Pan Yang, Gao Yuhe, Yan Lei, Pan Hu, Chen Jiafu, Yu Shuqin
Laboratory of Bond-Selective Chemistry, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, PR China.
Spectrochim Acta A Mol Biomol Spectrosc. 2007 Jan;66(1):63-7. doi: 10.1016/j.saa.2006.02.023. Epub 2006 Mar 2.
The property of the lowest excited triplet states of 1,8-dihydroxyanthraquinone (DHAQ) was investigated by using time-resolved laser flash photolysis at 355nm in organic solvents, i.e. acetonitrile and cyclohexane. The transient absorption spectra of the excited triplet DHAQ were obtained in acetonitrile, which have an absorption maximum at 480nm and two broad absorption bands around 350 and 650nm. 3DHAQ() is efficiently quenched by triphenylamine (TPA) via photoinduced electron transfer pathway, which was testified by the finding of TPA radical cation. In addition, aniline derivatives such as N,N-dimethylaniline (DMA), 3,5,N,N-tetramethylaniline (TMA), 4-dimethylaminobenzoic acid (DMABA) and dimethyl-p-toluidine (DMT) could also quench 3DHAQ() rapidly. Evidence for electron transfer interaction with anilines in acetonitrile was obtained from transient spectral characterization of formed radicals. Experimental k(q) values approach the diffusion-controlled rate limit, and decrease significantly from DMT (1.85x10(10)M-1s-1) to DMABA (1.95x10(9)M-1s-1). These k(q) values depend on the charge density on the "N" atom of anilines, which could be quantified by Hammett sigma constant.
采用时间分辨激光闪光光解技术，在355nm波长下于乙腈和环己烷等有机溶剂中研究了1,8 - 二羟基蒽醌（DHAQ）最低激发三重态的性质。在乙腈中获得了激发三重态DHAQ的瞬态吸收光谱，其在480nm处有一个吸收最大值，在350nm和650nm左右有两个宽吸收带。三苯胺（TPA）通过光诱导电子转移途径有效地猝灭了3DHAQ()，TPA自由基阳离子的发现证实了这一点。此外，苯胺衍生物如N,N - 二甲基苯胺（DMA）、3,5,N,N - 四甲基苯胺（TMA）、4 - 二甲基氨基苯甲酸（DMABA）和二甲基对甲苯胺（DMT）也能快速猝灭3DHAQ()。通过对形成的自由基的瞬态光谱表征获得了在乙腈中与苯胺发生电子转移相互作用的证据。实验得到的k(q)值接近扩散控制速率极限，并且从DMT（1.85×10(10)M-1s-1）到DMABA（1.95×10(9)M-1s-1）显著降低。这些k(q)值取决于苯胺“N”原子上的电荷密度，这可以通过哈米特σ常数来量化。
