Heavy-atom effects on the lowest triplet state properties by PMDR spectroscopy

The study of the intramolecular heavy atom effect in 9,10-dichlorophenanthrene and 1,2,3,4-tetrachloronaphthalene using PMDR techniques

“…In both processes the top two levels . (T and r ) ' ) are more activ~, with T 'the most favoured Recently , the dynamic properties of the triplet state of various haloaromatic compounds~~re studied (17). In this paper we report similar results for 9 10-dichiorophenanthrene (DCP ) and 1 ,2,3 4-tetrachloronaphthalene (TCN) in n-hexane at 1.6°K.…”

Heavy atom effects on the phosphorescent triplet states of several aromatic molecules

“…The mixing of the phosphorescent triplet state of the guest molecule with its singlet state, with the excited singlet state of the host, or with a created charge-transfer state of the 1 , * type in which the electron of the guest is promoted to a * orbital of the host. 5 The first two mechanisms would affect the relaxation rate constants of r2 and ry via spin-orbit interaction, but the tx sublevel would not be affected. The third mechanism would be less selective and the data in Table IV are consistent with this interpretation.…”

“…Their work is in rough agreement with pressure-acoustic work of Fisher. 5 The reaction of interest is the three-step multistate dissociation model developed by Eigen and Tamm2 to explain ultrasonic absorption relaxation spectra at atmospheric pressure:…”

“…Heavy atom effects have been a subject of interest to researchers in triplet state spectroscopy for many years.1™3 Interpretation has been limited to spectral properties such as vibrational analysis of the phosphorescence spectra and lifetime data at 77 K. With the use of the phosphorescence microwave double resonance (PMDR) method, a powerful and sensitive tool in the study of molecular perturbations, several workers have gained a better understanding of intraand intermolecular heavy atom effect in several azanaphthalenes. 4,5 In this paper we shall present a systematic study on the effect of chlorine substitution in aromatic molecules, viz., naphthalene and quinoline, and the effects of externally chlorinated solvents on the lowest phosphorescent triplet state of these molecules. The changes in the zero field splittings and the phosphorescence relaxation parameters due to intraand intermolecular heavy atom perturbation are interpreted in terms of the changes in the parameters relative to the parent molecules, naphthalene and quinoline.…”