Branched Oligophenylenes with Phenylene-Ethynylene Fragments for Optoelectronics Alexey I. Kovalev, Natalia S. Kushakova, Andrey I. Stakhanov, Ivan A. Abramov, Silvia Destri, and Irina A. Khotina* By Sonogashira reaction the branched oligophenylenethynylenes with phenyl, acenaphthenyl or hexynyl groups as the end groups were synthesized. The comparison of model compound and branched polyphenyleneethynylenes clearly shows that their optical properties depend on the presence of phenylacetylene moieties. 1. Introduction Organic macromolecules are widely used for light emitting diodes (OLED). [1–3] The obtaining of efficient blue electrolumi- nescence from polymer materials is a difficult problem. Existing blue-emitting materials (based on polyfluorenes) decolorize fast enough, and this does not meet the operational requirements. Branched soluble polyphenylenes are ideal structures to create a blue OLEDs by the most essential parameters. They are extremely heat and radiation resistant, and exhibit bright fluorescence in the blue region in solution. [4] But they reveal low quantum efficiency in solid probably due to low charge carriers mobility. A balanced transport could be established in these structures if to attach to polyphenylenes donor and/or acceptor groups, i.e. groups providing a charge carrier mobility. Acetylene groups could be inserted into the polyphenylene through a difunctional monomer to give polyphenyleneethyny- lenes with hole transport ability. There are many examples of interesting synthesis and optical properties of linear polyphenyleneethynylenes in the litera- ture. [5,6] However, branched polyphenyleneethynylenes and the corresponding dendrimers have been much less studied. In a study of Moore’s research team [7] the interaction of AB 2 -monomer (3,5-diiodophenylacetylene) with of a monomer [e.g., 1-(3,5-diiodophenyl)-3,5-diethyltriazene] afforded high- molecular branched poly(phenylene acetylenes) with molecular masses of 8–90 kDa and narrow molecular-mass distributions. Several dendrimers obtained by Moore’s team [8] contained an acetylene fragments inside of branch groups. By controlling the length of conjugated phenylacetylene branches, effective energy transfer can be provided from the dendritic environment to one chromophore core (perylene moiety) where the absorbed energy is converted to radiation at higher wavelength. Optical properties of phenylacetylene dendrimers were considered also in the other publications. [9–12] Via the Sonogashira reaction we synthesized a series of oligophenylenes containing electronacceptor phenylacetylene fragments with different end groups, emitting in the blue region of the visible light. These studies underscore the importance of learning how the structure of the building conjugated moieties affect the optical properties of the polymer. 2. Experimental Section 2.1. Materials Solvents were dried over suitable reagents and freshly distilled under argon before use. Catalysts other than hydrogen chloride were added under argon. Before and after Pd-Cu-catalyst addition, all reaction solutions were deoxygenated using the freeze-defreeze method (four cycles), and, at the end of the last cycle, the reaction mixtures were backfilled with argon and the Schlenk tube was sealed. 2.1.1. 5-Bromoacenaphtene To a suspension of acenaphthene (10 g, 65 mmol) in DMF (35 ml) at 5  C a solution of NBS (11.7 g, 65 mmol) in DMF (35ml) was added drop wise. The mixture was stirred at 5  C for 2 h. Then the reaction solution was poured into cold water (1.5 l). The precipitate was separated, washed with water and dried at reduced pressure. The mixture of 5-bromo- and 3-bromoacenaphtene in a ratio of 100:5 (NMR data) was obtained. Recrystallisation from ethanol did not lead to a substantial separation. The yield was 12.4g (82%). 2.1.2. Trimethyl(acenaphten-5-yl)ethynylsilane To a solution of 5-bromoacenaphtene (1.165 g, 5 mmol) and triethylamine (2.4 ml) in toluene (15 ml), trimethylsilylacetylene A. I. Kovalev, N. S. Kushakova, A. I. Stakhanov, I. A. Abramov, I. A. Khotina A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova 28, 119991 Moscow, Russia E-mail: khotina@ineos.ac.ru S. Destri Istituto per lo studio delle Macromolecule (ISMAC), CNR, via Corti 12, 20133 Milano, Italy DOI: 10.1002/masy.201700037 Macromolecular Symposia Phenylene ethynylenes www.ms-journal.de ARTICLE Macromol. Symp. 2017, 375, 1700037 © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1700037 (1 of 5)