Pressure dependence of acetophenone N,N,N′,N′-tetramethylbenzidine exciplex in supercritical carbon dioxide

Temperature dependence of local density augmentation around exciplex in supercritical carbon dioxide

“…A decrease of k 1 with increasing pressure was observed and was most likely caused by the resulting increase in viscosity. This trend can be well-explained for diffusion-controlled reactions [7]. Pressure dependence of the decay rate constant k 2 of exciplex (AP TMB) * decreased with increasing pressures, which probably can be attributed to the increase in the permittivity of the reaction medium.…”

“…An estimation of local density augmentation around short-lived species by the lifetime analysis was published in our previous paper [7]. The local density augmentation around short-lived species was estimated from pressure dependence of the decay rate constant of reaction intermediate by using time-resolved spectroscopy.…”

“…Local density augmentation in near-critical region of fluids has attracted much attention since its elucidation in the late 1980s [1,2] and as a phenomenon specific to the solvent state [3][4][5][6][7][8][9]. It has been investigated by spectroscopic methods such as UV/Vis absorption [3], fluorescence [4], NMR [5], and EPR [6].…”

“…We have reported on the local density augmentation around exciplex in supercritical carbon dioxide (SC-CO 2 ) by lifetime analysis of exciplex [7,8]. The acetophenone (AP) N,N,N ,N -tetramethylbenzidine (TMB) exciplex has been investigated by a transient absorption technique [7], and anthracene and N,N-dimethylaniline has been investigated by fluorescence lifetime analysis [8] at 40 • C. Bis(acetylacetonato)beryllium(II) in carbon dioxide has been investigated by Umecky et al [9], who found that the local density augmentation was temperature dependent.…”

“…The acetophenone (AP) N,N,N ,N -tetramethylbenzidine (TMB) exciplex has been investigated by a transient absorption technique [7], and anthracene and N,N-dimethylaniline has been investigated by fluorescence lifetime analysis [8] at 40 • C. Bis(acetylacetonato)beryllium(II) in carbon dioxide has been investigated by Umecky et al [9], who found that the local density augmentation was temperature dependent. Local density augmentation around short-lived species might also be expected to show similar behavior, but this topic has not been reported in the literature.…”