Tuning Octopolar NLO Chromophores:  Synthesis and Spectroscopic Characterization of Persubstituted 1,3,5-Tris(ethynylphenyl)benzenes

• Published in: Journal of organic chemistry Vol. 69; no. 15; pp. 5077 - 5081
• Main Authors: Hennrich, Gunther, Asselberghs, Inge, Clays, Koen, Persoons, André
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 23.07.2004; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Organic; Exact sciences and technology; Noncondensed benzenic compounds; Organic chemistry; Physical Sciences; Preparations and properties; Science & Technology; MULTIPHOTON FLUORESCENCE; CRYSTALS; HYPER-RAYLEIGH SCATTERING; DENDRIMERS; DEMODULATION; ABSORPTION; BENZENES; THREEFOLD SYMMETRY; MOLECULES; Substituent effect; Femtosecond; Rayleigh scattering; Acetylenic compound; Non linear optics; Octupoles; Fluorescence spectrometry; Characterization; Optical properties; Benzenic compound; Spectrophotometry; Chemical synthesis; Chromophore; Ultraviolet visible spectrometry
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo049279i

The synthesis of a series of octopolar 1,3,5-tris(ethynylphenyl)benzenes via Sonogashira coupling is described, varying the substituents on both the central benzene core as well as the acetylenic periphery. In particular, systems bearing an electron-rich core and an electron-poor periphery are obtained that display advanced optical properties. The linear (by UV−vis and fluorescence spectroscopy) and second-order nonlinear optical properties are studied, the latter by hyper-Rayleigh scattering (HRS) (Hendrickx, E.; Clays, K.; Persoons, A. Acc. Chem. Res. 1998, 31, 675−683). The influence of different core and periphery substitution is revealed by the optical properties and confirms the possibility of fine-tuning those. Because of the presence of (one-photon) fluorescence for all compounds, femtosecond hyper-Rayleigh scattering has been applied (Olbrechts, G.; Strobbe, R.; Clays, K.; Persoons, A. Rev. Sci. Instrum. 1998, 69, 2233−2241). The implementation of the deconvolution in the frequency domain allows for a demodulation and a phase shift between immediate (nonlinear) scattering and time-delayed (multiphoton) fluorescence for high modulation frequencies (Wostyn, K.; Binnemans, K.; Clays, K.; Persoons, A. Rev. Sci. Instrum. 2001 , 72, 3215−3220). In accordance with the linear optical properties, the second-order NLO properties can also be tuned by varying the core and peripheric substitutents.