Phosphorescence and TREPR spectra have been measured for 2-methyl-1,4-naphthoquinone (MNQ), 2,3-dimethyl-1,4-naphthoquinone (DMNQ), and 2-methoxynaphthoquinone (MeONQ) in several matrices at low temperatures. The |D| value of ZFS parameter decreases with increasing the electron-donating character of the substituent group. For MNQ, the T1 state is clearly assigned to be 3nπ* in character. The broad phosphorescence spectra and minor effects of the matrix polarity on the ZFS parameters lead to the conclusion that the character of the T1 states are mainly 3ππ* in DMNQ and MeONQ. The T1 states of the present naphthoquinone derivatives have more or less mixed character of the 3nπ* and 3ππ* states.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry