萤火虫氧化荧光素类似物电子光谱的理论研究

Theoretical Study of the Electronic Spectral Property of Firefly Oxyluciferin Analogues

对萤火虫氧化荧光素(S)-2-(6-羟基-2-苯并噻唑基)-2-噻唑啉-4-酮(BTZ)中苯并噻唑环的N和S原子进行取代,形成一系列萤火虫氧化荧光素类似物,并采用TD B3LYP/6-31+G(d)方法,通过计算氧化物中性态与羟基去质子化后的负一价态在气相、水溶液和模拟生物环境下的吸收与发射光谱,讨论环内不同取代原子对光谱的影响.结果表明,X1位以O原子取代S原子的化合物的最大吸收值发生蓝移,以N原子取代S原子的化合物的最大吸收值发生红移.去质子化可增加苯环上π轨道成份,降低能隙,从而有利于提高电子跃迁几率,使荧光发射波长红移;通过取代X1和X2位杂原子,可调节发射光谱红移达44 nm,蓝移达41 nm(在模拟蛋白中).6种化合物荧光发光范围较宽,振子强度较大,可以作为潜在的化学发光材料用于生物成像研究.

A series of firefly oxyluciferin analogues were designed, in which the zole of firefly oxyluciferin were substituted by other atoms. In aqueous solution N and S atoms of benzotma- and virtual protein environmerit, the absorption and emission spectrum were calculated by TD B3LYP/6-31 ＋G（d）. The resuhs of the calculation indicate that the absorption spectra of complexes with the O atom at Xl-site show more blue-shift than that with the S atom, while the spectra of complexes in which the S atom is replaced by the N atom show red-shift. The six complexes have similar orbital distributions and the overlapping volume between HOMO and LUMO is high. That benefits to the maintain of high fluorescence efficiency. Deprotonation can enhance the π orbital component of benzene fragment and make emission spectra shift to red. Thus electronic transition probability can be improved. Replaced by different atoms at X1 and X2 sites, the emission spectra can be adjusted to move to long wave up to 44 nm and move to short wave up to 41 nm（ in virtual protein environment）. The emission wavelength range of the six complexes is wide. So they can be used in biological imaging as new potential chemical luminescent material.