The absorption and CD spectra of a series of Frechet (compounds 7-10) and backfolding (compounds 11-12) dendrimers derived from enantiopure (S)- 2,2'-dihydroxy-1,1'-binaphthalene have been recorded (THF) in the range 200- 350 nm. All the compounds examined show a positive couplet between 200 and 240 nm (1B transition of the 2-naphthol chromophore), the intensity of which (Δε(max) of the low-energy branch) ranges between 100 and 40. By means of the DeVoe polarizability model the intensity of the 1B couplet has been calculated vs. the dihedral angle θ. This analysis provides θ angles of 95- 110° for the Frechet dendrimers and 100-110°for the backfolding compounds. These values clearly indicate that the torsional angle θ, defined by the two naphthalene planes, never exceeds the critical value of 110°. This investigation confirms the wide utility of CD spectroscopy to provide geometrical information that cannot be obtained by other types of structural analysis.

Enantiopure Dendrimers Derived from the 1,1’-Binaphtyl Moiety: A Correlation Between Chiroptical Properties and Conformation of the 1,1’-Binaphthyl Template

ROSINI, Carlo;SUPERCHI, Stefano;
2000

Abstract

The absorption and CD spectra of a series of Frechet (compounds 7-10) and backfolding (compounds 11-12) dendrimers derived from enantiopure (S)- 2,2'-dihydroxy-1,1'-binaphthalene have been recorded (THF) in the range 200- 350 nm. All the compounds examined show a positive couplet between 200 and 240 nm (1B transition of the 2-naphthol chromophore), the intensity of which (Δε(max) of the low-energy branch) ranges between 100 and 40. By means of the DeVoe polarizability model the intensity of the 1B couplet has been calculated vs. the dihedral angle θ. This analysis provides θ angles of 95- 110° for the Frechet dendrimers and 100-110°for the backfolding compounds. These values clearly indicate that the torsional angle θ, defined by the two naphthalene planes, never exceeds the critical value of 110°. This investigation confirms the wide utility of CD spectroscopy to provide geometrical information that cannot be obtained by other types of structural analysis.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11563/17680
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