title: Rationally designed calix[4]arene-pyrrolotetrathiafulvalene receptors for electron-deficient neutral guests.
abstract: Four upper rim bis-monopyrrolotetrathiafulvalene-calix[4]arene conjugates 2a,b and 3a,b have been efficiently synthesized using a modular construction approach. The new compounds feature a molecular tweezer architecture with a quasi-parallel arrangement of redox-active tetrathiafulvalene (TTF) arms, which serve as the guest binding centers. Complexation studies using UV/vis binding titrations revealed a high affinity of the calixarene-TTF receptors for planar electron-deficient guests, leading to formation of deeply colored charge-transfer complexes in solution. The binding efficiency of the receptors depends on the flexibility of the calixarene scaffolds and the electronic nature of the TTF arms: the highest binding efficiency is shown by receptor 2b, featuring a highly preorganized molecular structure and an electron-rich TTF moiety.
authors.affiliation: Department of Chemistry, University of Bremen, Leobener Strasse NW 2C, D-28359 Bremen, Germany.
authors.forename: Matthias H
authors.initials: MH
authors.lastname: Düker
authors.forename: Hannes
authors.initials: H
authors.lastname: Schäfer
authors.forename: Matthias
authors.initials: M
authors.lastname: Zeller
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Azov
mesh_terms: D047250:Calixarenes / Q000737:chemistry*; D004583:Electrons; D006571:Heterocyclic Compounds / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D010636:Phenols / Q000737:chemistry*
chemical_list: D006571:Heterocyclic Compounds; D010636:Phenols; C121325:calix(4)arene; D047250:Calixarenes; C063887:tetrathiafulvalene