title: Investigation of anion-π interactions involving thiophene walls incorporated calix[4]pyrroles.
abstract: Thiophene containing "two-wall" aryl extended calix[4]pyrroles were synthesized for the first time, through acid catalyzed condensation of 2-acetylthiophenes with pyrrole. Isomeric "two-walled" calix[4]pyrroles (8a-10a and 8b-10b) were obtained in satisfactory yields and their halide anion binding strengths were investigated in the solution phase by (1)H NMR and in the gas phase by computational methods and mass spectrometry. Change in the chemical shifts of thiophene -CH-protons during the course of NMR titrations entailed participation of the thiophene rings in anion binding; this fact was further substantiated by computational methods. The α,α-(cis)-isomers (8a, 9a, and 10a) showed strong binding toward F(-) and Cl(-) anions when compared to their isomeric α,β-(trans)-isomer (8b, 9b, and 10b). In both isomers, binding with F(-) anion was found to be stronger than that with Cl(-) anion. Both the solution-phase and gas-phase results revealed that the thiophene rings stabilize the anions through anion-π interactions.
authors.affiliation: National Centre for Mass Spectrometry, ‡Centre for Nuclear Magnetic Resonance and Structural Chemistry, ∥Organic Chemistry Division II (C P C Division), and ⊥Academy of Scientific and Innovative Research, CSIR-Indian Institute of Chemical Technology , Hyderabad 500 007, India.
authors.forename: Chinthapalli Dinesh
authors.initials: CD
authors.lastname: Kumar
authors.forename: Katukuri
authors.initials: K
authors.lastname: Sirisha
authors.forename: Devendra Kumar
authors.initials: DK
authors.lastname: Dhaked
authors.forename: Pulipati
authors.initials: P
authors.lastname: Lokesh
authors.forename: Akella V S
authors.initials: AV
authors.lastname: Sarma
authors.forename: Prasad V
authors.initials: PV
authors.lastname: Bharatam
authors.forename: Srinivas
authors.initials: S
authors.lastname: Kantevari
authors.forename: Prabhakar
authors.initials: P
authors.lastname: Sripadi
mesh_terms: D000838:Anions / Q000737:chemistry*; D047250:Calixarenes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D011166:Porphyrins / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry; D013237:Stereoisomerism; D013876:Thiophenes / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D000838:Anions; D011166:Porphyrins; D011758:Pyrroles; D013876:Thiophenes; C469811:calix(4)pyrrole; D047250:Calixarenes; C508419:2-acetylthiophene