Environmental Effects on Phosphorescence. IV. Triplet Decay of Halonaphthalenes in Compressed PMMA

The effects of high pressure (0–32 kbar) on the phosphorescence lifetime τp of seven monohalogen-substituted naphthalenes, dispersed in polymethylmethacrylate (PMMA), have been measured at room temperature. It is observed that the pressure-induced shortening of the lifetimes becomes less significant in those halonaphthalenes which possess the heavier atoms, i.e., the greater the intramolecular heavy-atom effect the less influential are environmental perturbations. “Activation volumes,” ranging in magnitude between − 0.25 < ΔV‡ < 0.0 Å3/molecule, were computed from linear lnτp-vs-P plots. Qualitative arguments are given to support the observed magnitudes and trends in the pressure-induced volume effects on triplet decay.