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SM ISO690:2012 LUCENTI, Elena, CARIATI, Elena, FORNI, Alessandra, RIGHETTO, S.. (2-pyrene-1-yl-vinyl) pyridine: a novel non linear optical material with acidochromic behavior. In: Materials Science and Condensed Matter Physics, Ed. 7, 16-19 septembrie 2014, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2014, Editia 7, p. 133. |
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Materials Science and Condensed Matter Physics Editia 7, 2014 |
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Conferința "Materials Science and Condensed Matter Physics" 7, Chișinău, Moldova, 16-19 septembrie 2014 | |||||
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Pag. 133-133 | |||||
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In the field of electrnoptic materials, the rational design and synthesis of chromophores endowed with high transparency together with large second order nonlinear optical (NLO) response is a field of intense research activity. Many organic and metallorganic second order NLO chromophores have been designed according to the "push-pull" strategy, where electrnn-donating (D) and electronwithdrawing (A) end groups interact through a delocalized n-electron bridge to generate an intramolecular charge ti·ansfer ti·ansition [1]. On the other hand, far less attention has been devoted to low dipole moment chromophores, though in some instance they have been shown to possess large hype1polarizability β [2]. Here we repo1i on the measurements, by the solution-phase electric-field induced second-hannonic (EFISH) generation method, of the second-order NLO properties of (2-pyrene-1-yl-vinyl)pyridine (PPY), a simple and highly ti·ansparent chromophore. The limited length of its n-electron bridge, moreover, ensures a greater stability with respect to standard D-n-A dyes. In spite of its relatively low dipole moment µ, PPY gives rise to unexpectedly large µ/}A. values (2000 x 10-48 esu), comparable to that of benchmark NLO chromophores. Moreover, by exposition to HCl vapours, PPY easily conve1is into the conesponding protonated fo1m [PPYH7cr displaying a sti·ong NLO conti·ast [3] characterized by an inversion of the µ β sign (-950 x 10-48 esu). The reaction is reversible and neuti·al PPY species can be easily restored by exposition to NH3 vapours. Interestingly, this protonation-deprotonation process is accompanied by a macroscopic variation in the emissive prope1iies. The acidochromic behavior of PPY has been rationalized by means of a theoretical investigation perfo1med at DFT and Time Dependent DFT level, which has allowed an analysis of the electi·onic origin of the NLO response in the neutral and protonated species. |
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