Geometry Relaxation-Induced Large Stokes Shift in Red-Emitting Borondipyrromethenes (BODIPY) and Applications in Fluorescent Thiol Probes

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• 作者：Yinghui Chen ; Jianzhang Zhao ; Huimin Guo ; Lijuan Xie
• 刊名：The Journal of Organic Chemistry
• 出版年：2012
• 出版时间：March 2, 2012
• 年：2012
• 卷：77
• 期：5
• 页码：2192-2206
• 全文大小：734K
• 年卷期：v.77,no.5(March 2, 2012)
• ISSN：1520-6904

文摘

2-Thienyl and 2,6-bisthienyl BODIPY derivatives (BS-SS and BS-DS) were prepared that show intense absorption (蔚 = 65000 M^鈥? cm^鈥? at 507 nm) and a large Stokes shift (96 nm) vs the small Stokes shift of typical BODIPY (<15 nm). Control compounds with a thienyl unit at the 8-position or phenyl substituents at the 2,6-positions were prepared (BS-1 and 9). BS-1 shows absorption/emission in the blue-shifted range and a small Stokes shift (12 nm). Compound 9 shows absorption in the red-shifted range, but the Stokes shift (<30 nm) is much smaller than that for BS-SS and BS-DS. DFT calculations propose the large Stokes shifts of BS-SS and BS-DS are due to the remarkable geometry relaxation upon photoexcitation and its substantial effect on the energy levels of molecular orbitals. For the dyes with small Stokes shifts, much smaller geometry relaxations were found. The fluorophores were used for fluorescent thiol probes, with 2,4-dinitrobenzenesulfonyl (DNBS) as the fluorescence switch. Both fluorescence OFF鈥揙N and unprecedented ON鈥揙FF transduction were observed, which are attributed to the different photoinduced intramolecular electron-transfer (PET) profile. All the photophysics were rationalized by DFT calculations based on the concept of 鈥渆lectronic states鈥?instead of the very often used approximation of 鈥渕olecular orbitals鈥?