title: Substituent Effects That Control Conjugated Oligomer Conformation through Non-covalent Interactions.
abstract: Although understanding the conformations and arrangements of conjugated materials as solids is key to their prospective applications, predictive power over these structural factors remains elusive. In this work, substituent effects tune non-covalent interactions between side-chain fluorinated benzyl esters and main-chain terminal arenes, in turn controlling the conformations and interchromophore aggregation of three-ring phenylene-ethynylenes (PEs). Cofacial fluoroarene-arene (ArF-ArH) interactions cause twisting in the PE backbone, interrupting intramolecular conjugation as well as blocking chromophore aggregation, both of which prevent the typically observed bathochromic shift observed upon transitioning PEs from solution to solid. This work highlights two structural factors that determine whether the ArF-ArH interactions, and the resulting twisted, unaggregated chromophores, occur in these solids: (i) the electron-releasing characteristic of substituents on ArH, with more electron-releasing character favoring ArF-ArH interactions, and (ii) the fluorination pattern of the ArF ring, with 2,3,4,5,6-pentafluorophenyl favoring ArF-ArH interactions over 2,4,6-trifluorophenyl. These trends indicate that considerations of electrostatic complementarity, whether through a polar-π or substituent-substituent mechanism, can serve as an effective design principle in controlling the interaction strengths, and therefore the optoelectronic properties, of these molecules as solids.
authors.affiliation: Department of Chemistry, Tufts University , Medford, Massachusetts 02155, United States.
authors.forename: Seth A
authors.initials: SA
authors.lastname: Sharber
authors.affiliation: Department of Chemistry, Tufts University , Medford, Massachusetts 02155, United States.
authors.forename: Rom Nath
authors.initials: RN
authors.lastname: Baral
authors.affiliation: Department of Chemistry, Tufts University , Medford, Massachusetts 02155, United States.
authors.forename: Fanny
authors.initials: F
authors.lastname: Frausto Arellano
authors.affiliation: Department of Chemistry, Tufts University , Medford, Massachusetts 02155, United States.
authors.forename: Terry E
authors.initials: TE
authors.lastname: Haas
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Peter
authors.initials: P
authors.lastname: Müller
authors.affiliation: Department of Chemistry, Tufts University , Medford, Massachusetts 02155, United States.
authors.forename: Samuel W
authors.identifier: 0000-0002-0811-9781
authors.initials: SW
authors.lastname: Thomas Iii