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 language | English |
|---|---|
| Pages (from-to) | 2219-2224 |
| Number of pages | 6 |
| Journal | Journal of Organic Chemistry |
| Volume | 77 |
| Issue number | 5 |
| DOIs | |
| State | Published - Mar 2 2012 |
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ASJC Scopus subject areas
- Organic Chemistry
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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 journal › Article
}
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.
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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 -