Efficient Two-Photon Absorbing Acceptor-π-Acceptor Polymethine Dyes
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- 作者：Lazaro A. Padilha ; Scott Webster ; Olga V. Przhonska ; Honghua Hu ; Davorin Peceli ; Trenton R. Ensley ; Mykhailo V. Bondar ; Andriy O. Gerasov ; Yuriy P. Kovtun ; Mykola P. Shandura ; Alexey D. Kachkovski ; Da
- 刊名：Journal of Physical Chemistry A
- 出版年：2010
- 出版时间：June 17, 2010
- 年：2010
- 卷：114
- 期：23
- 页码：6493-6501
- 全文大小：393K
- 年卷期：v.114,no.23(June 17, 2010)
- ISSN：1520-5215
文摘
We present an experimental and theoretical investigation of the linear and nonlinear optical properties of a series of acceptor-π-acceptor symmetrical anionic polymethine dyes with diethylamino-coumarin-dioxaborine terminal groups and different conjugation lengths. Two-photon absorption (2PA) cross sections (δ2PA) are enhanced with an increase of π-conjugation length in the investigated series of dyes. 2PA spectra for all dyes consist of two well-separated bands. The first band, located within the telecommunications window, occurs upon two-photon excitation into the vibrational levels of the main S0 → S1 transition, reaching a large δ2PA = 2200 GM (1 GM = 1 × 10−50 cm4 s/photon) at 1600 nm for the longest conjugated dye. The position of the second, and strongest, 2PA band for all anionic molecules corresponds to the second-excited final state, which is confirmed by quantum-chemical calculations and excitation anisotropy measurements. Large δ2PA values up to 17000 GM at 1100 nm are explained by the combination of the large ground- and excited-state transition dipole moments. The three shortest dyes show good photochemical stability and surprisingly large fluorescence quantum yields of ≈0.90, ≈0.66, and ≈0.18 at the red to near-IR region of ≈640, ≈730, and ≈840 nm, respectively. The excited-state absorption spectra for all samples are also studied and exhibit intense bands throughout the visible wavelength region with peak cross section close to 5 × 10−16 cm2 with a corresponding red shift with increasing conjugation lengths.