title: Asymmetric noncovalent synthesis of self-assembled one-dimensional stacks by a chiral supramolecular auxiliary approach.
abstract: Stereoselective noncovalent synthesis of one-dimensional helical self-assembled stacks of achiral oligo(p-phenylenevinylene) ureidotriazine (AOPV3) monomers is obtained by a chiral supramolecular auxiliary approach. The racemic mixture of helical stacks of achiral AOPV3 molecules is converted into homochiral helical stacks, as shown by both spectroscopic measurements and molecular modeling simulations. The conversion is promoted by an orthogonal two-point ion-pair interaction with the chiral auxiliary dibenzoyl tartaric acid (D- or L-TA) molecules, which biases the angle population distribution and thereby the stack helicity. The induced preferred helicity is maintained by the OPV stacks even after the removal of the chiral auxiliary by extraction with ethylenediamine (EDA), due to the kinetic stability of the OPV stacks at room temperature. Spectroscopic probing of the helical self-assembly and the racemization process of these π-conjugated OPV chromophores shed further light into the mechanistic pathways of this chiral asymmetric noncovalent synthesis and the kinetic stability of the stacks produced. The racemization of the stacks follows first-order kinetics and no switch in mechanism is observed as a result of a temperature change; therefore, a racemization via disassembly assembly is proposed. Remarkably, the preferred helicity of the stacks of achiral AOPV3 can be retained almost completely after a heating-cooling cycle where the stacks first partially depolymerize and then polymerize again with the still existing stacks being the seeds for self-assembly of achiral AOPV3. Only after a fully dissociated state is obtained at high temperatures, the optical activity of the supramolecular stack self-assembled at room temperature is lost.
authors.affiliation: Institute for Complex Molecular Systems and Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: Subi J
authors.initials: SJ
authors.lastname: George
authors.forename: Robin
authors.initials: R
authors.lastname: de Bruijn
authors.forename: Željko
authors.initials: Ž
authors.lastname: Tomović
authors.forename: Bernard
authors.initials: B
authors.lastname: Van Averbeke
authors.forename: David
authors.initials: D
authors.lastname: Beljonne
authors.forename: Roberto
authors.initials: R
authors.lastname: Lazzaroni
authors.forename: Albertus P H J
authors.initials: AP
authors.lastname: Schenning
authors.forename: E W
authors.initials: EW
authors.lastname: Meijer
mesh_terms: D046911:Macromolecular Substances / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure; D011145:Polyvinyls / Q000138:chemical synthesis* / Q000737:chemistry; D014227:Triazines / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D046911:Macromolecular Substances; D011145:Polyvinyls; D014227:Triazines; C470024:poly(4-phenylenevinylene)