Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (07): 1645-1650.doi: 10.3866/PKU.WHXB201205083

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

Theoretical Calculations on the PET Property of BODIPY Fluorescent pH Probes

WANG Feng-Jiao1, ZHOU Dan-Hong1, ZUO Shi-Ying1, CAO Jian-Fang2, PENG Xiao-Jun2   

  1. 1. Institute of Chemistry for Functionalized Materials, College of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian 116029, Liaoning Province, P. R. China;
    2. State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, Liaoning Province, P. R. China
  • Received:2012-03-17 Revised:2012-05-07 Published:2012-06-07
  • Contact: ZHOU Dan-Hong, PENG Xiao-Jun E-mail:dhzhou_lnnu@163.com
  • Supported by:

    The project was supported by the State Key Laboratory of Fine Chemicals, Dalian University of Technology, China (KF0907).

Abstract:

4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) fluorescent pH probes are fluorescent sensors and switchers based on photo-induced electron transfer (PET) mechanism. From experimental studies, different substituents on the amino nitrogen are known to result in variable photo sensitivities. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations are used to optimize the structures of six different BODIPY probe molecules with different substituted amines, and to study their exited states. In the ground state, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the probe molecules are located on the π and π* orbitals of the BODIPY dye, and the lone pair electrons from the amino nitrogen form the HOMO-1 orbital. In the first exited state, for the probes with two substituent groups on the amino nitrogen, the HOMO-1→ LUMO transition has a smaller emission energy than that of the HOMO→LUMO transition in the BODIPY host, which may induce the PET effect and quench the fluorescence. After the geometry optimization of the exited states, irrespective of whether one or two groups are linked on the amino nitrogen, the orbital symmetry of the nitrogen atom changes from sp3sp2, and the lone pair electrons occupy the p orbital situated between the HOMO and LUMO of BODIPY, resulting in the PET effect. The calculated results are in good agreement with the experimental results.

Key words: Time-dependent density functional theory, BODIPY dye, pH fluorescent probe, Photo-induced electron transfer

MSC2000: 

  • O641