ePrints@IIScePrints@IISc Home | About | Browse | Latest Additions | Advanced Search | Contact | Help

Dynamic Internal Cavities of Dendrimers as Constrained Media. A Study of Photochemical Isomerizations of Stilbene and Azobenzene Using Poly(alkyl aryl ether) Dendrimers

Natarajan, Baskar and Gupta, Shipra and Jayaraj, Nithyanandhan and Ramamurthy, V and Jayaraman, Narayanaswamy (2012) Dynamic Internal Cavities of Dendrimers as Constrained Media. A Study of Photochemical Isomerizations of Stilbene and Azobenzene Using Poly(alkyl aryl ether) Dendrimers. In: Journal of Organic Chemistry, 77 (5). pp. 2219-2224.

[img] PDF
Dynamic_Internal.pdf - Published Version
Restricted to Registered users only

Download (1756Kb) | Request a copy
Official URL: http://pubs.acs.org/doi/abs/10.1021/jo2024027

Abstract

Dendritic rnicroenvironments defined by dynamic internal cavities of a dendrimer were probed through geometric isomerization of stilbene and azobenzene. A third-generation poly(alkyl aryl ether) dendrimer with hydrophilic exterior and hydrophobic interior was used as a reaction cavity in aqueous medium. The dynamic inner cavity sizes were varied by utilizing alkyl linkers that connect the branch junctures from ethyl to n-pentyl moiety (C(2)G(3)-C(5)G(3)). Dendrimers constituted with n-pentyl linker were found to afford higher solubilities of stilbene and azobenzene. Direct irradiation of trans-stilbene showed that C(5)G(3) and C(4)G(3) dendrimers afforded considerable phenanthrene formation, in addition to cis-stilbene, whereas C(3)G(3) and C(2)G(3) gave only cis-stilbene. An electron-transfer sensitized trans-cis isomerization, using cresyl violet perchlorate as the sensitizer, also led to similar results. Thermal isomerization of cis-azobenzene to trans-azobenzene within dendritic microenvironments revealed that the activation energy of the cis- to trans-isomer was increasing in the series C(5)G(3) < C(4)G(3) < C(3)G(3) <C(2)G(3). With the change in the alkyl linker from C-5 to C-2 significant changes in the activation parameters were observed.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to American Chemical Society.
Department/Centre: Division of Chemical Sciences > Organic Chemistry
Date Deposited: 10 Apr 2012 07:33
Last Modified: 10 Apr 2012 07:33
URI: http://eprints.iisc.ernet.in/id/eprint/44160

Actions (login required)

View Item View Item