Papers by Gabriel Ramos-ortíz
Chemistry - A European Journal, 2015
The synthesis, crystal and electronic structures, and one-and two-photon absorption properties of... more The synthesis, crystal and electronic structures, and one-and two-photon absorption properties of two quadrupolar fluorenyl-substituted tetraphenyl carbo-benzenes are described. These all-hydrocarbon chromophores, differing in the nature of the linkers between the fluorenyl substituents and the carbo-benzene core (CÀC bonds for 3 a, CÀCCÀC expanders for 3 b), exhibit quasi-superimposable one-photon absorption (1PA) spectra but different twophoton absorption (2PA) cross-sections s 2PA . Z-scan measurements (under NIR femtosecond excitation) indeed showed that the CC expansion results in an approximately twofold increase in the s 2PA value, from 336 to 656 GM (1 GM = 10 À50 cm 4 s molecule À1 photon À1 ) at l = 800 nm. The first excited states of A u and A g symmetry accounting for 1PA and 2PA, respectively, were calculated at the TDDFT level of theory and used for sum-over-state estimations of s 2PA (l i ), in which l i = 2 hc/E i , h is Planck's constant, c is the speed of light, and E i is the energy of the 2PA-allowed transition. The calculated s 2PA values of 227 GM at 687 nm for 3 a and 349 GM at 708 nm for 3 b are in agreement with the Z-scan results. . It contains the synthetic principle of 5 b, photoluminescence spectra of 3 a and 3 b, the normalized transmittance curve of 3 b from Z-scan measurements, the near-frontier molecular orbitals of 3 a and 3 b, characteristics of the first singlet excited states of 3 a and 3 b (in vacuo and chloroform continuum), the contribution of intermediate 1PA-allowed states in the SOS expansion of the 2PA cross-section associated with the 4A g excited state of 3 a and 3 b, and copies of 1 H and 13 C NMR spectra, MS analyses, and voltammograms of 3 a and 3 b.
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Papers by Gabriel Ramos-ortíz