Synthesis and characterization of X-shaped oligo(para-phenylene) derivatives functionalized with fluorene ethynylene

A series of linear and X-shaped oligo（para-phenylene） derivatives functionalized with fluorene ethynylenes 1,3 and 4 were synthesized through sequent Sonogashira coupling and Suzuki-Miyaura reaction in high yield.The electron-donating group-OCH3 and electron-withdrawing counterparts-CF3 were introduced to tune the spectra properties of compounds 3 and 4.The detail investigation of their photophysical properties in solution and film indicated that the introduction of both -OCH3 and -CF3 makes maximum emission distinct red-shift in comparison with parent compound 1,but the latter more prominently.

Hydration effect on the electronic transport properties of oligomeric phenylene ethynylene molecular junctions

A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H2O molecules accumulated in the vicinity as recently reported by Na et al. [Nanotechnology 18 424001 （2007）]. The numerical results show that the hydrogen bonds between the oxygen atoms of the oligomeric phenylene ethynylene molecule and H2O molecules result in the localisation of the molecular orbitals and lead to the lower transition peaks. The H2O molecular chains accumulated in the vicinity of the molecular junction can not only change the electronic structure of the molecular junctions, but also open additional electronic transport pathways. The obvious influence of H2O molecules on the electronic structure of the molecular junction and its electronic transport properties is thus demonstrated.

Synthesis of linear and V-shaped oligo(phenylene ethynylene) derivatives:Geometric effects on photophysical properties

A series of linear and V-shaped oligo(phenylene ethynylene) derivatives 1-3 were synthesized through sequent Sonogashira coupling and propargyl alcohol deprotection reaction in high yields.The alkoxy chains(i.e.,n-hexyloxy groups) were introduced to assure good solubility of compounds 1-3 in common solvents.The photophysical properties of 1-3 in solution depend strongly on the geometries of these compounds.

Novel Poly(thienylene Ethynylene)s with Electron-accepting Groups

Novel n-conjugated polymers constituted of 2,1,3-benzothiadiazole or cyano-containing unit copolymers were synthesized and characterized by UV-Vis, IR and PL.

A-π-D-π-A Type Small Molecules Using Ethynylene Linkages for Organic Solar Cells with High Open-circuit Voltages

Introducing ethynylene linkages in a conjugated molecule can deepen the HOMO level, decrease the steric con- straints and better delocalize the n electrons and so on, which are beneficial for organic solar cells. Furthermore, the typical method of introducing acetylene linkages by Sonogashira reactions can avoid the usage of toxic stannyl in- termediates and potentially dangerous lithiation reactions. In this study, two simple small molecules BEDPP and NEDPP are designed and synthesized, in which two diketopyrrolopyrrole units are symmetrically connected to benzene and naphthalene cores, respectively, via acetylene linkages. And the BHJ （Bulk Heterojunction） solar cells based on BEDPP and NEDPP without using solvent additive and without any post-treatment for the active layers provide us power conversion efficieneies of 1.48% and 2.31% with remarkably high open circuit voltages up to 0.90 and 0.98 V, respectively.

AGGREGATION-INDUCED EMISSION ENHANCEMENT IN POLY(PHENYLENE ETHYNYLENE)S BEARING ANILINE GROUPS

Poly（phenylene ethynylene）s （P1） with 4-vinylaniline pendant groups were successfully prepared by the Sonogashira coupling polymerization bevween 1,4-diethynyl-2,5-bis（pentyloxy）benzene and 4-[2-（2,5-dibromophenyl）vinyl]- aniline. In comparison with its analogue P2 without amino group, the emission of F＇I is only enihanced by aggregation when adding n-hexane into its THF solution, exhibiting an aggregation-induced emission enhancement （AIEE） effect. When methanol or water instead of hexane was added into THF solution, P1, however, didn＇t show AII：~E. The results indicated that amino groups strengthen the inter-chain and intra-chain interactions in P1 and restrict the no^-radiative energy transition. This strategy can provide a platform for developing highly sensitive and efficient bio- and chemosensors.

The amplified fluorescence quenching of heteroatomic conjugated polymers based on the “molecular wire”effects

Tremendous interest has been evoked in the utility of the fluorescent conjugated polymers towards the creation of ultra-sensitive systems based on the molecular wire effects which can amplify the transduction events. Here, a series of new polymers pyridine substitute poly (phen- ylene ethynylene)s are synthesized by Sonogashira-Hagihara coupling reaction. The impact of structure modification on the physical properties and spectral characteristics of poly-mers has been investigated. The quenching studies are car-ried out and exhibit that recognition site (pyridyle group) highly influences the quenching efficiency. The results show that polymer PI with pyridyl group entrapped in the conju-gated backbone has the specific and sensitive response to Pd(Ⅱ). The fluorescence quenching of PⅠby Pd(Ⅱ) is about 65 times greater than that of model monomer.

1,2,5,6-Naphthalenediimide-based Conjugated Copolymers Linked by Ethynyl Units

Two copolymers of P1 and P2 comprising benzothiadiazole, 1,4-bis（dodecyloxy）-benzene units were synthesized by Sonogashira coupling polymerization based on ethynyl-linked 1,2,5,6-naphthalenediimide. Their thermal, optical, electrochemical as well as charge transport properties were studied. Bottom-gate top-contact organic field-effect transistors （OFETs） measurements of P1 and P2 thin films showed different charge transport behaviors. P1 displayed pure electron transport behaviors in OFETs with electron mobility up to 10^-3 cm^2·V-1·s^-1, while P2 exhibited hole transport features. The molecular structure analysis revealed that the structure of P1 has the acceptor-linker-acceptor＇ （A-L-A＇） characteristic, and P2 possesses the donor-linker-acceptor （D-L-A） structure feature. The results demonstrate that different molecular structures lead them to have distinct charge transport behaviors. In particular, the first pure electron transport copolymer in OFETs based on 1,2,5,6-naphthalenediimide is achieved.