镧系荧光探针DATTA-Eu^(3+)光诱导电子转移机理的理论计算

Theoretical calculation on the photoinduced electron transfer mechanism of lanthanide fluorescent probe DATTA-Eu^(3+)

含有镧系金属铕的DATTA-Eu^(3+)络合物是基于光诱导电子转移(PET)的荧光探针分子,能够高灵敏、高选择性地监控一氧化氮.应用含时密度泛函理论计算方法研究该探针分子的荧光开-关效应和PET机理.结果表明:联三吡啶分子作为配体和荧光母体,受光激发后发生HOMO到LUMO的电子跃迁,由于与其共价相连的邻二氨基苯氧基团的HOMO轨道能级高于联三吡啶HOMO轨道能级,能够将电子转移到单电子占据的联三吡啶HOMO轨道,使激发态电子无法正常回落,阻断了能量向中心Eu^(3+)离子的转移,无法产生铕的特征荧光.当邻二氨基苯氧基团与NO反应生成苯并三唑后,其HOMO轨道能级降低,PET过程被阻断,联三吡啶返回基态时将能量转移到Eu^(3+)离子而产生铕的特征荧光.

DATTA-Eu3+complex containing lanthanide europium is a fluorescent probe molecule based on photoinduced electron transfer(PET).It can monitor nitric oxide with high sensitivity and selectivity.Time-dependent density functional theory(TDDFT)was used to study the fluoresce on-off nature and PET mechanism of DATTA-Eu3+probe.The results show that terpyridine is fluorophore and ligand,and occurs electronic transition from HOMO to LUMO by excitation.The HOMO orbital level of the recognition group o-diaminophenoxy is higher than that of the bipyridine and can transfers one electron to the single electron occupied HOMO of terpyridine.This hinders descent of the excited state electron and impedes the energy transfer to the Eu3+ion,resulting in no characteristic fluorescence of the europium.After the probe reacts specifically with NO,o-diaminophenoxy is oxidized to form benzotriazole derivative which has lower HOMO energy level,and the PET process is prevented.Consequently,the emission of the excided terpyridine occurs normally that the energy is transferred to the Eu3+ion to produce characteristic fluorescence of the europium.