Synthetic Metals 166 (2013) 70–76 Contents lists available at SciVerse ScienceDirect Synthetic Metals journa l h o me pag e: www.elsevier.com/locate/synmet Absorption and emission properties of the corrole–fullerene dyad Kornelia Lewandowska a , Bolesław Barszcz a , Andrzej Graja a,∗,1 , Bartosz Bursa b , Andrzej Biadasz b , Danuta Wróbel b,∗,2 , Waldemar Bednarski a , Stefan Waplak a , Marek Grzybowski c , Daniel T. Gryko c,∗,3 a Institute of Molecular Physics, Polish Academy of Sciences, 60-179 Pozna´ n, Poland b Faculty of Technical Physics, Institute of Physics, Poznan University of Technology, 60-965 Pozna´ n, Poland c Institute of Organic Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland a r t i c l e i n f o Article history: Received 30 November 2012 Received in revised form 23 January 2013 Accepted 23 January 2013 Keywords: Corrole–fullerene dyad Electronic absorption and fluorescence spectra Fluorescence quantum yield and lifetime Charge localization and distribution Electron magnetic resonance a b s t r a c t The bichromophoric systems comprising of corrole and fullerene units and representing one of the rare cases of elaborate structures based on corrole have been studied with the use of photophysical meth- ods. The dyad displays spectroscopic properties which are the superposition of the component spectra, indicating a very weak electronic coupling. Excitation of the corrole unit leads to charge redistribution. The results of UV–vis absorption and fluorescence and also fluorescence kinetics suggest the presence of charge separation. It was shown that light absorption of the corrole–fullerene dyad is better fitted to the sunlight spectrum than porphyrin. Electron paramagnetic resonance investigations suggest partial spin density redistribution at low temperature between corrole and fullerene in the dyad. Quantum chemical calculations support experimental results. © 2013 Published by Elsevier B.V. 1. Introduction Due to the excellent properties and availability of porphyrins, they have constituted for several decades the most used compo- nents of models for light energy collection and conversion [1,2]. However, the need of the performance improvement and increase the variety of such molecular systems encouraged the use of other porphyrinoids. Solving the energy problems requires searching for novel molecular materials, which should be characterized by a large absorption coefficient, fast process of charge separation and much slower process of charge recombination [3–5]. Among various materials fulfilled these requirements there are organic donor–acceptor systems containing fullerene C 60 as an elec- tron acceptor and an organic dye as electron donor. The excellent electron-accepting capability of fullerenes makes them appropriate building blocks for designing various photovoltaic devices [6,7]. Corroles are one-carbon-shorter analogs of porphyrins possess- ing the skeleton of corrin with three meso-carbons between the four pyrrole rings. They were found to be suitable replacement for porphyrins in these electron-donor/electron-acceptor systems [8]. ∗ Corresponding authors. E-mail addresses: graja@ifmpan.poznan.pl (A. Graja), danuta.wrobel@put.poznan.pl (D. Wróbel), danieltgryko@gmail.com, daniel@icho.edu.pl (D.T. Gryko). 1 Tel. +48 61 86 95 275. 2 Tel. +48 61 66 53 179. 3 Tel. +48 22 34 33 063. When compared with porphyrins, these tribasic aromatic macro- cycles exhibit lower oxidation potentials, higher fluorescence quantum yields, larger Stokes shifts, and more intense absorption of red light [9,10]. Free-base corroles reveal the Soret-type absorption in the 400–440 nm region and Q band transitions between 500 and 700 nm. Spectral properties of corroles, similarly as of porphyrins can be tuned via: introducing various central metals, putting suit- able substituents on the periphery of conjugated ring systems, or solvent conditions [8–11]. It is necessary to add, that the effect of substitution on the optical properties of corroles is significantly larger than in porphyrins. Finally, corroles can be very emissive, with high quantum yields of fluorescence [8–11]. The corroles are, in general, less stable than porphyrins, but the stability of their dyads is better than that of the corresponding component cor- roles [12]. In the last decade, meso-substituted corroles are among the most widely investigated compounds as potential materials for application in photovoltaic systems [8,9,12–14]. Recently, we have described synthesis and vibrational prop- erties of a new corrole-based-fullerene dyad (named 3) and its components: modified corrole (2) and a suitable spacer (pentaflu- orophenyl 1) [15] shown in Fig. 1. In the paper [15] our systematic spectral studies of the dyad and its components were presented for the first time. The infrared absorption and Raman scattering spec- tra were supported by the quantum chemical calculations of the equilibrium geometry and normal mode vibrations of the investi- gated molecules. It was found that the strongest excitations in the dyad are mainly related to the excitations of the modified corrole part with some influence of the spacer and fullerene parts [15]. 0379-6779/$ – see front matter © 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.synthmet.2013.01.014