Synthesis and Structure-Linear and Structure-Nonlinear Optical Properties of Multi-Dipolar Zigzag Oligoaryleneethynylenes
摘要:
A novel series of monodisperse, multi-dipolar zigzag oligoaryleneethynylenes DA(n) and D-Ar-A(n), bearing electron-donating dibenzothiophene and electron-accepting dibenzothiophene dioxide as arenes, with up to six charge-transfer (dipolar) units have been designed and synthesized by palladium-catalyzed Sonogashira coupling reactions. The linear and nonlinear optical properties of these multi-dipolar oligoaryleneethynylenes can easily be modified or enhanced by incorporating/extending with various central aryleneethynyl moieties such as phenylethynyl, oligo(9,9-dibutylfluorenyl)ethynyl, and oligothienylethynyl within the donor-acceptor units. Interestingly, the absorption and emission of these zigzag oligoaryleneethynylenes are not dependent on the number of covalently linked dipolar chromophores; however, the fluorescence quantum efficiencies consistently decrease with increased number of covalently linked dipolar units. These zigzag oligoaryleneethynylenes exhibit a linear increase in the two-photon absorption (TPA) cross-sections with increased number of covalently linked dipolar units without red-shifting the absorption and emission spectra. In addition, very large TPA cross-sections in the femtosecond regime (sigma(800) = 1306 GM in DMF or sigma(750) = 1522 GM in CH2Cl2) were obtained for D-TF-A(4) despite the moderate strength of the donor-acceptor pair. Our results suggest that the TPA properties of these zigzag oligoaryleneethynylenes including TPA wavelength and TPA cross-section can easily be tuned by means of modifying the central aryleneethynylene units and increasing the number of dipolar units, respectively. This approach provides an alternative means to tune or enhance the TPA cross-section at a specific wavelength.
Rhodamine-labelled new architecture for dual sensing of Co2+ and Hg2+ ions
摘要:
A new rhodamine-based chemosensor 1 has been designed and synthesized. The receptor selectively recognizes Co2+ and Hg2+ in CH3CN/water (4:1, v/v; 10 mu M tris HCl buffer, pH 6.8) by showing different extents of change in emission. The disappearance of colour of mercury-ensemble of 1 followed by appearance of distinct bluish colour under UV illumination upon addition of L-cysteine distinguishes Hg2+ from Co2+ ions. The receptor shows in vitro detection of both the ions in human cervical cancer (HeLa) cells. (C) 2013 Elsevier Ltd. All rights reserved.
Chain-length dependent conformational behaviour of triblock oligomers α-octyl-ω-n-alkoxytetrakis(oxyethylene)s in the solid state studied by Raman spectroscopy
Abstract The Raman spectra of triblock oligomers α-octyl-ω-n-alkoxytetrakis(oxyethylene)s, H(CH2)8(OCH2CH2)4O(CH2)nH with n = 2–7, were measured in the solidstate, and the conformational behaviour with changing alkyl chain length was examined. The molecularconformations of these compounds were determined by spectral analysis based on normal coordinate calculations. The conformation changes from the