The 1,2-dioxetane molecule is the parent molecular system for chemiluminescence. That the origin of chemi- and bioluminescence is a non-adiabatic process originating from the breakage of a peroxide bond is well understood. However, a lot of details in the mechanisms of chemi- and bioluminescence are not well understood. In this lecture we will unravel one of these lesser understood experimental observations. This is the intriguing and dramatic increase - 0.003 to 0.35 - of the quantum yield of the phosphorescence for the series of 1,2-dioxetane molecules substituted with none up to four methyl groups. This changes of quantum yield, more than two orders of magnitude, is studied in a series of non-adiabatic surface hopping dynamics simulations using multi-configurational electron structure theory. The dynamics reveal how the seamingly innocent methyl groups retards the dynamic of the fragmentation process - 1,2-dioxetane thermally fragments to two formaldehyde - in a so-called entropic trap, there by enhancing the interstate crossing efficiency.  The lecture will initially give a brief background to the field of chemi- and bioluminescence, followed by the details for the problem and simulations listed above. The presentation will conclude with some guidelines to the design of newer even more effcicent chemiluminescent compounds.

Non-adabatic dynamics of the 1,2-dioxetane chemiluminescence

254th National Meeting (2017)

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