Catalysis chemiluminescence mechanism

Following the disclosure of the outstanding catalytic ability of imidazole compared to other bases, the catalysis of the POCL reaction by imidazole was studied in more detail [163], and it was concluded that the POCL reaction mechanism included the concurrent catalysis by two imidazole molecules, by what was described as general-base and nucleophilic pathways, respectively. The mechanism for this was suggested to be a base catalysis of imidazole catalysis by imidazole itself as previously reported for imidazole-catalyzed reaction of esters [164, 165], Despite this, it was not until the introduction [151] of 1,1 -oxalyldiimidazole (ODI) as a chemiluminescence reagent, and the postulation of its intermediate appearance in the imidazole-catalysed POCL reaction, that the... 

Final evidence for the involvement of a ground-state complex with [21] on the catalytic chemiluminescence pathway comes from the inhibition of the special catalysis by the addition of donor molecules capable of competitive complexation. Both the rate constant for the reaction of [21] catalyzed by MgTPP and the initial chemiluminescence intensity are decreased markedly by the addition of diethyl ether and even more dramatically by the addition of pyridine. This inhibition of catalysis apparently derives from complexation of the diethyl ether or pyridine to MgTPP. The added donor competes with [21] for the formation of the weak ground state complex, thereby inhibiting the otherwise effective catalysis. The special catalysis of ZnTPP and MgTPP is thus fully consistent with and readily accommodated by the CIEEL mechanism. 

The mechanism of peroxyoxalate chemiluminescence centers on the nature of the postulated key intermediate and its mode of interaction with, and excitation of, the fluorophore. An early proposal for this key intermediate, the highly strained 1,2-dioxetanedione, was confirmed more than three decades later using low-temperature nuclear magnetic resonance spectroscopy in combination with ab initio calculations. As shown in Scheme 2, the formation of the key intermediate is subject to both nucleophilic and general-base catalysis by concurrent mechanisms. 

Evmiridis, N.P. Papamichael, E.M. (1991). Investigation of the error structure of the calibration curve for periodate determination by flow-injection analysis and chemiluminescence detection. Chemom. Intell. Lab. Systems,Vol. 12, p>p. 39-47 Fersht, A. (1999) Structure and Mechanism in Protein Science A Guide to Enzyme Catalysis and Protein Folding, (1st edition),W.H. Freeman, ISBN-10 0-7167-3268-8, New York] Fletcher, R. (1%5). Function minimization without evaluating derivatives - a review. Computer Journal, VoL.8, pp. 33 1... 

---