Triarylamine-Bearing Poly(1,4-phenylenevinylene): Facile Preparation and Its Durable Aminium Polyradical

Abstract

ABSTRACT:Poly[2-{bis(4-methoxyphenyl)amino}phenyl-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] 1 was prepared via the Gilch reaction of the p-bis(chloromethyl)benzene monomer, 2-{bis(4-methoxyphenyl)aminophenyl}-, 0 -dichloro-p-xylene. The Gilch reaction facilitated the preparation of the polyphenylenevinylene with a triarylamine pendant group when compared to that via the Heck polycondensation. The molecular weight of the polymer was approximately 4:0 Â 10 5 , and it was soluble in common solvents and was reversibly redoxed due to the pendant arylamine moiety. Chemical oxidation of 1 afforded the corresponding aminium polyradical 1 þ with the half life-time of ca. 2 weeks under ambient conditions. ESR and magnetization measurements of 1 þ revealed a forbidden multiplet signal and an average spin quantum number (S) of 3/2 at low temperature, respectively. The polyradical 1 þ was the first example of a high molecular weight, high-spin organic polymer with solvent-solubility and film formability. 2,3-Bis[N,N-bis(4-methoxyphenyl)aminophenyl]stilbene 2 and its aminium diradical 2 þ were also prepared as the model dimer compounds; 2 þ was a triplet molecule at low temperature. The effect of the %-conjugated poly(1,4-phenylenevinylene) backbone on the high-spin alignment was also discussed. [doi:10.1295/polymj.PJ2006226] KEY WORDS Poly(phenylenevinylene) / Gilch Reaction / Aminium Radical / High-Spin Molecule / %-Conjugated Polymer / Radical Polymer / %-Conjugated and high-spin radical polymers have drawn the attention of researchers due to the possible creation of a purely organic-derived magnetic material.1,2 The target radical polymers have been molecular-designed by satisfying a non-Kekulé and nondisjoint fashion upon the %-conjugated connectivity among the radical moieties in order to realize an effective overlap of singly occupied molecular orbitals and a strong ferromagnetic interaction of the unpaired electrons of the radical moieties.1,3 Rajca et al. synthesized a two-dimensionally macrocyclic polyradical, poly(1,3-phenylenephenylmethine), and succeeded in producing very high magnetic moments and a spin quantum number (S > 5400) at very low temperature. 4 However, the arylmethine radical did not exist above 200 K, which prevents further development of the high-spin organic polymer.A triarylaminium radical possesses a high durability under ambient conditions due to the delocalized unpaired electron, which could also contribute to an efficient spin-exchange interaction in the molecule. Recently, we succeeded in synthesizing a durable poly(1,2-phenylenevinylene anisylaminium) derivative with a molecular weight of several thousands, in which the stilbene linker worked as an effective ferromagnetic spin coupler through the extended %-conjugated structure to give S of 3/2-7/2 at room temperature. 5,6 Such durable radical-bearing %-conjugated polymers possess a solvent solubility and tolerance for the spin-defect because the pendant spins are expected to interact not only with neighboring, but also with discrete spin...

Polymers for electronics and spintronics

“…In the 1990's, thanks to the progress in the synthesis of conjugated polymers, several groups started to synthesize polymers with linear conjugated polymer backbones and pendant radical groups using mild conditions of polymerization such as Heck reaction, 466 metathesis 467,468 or Gilch reaction. 469 Such a strategy was reviewed by Nishide in 1995. 466 This section will be devoted to the polymers obtained by such mild synthetic processes, starting with selected systems reported in the 1995 Nishide's review and focusing on the most recent reports of high-spin polymers.…”

“…However, by dispersing 6.68-OMe in a poly(styrenesulfonate tetrabutylammonium) matrix the magnetic properties could be enhanced to 0.63 spin/unit and S = 5/2 persisting at room temperature. The synthesis of poly(phenylenevinylene) grafted with both arylamine radical cations and long aliphatic chains was also reported (Scheme 64, structure 6.69), 469 with the aim to improve the solubility and film forming properties. A S = 3/2 spin multiplicity was measured for samples dispersed in poly(styrenesulfonate tetrabutylammonium).…”

Linear Oligoarylamines: Electrochemical, EPR, and Computational Studies of Their Oxidative States

“…Some investigations are typical examples of studies of organic mixed-valence molecules as hole transport materials to examine the intramolecular charge transfer (ICT) process, [11][12] and some are those of high-spin organic polyradicals to elucidate their stable multiredox properties of the magnetic triarylamine derivatives. [13][14][15][16][17][18][19][20][21] In comparison with the above, both these two cases incorporated "branching points" within dendrimers to link each triarylamine unit.…”

Magnetic properties of a doped linear polyarylamine bearing a high concentration of coupled spins (S = 1)

“…The first approach was mainly developed by Nishide's group. It consists in introducing stable free radicals as pendant groups along a conducting polymer backbone that can be linear [5][6][7][8][9][10][11][12][13][14] or branched. 15,16 In polymer systems following this approach spin states as high as S = 5 were reported.…”