Alkylated Trimethylene-Bridged Bis(p-Phenylenediamines)

Abstract

One and two electron oxidation of N,N',N'',N'''-tetramethyl-1,5,12,16-tetraaza[5,5]paracyclophane (Me3C), a bis-trimethylene bridged bis-p-phenylene diamine (PD), and its ethyl and isopropyl analogues are discussed. The monocation and dication are both stable, as demonstrated by optical studies that show they are in equilibrium in solution, with an especially small difference in first and second oxidation potentials for Me3C in MeCN (+23 to -20 mV, measured by simulation of the optical spectrum and of the cyclic voltammogram, respectively). The monocations have charge localized in one PD unit and show a Hush-type mixed valence transition between their PD0 and PD.+ groups. The dications Me3C2+ and Et3C2+ have optical spectra that appear to show large splittings between their PD.+ groups and have a weak ESR spectrum, and 1H NMR data show that the former is a ground-state singlet. iPr3C2+ has a very different optical spectrum and exhibits a triplet ESR spectrum at 120 K. X-ray crystal structures show that for Me3C0 the N(CH2)3N units on each side are in doubly anti (aa) conformations that put the aryl rings as far apart as possible, but Me3C2+ has doubly gg N(CH2)3N trimethylene bridges and both N,N and C,C distances between the PD.+ groups that are significantly below van der Walls contact. In contrast, iPr3C0 is in a doubly ag conformation, and its diradical dication is suggested to be a triplet because it does not attain the doubly gg conformation.

Oxidation Products of Doubly Trimethylene-Bridged Tetrabenzylp-Phenylenediamine Paracyclophane

“…The singly Together with previous studies, [26][27][28][29]38 this work shows that molecular interactions of the organic radical ions are clearly sensitive to the solvent and counterion environment, which is also shown by theoretical studies on the spontaneous dimerization of TMPD radical cations. 39 We expect that deeper understanding from the molecular prospective of the intermolecular binding nature of the open-shell organic radicals can provide the basis for future discoveries of novel organic materials.…”

Polycationic States of Oligoanilines Based on Wurster's Blue

“…[2] Its stability can be explained by π-electron delocalization in the semi-quinone structure (Scheme 1). However, the use of TMPD ·+ as a spin-containing unit to exploit high-spin organic systems has not often been examined, [3][4][5][6] probably because the cou-pling reaction between aryl bromide and N-methylarylamine is not a feasible process. Recent progress in Pd-catalyzed C-N coupling reactions has facilitated the synthesis of various arylamines.…”

“…Moreover, very recently, Nelsen et al found that the spin preference of the bis(radical cation) of a trimethylene-bridged cyclophane with two TMPD units depends on the conformations between two p-phenylenediamine (PD) units. [6] In this context, our attention was drawn to the extended oligomer models of TMPD-based high-spin polymers. In relation to TMPDbased high-spin oligomers, the polycationic states of the related m,p-arylamine oligomers have already been examined by Wienk and Janssen in detail.…”

Intermolecular π‐dimer of oxoverdazyl radicals with long‐distance multicenter (2e/8c) bonding via nitrogen atoms

“…Starting from the works of Hausser and Murrell1 and Kosover,2–4 numerous UV‐Vis and ESR spectroscopic studies have demonstrated the tendency of various cationic, anionic, and neutral π ‐radicals to form diamagnetic associates with characteristic absorption bands in the near‐IR region 5–24. X‐ray crystallographic measurements of these supramolecular complexes revealed ‘face‐to‐face’ arrangements of the π ‐bonded fragments with interatomic contacts of approximately 0.1–0.5 Å closer than the van der Waals separations 25–32.…”