1,2-dioxetanone derivatives, which support the occurrence of an intermolecular electron transfer from the activator to the peroxide. The low efficiency of the studied systems is associated with steric hindrance during the chemiexcitation sequence, rationalized using the concept of supermolecule formation between the peroxide and the catalyst. This approach explains the difference in the chemiexcitation efficiencies in the decomposition of four-membered cyclic peroxide derivatives: 1,2-dioxetanes, 1,2-dioxetanones, and 1,2-dioxetanedione (the intermediate in the peroxyoxalate reaction), which are the most important model compounds for excited-state formation in chemiluminescence and bioluminescence processes.

Revision of singlet quantum yields in the catalyzed decomposition of cyclic peroxides.

The chemiluminescence of cyclic peroxides activated by oxidizable fluorescent dyes is an example of chemically initiated electron exchange luminescence (CIEEL), which has been used also to explain the efficient bioluminescence of fireflies. Diphenoyl peroxide and dimethyl-1,2-dioxetanone were used as model compounds for the development of this CIEEL mechanism. However, the chemiexcitation efficiency of diphenoyl peroxide was found to be much lower than originally described. In this work, we redetermine the chemiexcitation quantum efficiency of dimethyl-1,2-dioxetanone, a more adequate model for firefly bioluminescence, and found a singlet quantum yield (Φ(S)) of 0.1%, a value at least 2 orders of magnitude lower than previously reported. Furthermore, we synthesized two other 1,2-dioxetanone derivatives and confirm the low chemiexcitation efficiency (Φ(S) < 0.1%) of the intermolecular CIEEL-activated decomposition of this class of cyclic peroxides. These results are compared with other chemiluminescent reactions, supporting the general trend that intermolecular CIEEL systems are much less efficient in generating singlet excited states than analogous intramolecular processes (Φ(S) ≈ 50%), with the notable exception of the peroxyoxalate reaction (Φ(S) ≈ 60%).

Studies on PVP hydrogel-supported luminol chemiluminescence: 2. Luminometer calibration and potential analytical applications.

The use of poly(N-vinyl-2-pyrrolidone) (PVP) hydrogel-supported luminol chemiluminescence (CL) for the automatic determination of hydrogen peroxide and the quantification of the antiradical capacity of Trolox is described. The hydrogel containing luminol and hemin is prepared directly on a 96-well microplate and can be stored for up to 3 months without significant decrease in CL quantum yields. Furthermore, this system can also be used as a secondary light standard for the calibration of microplate luminometers.

Studies on PVP hydrogel-supported luminol chemiluminescence: 1. Kinetic and mechanistic aspects using multivariate factorial analysis.

The chemiluminescent oxidation of luminol by hydrogen peroxide in the presence of hemin is revisited in an UV-C cross-linked PVP hydrogel. Chemiluminescence properties such as initial light intensity (I(0)), area of emission (S) and observed rate constants (k(obs)) are studied, varying the concentration of all reactants using a multivariate factorial approach.