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| Titel: |
E.P.R. and zero-field odmr studies of the T1 states of halogen-containing benzonitriles, anisoles and anilines |
| Auteur: |
Niizuma, Shigeya Kwan, Lawrence Hirota, Noboru |
| Verschenen in: |
Molecular physics |
| Paginering: | Jaargang 35 (1978) nr. 4 pagina's 1029-1046 |
| Jaar: |
1978-04 |
| Inhoud: |
The magnetic and dynamic properties of bromo and chloro substituted benzonitriles, anisoles and anilines were studied by means of E.P.R. and zero-field odmr at 1·2-4·2 K. Single-crystal E.P.R. studies showed that the zero-field splitting parameter D of bromo substituted molecules are positive as in other aromatic molecules. It was also shown that para bromo substitution depresses the energies of the Tx and Ty sublevels preferentially. This indicates that the second-order effect of the spin-orbit mixing of the T1 state with the 3nπ* state is the most important in affecting the zero-field splitting. Single-crystal E.P.R. spectra of 4-bromobenzonitrile and 4-bromoanisole gave resolved hyperfine splittings at certain orientations. The analysis of the in-plane hyperfine structure of 4-bromobenzonitrile gives Azz = 16 G and Ayy = 13 G, which are considerably different from the values expected from the spin densities in benzonitrile and the 81Br hyperfine coupling of α-bromomaleic acid. The large value of Axx indicates considerable delocalization of the π electron onto the bromine atom. Hyperfine data were also used to ascertain the zero-field sublevel schemes and the directions of the principal axes of the zero-field tensor. It was found that the Tz sublevel is radiatively active at the electronic origin in most of the systems studied here. Possible causes of this activity are considered. In particular, mixing of the 3nπ* and 1nπ* states with the T1 state is suggested as the possible cause of the radiative activity of the Tz sublevel. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 6 van 20 gevonden artikelen
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