Naphtho[4,3,2,1-lmn][2,9]phenanthrolines: Synthesis, characterization, optical properties and light-induced electron transfer in composites with the semiconducting polymer MEH-PPV Denis S. Baranov a, b , Alexandr G. Popov a, b , Mikhail N. Uvarov a, *, Maxim S. Kazantsev b, c , Evgeny A. Mostovich b, c , Evgeni M. Glebov a, b , Leonid V. Kulik a, b a V.V. Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Science, 630090 Novosibirsk, Russian Federation b Novosibirsk State University, 630090 Novosibirsk, Russian Federation c N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Science, 630090 Novosibirsk, Russian Federation A R T I C L E I N F O Article history: Received 20 October 2014 Received in revised form 12 January 2015 Accepted 13 January 2015 Available online xxx Keywords: Diazapyrenes Synthesis Spectroscopy Light-induced electron transfer A B S T R A C T Novel naphtho[4,3,2,1-lmn][2,9]phenanthrolines were synthesized via reaction between 1,5-diethynyl- 9,10-anthraquinones and urea in DMF. Their HOMO and LUMO levels determined from optical spectroscopy and cyclic voltammetry are in good agreement with those determined from quantum chemical calculation. Light-induced electron transfer from the semiconducting polymer MEH-PPV to the synthesized molecules was detected by EPR-spectroscopy, showing their possible applicability as electron acceptors in bulk heterojunction organic solar cells. The synthesized naphtho[4,3,2,1-lmn][2,9] phenanthrolines can be used as building blocks for larger molecules with an extended p-conjugated system, which can be used as acceptors in organic photovoltaics. ã 2015 Elsevier B.V. All rights reserved. 1. Introduction In organic photovoltaics, considerable attention is devoted to solar cells with a bulk heterojunction structure where fullerenes are used as a semiconducting acceptor component [1]. Owing to the success of these devices, the fullerenes are prominent amongst a small series of acceptor materials suitable for organic solar cells [2]. Nevertheless, the search for effective acceptor materials is progressing rapidly and molecules of novel types are coming to view [3]. There is potential in an alternative approach based on the application of simpler and cheaper acceptor materials with small molecules [4,5]. The number of tested substances is constantly growing, however their variety is limited and represented mostly by perylene derivatives [6,7]. Simultaneously a large number of similar polycondensed systems remain unexplored. Of particular interest are the polycyclic heteroaromatic compounds containing either heteroatoms or acceptor substitutes and the hybrid molecules that combine the conjugated acceptor and donor parts [8]. The special significance of polycyclic arenes (pyrene, perylene, coronene) for organic electronics [9] makes the analysis of similar heteroaromatic systems interesting. Additionally, the insertion of nitrogen atoms into polycondensed system enhances resistance to degradation [10]. Therefore, we have paid attention to the development and study of new, polycondensed diazahetarenes, the analogues of perylene [11] and benzopyrene. 2. Experimental 2.1. Synthesis 2.1.1. Copper(I) acetylides (general procedure) (1) A mixture of CuCl (2.5 g, 0.025 mol), NH 4 Cl (5.3 g, 0.1 mol), NH 2 OHHCl (0.7 g, 0.01 mol), 25% aqueous NH 3 (13 ml) in 100 ml H 2 O was stirred at room temperature under argon atmosphere. After stirring for 20 min, alkyne (0.02 mol) was added into the mixture over a period of 1 h. After stirring the reaction mixture for a further 4 h, the yellow precipitate copper acetylide was filtered, washed with EtOH, and dried in vacuum. 2.1.2. 1,4-Diiodo-9,10-anthraquinone (2) 1,4-Diamino-9,10-anthraquinone (2.4 g, 0.01 mol) was sus- pended in a mixture of AcOH (55 ml) and H 2 SO 4 (10 ml). Nitrosylsulfuric acid (2 g NaNO 2 , 20 ml H 2 SO 4 ) was added over 30 min. After the mixture had been stirred for 30 min, the dark solids were filtered. The filtrate was added in portions in a mixture of KI (6 g, 0.036 mol) and AcOH (50 ml) at 50–60  C. Then the * Corresponding author. Tel.: +7 383 333 22 97; fax: +7 383 330 73 50. E-mail address: uvarov@kinetics.nsc.ru (M.N. Uvarov). http://dx.doi.org/10.1016/j.synthmet.2015.01.012 0379-6779/ ã 2015 Elsevier B.V. All rights reserved. Synthetic Metals 201 (2015) 43–48 Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.elsevier.com/locate/sy nmet