High-spin polyradical

The physical organic chemistry of very high-spin polyradicals, 40, 153 Thermodynamic stabilities of carbocations, 37, 57 Topochemical phenomena in solid-slate chemistry, 15, 63 Transition state analysis using multiple kinetic isotope effects, 37, 239 Transition state structure, crystallographic approaches to, 29, 87 Transition state structure, in solution, effective charge and 27, 1... 

While rather lengthy synthetic efforts may be necessary for constructing high-spin polyradicals, samples having intermolecular spin order can be prepared by a combination of rather simple components like appropriate donors and acceptors. 

Rajca and co-workers have studied star-branched and dendritic high-spin polyradicals which are potential organic magnets. Representative data were obtained for the model tetra-anionic compound 55. Three redox waves were observed by cyclic voltammetry and differential pulse voltammetry for a four-electron process between the potentials of -2.00 and -1.20 V (vs. SCE). Electrochemical experiments with these materials have usually been performed at 200 K. The polyradicals, which are less stable for systems with more unpaired electrons, have been characterized by spectroscopic studies, ESR data, and SQUID magnetometiy. 

Fig. 6 High spin polyradical PAM26 (26 radical sites), designed by Rajca group using spin parity modeling.

It should be noted here for triarylamine networks and dendrimers [104], respectively, the radical cations have interesting properties like the formation of high-spin polyradicals with ferromagnetic coupling [105] or conducting polymers [106]. Very often, triarylamines have been used as the hole-transport layer in electroluminescent devices [107]. 

The physical organic chemistry of very high-spin polyradicals... 

This review outlines the design and characterization of very high-spin polyradicals. The rational, bottom-up design and characterization of polyarylmethyl polyradicals with increasing number of exchange coupled unpaired electron spins are described. 

A very high-spin polyradical may be defined as a molecule or polymer in which the electronic ground state possesses very large value of total spin quantum number S (high-spin ground state). Since the values of S are related to the net number of ferromagnetically coupled unpaired electrons (parallel spins), such molecules and... 

THE PHYSICAL ORGANIC CHEMISTRY OF VERY HIGH-SPIN POLYRADICALS 155... 

Selected intermediate radical anion species could be prepared and studied, primarily in solution (Fig. 22).88 Of particular interest were diradical anions 2521 -282 1- and diradical dianions 332 2 -352 2, i.e., diradicals related to the corresponding high-spin polyradicals by different occupancy of their non-bonding MOs (Fig. 22). 

Fig. 25 Chemical defects in Class I and II high-spin polyradicals.

Gomberg s statement, This work will be continued and I wish to reserve the field for myself, with which he concluded one of his original articles on triphenyl-methyl,27 may be paraphrased as follows. Indeed, this work was successfully continued polyarylmethyls reserved for themselves the field of high-spin polyradicals, but predictably, for not too long. 

Nishide, H., Ozawa, T., Miyasaka, M. and Tsuchida, E. (2001). Nanometer-sized high-spin polyradical poly(4-phenoxyl-l,2-phenylenevinylene) planarily extended in a non-kekule fashion and its magnetic force microscopic images. J. Am. Chem. Soc. 123, 5942-5946... 

Rajca, A. (1996). Very-high-spin polyradicals. In ACS Symposium Series 644, Molecule-Based Magnetic Materials, Turnbull, M.M, Sugimoto, T. and Thompson, L.K. (eds), Chapter 17, pp. 258-265. American Chemical Society, Washington, DC... 

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