The fluorescence of a chelating two-photon-absorbing dye is enhanced with the addition of transition metal ions but quenched in the presence of acid

A pseudo-symmetric two-photon absorbing dye (1) containing a central piperazine unit substituted with (benzothiazol-2- yl)-9,9-diethylfluoren-2-yl pendant groups has been synthesized and characterized. The molecule has a two-photonabsorption cross-section of σ2 = 140 GM in tetrahydrofuran at ~ 740 nm and shows significant solvatochromism in the excited-state fluorescence spectra. The emission spectra broaden and the maxima bathochromically shift from 411 nm to 524 nm in n-hexane and acetonitrile, respectively. Moreover, the central piperazine moiety serves as a potential chelation site for ions. Addition of copper(I) hexafluorophosphate and zinc(II) triflate in acetonitrile indicate ground-state complexation with a shift in the emission maximum from 524 nm to 489 nm and 487 nm, respectively. Interestingly, the newly formed Cu and Zn complexes are more strongly emissive than the free dye. Finally, addition of p-toluenesulfonic acid in tetrahydrofuran also blue-shifts the emission maximum, but the intensity is quenched. Due to the photophysical changes induced by addition of metal ions and protons, the dye shows promise as a potential sensor.

[1]  Robert J. Twieg,et al.  Zinc Sensing via Enhancement of Two-Photon Excited Fluorescence , 2007 .

[2]  Ken-Tsung Wong,et al.  Fluorene as the π–spacer for new two-photon absorption chromophores , 2011 .

[3]  W. Denk,et al.  Deep tissue two-photon microscopy , 2005, Nature Methods.

[4]  Ran Lu,et al.  Linear and nonlinear optical properties of two novel D–π–A–π–D type conjugated oligomers with different donors , 2013 .

[5]  M. V. Bondar,et al.  Steady-State Spectroscopic and Fluorescence Lifetime Measurements of New Two-Photon Absorbing Fluorene Derivatives , 2002, Journal of Fluorescence.

[6]  Tommaso Baldacchini,et al.  Multiphoton fabrication. , 2007, Angewandte Chemie.

[7]  C. Spangler.  Recent development in the design of organic materials for optical power limiting , 1999 .

[8]  Theodore Goodson,et al.  Investigation of two-photon absorption properties in branched alkene and alkyne chromophores. , 2006, Journal of the American Chemical Society.

[9]  Paras N. Prasad,et al.  Diphenylaminofluorene-Based Two-Photon-Absorbing Chromophores with Various π-Electron Acceptors , 2001 .

[10]  Peter Persephonis,et al.  The photophysics and two-photon absorption of a series of quadrupolar and tribranched molecules : The role of the edge substituent , 2009 .

[11]  Theodore Goodson,et al.  Excited-state deactivation of branched two-photon absorbing chromophores: a femtosecond transient absorption investigation. , 2007, The journal of physical chemistry. A.

[12]  Paras N. Prasad,et al.  Highly Active Two-Photon Dyes: Design, Synthesis, and Characterization toward Application , 1998 .

[13]  Ben Zhong Tang,et al.  Click polymerization : facile synthesis of functional poly(aroyltriazole)s by metal-free, regioselective 1,3-dipolar polycycloaddition , 2007 .

[14]  Dongho Kim,et al.  Charge transfer induced enhancement of near-IR two-photon absorption of 5,15-bis(azulenylethynyl) zinc(II) porphyrins. , 2007, Chemical communications.

[15]  Kevin D Belfield,et al.  Fluorescence Sensing of Zinc and Mercury Ions with Hydrophilic 1,2,3-Triazolyl Fluorene Probes. , 2010, Chemistry of materials : a publication of the American Chemical Society.

[16]  William V. Moreshead,et al.  Design of a New Optical Material with Broad Spectrum Linear and Two-Photon Absorption and Solvatochromism , 2013 .

[17]  Wen Jun Yang,et al.  Two-photon absorption properties of 2,6-bis(styryl)anthracene derivatives: effects of donor-acceptor substituents and the pi center. , 2005, Chemistry.

[18]  Claudine Katan,et al.  Effects of (multi)branching of dipolar chromophores on photophysical properties and two-photon absorption. , 2005, The journal of physical chemistry. A.

[19]  W. Webb,et al.  Nonlinear magic: multiphoton microscopy in the biosciences , 2003, Nature Biotechnology.

[20]  David J. Hagan,et al.  Synthesis, characterization, and optical properties of new two-photon-absorbing fluorene derivatives , 2004 .

[21]  Paras N. Prasad,et al.  Toward Highly Active Two-Photon Absorbing Liquids. Synthesis and Characterization of 1,3,5-Triazine-Based Octupolar Molecules , 2004 .

[22]  Thomas M. Cooper,et al.  Photophysical Characterization of a Series of Platinum(II)-Containing Phenyl-Ethynyl Oligomers , 2002 .

[23]  J. Demas,et al.  Measurement of photoluminescence quantum yields. Review , 1971 .

[24]  David J. Hagan,et al.  New Two-Photon Absorbing Fluorene Derivatives: Synthesis and Nonlinear Optical Characterization , 1999 .

[25]  Ruth Pachter,et al.  Effects of conjugation in length and dimension on spectroscopic properties of fluorene-based chromophores from experiment and theory. , 2006, The journal of physical chemistry. A.

[26]  David J. Stewart,et al.  Symmetry- and solvent-dependent photophysics of fluorenes containing donor and acceptor groups. , 2014, The journal of physical chemistry. A.

[27]  Claudine Katan,et al.  Synthesis, fluorescence, and two-photon absorption of a series of elongated rodlike and banana-shaped quadrupolar fluorophores: a comprehensive study of structure-property relationships. , 2007, Chemistry.

[28]  Nisan Siegel,et al.  Design of emission ratiometric metal-ion sensors with enhanced two-photon cross section and brightness. , 2007, Journal of the American Chemical Society.

[29]  Egbert Zojer,et al.  Metal-ion sensing fluorophores with large two-photon absorption cross sections: aza-crown ether substituted donor-acceptor-donor distyrylbenzenes. , 2004, Journal of the American Chemical Society.

[30]  Rachel Jakubiak,et al.  Insight into the nonlinear absorbance of two related series of two-photon absorbing chromophores. , 2007, The journal of physical chemistry. A.

[31]  E. A. Wachter,et al.  Simultaneous Two‐Photon Activation of Type‐I Photodynamic Therapy Agents , 1997, Photochemistry and photobiology.

[32]  Richard L. Sutherland,et al.  Understanding the one-photon photophysical properties of a two-photon absorbing chromophore , 2004 .

[33]  B R Masters,et al.  Two-photon excitation fluorescence microscopy. , 2000, Annual review of biomedical engineering.

[34]  Alex K.-Y. Jen,et al.  2-(2′-Hydroxyphenyl)benzoxazole-Containing Two-Photon-Absorbing Chromophores as Sensors for Zinc and Hydroxide Ions , 2008 .

[35]  Zhenning Yu,et al.  Steric hindrance inhibits excited-state relaxation and lowers the extent of intramolecular charge transfer in two-photon absorbing dyes. , 2016, Physical chemistry chemical physics : PCCP.

[36]  Daniel G. McLean,et al.  Development of novel two-photon absorbing chromophores , 2006, SPIE Optics + Photonics.