The experimental verification of theories on the kinetics of electron transfer (ET)''] requires the synthesis of compounds with known and well-defined structures. To this end, molecules that consist of two identical subunits symmetrically connected by a rigid spacer are especially well-suited. Both the neutral molecule and its oxidized or reduced form must be stable. Most organic compounds that fulfill these conditions, ['] however, show such rapid ET for the intermolecular case already that its exact measurement for the intramolecular case is cumbersome and fraught with difficulties. In addition, theoretical predictions may not be equally valid for slow and fast ET processes. To reduce the rate constant, the inner reorganization energy131 of the ET process has to be increased; this reorganization energy is a measure of the energetic difference between the structures of the neutral molecule and its oxidized (or reduced) form. In this context, Nelsen et al. have synthesized and studied bis-(hydrazines) . [41 We reasoned that the oxidation of hexaaminobenzene derivatives should also have a high inner reorganization energy : investigations by several groups ['] have shown that the n-system of benzenes substituted at least in I-, 2-, 4-, and 5-positions with amino groups as in 2-4 reorganizes to a trimethinecyanine cation and a trimethinecyanine radical on loss of one electron, and to a bis(trimethinecyanine) such as 2a on loss of two electrons. Not only is a drastic change in bond lengths associated with these oxidations, the rings also become quite nonplanar and adopt twist conformations. These effects lead to a high 1 1 2 0 Me2N NMe2 NMe2 2 2a a =1.38A,b =1.53A NMe2 3 4kinetic barrier towards intermolecular electron transfer.r61 To peruse this intrinsic high barrier in an intramolecular process we synthesized dimeric hexaaminobenzene derivatives that are linked together through three spacers, for example methylene chains. The distance between the two arenes should be easily adjustable. Here we report on the synthesis and the structure of 1 , a representative of this class of compounds. None of the standard cyclophane syntheses[71 are suitable for the construction of the sterically encumbered 1. We reasoned, however, that the cyclization of a hexaaminobenzene derivative of type 5 with trinitrotrichlorobenzene (6) in a nucleophilic aromatic substitution reaction should be possible. First, we found that 6 and the model compound hexakis(dimethylamin0)benzene (3) form a weak charge transfer (CT) complex.[si Preor-NMeR CI + RMeN NMeR NMe? 5 NO2 6 R = -(CH2)4NH2 \f/le2N MeN M e N * ) % k 2 Me2N NMe 7ganization of reactants 5 and 6 is therefore possible. Moreover, the ring in amino-substituted trinitrobenzenes deviates strongly from planarity, L91 and cyclization is thus facilitated. Furthermore, we had found that the second and especially the third substitution of the chloro groups in 6 with monoalkylamines by the S,Ar mechanism are favored with respect to the first substitution even though the electron density forma...
