Azacalix[4]arene cation radicals: spin-delocalised doublet- and triplet-ground states observed in the macrocyclic m-phenylene system connected with nitrogen atoms

Ishibashi, Koichi; Tsue, Hirohito; Sakai, Naoko; Tokita, Satoshi; Matsui, Kazuhiro; Yamauchi, Jun; Tamura, Rui

doi:10.1039/b801127c

Cited by 32 publications

(15 citation statements)

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“…Notably, the first and second oxidation potentials of the macrocyclic oligmer 1 are much lower than the first oxidation potentials of the related linear oligomers [−0.13 V for the dimer 4 and −0.11 V for the trimer 5 ], 10 which were measured under the same conditions. Furthermore, the increase of electron‐donating ability by macrocyclization of oligo‐ p ‐arylamines is remarkable as compared with that by macrocyclization of oligo‐ m ‐arylamines 11…”

Section: Methodsmentioning

confidence: 98%

Preparation and Characterization of N‐Anisyl‐Substituted Hexaaza[1₆]paracyclophane

et al. 2010

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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-

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Section: Methodsmentioning

confidence: 98%

Preparation and Characterization of N‐Anisyl‐Substituted Hexaaza[1₆]paracyclophane

et al. 2010

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“…Toluene, CH 2 Cl 2 , and DMF were refluxed over and then distilled from CaH 2 under Ar before use. Palladium bis(benzylideneacetone) ([PdA C H T U N G T R E N N U N G (dba) 2 ]), [24] calix [6]arene 3, [25] and compounds 4 [15] , 6 [16] , and 8 [12] were prepared according to the described procedure. Other chemicals were purchased from commercial suppliers and used as received.…”

Section: Methodsmentioning

confidence: 99%

“…N,N'-Bis[3-(N''-benzyl-3-bromo-5-tert-butyl-2-methoxyanilino)-5-tertbutyl-2-methoxyphenyl]-N,N'-dibenzyl-5-tert-butyl-2-methoxy-1,3-phenylenediamine (5): 60 % NaH (481 mg, 12.0 mmol) was added to a solution of 4 [15] (2.06 g, 2.00 mmol) in anhydrous DMF (40 mL) at 0 8C under Ar. After the reaction mixture had been stirred for 5 min, BnBr (1.1 mL, 9.0 mmol) was added.…”

Section: Methodsmentioning

confidence: 99%

Azacalix[6]arene Hexamethyl Ether: Synthesis, Structure, and Selective Uptake of Carbon Dioxide in the Solid State

Tsue

Ishibashi

Tokita

et al. 2008

Chemistry A European J

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To investigate dynamic solid-state complexation hitherto unexplored in nitrogen-bridged calixarene analogues, azacalix[6]arene hexamethyl ether has been prepared in three steps by applying a 5+1 fragment-coupling approach by using a Buchwald- Hartwig aryl amination reaction with the aid of our previously devised temporal N-silylation protocol. X-ray crystallographic analysis and NMR spectroscopic measurements have revealed that the azacalix[6]arene is well endowed with hydrogen-bonding ability, by which both the molecular and crystal structures are controlled. The azacalix[6]arene is conformationally flexible in solution on the NMR time scale, whereas it adopts a definite 1,2,3-alternate conformation with S2 symmetry in the solid state as a result of intramolecular bifurcated hydrogen-bonding interactions. In the crystal, molecules of the azacalix[6]arene are mutually interacted by intermolecular hydrogen bonds to establish one-dimensional hexane-filled nanochannel crystal architecture. Although the single crystal was broken after desolvation, the resultant polycrystalline powder material was capable of selectively adsorbing CO2 among the four main gaseous components of the atmosphere. In contrast, carbocyclic p-tert-butylcalix[6]arene hexamethyl ether, the crystal structure of which was also elucidated for the first time in the present study, gave rise to almost no uptake of CO2. Additional solid-gas adsorption experiments for another three gases, such as N2, O2, and Ar, suggested that quadrupole/induced-dipole interactions and/or hydrogen-bonding interactions played an important role in permitting the observed selective uptake of CO2 by this new azacalix[6]arene in the solid state.

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“…[12][13][14][15][16][17][18][19][20] Among the heteracalixarenes, N(R)-bridged azacalix[4]arenes of type 2, also called aza [1 4 ]metacyclophanes, are an emerging class of macrocycles owing to the presence of the nitrogen bridges, which open new perspectives in molecular magnetism and in supramolecular chemistry as hosts. [15,21] Curiously, inclusion properties of macrocycles of type 2 remain poorly explored, as only one example was described in the literature (R 1 = Me for K + complexation). [22] N(H)-bridged aza[1 4 ]metacyclophanes have been strikingly less investigated [19,21,23] but are much more attractive owing to the presence of additional hydrogen-bonding sites, and pos- [ sible direct functionalization of the NH sites has curiously never been reported.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Properties of the Emerging Azacalix[1₄]arenes

Touil¹,

Elhabiri²,

Lachkar³

et al. 2011

Eur J Org Chem

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Azacalix[4]arene cation radicals: spin-delocalised doublet- and triplet-ground states observed in the macrocyclic m-phenylene system connected with nitrogen atoms

Abstract: Electron paramagnetic resonance spectroscopy has unmasked for the first time the spin-delocalised doublet- and triplet-ground states of azacalix[4]arene cation radicals.

Cited by 32 publications

References 19 publications

Preparation and Characterization of N‐Anisyl‐Substituted Hexaaza[1₆]paracyclophane

Preparation and Characterization of N‐Anisyl‐Substituted Hexaaza[1₆]paracyclophane

Azacalix[6]arene Hexamethyl Ether: Synthesis, Structure, and Selective Uptake of Carbon Dioxide in the Solid State

Synthesis and Properties of the Emerging Azacalix[1₄]arenes

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Azacalix[4]arene cation radicals: spin-delocalised doublet- and triplet-ground states observed in the macrocyclic m-phenylene system connected with nitrogen atoms

Abstract: Electron paramagnetic resonance spectroscopy has unmasked for the first time the spin-delocalised doublet- and triplet-ground states of azacalix[4]arene cation radicals.

Cited by 32 publications

References 19 publications

Preparation and Characterization of N‐Anisyl‐Substituted Hexaaza[16]paracyclophane

Preparation and Characterization of N‐Anisyl‐Substituted Hexaaza[16]paracyclophane

Azacalix[6]arene Hexamethyl Ether: Synthesis, Structure, and Selective Uptake of Carbon Dioxide in the Solid State

Synthesis and Properties of the Emerging Azacalix[14]arenes

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Preparation and Characterization of N‐Anisyl‐Substituted Hexaaza[1₆]paracyclophane

Preparation and Characterization of N‐Anisyl‐Substituted Hexaaza[1₆]paracyclophane

Synthesis and Properties of the Emerging Azacalix[1₄]arenes