Steady-State And Femtosecond Transient Absorption Spectroscopy Of New Two-Photon Absorbing Fluorene-Containing Quinolizinium Cation Membrane Probes

Keywords

femtosecond transient absorption spectroscopy; fluorescence bioimaging; fluorescence probes; quinolizinium derivatives; two-photon absorption

Abstract

The synthesis, linear photophysical characterization, and nonlinear optical properties of two new symmetrical fluorene-containing quinolizinium derivatives, 2,8-bis((E)-2-(7-(diphenylamino)-9,9-dihexyl-9H-fluoren-2-yl)vinyl)quinolizinium hexafluorophosphate (1) and 2,8-bis((E)-2-(7-((7-(diphenylamino)-9,9-dihexyl-9H-fluoren-2-yl)ethynyl)-9,9-dihexyl-9H-fluoren-2yl)vinyl)quinolizinium hexafluorophosphate (2), are reported. The nature of the dual-band steady-state fluorescence emission of 1 and 2 was determined, and violation of Kashas rule along with a strong dependence on solvent polarity were shown. A relatively complex structure of two-photon absorption (2PA) spectra of 1 and 2, with maximum cross sections of ∼400-600 GM, was determined using the open aperture Z-scan method. Different types of fast relaxation processes with characteristic times of 0.3-0.5 ps and 1.5-2 ps were observed in the excited states of the new compounds via femtosecond transient absorption pump-probe spectroscopy. To better understand the photophysical behavior of 1 and 2, a quantum-mechanical study was undertaken using TD-DFT and ZINDO/S methods. Simulated linear absorption spectra were found to be in good agreement with experimental data, while 2PA cross sections were overestimated. Although the new dyes were highly fluorescent in nonpolar solvents, they were essentially nonfluorescent in polar media. Significantly, the quinolizinium dyes exhibited fluorescence turn-on behavior upon binding to bovine serum album (BSA) protein, exhibiting over 4-fold fluorescence enhancement, which was a finding that was leveraged to demonstrate cell membrane fluorescence imaging of HeLa cells.

Publication Date

2-4-2015

Publication Title

ACS Applied Materials and Interfaces

Volume

7

Issue

4

Number of Pages

2833-2846

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1021/am508093p

Socpus ID

84922454663 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/84922454663

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