posted on 2016-06-09, 00:00authored byArturo Jiménez-Sánchez, Itzel Isunza-Manrique, Gabriel Ramos-Ortiz, Jesús Rodríguez-Romero, Norberto Farfán, Rosa Santillan
Design
parameters derived from structure–property relationships
play a very important role in the development of efficient molecular-based
functional materials with optical properties. Here, we report on the
linear and nonlinear optical properties of a fluorene-derived dipolar
system (DS) and its octupolar analogue (OS), in which donor and acceptor groups are connected by a phenylacetylene
linkage, as a strategy to increase the number of delocalized electrons
in the π-conjugated system. The optical nonlinear response was
analyzed in detail by experimental and theoretical methods, showing
that, in the octupolar system OS, the dipolar effects
induced a strong two-photon absorption process whose magnitude is
as large as 2210 GM at infrared wavelengths. Solvatochromism studies
were implemented to obtain further insight on the charge transfer
process. We found that the triple bond plays a fundamental role in
the linear and nonlinear optical responses. The strong solvatochromism
behavior in DS and OS was analyzed by using
four empirical solvent scales, namely Lippert–Mataga, Kamlet–Taft,
Catalán, and the recently proposed scale of Laurence et al.,
finding consistent results of strong solvent polarizability and viscosity
dependence. Finally, the role of the acceptor groups was further studied
by synthesizing the analogous compound 2DS, having no
acceptor group.