The authors report the synthesis, the photophys., conductometric, and 2nd-order nonlinear optical (NLO) characterization of an ensemble of four NLO active org. tails nanoorganized on a cyclotetrasiloxane ring, to produce various macrocyclic NLO chromophores. The 2nd-order NLO response of the macrocyclic NLO chromophores measured by the EFISH technique as .mu..beta.1.91, where .mu. is the dipole moment and .beta.1.91 the projection along the dipole moment axis of the vectorial component of the quadratic hyperpolarizability working with an incident wavelength of 1.907 .mu.m, increases, compared to the ref. monomeric NLO chromophores, from 2.8 up to 3.5 times for nonionic macrocyclic NLO chromophores. The increase is mainly due to an increase of the dipole moment when compared to ref. monomeric NLO chromophores while the .beta.1.91 values remain almost unchanged. These macrocyclic NLO chromophores can be also considered as a simple model of a monolayer of org. NLO chromophores on a chem. engineered SiO2 surface. Since the factor controlling their 2nd-order NLO response is the orientation toward the dipole moment axis of the single org. NLO active tails, this kind of model confirms that the 2nd-order NLO response of a monolayer of org. NLO chromophores on a chem. engineered SiO2 surface is controlled by the topol. of the binding sites on the surface, as suggested by previous studies on multilayers on chem. engineered SiO2 surface. The macrocyclic NLO chromophore with a ionic org. NLO active tail shows a strong concn. dependence of its 2nd-order NLO response to be ascribed to a larger increase of its ionic dissocn. by diln., when compared to that of the ref. ionic monomeric NLO chromophore. This behavior is evidence of a cooperative effect due to the nanoorganization, to be ascribed to a more facile ionic dissocn. of the single ionic org. tail originated by a local increase of the solvent polarity favored by the closeness of the pos. charges of the four org. tails. Finally the Si(OSiMe3)3 group behaves in a classical org. push-pull NLO chromophore as a pull group as strong as the nitro group.

Second-Order Nonlinear Optical (NLO) Properties of a Multichromophoric System Based on an Ensemble of Four Organic NLO Chromophores Nanoorganized on a Cyclotetrasiloxane Architecture. / M. Ronchi, M. Pizzotti, A. Orbelli Biroli, S. Righetto, R. Ugo, P. Mussini, M. Cavazzini, E. Lucenti, M. Salsa, P. Fantucci. - In: JOURNAL OF PHYSICAL CHEMISTRY. C. - ISSN 1932-7447. - 113:7(2009), pp. 2745-2760.

Second-Order Nonlinear Optical (NLO) Properties of a Multichromophoric System Based on an Ensemble of Four Organic NLO Chromophores Nanoorganized on a Cyclotetrasiloxane Architecture.

M. Ronchi
Primo
;
M. Pizzotti
Secondo
;
A. Orbelli Biroli;S. Righetto;R. Ugo;P. Mussini;E. Lucenti;M. Salsa
Penultimo
;
2009

Abstract

The authors report the synthesis, the photophys., conductometric, and 2nd-order nonlinear optical (NLO) characterization of an ensemble of four NLO active org. tails nanoorganized on a cyclotetrasiloxane ring, to produce various macrocyclic NLO chromophores. The 2nd-order NLO response of the macrocyclic NLO chromophores measured by the EFISH technique as .mu..beta.1.91, where .mu. is the dipole moment and .beta.1.91 the projection along the dipole moment axis of the vectorial component of the quadratic hyperpolarizability working with an incident wavelength of 1.907 .mu.m, increases, compared to the ref. monomeric NLO chromophores, from 2.8 up to 3.5 times for nonionic macrocyclic NLO chromophores. The increase is mainly due to an increase of the dipole moment when compared to ref. monomeric NLO chromophores while the .beta.1.91 values remain almost unchanged. These macrocyclic NLO chromophores can be also considered as a simple model of a monolayer of org. NLO chromophores on a chem. engineered SiO2 surface. Since the factor controlling their 2nd-order NLO response is the orientation toward the dipole moment axis of the single org. NLO active tails, this kind of model confirms that the 2nd-order NLO response of a monolayer of org. NLO chromophores on a chem. engineered SiO2 surface is controlled by the topol. of the binding sites on the surface, as suggested by previous studies on multilayers on chem. engineered SiO2 surface. The macrocyclic NLO chromophore with a ionic org. NLO active tail shows a strong concn. dependence of its 2nd-order NLO response to be ascribed to a larger increase of its ionic dissocn. by diln., when compared to that of the ref. ionic monomeric NLO chromophore. This behavior is evidence of a cooperative effect due to the nanoorganization, to be ascribed to a more facile ionic dissocn. of the single ionic org. tail originated by a local increase of the solvent polarity favored by the closeness of the pos. charges of the four org. tails. Finally the Si(OSiMe3)3 group behaves in a classical org. push-pull NLO chromophore as a pull group as strong as the nitro group.
Settore CHIM/01 - Chimica Analitica
Settore CHIM/03 - Chimica Generale e Inorganica
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/62466
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