The synthesis of the first polyacetylenes bearing chiral fluorene-based pendant groups is described. Poly{9,9-bis[(S)-3,7-dimethyloctyl]fluoren-2-ylacetylene} (PFA1), poly{9,9-bis[(S)-2-methylbutyl]fluoren-2-ylacetylene} (PFA2), and poly{9,9,9',9',9",9"-hexakis[(S)-2-methylbutyl]-7,2';7',2"-terfluoren-2-ylacetylene} (PFA3) have been obtained by Rh(I)-catalyzed polymerization of the corresponding terminal acetylene monomers 2-ethynyl-9,9-bis[(S)-3,7-dimethyloctyl]fluorene (2a), 2-ethynyl-9,9-bis[(S)-2-methylbutyl]fluorene (2b), and 2-ethynyl-9,9,9',9',9",9"-hexakis[(S)-2-methylbutyl]-7,2';7',2"-terfluorene (10). The effect of the alkyl chain length at the C-9 position of fluorene on the structural and conformational aspects of the polymers PFA1 and PFA2 as well as on their chiroptical properties was studied by XRD, DSC, TGA, GPC, UV-vis, and CD. A more planar conformation of the polyenic backbone of PFA1 with respect to PFA2 can be inferred by a red shift of the pi-pi* transition in the UV-vis spectra. Their photoluminescence properties are those typical of fluorene systems. CD measurements evidenced Cotton effects of opposite signs in correspondence of the backbone absorption region, ascribable to an excess of a screw sense of the helical conformations assumed by the two polymers. PFA3 revealed an amorphous structure and exhibited peculiar thermal stability features (as indicated by TGA and DSC). Its emission spectra interest the violet-blue region and do not show any substantial red shift passing from solution to solid state, thus pointing out an aggregation prevention of terfluorene groups by means of the polyacetylene backbone.

Polyacetylenes Bearing Chiral-Substituted Fluorene and Terfluorene Pendant Groups:  Synthesis and Properties

Piero Mastrorilli;Cosimo Francesco Nobile;Roberto Grisorio;Antonino Rizzuti;Gian Paolo Suranna;
2004

Abstract

The synthesis of the first polyacetylenes bearing chiral fluorene-based pendant groups is described. Poly{9,9-bis[(S)-3,7-dimethyloctyl]fluoren-2-ylacetylene} (PFA1), poly{9,9-bis[(S)-2-methylbutyl]fluoren-2-ylacetylene} (PFA2), and poly{9,9,9',9',9",9"-hexakis[(S)-2-methylbutyl]-7,2';7',2"-terfluoren-2-ylacetylene} (PFA3) have been obtained by Rh(I)-catalyzed polymerization of the corresponding terminal acetylene monomers 2-ethynyl-9,9-bis[(S)-3,7-dimethyloctyl]fluorene (2a), 2-ethynyl-9,9-bis[(S)-2-methylbutyl]fluorene (2b), and 2-ethynyl-9,9,9',9',9",9"-hexakis[(S)-2-methylbutyl]-7,2';7',2"-terfluorene (10). The effect of the alkyl chain length at the C-9 position of fluorene on the structural and conformational aspects of the polymers PFA1 and PFA2 as well as on their chiroptical properties was studied by XRD, DSC, TGA, GPC, UV-vis, and CD. A more planar conformation of the polyenic backbone of PFA1 with respect to PFA2 can be inferred by a red shift of the pi-pi* transition in the UV-vis spectra. Their photoluminescence properties are those typical of fluorene systems. CD measurements evidenced Cotton effects of opposite signs in correspondence of the backbone absorption region, ascribable to an excess of a screw sense of the helical conformations assumed by the two polymers. PFA3 revealed an amorphous structure and exhibited peculiar thermal stability features (as indicated by TGA and DSC). Its emission spectra interest the violet-blue region and do not show any substantial red shift passing from solution to solid state, thus pointing out an aggregation prevention of terfluorene groups by means of the polyacetylene backbone.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11589/2414
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