title: Low-Band-Gap BODIPY Conjugated Copolymers for Sensing Volatile Organic Compounds.
abstract: Conjugated polymers with strong photophysical properties are used in many applications. A homopolymer (P1) and five new low band gap copolymers based on 4,4'-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) and acceptors 3,6-dithienyldiketopyrrolopyrrole (P2), phthalimide (P3), benzotriazole (P4), 4,7-dithienyl[1,2,3]triazolo[4,5g]quinoxaline (P5), and 2,5-dithienylthieno[3,4-b]pyrazine (P6) were prepared by means of Sonogashira polymerization. The characterization of polymers by using (1) H NMR, absorption, and emission spectroscopy is discussed. All polymers with high molecular weights (Mn ) of 16 000 to 89 000 g mol(-1) showed absorption maxima in the deep-red region (λ=630-760 nm) in solution and exhibited significant redshifts (up to 70 nm) in thin films. Polymers P2, P5, and P6 showed narrow optical band gaps of 1.38, 1.35, and 1.38 eV, respectively, which are significantly lower than that of P1 (1.63 eV). The HOMO and LUMO energy levels of the polymers were calculated by using cyclic voltammetry measurements. The LUMO energy levels of BODIPY-based alternating copolymers were independent of the acceptors; this suggests that the major factor that tunes the LUMO energy levels of the polymers could be the BODIPY core. All polymers showed selective and reproducible detection of volatile organic solvents, such as toluene and benzene, which could be used for developing sensors.
authors.affiliation: Faculty of Science, Department of Chemistry, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore).
authors.forename: Choong Ping
authors.initials: CP
authors.lastname: Sen
authors.affiliation: World Premier International Center for Materials, Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Ibaraki, Tsukuba 305-0044 (Japan).
authors.forename: Rekha Goswami
authors.initials: RG
authors.lastname: Shrestha
authors.affiliation: World Premier International Center for Materials, Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Ibaraki, Tsukuba 305-0044 (Japan).
authors.forename: Lok Kumar
authors.initials: LK
authors.lastname: Shrestha
authors.affiliation: World Premier International Center for Materials, Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Ibaraki, Tsukuba 305-0044 (Japan).
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Ariga
authors.affiliation: Faculty of Science, Department of Chemistry, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore). chmsv@nus.edu.sg.
authors.forename: Suresh
authors.initials: S
authors.lastname: Valiyaveettil
keywords: electrochemistry; polymers; sensors; supramolecular chemistry; volatile organic vapors