title: Switching of emissive and NLO properties in push-pull chromophores with crescent PPV-like structures.
abstract: We report on a series of novel homologous push-pull compounds, in which identical donor (a dimethylamino) and acceptor (a malonate ester) functionalities endcap crescent PPV fragments, bearing, respectively, 1, 2 and 3 p-phenylenevinylene units in direct linear conjugation (compounds 7-9). The three compounds exhibit striking differences in their linear and nonlinear optical properties. The shorter compound 7 exhibits aggregation-induced emission with a strong luminescence in the solid state (blue emission, photoluminescence quantum yield 38%), and it is nonemissive in solution; the more extended conjugated systems 8 and 9 show classical aggregation-caused quenching in the solid state, while high quantum yield photoluminescence (21 and 93% in toluene) is restored in diluted solutions, through mechanisms involving intramolecular charge transfer in the excited states. EFISH measurements in solutions demonstrate a strong solvent and concentration dependence. As rationalized with the aid of molecular modelling, compounds 8 and, more markedly, 9 aggregate in stable centrosymmetric dimers in solution.
authors.affiliation: Department of Chemistry, University of Pavia, Viale Taramelli, 10-27100 Pavia, Italy.
authors.forename: Carmine
authors.initials: C
authors.lastname: Coluccini
authors.forename: Arvind K
authors.initials: AK
authors.lastname: Sharma
authors.forename: Marco
authors.initials: M
authors.lastname: Caricato
authors.forename: Angelo
authors.initials: A
authors.lastname: Sironi
authors.forename: Elena
authors.initials: E
authors.lastname: Cariati
authors.forename: Stefania
authors.initials: S
authors.lastname: Righetto
authors.forename: Elisa
authors.initials: E
authors.lastname: Tordin
authors.forename: Chiara
authors.initials: C
authors.lastname: Botta
authors.forename: Alessandra
authors.initials: A
authors.lastname: Forni
authors.forename: Dario
authors.initials: D
authors.lastname: Pasini