Study of confined 5-aza[5]helicene in ytterbium(III) bis(2-ethylhexyl) sulfosuccinate reversed micelles.
Some relevant physicochemical properties of 5-aza[5]helicene (H5) in solutions of ytterbium bis(2-ethylhexyl) sulfosuccinate (Yb(DEHSS)3) reversed micelles have been investigated by UV-vis-NIR, photoluminescence, and FT-IR techniques with the aim of emphasizing the role played by specific Yb(III)/H5 interactions and confinement effects as driving forces of its binding to reversed micelles, preferential solubilization site, and local photophysical properties. It has been found that the binding strength of 5-aza[5]helicene to reversed micelles, triggered by steric and orientational constrains as well as the water content, is mainly regulated by its interaction with the Yb(III) counterion. Moreover, when H5 is entrapped in Yb(DEHSS)3 reversed micelles, the combined action of this interaction and of confinement effects leads to marked changes of its photophysical properties with respect to those of H5 molecularly dispersed in apolar medium. The influence of the entrapment of finite amounts of H5 on the reversed micelle structure was investigated by SAXS. The analysis of experimental results brings to the hypothesis that H5 is preferentially solubilized and opportunely oriented in the micellar palisade layer and that its insertion causes an unidimensional growth of reversed micelles. From an analysis of WAXS spectra of H5/Yb(DEHSS)3 composites, obtained by complete evaporation of the volatile components of the H5/water/Yb(DEHSS)3/n-heptane solutions, it was ascertained that also on these systems H5 is dispersed molecularly or in a quite amorphous state in the surfactant liquid crystals without forming a separate crystalline nanophase.
Abbate
Sergio
S
Dipartimento di Scienze Biomediche e Biotecnologie, Università di Brescia, Viale Europa 11, 25123 Brescia, Italy.
Caronna
Tullio
T
Longo
Alessandro
A
Ruggirello
Angela
A
Liveri
Vincenzo Turco
VT
D001372:Aza Compounds / Q000737:chemistry*; D006576:Heterocyclic Compounds, 4 or More Rings / Q000737:chemistry*; D008823:Micelles; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D019265:Spectroscopy, Near-Infrared; D013386:Succinates / Q000737:chemistry*; D015018:Ytterbium / Q000737:chemistry
C519953:5-aza(5)helicene; D001372:Aza Compounds; D006576:Heterocyclic Compounds, 4 or More Rings; D008823:Micelles; D013386:Succinates; C511925:bis(2-ethylhexyl)sulfosuccinate; D015018:Ytterbium