Reactivity of aromatic amines with triplet 1,8-dihydroxyanthraquinone: a laser flash photolysis study.
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.
Pan
Yang
Y
Laboratory of Bond-Selective Chemistry, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, PR China.
Gao
Yuhe
Y
Yan
Lei
L
Pan
Hu
H
Chen
Jiafu
J
Yu
Shuqin
S
D000814:Aniline Compounds / Q000737:chemistry*; D000880:Anthraquinones / Q000737:chemistry*; D007834:Lasers; D010777:Photochemistry / Q000379:methods
D000814:Aniline Compounds; D000880:Anthraquinones; C004315:danthron