1

Convergent Synthesis of Alternating Fluorene-p-xylene Oligomers and Delineation of the (Silver) Cation-Induc

ed Folding

Vincent J. Chebny and Rajendra Rathore*

J. Am. Chem. Soc. 2007, 129, 8458-8465

2

The Biopolymers Permit Structure Modulationby Difference Interaction

1. Hydrogen bonding2. -stacking 3. Columbic interactions 4. Metal-ion binding

3

DAN: 1,5-dialkoxynaphthaleneDonor

The Biopolymers Permit Structure Modulation by -Stacking

Zych, A. J.; Iverson, B. L. J. Am. Chem. Soc. 2000, 122, 8898

NDI :1,4,5,8-naphthalenetetracarboxylic diimideacceptor

4Khan, A.; Kaiser, C.; Hecht, S. Angew. Chem., Int. Ed. 2006, 45, 1878.

Irradiation at 365 nm

Artificial Polymeric Materials can be Modulated by Light

5

Suzuki, Y. J. Phys. Chem. B 1998, 102, 7910

Artificial Polymeric Materials can be Modulated by Metal-ion Binding

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Selective Zinc Sensor Molecules

Kikuchi. K. J. Am. Chem. Soc. 2005, 127, 10197

7Rathore, R. et. al J. Am. Chem. Soc. 2005, 127, 8012

Synthesis of Receptor (a) and Its Model Compound (b)

b a

8Rathore, R. et. al J. Am. Chem. Soc. 2005, 127, 8012

Optimized Structures of the Isoenergetic Conformers of 1

density functional theory (DFT) calculations at the B3LYP/6-31G* level

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X-ray Structure of 1 Showing the Extended Conformer

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An Extended Conformer to an Delta Conformer by Binding a Single Silver Cation

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A Hitherto Unknown Polymeric Structure A

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A Similar Mixture of Cyclic Oligomers

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1H/13C NMR Spectra of the Mixture of Cyclic Oligomers

a

bb

a

c

cd

de

e 1

2

3

123

4

4

5

5

6

6

7,8

910

10

9

7,8

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The Syntheses of Acyclic Oligomers

(a) n-BuLi/THF/-78 °C. (b) n-BuLi/-78 °C/ethyl-4-(bromomethyl)benzote. (c) LiAIH4/THF/reflux. (d) SOCI2/CHCI3/0 °C

F: fluorenes group, H: hydrogens group, M: methyls group, E: ester group, A: alcohol group, C: chloro group, X:xylyl group

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(a) n-BuLi/THF/-78 °C. (b) n-BuLi/-78 °C/ethyl-4-(bromomethyl)benzote. (c) LiAIH4/THF/reflux. (d) SOCI2/CHCI3/0 °C. (e) Fluorene/n-BuLi/THF/-78 °C.

The Syntheses of Acyclic Oligomers

F: fluorenes group, H: hydrogens group, M: methyls group, E: ester group, A: alcohol group, C: chloro group, X:xylyl group

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The Syntheses of Acyclic OligomersZ2-Z8

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The Syntheses of Acyclic OligomersZ2-Z8

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A Comparison of the 1H NMR Spectra of Z1-Z9 Oligomers.

a:b:c= 6:4n+4:4n+4

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1H NMR Spectra of Z1 and Plot of Changesin the Chemical Shifts of the Xylenic Protons

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The Maximum Number of Ag+ Cations Captured by Zn

Zn receptors Z1 Z3 Z5 Z7 Z9

Max. number of Ag+ cation 1 2 3 4 5

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The Maximum Number of Ag+ Cations Captured by Z1

Joe’s plot

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The Binding of multiple Silver Cations to Representative Zn Receptors

Zn receptors Z1 Z2 Z3 Z4 Z5 Z6 Z7 Z8 Z9

Max. number of Ag+ cation 1 1 2 2 3 3 4 4 5

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It is important to note that the simplicity of the 1H NMR spectra, obtained in the presence of varying equivalents of Ag+, suggests the dynamic nature of the binding of Ag+ to the multiple receptor sites of Z2-Z9

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The Formation of Multiple -prismand-like Cavities for Binding of Ag+ Cations.

25Benesi, H. A.; Hildebrand, J. J. J. Am. Chem. Soc. 1949, 71, 2703

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Four Isoenergetic Conformers of the Oligomer Z3

density functional theory (DFT) calculations at the B3LYP/6-31G* level

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1H NMR Spectra of Z3 and Plot of Changes in the Chemical Shifts

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1. They developed convergent syntheses of hitherto unknown fluorene-p-xylene oligomers Z1-Z9 in excellent yields with the aid of four repetitive sequences of reactions.

2. The binding of multiple silver cations to Z3-Z9 was possible due to the folding of these oligomers, by simple C-C bond rotations.

3. We are actively exploring the syntheses of the Zn analogues containing different substituents to further modulate the binding and selectivity of various metal cations.

Conclusions

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2 eq. Ag+

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Possible Structures of Z3 upon Exposure to 1 and 2 Equiv of Silver Cations

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Four Isoenergetic Conformers of the Oligomer Z3

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A313 : molar absorbance ε313: extinction coefficient of the new absorption bandK : association constant

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C

O

R OR'LiAlH4

H2ORCH2OH + R'OH

SOCl2

RCH2Cl + SO2 + HCl

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35

462 nm, typical of pyrene excimer fluorescence

J.Am. Chem. Soc. 2003, 125, 2884.