Dynamic internal cavities of dendrimers as constrained media. A study of photochemical isomerizations of stilbene and azobenzene using poly(alkyl aryl ether) dendrimers

Baskar Natarajan, Shipra Gupta, Nithyanandhan Jayaraj, Vaidhyanathan Ramamurthy, Narayanaswamy Jayaraman

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Dendritic microenvironments 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 2G3-C 5G3). Dendrimers constituted with n-pentyl linker were found to afford higher solubilitiesof stilbene and azobenzene. Direct irradiation of trans-stilbene showed that C 5G3 and C 4G3 dendrimers afforded considerable phenanthrene formation, in addition to cis-stilbene, whereas C 3G3 and C 2G3 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 5G3 < C 4G3 <C 3G3 <C 2G3. With the change in the alkyl linker from C 5 to C 2, significant changes in the activation parameters were observed.

Original languageEnglish
Pages (from-to)2219-2224
Number of pages6
JournalJournal of Organic Chemistry
Volume77
Issue number5
DOIs
StatePublished - Mar 2 2012

Fingerprint

Dendrimers
Stilbenes
Isomerization
Ether
Isomers
Activation energy
Chemical activation
azobenzene
Irradiation
Electrons

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

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; Gupta, Shipra; Jayaraj, Nithyanandhan; Ramamurthy, Vaidhyanathan; Jayaraman, Narayanaswamy.

In: Journal of Organic Chemistry, Vol. 77, No. 5, 02.03.2012, p. 2219-2224.

Research output: Contribution to journalArticle

@article{1fd69366cb0c4384bafb7acac06579d4,
title = "Dynamic internal cavities of dendrimers as constrained media. A study of photochemical isomerizations of stilbene and azobenzene using poly(alkyl aryl ether) dendrimers",
abstract = "Dendritic microenvironments 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 2G3-C 5G3). Dendrimers constituted with n-pentyl linker were found to afford higher solubilitiesof stilbene and azobenzene. Direct irradiation of trans-stilbene showed that C 5G3 and C 4G3 dendrimers afforded considerable phenanthrene formation, in addition to cis-stilbene, whereas C 3G3 and C 2G3 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 5G3 < C 4G3 <C 3G3 <C 2G3. With the change in the alkyl linker from C 5 to C 2, significant changes in the activation parameters were observed.",
author = "Baskar Natarajan and Shipra Gupta and Nithyanandhan Jayaraj and Vaidhyanathan Ramamurthy and Narayanaswamy Jayaraman",
year = "2012",
month = "3",
day = "2",
doi = "10.1021/jo2024027",
language = "English",
volume = "77",
pages = "2219--2224",
journal = "Journal of Organic Chemistry",
issn = "0022-3263",
publisher = "American Chemical Society",
number = "5",

}

TY - JOUR

T1 - Dynamic internal cavities of dendrimers as constrained media. A study of photochemical isomerizations of stilbene and azobenzene using poly(alkyl aryl ether) dendrimers

AU - Natarajan, Baskar

AU - Gupta, Shipra

AU - Jayaraj, Nithyanandhan

AU - Ramamurthy, Vaidhyanathan

AU - Jayaraman, Narayanaswamy

PY - 2012/3/2

Y1 - 2012/3/2

N2 - Dendritic microenvironments 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 2G3-C 5G3). Dendrimers constituted with n-pentyl linker were found to afford higher solubilitiesof stilbene and azobenzene. Direct irradiation of trans-stilbene showed that C 5G3 and C 4G3 dendrimers afforded considerable phenanthrene formation, in addition to cis-stilbene, whereas C 3G3 and C 2G3 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 5G3 < C 4G3 <C 3G3 <C 2G3. With the change in the alkyl linker from C 5 to C 2, significant changes in the activation parameters were observed.

AB - Dendritic microenvironments 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 2G3-C 5G3). Dendrimers constituted with n-pentyl linker were found to afford higher solubilitiesof stilbene and azobenzene. Direct irradiation of trans-stilbene showed that C 5G3 and C 4G3 dendrimers afforded considerable phenanthrene formation, in addition to cis-stilbene, whereas C 3G3 and C 2G3 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 5G3 < C 4G3 <C 3G3 <C 2G3. With the change in the alkyl linker from C 5 to C 2, significant changes in the activation parameters were observed.

UR - http://www.scopus.com/inward/record.url?scp=84863243793&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84863243793&partnerID=8YFLogxK

U2 - 10.1021/jo2024027

DO - 10.1021/jo2024027

M3 - Article

VL - 77

SP - 2219

EP - 2224

JO - Journal of Organic Chemistry

JF - Journal of Organic Chemistry

SN - 0022-3263

IS - 5

ER -