Excited states and electron transfer reactions of C60(OH)18 in aqueous solution
Excited states and electron transfer reactions of C60(OH)18 in aqueous solution
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DOI：
10.1039/a705293f
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发表时间：
1998-02-07
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影响因子：
--
通讯作者：
Guldi, DM
中科院分区：
文献类型：
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作者：
Mohan, H;Palit, DK;Guldi, DM
富勒烯醇溶液[C-60(OH)(18)]的动态光散射显示，在高溶质浓度(高达3.85×10(-2)moldm(-3))时，富勒烯聚集体的形成是有证据的。这种亲水性富勒烯衍生物无论其浓度如何，都会发出非常微弱的荧光。C-60(OH)(18)在水溶液中的光解(35ps；lambda(Ex)=355 nm)立即形成一个在550-800 nm范围内具有宽吸收的瞬态单重态激发态，其epsilon(670 Nm)=2130 dm(3)mol(-1)cm(-1)。能量较高的单重态激发态通过系间交叉(即tau(1/2)=500ps)转变为宽吸收(550-800 nm)的三重态激发态。相反，在低溶质浓度下，(*T-1->；*T-n)的吸收特征明显不同，在650 nm处有最大吸收，而肩峰在570 nm处。富勒烯酚的pi-自由基阴离子[C-60(OH)(18)](.-)，由水合电子与(CH3)(2)C-.(OH)自由基转移产生，在870,980和1050 nm处与最大吸收峰发生吸收。基于合适的电子给体/受体底物的电子转移研究，C-60(OH)(18)/[C-60(OH)(18)](.-)对的还原电位估计在-0.358~-0.465 V与NHE之间。
Dynamic light scattering of fullerenol solutions [C-60(OH)(18)] reveals evidence for the formation of fullerene aggregates at high solute concentration (up to 3.85 x 10(-2) mol dm(-3)). This hydrophilic fullerene derivative emits very weak fluorescence regardless of its concentration. Photolysis (35 ps; lambda(ex) = 355 nm) of C-60(OH)(18) in aqueous solution yields the immediate formation of a transient singlet excited state with broad absorption in the 550-800 nm region with epsilon(670nm) = 2130 dm(3) mol(-1) cm(-1). The energetically higher-lying singlet excited state transforms via intersystem crossing (i.e., with tau(1/2) = 500 ps) to the also broadly absorbing (550-800 nm), triplet excited state. In contrast, at low solute concentration, the features of the (*T-1 --> *T-n) absorption differ significantly exhibiting an absorption maximum at 650 nm concomitant to a shoulder at 570 nm. The pi-radical anion of fullerenol, [C-60(OH)(18)](.-), generated by electron transfer from hydrated electrons and (CH3)(2)C-.(OH) radicals, absorbs with lambda(max) at 870, 980 and 1050 nm. Based on electron transfer studies with suitable electron donor/acceptor substrates, the reduction potential of the C-60(OH)(18)/[C-60(OH)(18)](.-) couple was estimated to be in the range between -0.358 and -0.465 V vs. NHE.