1 Convergent Synthesis of Alternating Fluorene-p-xylene Oligomers and Delineation of the (Silver) Cation- Induced Folding Vincent J. Chebny and Rajendra Rathore* J. Am. Chem. Soc. 2007, 129,

2 The Biopolymers Permit Structure Modulation by Difference Interaction 1. Hydrogen bonding 2.  -stacking 3. Columbic interactions 4. Metal-ion binding

3 DAN: 1,5-dialkoxynaphthalene Donor 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 diimide acceptor

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

6 Selective Zinc Sensor Molecules Kikuchi. K. J. Am. Chem. Soc. 2005, 127, 10197

7 Rathore, R. et. al J. Am. Chem. Soc. 2005, 127, 8012 Synthesis of Receptor (a) and Its Model Compound (b) ba

8 Rathore, 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

9 X-ray Structure of 1 Showing the Extended Conformer

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

11 A Hitherto Unknown Polymeric Structure A

12 A Similar Mixture of Cyclic Oligomers

13 1 H/ 13 C NMR Spectra of the Mixture of Cyclic Oligomers a b b a c c d d e e , ,8

14 The Syntheses of Acyclic Oligomers (a)n-BuLi/THF/-78 °C. (b) n-BuLi/-78 °C/ethyl-4-(bromomethyl)benzote. (c) LiAIH 4 /THF/reflux. (d) SOCI 2 /CHCI 3 /0 °C F: fluorenes group, H: hydrogens group, M: methyls group, E: ester group, A: alcohol group, C: chloro group, X:xylyl group

15 (a) n-BuLi/THF/-78 °C. (b) n-BuLi/-78 °C/ethyl-4-(bromomethyl)benzote. (c) LiAIH4/THF/reflux. (d) SOCI 2 /CHCI 3 /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

16 The Syntheses of Acyclic Oligomers Z2-Z8

17 The Syntheses of Acyclic Oligomers Z2-Z8

18 A Comparison of the 1 H NMR Spectra of Z1-Z9 Oligomers. a:b:c= 6:4n+4:4n+4

19 1 H NMR Spectra of Z1 and Plot of Changes in the Chemical Shifts of the Xylenic Protons

20 The Maximum Number of Ag + Cations Captured by Zn Zn receptorsZ1Z3Z5Z7Z9 Max. number of Ag + cation12345

21 The Maximum Number of Ag + Cations Captured by Z1 Joe’s plot

22 The Binding of multiple Silver Cations to Representative Zn Receptors Zn receptorsZ1Z2Z3Z4Z5Z6Z7Z8Z9 Max. number of Ag + cation

23 It is important to note that the simplicity of the 1 H 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

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

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

26 Four Isoenergetic Conformers of the Oligomer Z3 density functional theory (DFT) calculations at the B3LYP/6-31G* level

27 1 H NMR Spectra of Z3 and Plot of Changes in the Chemical Shifts

28 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

29

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

31 Four Isoenergetic Conformers of the Oligomer Z3

32 A 313 : molar absorbance ε 313 : extinction coefficient of the new absorption band K : association constant

33

34

nm, typical of pyrene excimer fluorescence J.Am. Chem. Soc. 2003, 125, 2884.