화학공학소재연구정보센터
Journal of Physical Chemistry A, Vol.110, No.3, 884-891, 2006
Photoinduced processes in a tricomponent molecule consisting of diphenylaminofluorene-dicyanoethylene-methano[60]fullerene
Photoinduced intramolecular processes in a tricomponent molecule C-60(>(CN)(2)-DPAF), consisting of an electron-accepting methano[60]fullerene moiety (C-60>) covalently bound to an electron-donating diphenylaminofluorene (DPAF) unit via a bridging dicyanoethylenyl group [(CN)(2)], were investigated in comparison with (CN)2-DPAF. On the basis of the molecular orbital calculations, the lowest charge-separated state of C-60(>(CN)(2)-DPAF(center dot+)) with the negative charge localized on the C-60(>(CN)(2)-DPAF) is suggested to be C-60(center dot) fullerene cage, while the upper state is C-60(>(CN)(2)(center dot-)-DPAF(center dot+)). The excited-state events of C-60(>(CN)(2)-DPAF) were monitored by both time-resolved emission and nanosecond transient absorption techniques. In both nonpolar and polar solvents, the excited charge-transfer state decayed mainly through initial energy-transfer process to the C-60 moiety yielding the corresponding C-1(60)*, from which charge separation took place leading to the formation of C-60(center dot-)(>(CN)(2)-DPAF(center dot+)) in a fast rate and high efficiency. In addition, multistep charge separation from C-60(>(CN)(2)(center dot-)-DPAF(center dot+)) to C-60(center dot-)(>(CN)(2)-DPAF(center dot+)) may be possible with the excitation of charae-transfer band. The lifetimes Of C-60(>(CN)(2)-DPAF(center dot+)) are longer than the previously reported methano[60]fullerene-diphenylaminofluorene C-60(>(C=O)-DPAF) with the C-60 and DPAF moieties linked by a methanoketo group. These findings suggest an important role of dicyanoethylenyl group as an electron mediating bridge in C-60(>(CN)(2)-DPAF).