Tetramethyl-1,2-dioxetane. Experiments in chemiexcitation, chemiluminescence, photochemistry, chemical dynamics, and spectroscopy

Abstract

An effective way of generating student interest in chemical processes is the simple, visual demonstration of unusual chemical phenomena.1 A splendid example is a chemiluminescence reaction. The observation of "cold liquid light" streaming out of a flask is a delight to behold and a fascinating challenge to understand. In nature, many charming examples of chemiluminescence have been noted in the biolumi-nescence2 of the firefly and in luminous bacteria, fungi, deep sea fish, and other species.Chemiluminescence occurs when a sizable fraction of the exothermicity (AH) of a chemical reaction is converted into electronic excitation energy (*) of a reaction product,3 which then emits a photon of light (hv). We can describe chemiluminescence as a AH -* * -*• hv sequence. The heart of the latter is the chemiexcitation (AH -*) step. The * hv process is an ordinary and well-understood luminescence step which serves to announce the presence of an electronically excited state. If we consider photochemistry as a hv -* * -» ' AH sequence, we can imagine that a conceptual link exists between chemiluminescence Nicholas Turro received a B.A. degree from Wesleyan University In 1960, took his Ph.D. from Caltech, did a year's postdoctoral work at Harvard, and then joined the faculty at Columbia, where he is now Professor of Chemistry. He has research interests In many areas, Including work on cyclopropanes and on molecular photochemistry of alkanones In solution, which have been the subjects of previous Accounts. He Is recipient of the 1974 ACS Award in Pure Chemistry sponsored by Alpha Chi Sigma Fraternity and of the 1973 Fresenius Award In Chemistry sponsored by the Psi Lambda Upsilon Fraternity.Peter Lechtken was awarded the Ph.D. by Universitat Erlangen and returned there to join the faculty on completion of a NATO Postdoctoral Fellowship at Columbia In 1972-1973 Schore, who is a postdoctoral fellow at Caltech, received his Ph.D. at Columbia working with Dr. Turro. Gary Schuster's Ph.D. work was done at the University of Rochester. Following a hitch in the Army, Dr. Schuster is doing postdoctoral research at Columbia. Hans-Christian Steinmetzer received the Ph.D. from Universitat Würzburg, did postdoctoral work at Columbia, and is now at Universitat Frankfurt. Ahmad Yekta, who is now on the faculty of Ayra-Mehr University in Tehran, obtained the Ph.D. at Columbia in 1973. phenomena (photochemistry in reverse!) and photochemical reactions.

Preparation and Thermolysis of Some 1,2-Dioxetanes

“…15 Since the first report of the isolation and luminescence of a stable dioxetane numerous members of this class of compound have been prepared (4-7) and many energy transfer experiments have been performed with 3 (6d, 37) and 11. A review article has already been written about experiments carried out with 11 (38) and dioxetanes have been suggested as being sources of energy for some dark biological reactions (36h 39). The thermochemistry and the possible mechanisms of the thermolysis 14A referee has suggested that there may be compensating errors in E, and AS* for thermolysis of 15, and that if AS* were -5e.u., E, would become 23.2 kcal/mol.…”

The gas-phase thermal and photochemical decomposition of heterocyclic compounds containing nitrogen, oxygen, or sulfur

“…It was pointed out that The preference for triplet formation is a strong violation of the spin conservation rules and indicates that reaction 72c is the favored pathway. This spin conservation violation was attributed by Turro et al 125 to electron spin-electron orbital coupling because of the change in orbitals of the p electrons on the oxygen atom. Of even more fundamental importance is why electronically excited state formation is so important.…”

“…Another interesting effect discussed by Turro et al 125 is that the triplet acetone produced can sensitize the decomposition of tetramethyl-l,2-dioxetane which regenerates the triplet acetone. The chain length of this process can reach 1000 in CH3CN solution.…”

“…OLt + M -OL + M 3Lr' -+ C3H6 f cop (125) 3Lrr + M -O L + M (126) where L stands for butyrolactone, t represents vibrational excitation, and the superscripts 0, 1, and 3 stand for ground, singlet, and triplet, respectively. There are two different triplets 3L' and 3L''.…”

Recent advances in mechanoluminescent polymers

“…They designed a chemiluminescent mechanophore from the well-known chemiluminescence 1,2-dioxetane unit [75] which could be activated by acid or heating. Because of its sensitivity, dioxetane luminescence is used extensively in biological assays [76].…”