As opposed to the thoroughly studied carbon-bridged calixarenes, [1] heteroatom-bridged [1 n ]metacyclophanes and their derivatives have recently attracted much attention mainly because of novel structure-property relationships originating from the replacement of methylene bridges with heteroatom bridges.[2] On the other hand, only a few reports are known for [1 n ]paracyclophanes, probably as a result of the difficulty in synthesizing them (Scheme 1). [3,4] Aza[1 n ]paracyclophanes can be viewed as macrocyclic oligomers of polyaniline, which is one of the well-known organic conducting polymers. [5] As is apparent from the simple Hückel MO calculations, the HOMOs for linear and cyclic oligoanilines assume different aspects, as exemplified in Scheme 2. As for the linear hexamer, the large MO coefficients are concentrated on the central para-phenylenediamine (PD) moiety. Owing to the localized HOMO character, the ESR studies on the radical cations of linear oligoanilines showed that the spin was confined to the central PD moiety, and therefore, spin delocalization took place only to a small extent.[6] In contrast, the HOMO coefficients of the cyclic hexamer is mainly distributed equally on six nitrogen nuclei. In fact, according to the DFT calculations, the HOMO coefficients of all-N-phenyl-substituted hexaaza[1 6 ]paracyclophane (1') is delocalized over the macrocyclic molecular backbone, and therefore, the DFT-predicted spin density distribution in the corresponding radical cation discerns the delocalized character (Figure 1). In this respect, it is interesting to examine the spin distribution of the radical cation of cyclic oligoanilines in conjunction with the question: to what extent is an unpaired electron delocalized within the polyaniline backbone?However, the preparation of aza[1 n ]paracyclophanes are hitherto unknown, and the elucidation of their electronic properties is in demand from the viewpoint of materials chemistry. This communication reports the synthesis and characterization of electronic structures of all-N-anisyl-substituted hexaaza[1 6 ]paracyclophane (1) and its oxidized species.The title compound (1) was not obtained by the simple single-step coupling reaction from para-halogenated secondary arylamines. In addition, convergent fragment coupling synthesis [1] from the combinations of simple secondary arylamines and aryl halides was also unsatisfactory to us. For example, an equimolar coupling reaction of N,N'-bis(4-

Triphenylaminium radical cations are well-known for their remarkable stability; furthermore, the oxidation potential is adjustable by the introduction of a series of substituents, in particular, at the para positions. Thus, they are widely used not only as one-electron oxidative reagents but also as catalysts in organic chemistry. [1] Besides such an application as versatile chemical reagents, the ambient stable radical cations generated from triphenylamine (TPA) derivatives could be utilized as spin sources in molecule-based magnetic materials. In fact, a considerable number of TPA-based molecular multi-spin systems have appeared in the literature. However, from the viewpoint of assemblage of the spin sources into the architecture of the reported molecular systems, the spin-spin exchange coupling pathway has been confined to one-and two-dimensionalities, [2] and accordingly, TPA-based multispin systems with three-dimensional (3D) connectivity are rare.In 1985, Neugebauer and co-workers reported the first synthesis of a TPA double-decker 1 (Scheme 1) [3] in which two TPA moieties are directly connected by threefold o,o'-linkage, in association with an interest in intramolecular interaction between two nitrogen lone pairs.[4] In spite of its sensitivity to oxidation and the formation of persistent radical cation, no detailed information was available concerning the electronic structure. Such a cage-like oligo(triphenylamine) can be regarded as a potent building block to afford the opportunity furnishing new TPA-based macromolecular systems with genuine 3D connectivity. Although neither the parent 1 nor its derivatives have been reported since then, [5] an analogue 2 in which two TPA moieties are connected at para positions of all phenyl groups by three meta-phenylenediamine pillars, was successfully prepared in our laboratory.Slow evaporation of a dilute mixed solution (CH 3 OH and CH 2 Cl 2 ) of a pale yellow product 2, which was obtained by using Buchwald-Hartwig cross-coupling reaction [6] between 4,4',4''-tribromo-TPA as a deck and meta-phenylenediamine as a pillar in a ratio of 2:3, [7] gave yellow block crystals suitable for X-ray structure analysis.[21] The crystal belongs to the space group P2 1 , and contains two molecules of 2 per unit cell in which there exist three sites for CH 2 Cl 2 molecules so as to fill spaces between the double-deckers (Supporting Information, Table S1).The X-ray structure of 2 has almost C 3h symmetrical trichetria-like [8] shape when all the methoxy substituents are ignored, and the upper and lower TPA decks adopt almost planar propeller-like conformation (the tilted angles of phenyl rings range from 428 to 538), and moreover, are totally eclipsed (Figure 1). Three meta-phenylenediamine planes are perpendicular to the TPA planes, and therefore, the distance between two TPA decks are estimated to be about 4.9 at the peripheral three nitrogen pairs and 5.8 at the central nitrogen pair, indicating the direct transannular p-p interaction between two TPA decks is virtually ignorabl...

As opposed to the thoroughly studied carbon-bridged calixarenes, [1] heteroatom-bridged [1 n ]metacyclophanes and their derivatives have recently attracted much attention mainly because of novel structure-property relationships originating from the replacement of methylene bridges with heteroatom bridges. [2] On the other hand, only a few reports are known for [1 n ]paracyclophanes, probably as a result of the difficulty in synthesizing them (Scheme 1). [3,4] Aza[1 n ]paracyclophanes can be viewed as macrocyclic oligomers of polyaniline, which is one of the well-known organic conducting polymers. [5] As is apparent from the simple Hückel MO calculations, the HOMOs for linear and cyclic oligoanilines assume different aspects, as exemplified in Scheme 2. As for the linear hexamer, the large MO coefficients are concentrated on the central para-phenylenediamine (PD) moiety. Owing to the localized HOMO character, the ESR studies on the radical cations of linear oligoanilines showed that the spin was confined to the central PD moiety, and therefore, spin delocalization took place only to a small extent. [6] In contrast, the HOMO coefficients of the cyclic hexamer is mainly distributed equally on six nitrogen nuclei. In fact, according to the DFT calculations, the HOMO coefficients of all-N-phenyl-substituted hexaaza[1 6 ]paracyclophane (1') is delocalized over the macrocyclic molecular backbone, and therefore, the DFT-predicted spin density distribution in the corresponding radical cation discerns the delocalized character (Figure 1). In this respect, it is interesting to examine the spin distribution of the radical cation of cyclic oligoanilines in conjunction with the question: to what extent is an unpaired electron delocalized within the polyaniline backbone?However, the preparation of aza[1 n ]paracyclophanes are hitherto unknown, and the elucidation of their electronic properties is in demand from the viewpoint of materials chemistry. This communication reports the synthesis and characterization of electronic structures of all-N-anisyl-substituted hexaaza[1 6 ]paracyclophane (1) and its oxidized species.The title compound (1) was not obtained by the simple single-step coupling reaction from para-halogenated secondary arylamines. In addition, convergent fragment coupling synthesis [1] from the combinations of simple secondary arylamines and aryl halides was also unsatisfactory to us. For example, an equimolar coupling reaction of N,N'-bis(4-Scheme 2. Schematic views of HOMOs of a) linear and b) cyclic hexamers of polyaniline. Scheme 1. Reported heteroatom-bridged [1 n ]paracyclophanes and hexaaza[1 6 ]paracyclophane 1 and 1'.

Scheme 1. The first reported TPA double-decker 1 [3] and meta-phenylenediamine-bridged TPA double-decker 2.