蓝移型萘酰亚胺类Cu^(2+)比率荧光探针的发光机理

Luminescence mechanism of the naphthalimide-based Cu^(2+) blue-shift ratiometric fluorescent probe

应用密度泛函理论(DFT)和含时密度泛函理论(TDDFT)方法,研究了1,8-萘酰亚胺类荧光探针BF1(N-丁基-4,5-二[(吡啶-2-甲基)氨基]1,8-萘酰亚胺)与Cu^(2+)的络合以及产生蓝移荧光的机理.计算结果表明:BF1受光激发后,萘氨基与萘环之间的N—C键扭转形成NC醌型结构,导致N上p电子向萘环π*轨道转移,形成分子内电荷转移(ICT),荧光波长红移.BF1与Cu^(2+)络合后,使N—C键扭转受到限制,阻断了ICT作用,只存在局域发射(LE)荧光,相对于BF1的荧光波长发生蓝移.

Density functional theory （DFT） and time-dependent density functional theory （TDDFT） were used to study the coordination of the naphthalimide-based fluorescent probe BF1 （N-Buytl-4,5- di[（pyridin-2-ylmethyl） amino]-1,8-naphthalirnide） with Cu2＋, and the mechanism for the fluores- cence blue-shift. The results indicated that in the exited state of probe BE1, the N-C bond between the 4-amino group and naphthalene turns to form a N=C quinone type structure that the p electrons of N transfer into the π＊ system of naphthalene,forming intramolecular charge transfer （ICT） and the red- shifted fluorescence. In the coordination complex BF1-Cu2＋ complex, the distortion of N--C bond is hindered,and the ICT state is interdicted. Therefore,only the local excited （LE） state can be ob- served which looks like a fluorescent blue shift with respect to that of probe BF1.