Synthesis, and Optical and Electrochemical Properties of Cyclophane-Type Molecular Dyads Containing a Porphyrin in Close, Tangential Orientation Relative to the Surface of trans-1 Functionalized C60. Preliminary Communication
✍ Scribed by Jean-Pascal Bourgeois; François Diederich; Luis Echegoyen; Jean-François Nierengarten
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- German
- Weight
- 170 KB
- Volume
- 81
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
The synthesis of the cyclophane-type molecular dyads 1 and 1 . Zn was accomplished by Bingel macrocyclization of porphyrin-tethered bis-malonates 5 or 5 . Zn, respectively, with C 60 ( Scheme). In these macrocycles, the doubly bridged porphyrin adopts a close, tangential orientation relative to the surface of the Csphere. The porphyrin derivatives 6 and 6 . Zn with two appended, singly-linked C 60 moieties were also formed as side products in the Bingel macrocyclizations. The trans-1 addition pattern of the fullerene moiety in 1 and 1 . Zn was unambiguously established by 1 H-and 13 C-NMR spectroscopy. Due to the close spatial relationship between the fullerene and porphyrin components in 1 and 6 and the corresponding Zn II complexes, the porphyrin fluorescence is efficiently quenched as compared to the luminescence emitted by 5 and 5 . Zn, respectively ( Fig. ). Cyclic-voltammetry studies show that the mutual electronic effects exerted by the fullerene on the porphyrin and vice versa in 1 and 1 . Zn are relatively small despite the close proximity between the porphyrin donor and the fullerene acceptor ( Fig. ).
We have reported the efficient regio-and stereoselective preparation of bis(cyclopropanated) [60]fullerene derivatives by macrocyclization of the C-sphere via double Bingel addition [1]. This reaction provides a highly effective method for precisely positioning organic chromophores in close proximity to the fullerene surface, thus offering the potential for inducing profound changes in the properties of the C-allotrope. Thus, we recently observed a significant perturbation of the electronic structure of C 60 in trans-1, trans-2, and trans-3 bis-adducts in which a dibenzo [18]crown-6 moiety is attached by double Bingel addition, and adopts a close, tangential orientation relative to the surface of the C-sphere [2]. Upon complexation with K , the first reduction step of the fullerene becomes greatly facilitated as evidenced by anodic shifts in the cyclic voltammogram (CV ). The largest anodic shift ( 90 mV ) was observed for the trans-1 derivative in which the distance between the crown ether bound cation and C 60 is smallest. In all previous crown ether conjugates [1b] (for recent examples of fullerenecrown ether conjugates, see ), the ionophore part was located at a much greater distance from the surface of the fullerene, and, correspondingly, significant cationmediated electrochemical effects were not detected.