香豆素C1F和C2F在醇类溶剂中的激发态溶剂效应

EFFECTS OF SOLVENT ON EXCITED STATE RELAXATION OF COUMARIN C1F AND C2F IN ALCOHOLS

本文在Grabowski模型基础上,提出了一种描述TICT态生成动力学的理论模型,并采用时间相关单光予计数荧光光谱方法,测量了香豆素C1F和C2F在醇类溶剂中的荧光寿命,考察了各种溶剂效应(极性、粘度和温度)对TICT态生成速率的影响,并将结果与DSE关系比较,指出在醇类溶剂中,氢链效应的影响是十分重要的.

In this paper, a theoretical model based on the Grabowski's theory of twisted intramolecular charge transfer (TICT) excited state is propo- sed to deal with the formation dynamics of TICT excited state. It is shown that the TICT excited state is a.main nonradiative relaxation path of S1p singlet state: knrp= kic+ k1sp+ kpt .The fluorescence lifetime of 7-aminocoumarin C1F and C2F in alcohols was measured using the time--correlated single photon counting methods.And the effects of different solvent on lifetime (τf), nonradiative relaxation rate (knr) and the formation rate of TICT excited state (kpt,) were investigated. It is found that kp1-1 of cournarin molecules depends on η/T in. the monobasic alcohols, and increases nonlinearly with η/T in polybasic alcohols. The former agrees with Debye-Stokes-Einstein's theory. And it is also found that H-bond effect among alcohol molecules and between solute and alcohol molecules is an important factor which affects the process and can not be neglected.