Optimizing Simultaneous Two-Photon Absorption and Transient Triplet−Triplet Absorption in Platinum Acetylide Chromophores

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• 作者：Kye-Young Kim ; Abigail H. Shelton ; Mikhail Drobizhev ; Nikolay Makarov ; Aleksander Rebane ; Kirk S. Schanze
• 刊名：Journal of Physical Chemistry A
• 出版年：2010
• 出版时间：July 8, 2010
• 年：2010
• 卷：114
• 期：26
• 页码：7003-7013
• 全文大小：486K
• 年卷期：v.114,no.26(July 8, 2010)
• ISSN：1520-5215

文摘

A series of platinum-containing organometallic dimer complexes has been synthesized and the photophysical properties have been investigated under one- and two-photon (2PA) absorption conditions. The complexes have the general structure [DPAF−C≡C−Pt(PBu₃)₂−C≡C−Ar−C≡C−Pt(PBu₃)₂−C≡C−DPAF], where Ar is a π-conjugated unit, Bu = n-butyl, and DPAF = diphenylamino-2,7-fluorenylene. The core Ar units include 1,4-phenylene, 2,5-thienylene, 5,5′-(2,2′-bithienylene), 2,5-(3,4-ethylenedioxythiophene, 2,1,3-benzothiadiazole, and 4,7-dithien-2-yl-2,1,3-benzothiadiazole. Absorption and photoluminescence spectroscopy indicates that the complexes feature low-lying excited states based on both the core [-Pt(PBu₃)₂−C≡C−Ar−C≡C−Pt(PBu₃)₂-] chromophore as well as the DPAF units. Photoexcitation of the complexes produces a singlet state excited state, which rapidly undergos intersystem crossing to afford a triplet state that has a lifetime in the microsecond time domain. In most cases, the lowest energy triplet state is localized on the core chromophore. Femtosecond 2PA spectra are measured along with triplet−triplet absorption spectra and nanosecond intensity-dependent transmission for solutions of the complexes. Each of the complexes features a 2PA absorption band in the near-infrared region (λ ≈ 700−750 nm) with a cross section 50−200 GM that is ascribed to the DPAF chromophore. The complexes also feature broad triplet−triplet absorption throughout the visible and near-infrared regions (λ ≈ 500−800 nm, _TT ≈ 5−10 × 10⁴ M⁻¹cm⁻¹). Each of the complexes exhibits efficient nonlinear absorption of nanosecond pulses in the near-infrared region (600−800 nm), and we demonstrate that effect is most efficient in the chromophores where the 2PA cross section maxima coincides spectrally with the excited triplet state absorption.