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Calix[n]bispyrrolylbenzenes: synthesis, characterization, and preliminary anion binding studies
Jonathan L Sessler1, Deqiang An, Won-Seob Cho
1Department of Chemistry and Biochemistry, Institute of Cellular and Molecular Biology, University of Texas at Austin, 1 University Station-A5300, Austin, TX 78712-1167, USA. sessler@mail.utexas.edu
Chemistry (Weinheim an Der Bergstrasse, Germany)
|December 30, 2004
Summary
Novel macrocycles, calix[n]bis(pyrrol-2-yl)benzene (calix[n]BPBs), show enhanced anion binding affinities compared to existing calixpyrroles. These findings advance the design of new anion receptors for various applications.
Area of Science:
- Supramolecular Chemistry
- Organic Synthesis
- Host-Guest Chemistry
Background:
- Calixpyrroles are known macrocyclic hosts for anion recognition.
- Developing new macrocyclic structures with improved binding properties is an ongoing area of research.
Purpose of the Study:
- To synthesize and characterize novel calixpyrrole-like macrocycles, calix[n]bis(pyrrol-2-yl)benzene (calix[n]BPBs).
- To investigate the anion binding affinities and structural properties of these new macrocycles.
Main Methods:
- Trifluoroacetic acid (TFA)-catalyzed condensation reactions for synthesis.
- (1)H NMR spectroscopic titrations and isothermal titration calorimetry (ITC) for solution-phase binding studies.
- Single-crystal X-ray diffraction for structural analysis.
Main Results:
- Successfully synthesized calix[n]BPBs (n=2-4).
- Calix[2]BPB (9a) exhibited significantly higher anion binding affinities than calix[4]pyrrole (1).
- Structural studies confirmed the stabilization of anion complexes (chloride, nitrate) in the solid state.
Conclusions:
- The incorporation of benzene rings into the macrocyclic framework enhances anion binding.
- Calix[n]BPBs represent a promising new class of anion receptors.
- Structural insights provide a basis for further rational design of host molecules.