Excited-State Proton Transfer of Cyanonaphthols in Protic Ionic Liquids: Appearance of a New Fluorescent Species
Excited-State Proton Transfer of Cyanonaphthols in Protic Ionic Liquids: Appearance of a New Fluorescent Species
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DOI：
10.1021/acs.jpcb.7b03658
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发表时间：
2017-06-22
影响因子：
3.3
通讯作者：
Kimura, Yoshifumi
中科院分区：
文献类型：
--
作者：
Fujii, Kaori;Yasaka, Yoshiro;Kimura, Yoshifumi
采用时间分辨荧光法研究了5-氰基-2-萘酚（5CN 2）和5，8-二氰基-2-萘酚（DCN 2）在三乙基三氟甲磺酸铵（[N222 H][CF 3SO 3]）、三乙基甲磺酸铵（[N222 H][CH 3SO 3]）和三乙基三氟乙酸铵（[N222 H][CF 3COO]）三种质子离子液体（PIL）中的激发态质子转移（ESPT）.在[N222 H][CF 3SO 3]中，5CN 2和DCN 2均仅显示来自ROH*（激发态取代萘酚的正常形式）的荧光，表明在[N222 H][CF 3SO 3]中没有ESPT发生。对于在[N222 H][CH 3SO 3]中的5CN 2，观察到来自ROH* 和RO-*（激发态的取代萘酚的阴离子形式）的荧光带，表明5CN 2可以将质子解离到周围的溶剂中并形成RO-*。更有趣的是，在[N222 H][CF 3COO]中的5CN 2和在[N222 H][CH 3SO 3]和[N222 H][CF 3COO]中的DCN 2显示出在470 nm（5CN 2）或520 nm（DCN 2）附近的异常荧光带，这在以前没有报道过。基于荧光强度的时间曲线分析5CN 2和DCN 2的每个荧光组分的动力学。根据离子液体中阴离子的碱性和动力学，讨论了5CN 2和DCN 2的合理ESPT方案。
Excited-state proton transfer (ESPT) of 5-cyano-2-naphthol (5CN2) and 5,8-dicyano-2-naphthol (DCN2) in three different protic ionic liquids (PILs), triethylammonium trifluoromethanesulfonate ([N222H][CF3SO3]), triethylammonium methanesulfonate ([N222H][CH3SO3]), and triethylammonium trifluoroacetate ([N222H][CF3COO]), was studied by time-resolved fluorescence. In [N222H][CF3SO3], both 5CN2 and DCN2 showed fluorescence only from ROH* (normal form of substituted naphthol in the excited states), indicating that no ESPT occurred in [N222H][CF3SO3]. For 5CN2 in [N222H][CH3SO3], fluorescence bands from ROH* and RO-* (anionic form of substituted naphthol in the excited states) were observed, indicating that 5CN2 could dissociate proton to surrounding solvents and form RO-*. More interestingly, 5CN2 in [N222H][CF3COO] and DCN2 in [N222H][CH3SO3] and [N222H][CF3COO] showed an anomalous fluorescence band around 470 nm (5CN2) or around 520 nm (DCN2) which has not been reported previously. The kinetics of each fluorescent component of 5CN2 and DCN2 was analyzed on the basis of the time profile of fluorescence intensity. Plausible ESPT schemes of 5CN2 and DCN2 were discussed on the basis of the kinetics and the basicity of anion in PILs.