ZEOLITE-SUPPORTED TETRAMETHYL-1,2-DIOXETANE: NEW PATHWAYS TO CHEMILUMINESCENCE

Article abstract of DOI:10.1016/S0040-4020(01)90275-3

The thermal decomposition of tetramethyl-1,2-dioxetane (TMD) sorbed into zeolite Y containing Eu(3+) ions and 2,2'-bipyridine (samples abbreviated as ZYEBT) has been investigated.Decomposition of TMD yields, by energy transfer processes, chemiluminescence (CL) characteristic of the Eu(3+) ion.At loading levels corresponding to an upper-limit average of 0.5, 1.0, and 2.0 TMD molecules per unit cell, the CL decay curves are nonexponential at short times; at longer times, roughly exponential curves are characterized by a unimolecular rate constant k.Analyses of the long-time decays based on an Arrhenius expression for the rate constant provide evidence for a kinetic compensation effect: plots of log k vs. the activation energy E_a as a function of TMD loading level are linear.Solution data (benzene, benzonitrile) fall on the same line, suggesting that TMD decomposes by a common rate-limiting mechanism in these various environments.The Arrhenius parameters (E_a and the pre-exponential factor A) are smaller than the solution values and increase with TMD loading.When TMD is sorbed to the extent of an upper-limit average of ca. 7 molecules per unit cell, CL decay curves are initially nearly flat and then show an increase in decomposition rate with time.Mechanistic implications of these results are discussed.