Design of a New Optical Material with Broad Spectrum Linear and Two-Photon Absorption and Solvatochromism

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• 作者：William V. Moreshead ; Olga V. Przhonska ; Mykhailo V. Bondar ; Alexei D. Kachkovski ; Iffat H. Nayyar ; Art毛m E. Masunov ; Adam W. Woodward ; Kevin D. Belfield
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：November 7, 2013
• 年：2013
• 卷：117
• 期：44
• 页码：23133-23147
• 全文大小：736K
• 年卷期：v.117,no.44(November 7, 2013)
• ISSN：1932-7455

文摘

A fluorene-bridged squaraine dimer (SD-FLU-SD) was designed with the purpose of combining various chromophores in one molecule and enhancing its two-photon absorption properties using intra- and interchromophore transitions. Linear and nonlinear absorption properties of SD-FLU-SD were investigated with the goals of understanding the nature of one- and two-photon absorption spectra, determining the molecular optical parameters, and performing modeling of the photophysical processes. The optical behavior of this new SD-FLU-SD 鈥渉ybrid鈥?molecule was compared with its separate squaraine constituent moiety. Linear spectroscopic characterization includes absorption, fluorescence, excitation and emission anisotropy, and quantum yield measurements in solvents of different polarity and viscosity. Spectral positions of the absorption鈥揻luorescence peaks and quantum yields of SD-FLU-SD and its separate squaraine moiety exhibited complex and nontrivial behavior as a function of solvent polarity. Comprehensive study of this unusual solvatochromism was conducted and interpreted using various models. Nonlinear spectroscopic studies included two-photon absorption measurements using the femtosecond Z-scan technique. The two-photon absorption spectrum of SD-FLU-SD was broad, covering the spectral range from 800 to 1400 nm with a maximum two-photon absorption cross section of 2鈥?50 GM (1 GM = 1 脳 10^鈥?0 cm⁴ s/photon). Quantum chemical analysis, based on time-dependent density functional theory, agreed with the experimental data and revealed details on the energy-level structure and origin of the linear and nonlinear absorption behavior of this novel SD-FLU-SD compound. These investigations advance the understanding of the nature of electronic transitions and the structure鈥損roperty relations in long conjugated molecules, which are important for the rational design of new organic optical materials.