title: Conformation of Novel Azo-Dyes Bearing End-Capped Oligo(ethylene glycol) Studied by UV-vis and NMR Spectroscopy.
abstract: Two novel azo-dyes bearing an end-capped oligo(ethylene glycol) chain were synthesized and then studied by UV-visible and NMR spectroscopy. For both azobenzenes, the end-capped oligo(ethylene glycol) segment is on the para position of the first phenyl ring. On the second phenyl ring, a methoxy group is added on the para position for one azo-dye and no substitution group on the other, which made them electronically a push-push and a push system, respectively. The presence of the methoxy group changes significantly the absorption and the photoisomerization behaviors and results in a much less intense absorbance for the trans isomer and a shift from 350 to 360 nm. In the kinetic studies the azobenzene bearing a methoxy group shows a zero-order and a first-order kinetics as a function of the time scale of the study as well as an aggregation phenomenon. This azo-dye in different solvents has been studied by (1)H NMR and pulsed gradient NMR experiments to understand the effects of the photoisomerization and the aggregation on the self-diffusion of these molecules in solutions.
authors: Département de chimie, Université de Montréal , C.P. 6128, Succursale Centre-ville, Montréal, Québec H3C 3J7, Canada.
authors: Cassandre
authors: C
authors: Kouvatas
authors: Département de chimie, Université de Montréal , C.P. 6128, Succursale Centre-ville, Montréal, Québec H3C 3J7, Canada.
authors: Wilms E
authors: WE
authors: Baille
authors: Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Circuito Exterior Ciudad Universitaria , C.P. 04510 México D.F., México.
authors: Jesús
authors: J
authors: Ortíz-Palacios
authors: Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Circuito Exterior Ciudad Universitaria , C.P. 04510 México D.F., México.
authors: Edgar
authors: E
authors: Aguilar-Ortíz
authors: Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Circuito Exterior Ciudad Universitaria , C.P. 04510 México D.F., México.
authors: Ernesto
authors: E
authors: Rivera
authors: Département de chimie, Université de Montréal , C.P. 6128, Succursale Centre-ville, Montréal, Québec H3C 3J7, Canada.
authors: X X
authors: XX
authors: Zhu