Dual Flrorescence of Anilino Substituted Benzanilides in Non-polar Solvent Cyclohexane——Direct Spectroscopic Evidence for the Excited-state Charge Transfer

Abstract

The f luo rescence spect ra in cyclohexane of a series of benzan ilides (BA s) with different p a ra2sub st ituen t s at the an ilino mo iety revealed that BA s em it ted dual f luo rescence, w ith one no rm al w eak em ission at ca. 330 nm and an abno rm ally long2w avelength em ission ranging f rom 460 to 550 nm. The long2w avelength em ission w as found st rongly dependen t of the elect ron donat ing capacity of the sub st ituen t at the an ilino mo iety and a st ronger elect ron donat ing sub st ituen t led to a red2sh if t in the em ission. The energies of the long2w avelength em ission of the BA s w ere co rrelated to the ox ida2t ion po ten t ials of the dono rs, EDöD + , and a n ice linear co rrelat ion w as found w ith a slope of + 0166, w h ich clearly po in ted to the charge t ran sfer character of the em issive state fo r the long2w avelength e2 m ission and the h igh decoup ling ex ten t of the charges in the CT state. Th is is the f irst repo rt that show s the direct evidence fo r the CT natu re. The resu lt sm igh t be of sign if icance in understanding the photophysics of pep t ide and p ro tein and in designing novel fluorescent chemosensors.国家自然科学基金 (批准号 :2 9975 0 2 32 0 175 0 2 0 );教育部优秀青年教师奖励计划 (2 0 0 1年 );德国大众基金 (批准号 :I/770 72 )资助