Synthesis and Purification of Coronene

Fluorescence and Phosphorescence from Higher Excited States of Organic Molecules

“…However, recent investigation based on careful purification of coronene sample revealed that the S 2 and S 3 fluorescences reported by Nakajima likely originate from impurities and that the real S 2 and S 3 fluorescences are much weaker than those reported by Nakajima. , Further, the S 2 and S 3 fluorescences of coronene vapor were analyzed as prompt fluorescence, which does not involve the fluorescence occurring through reverse internal conversion . In general, the purification of coronene is tremendously difficult . In any case, the occurrence of the S 2 fluorescence for most of the medium- to large-size acenes such as pyrene, benzopyrene, benzanthracene, and benzoperylene in the vapor phase at low pressure can be interpreted by the relaxation model involving the reversible internal conversion between S 1 and S 2 .…”

“…116 In general, the purification of coronene is tremendously difficult. 117 In any case, the occurrence of the S 2 fluorescence for most of the medium-to large-size acenes such as pyrene, benzopyrene, benzanthracene, and benzoperylene in the vapor phase at low pressure can be interpreted by the relaxation model involving the reversible internal conversion between S 1 and S 2 . The excitation-energy dependence of the relative S 2 /S 1 fluorescence quantum yield ratio can be interpreted at least qualitatively using Fermi's golden rule.…”

Multiple fluorescence and the electronic relaxation processes of coronene vapor: The fluorescence from the S1, S2, and S3 states

“…There are a considerable amount of works on the spectroscopy of this molecule [1][2][3][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. It is known that coronene exhibits weak S 2 ( 1 B 1u ) fluorescence in addition to the S 1 ( 1 B 2u ) fluorescence in room temperature solution and in a low temperature matrix [1].…”

“…Weak emission which can be regarded as the fluorescence from the third excited singlet state, S 3 ( 1 E 1u ), was observed in addition to the S 1 and S 2 fluorescence for coronene vapor. It should be stressed that the observed S 2 and S 3 fluorescence are substantially different from those reported previously for coronene vapor and that the S 3 fluorescence reported previously is most likely to be originating from impurities [2].…”

“…Addition of oxygen decreased the S 1 fluorescence intensity significantly, indicating the faster decay rate of the S 2 state than that of S 1 . Excitation energy dependence of the fluorescence quantum yields of the S 1 , S 2 and S 3 fluorescence (U F (S 1 ), erature to remove the fluorescent impurities [3]. The sample thus treated chemically was purified again by the combination of vacuum sublimation and repeated recrystallization from THF (tetrahydrofuran), and finally passed through a silica column.…”