Calix[n]bispyrrolylbenzenes: synthesis, characterization, and preliminary anion binding studies.
A series of novel calixpyrrole-like macrocycles, calix[n]bis(pyrrol-2-yl)benzene (calix[n]BPBs, n=2-4) 9 a-11 a, have been synthesized by means of the TFA-catalyzed condensation reaction of bis(pyrrol-2-yl)benzene 8 a with acetone. Calix[2]BPB 9 a represents an expanded version of calix[4]pyrrole in which two of the four meso bridges are replaced by benzene rings. By contrast, systems 10 a and 11 a, which bear great considerable to calixbipyrroles 2 and 3, represent higher homologues of the basic calix[n]BPB motif. Solution-phase anion binding studies, carried out by means of (1)H NMR spectroscopic titrations in [D2]dichloromethane and isothermal titration calorimetry (ITC) in 1,2-dichloroethane, reveal that 9 a binds typical small anions with substantially higher affinities than 1, even though the same number of hydrogen bonding donor groups are found in both compounds. The basic building block for 9 a, benzene dipyrrole 8 a, also displays a higher affinity for anions than the building block for 1, dimethyldipyrromethane 16. Structural studies, carried out by single-crystal X-ray diffraction analyses, are consistent with the solution-phase results and reveal that 9 a is able to stabilize complexes with chloride and nitrate in the solid state. Structures of the PF6- and NO3- complexes of 10 a were also solved as were those of the acetone adduct of 9 a and the ethyl acetate adduct of 11 a.
Sessler
Jonathan L
JL
Department 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
An
Deqiang
D
Cho
Won-Seob
WS
Lynch
Vincent
V
Marquez
Manuel
M
D000838:Anions / Q000737:chemistry*; D001555:Benzene Derivatives / Q000138:chemical synthesis* / Q000737:chemistry*; D018360:Crystallography, X-Ray; D047028:Macrocyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D011758:Pyrroles / Q000138:chemical synthesis* / Q000737:chemistry*; D013237:Stereoisomerism
D000838:Anions; D001555:Benzene Derivatives; D047028:Macrocyclic Compounds; D011758:Pyrroles