Contact Ion Pairs Formed from Photolyzed TMPD-CCl4 and TMPD-CCl4-C6H6 Solutions Studied by the Time-Resolved Microwave Dielectric Absorption Technique

Article abstract of DOI:10.1021/j100169a032

One-photon ionization of TMPD has been investigated by observing the time variation of microwave dielectric loss caused by irradiation of 355-nm laser pulse on a solution of TMPD in CCl4 and on that containing both TMPD and CCl4 in C6H6 solvent.In the TMPD-CCl4 system the observed signal shows a rapid growth followed by a second-order decay along with much slower decays.These features can be interpreted as reflecting the formation of contact ion pairs (TMPD(1+)Cl(1-)) and their mutual association leading to ion-pair dimers and clusters.In the TMPD-CCl4-C6H6 system a first-order growth of the dielectric absorption is observed, which corresponds to ion-pair formation by electron transfer from the excited triplet state of TMPD to CCl4, and the reaction rate is diffusion-controlled.The dipole moment of the ion pair has been estimated to be 11 +/- 3 D from two different methods; one based on the amplitude of the detected signal and the other on the rate constant for the ion-pair association.The dipole moment of the ion pair dimer appears to be larger than that of the ion pair itself.The analysis of the data leads to a suggestion that the quantum yield of the ion-pair formation is close to unity.