1221066-38-1Relevant articles and documents
Variation of the backbone conjugation in NLO model compounds: Torsion-angle-restricted, biphenyl-based push-pull-systems
Rotzler, Juergen,Vonlanthen, David,Barsella, Alberto,Boeglin, Alex,Fort, Alain,Mayor, Marcel
experimental part, p. 1096 - 1110 (2010/04/27)
Terminal piperidinyl- and nitro-functionalized biphenyls, bridged between the 2 and. 2′ positions by a variable number of methylene groups, are synthesized and fully characterized. These push-pull systems with defined and restricted torsion angles between their phenyl rings are ideal model compounds to investigate the influence of the chromophore's conjugation in nonlinear optic (NLO) responses, A general synthetic route that can be implemented to access these model compounds is reported, starting from dibromo or ditriflate biphenyls. Hartwig-Buchwald cross-coupling, a selective azacycloalkylation of diaminobiphenyls and a mild oxidation of primary amines to nitro groups in the presence of a tertiary amine summarizes the synthetic pathway towards the desired model compounds. NLO properties of the series of torsionally constrained push-pull biphenyls are collected by electric-field-induced second-harmonic generation (EFISH) experiments. The results agree qualitatively with semi-empirical simulations based on the AM1 Hamiltonian. A. linear dependence of the quadratic response on the cos2(o) of the inter-aryl dihedral angle is observed, which points to oscillator strength loss as the dominant effect of increasing backbone twist
