痂囊腔菌素A与咔唑化合物间的光致电子转移

Photoinduced electron-transfer between elsinochrome A and carbazole chemicals

研究了咔唑、咔唑-9-乙酸、3-溴-咔唑-9-乙酸在缺氧条件下对天然苝醌化合物痂囊腔菌素A(简记为EA)的荧光猝灭行为;由竹红菌甲素(HA)和乙素(HB)的荧光寿命估算了EA在乙腈中的荧光寿命,并进而计算了三个咔唑化合物的双分子猝灭速度常数.结果表明,三个咔唑化合物在EA的可见光吸收区无光吸收,据此推测其对EA的荧光猝灭作用归因于咔唑化合物作为电子给体而EA作为电子受体的光致电子转移作用.三个咔唑化合物的Stern-Volmer猝灭常数分别为698、704和1 063L·mol-1;乙酸基对咔唑环的光致电子转移速率几乎没有影响,而溴原子取代能够增加咔唑化合物对EA的荧光猝灭程度和光致电子转移速率.此外,EA在乙腈中的荧光寿命为1.98ns,而三个咔唑化合物的双分子猝灭速率常数分别为3.52×1011,3.56×1011和5.37×1011 L·mol-1·s-1.

The fluorescence quenching of elsinochrome A （denoted as EA ） ,a natural peryle-nequinone ,by carbazole ,carbazol-9-yl-acetic acid ,and 3-Br-carbazol-9-yl-acetic acid under an-aerobic condition was studied .The fluorescence lifetime of EA in acetonitrile was estimated from the lifetimes of hypocrellin A and hypocrellin B ;and the bimolecular quenching rate con-stants of the three carbazole compounds were calculated accordingly .Results indicate that the three carbazole compounds exhibit no absorbance in the visible light absorbance area of EA . Hence it can be inferred that they quench the fluorescence of EA by photoinduced electron transfer with carbazole compounds as the donors and EA as the acceptor .In the meantime ,the quenching constants of the three carbazole compounds are 698 ,704 and 1 063 L ·mol-1 ,re-spectively .Besides ,the acetic acid group has almost no effect on photoinduced electron transfer rate ,w hile the substitution of bromine atom on carbazole ring increases the photoinduced elec-tron transfer rate .Moreover ,EA in acetonitrile has a fluorescence lifetime of 1 9.8 ns ,and the bimolecular quenching rate constants of the three carbazole compounds are 3 5.2x 10^11 , 3 5.6x 10^11 and 5 3.7x10^11 L ·mol-1 ·s-1 ,respectively .